Tremor while in gear & need help - 97 Thunderbird LX Sport 4.6L

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Las Vegas, NV
Vehicle Details
1997 Ford Thunderbird LX Sport with 4.6L V8
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Hi all...

My 1997 Bird LX Sport 4.6L (69K miles) has recently developed a tremor while in any gear, except for Park. I say tremor, because it's not quite a typical rough idle.

I've been all over this board & TCCOA for the past couple weeks, reading all I can to learn more & diagnose this on my own...but I don't know enough to properly interpret the data & diagnose this, so I'm at an impasse and need advice from people who know more than I do.

Timeline of events and what's been done so far:
  1. There's no coolant or engine oil leaks and plug wells have always been bone dry.

  2. Intake manifold was replaced by Ford under the recall, around year 2000-ish. Never had an issue after the replacement.

  3. In February 2024, did a complete overhaul/replacement of the non-ABS/non-traction control brake system, because she was still running the factory brakes/calipers and getting spongy.
    1. Including this info, because don't know if related to tremor issue.
    2. Personally rebuilt all four calipers, replaced all four brake hoses, all disc pads, installed new (not rebuilt) master cylinder, and replaced all rotors with Motorcraft rotors. Never did brakes before and wanted to teach myself, using the 97 Ford Bird service manual as guidance.
    3. Bled the brakes with several quarts of Motorcraft/Prestone DOT 3...but brakes remain kinda spongy no matter what's been done.
    4. All the work & bleeding was later inspected by @supergordo (Gordon) who said everything looked great and also replaced the master cylinder & did more brake bleeding...but brakes are still soft/ spongy-ish.
    5. Car stops fine, but not the crisp & solid brake pedal feel you'd expect after throwing all that money & parts at it. Will address this again with Gordon in the near future.
  4. A few months ago, before brake job, CEL lit up with a P0301 code, Cyl#1 misfire. Pulled the plug and re-gapped it...cleared the CEL and all was fine after that.

  5. Shortly afterwards, decided to replace all the plugs with Autolite Double-Plats gapped to 0.052", as well as replace the wires and ignition coils with Motorcraft parts, due to age and growing scarcity of Motorcraft parts.

  6. Prior to plug change, the plug wells were clean, no debris, and bone dry with no coolant leaks...then blew out all the plug wells with a compressor and changed plugs/wires. Also, coated inside of plug wires with dielectric grease and torqued new plugs to spec.
    1. The car was always smooth, but after the parts change, she was silky smooth and happier.
  7. Disconnected battery and cleaned the throttle body and MAF with appropriate spray chemicals, never touching the MAF wire. The MAF is original, never been removed/cleaned before, but was spotless and looked new before I cleaned it.

  8. Later, cleaned & detailed the engine and engine bay with a couple cans of Gunk Engine Cleaner and a thorough hose down & drying, after disconnecting battery and wrapping & protecting the electronics & other sensitive parts. Pulled all plug wires and all wells were still bone dry.

  9. After this, engine still ran smoothly & beautifully.

  10. But a couple weeks later, she developed a slight tremor while in gear...not quite a rough idle, but the tremor is noticeable in the steering wheel. While in Park, idle increases like normal and the tremor seems to vanish or be hidden.

  11. While idling in the garage, I can hear that her 'breathing' seems odd; there's a barely perceptible & slight up and down in her idle speed humming, like a few RPM's difference every few seconds. A slow, rhythmic up & down in her RPM humming.

  12. But acceleration & performance are great...she goes like a bat out of hell...no issues at all...tranny shifts fine and engine is butter smooth under all driving conditions, except for the tremor in Drive.

  13. Couple weeks ago, replaced all vac/emissions lines, according to the long-standing PDF on TCCOA that we all reference, plus a couple other lines. No change in tremor.

  14. Replaced the fuel filter with a new Motorcraft one. No change in tremor.

  15. Air filter is clean.

  16. PCV valve is clean & rattles.

  17. In Park, she idles around 800-ish. In Drive, she idles around 560-580-ish.
    .
  18. Disconnecting the MAF & IAC:
    1. Disconnecting the MAF results in the idle dropping & smoothing out a bit.
    2. Disconnecting the IAC results in a bit of momentary engine stumbling & rougher idle, but remains running.
    3. Disconnecting both the MAF & IAC results in momentary engine stumbling & rougher idle, but remains running.
Note: Most parts on this car are factory original, since she's always been garaged, has only clocked 69K miles, and has rarely had an issue.
She also passed smog a couple months ago without an issue, before all the parts changes & tremor occurred. In fact, she's passed smog tests every year for her 27 years without any issues.

She's my baby and I love her...but I don't know what else to try/do to solve this tremor issue. There's no codes being thrown and I can't detect any obvious issues. I did a 'Live Data' & 'Print All Data' off my Autel 419 OBDII scanner on 04/26/2024 and have included the PDF's in this posting...but I don't know how to interpret this data or what to look for...so I'm asking for help to determine if the data looks good or something is amiss and what needs to be fixed/replaced.

If there's any questions, info, or clarity needed about something, please let me know and I'll respond ASAP.

Thank you, everyone.
Photos included are for pure Bird porn pleasure 8-)

Rain Bird 2 02272023.jpg

shopping 01252024.jpg

IMG_20240314_185819888.jpg

IMG_20240314_185752863.jpg

IMG_20240314_180037864.jpg
 

Attachments

  • print all data - 97 Bird 4.6L 04262024.pdf
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  • live data 97 Bird 4.6L 04262024.pdf
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Fuel trims are switching normally, so the front O2s are doing their job. Long term trims indicate a potential for a minor (2-3%) rich condition, but it's within tolerances. Just an observation - if it were indicating lean, then that would be a red herring for a vacuum leak. As far as I can tell though, that's not the case here at all.

Does the stumbling occur after a cold start, or does it only manifest after the car has been running for a few moments?

Are you logging all the available data points in your software? There are a few PIDs I can think of that might help with narrowing things down further, but it won't do any good if they're unavailable to you.
 
Beautiful Thunderbird! Obviously very well taken care of, it shows.
I can't help much because it sounds like you have done all the right things to try and fix the problem.
Maybe something simple has been somehow overlooked? You changed the plugs and wires recently. I had a plug wire that wasn't fully seated cause strange roughness on my past 96 4.6 . After pushing down on all the wires, I discovered one of them wasn't fully connected. I heard it click into place and it completely fixed the problem.
 
Interesting. I'm curious to see it in person.
 
Fuel trims are switching normally, so the front O2s are doing their job. Long term trims indicate a potential for a minor (2-3%) rich condition, but it's within tolerances. Just an observation - if it were indicating lean, then that would be a red herring for a vacuum leak. As far as I can tell though, that's not the case here at all.

Does the stumbling occur after a cold start, or does it only manifest after the car has been running for a few moments?

Are you logging all the available data points in your software? There are a few PIDs I can think of that might help with narrowing things down further, but it won't do any good if they're unavailable to you.
The tremor occurs at all times, whether cold start or after fully warmed up from driving, such as sitting at a stop light. It's always there when in gear, but I suspect hidden when the idle is higher in Park.

As for data, I'm logging everything I think is available? I bought the scanner in 2018 and I'm not sure if it's missing features or if a better scanner is needed. I really don't know if the scanner is lacking the capability to do more with the car, but I'm open to suggestions if you have a better recommendation or can tell me what to look for to record in my existing scanner. It's this one on Amazon:

Thanks
 
Beautiful Thunderbird! Obviously very well taken care of, it shows.
I can't help much because it sounds like you have done all the right things to try and fix the problem.
Maybe something simple has been somehow overlooked? You changed the plugs and wires recently. I had a plug wire that wasn't fully seated cause strange roughness on my past 96 4.6 . After pushing down on all the wires, I discovered one of them wasn't fully connected. I heard it click into place and it completely fixed the problem.
Thanks...I try hard to keep her as original & well-maintained as possible, considering what a rare species they are today.

I'll try re-seating the plug wires again, but I've done it a couple times now and they do 'click' into place and seal the plug well properly. My only question is the directionality of the plug boots, since they should go in only one way, due to the angle of the well and the angle of the top lip of the boot needing to mate properly for a proper seal. I posted about this in TCCOA a week or so ago and no one has responded. Might re-post here later tonight to see what the thoughts are.
 
Interesting. I'm curious to see it in person.
You're welcome any time, Gordon. And I still have your socket in my toolbox.
I figured you'd call & drop by someday, when you're in the area.

As a side note, the brakes are no better and still softish, even after 50 miles of highway driving one night, being hard on the brakes several times, and doing other things I've read in the forums that 'might' cure sponginess or air in the lines. Something's not right...as you said yourself, they should be grabbing like NASCAR brakes after all the money, parts, and work done. It's just about a whole new brake system and should be better than this.
 
It looks like the PIDs you get are all the scanner supports.

I use my XCal2 hooked up to a laptop via USB, with the LiveLink software to record any and all PIDs relevant for tuning, which is usually more than most generic OBD-II scanners support. It has a high data capture resolution and can chart historical log sessions as well, which comes in very useful for narrowing in on specific quirks.

Based on the fact that it's not specific to cold or hot conditions (open or closed loop), I'll go out on a limb and say the O2 sensors and MAF are not contributing. Idle speed in neutral/park is correct, but in drive it should be closer to 560 than 625 (I assume you were reading this off your scanner).

The ISC_INGEGRATOR PID in LiveLink is useful to help determine if the car is adding or subtracting idle air via the IAC duty cycle to bring idle to the ballpark desired RPM. The idle fine tuning is done by varying the timing, however.

What happens if you clear the PCM's adaptive memory (pull the fuse and/or battery to reset it)?

Regarding brakes, I've found that calipers that retract slightly too much after brake line pressure returns to 0 have a huge impact on the responsiveness of the initial bite. I found on my car that one of the rear calipers retracted a good 1/16" from pad contact, and that contributed to asymmetrical braking and a horribly mushy top 1/3 of pedal travel. YMMV. :)
 
You're welcome any time, Gordon. And I still have your socket in my toolbox.
I figured you'd call & drop by someday, when you're in the area.

As a side note, the brakes are no better and still softish, even after 50 miles of highway driving one night, being hard on the brakes several times, and doing other things I've read in the forums that 'might' cure sponginess or air in the lines. Something's not right...as you said yourself, they should be grabbing like NASCAR brakes after all the money, parts, and work done. It's just about a whole new brake system and should be better than this.
Let's connect. We can figure something out.
 
Let's connect. We can figure something out.
You can drop by any time...or I can come to you, if you think having your tool assets at your fingertips would be better.

Let me know or call/text me and we'll pencil it in. There's no clock in my world, so any time works for me.
 
Let's connect. We can figure something out.
It looks like the PIDs you get are all the scanner supports.

I use my XCal2 hooked up to a laptop via USB, with the LiveLink software to record any and all PIDs relevant for tuning, which is usually more than most generic OBD-II scanners support. It has a high data capture resolution and can chart historical log sessions as well, which comes in very useful for narrowing in on specific quirks.

Based on the fact that it's not specific to cold or hot conditions (open or closed loop), I'll go out on a limb and say the O2 sensors and MAF are not contributing. Idle speed in neutral/park is correct, but in drive it should be closer to 560 than 625 (I assume you were reading this off your scanner).

The ISC_INGEGRATOR PID in LiveLink is useful to help determine if the car is adding or subtracting idle air via the IAC duty cycle to bring idle to the ballpark desired RPM. The idle fine tuning is done by varying the timing, however.

What happens if you clear the PCM's adaptive memory (pull the fuse and/or battery to reset it)?

Regarding brakes, I've found that calipers that retract slightly too much after brake line pressure returns to 0 have a huge impact on the responsiveness of the initial bite. I found on my car that one of the rear calipers retracted a good 1/16" from pad contact, and that contributed to asymmetrical braking and a horribly mushy top 1/3 of pedal travel. YMMV. :)

I did some reading on XCal2 after you mentioned it...and while being thoroughly confused about it & the software, it sounds way overkill for my needs. I also read about FORScan, which also leaves me wondering, 'Wut?'

Oddly, because this car has been so trouble-free her whole life, it hasn't given me much chance to learn all these diagnostic methods...so I'm way behind the curve on understanding all of this or the data.

But it sounds apparent that I need a more sophisticated scanner than my Autel. What about a BlueDriver scanner, like this one on Amazon...or do you have a better recommendation for a solid scanner that's reasonably priced and will provide all the data we need:
https://a.co/d/eLtVAwV

"...but in drive it should be closer to 560 than 625 (I assume you were reading this off your scanner)."
> I don't recall if I was reading the scanner or the tach. I'll hook up the scanner again today, when I run errands, and confirm what it says.

"What happens if you clear the PCM's adaptive memory (pull the fuse and/or battery to reset it)?"
> I've pulled the battery cable several times when I was replacing all those parts...but never did after the tremor started. That was in my notes to try, but haven't yet. I'll do that today and see how she goes.

Out of curiosity, what could the PCM be doing that pulling the battery/fuse would potentially solve?

Brakes:
I've examined the brake pad/rotor distances and they're all skin-tight, with just enough clearance to allow the rotors to turn while whispering past the pads. Car also tracks straight under normal braking, heavy braking, and panic stops that I tested on a deserted road. But your comment about the 'mushy top 1/3 of pedal travel' is similar to what I'm experiencing.
 
It looks like the PIDs you get are all the scanner supports.

I use my XCal2 hooked up to a laptop via USB, with the LiveLink software to record any and all PIDs relevant for tuning, which is usually more than most generic OBD-II scanners support. It has a high data capture resolution and can chart historical log sessions as well, which comes in very useful for narrowing in on specific quirks.

Based on the fact that it's not specific to cold or hot conditions (open or closed loop), I'll go out on a limb and say the O2 sensors and MAF are not contributing. Idle speed in neutral/park is correct, but in drive it should be closer to 560 than 625 (I assume you were reading this off your scanner).

The ISC_INGEGRATOR PID in LiveLink is useful to help determine if the car is adding or subtracting idle air via the IAC duty cycle to bring idle to the ballpark desired RPM. The idle fine tuning is done by varying the timing, however.

What happens if you clear the PCM's adaptive memory (pull the fuse and/or battery to reset it)?

Regarding brakes, I've found that calipers that retract slightly too much after brake line pressure returns to 0 have a huge impact on the responsiveness of the initial bite. I found on my car that one of the rear calipers retracted a good 1/16" from pad contact, and that contributed to asymmetrical braking and a horribly mushy top 1/3 of pedal travel. YMMV. :)
Did several things this morning to answer your questions:
  1. You were right...scanner reading of RPM's in Drive = bouncing around 560-580ish, not the 625+ I misread from the tach.
  2. Scanner reading of RPM's in Park = bouncing around 780-800ish.
  3. Pulled fuse 15, cranked engine a few times, replaced fuse 15, then ignited engine.
    1. Tremor still exists
  4. Idled in garage for 30 minutes to allow time for things to warm up & PCM to settle, then drove to store with scanner recording live data
    1. (Live Data PDF #1 attached)
    2. Tremor still exists
  5. After half hour in store, returned to car and recorded live data while driving home
    1. (Live Data PDF #2 attached)
    2. Tremor still exists
  6. After returning home, idled car in garage for 5-10 mins while unloading groceries.
    1. Tremor still exists
  7. Also attached is the PDF for the 'Print All Data' version of the readout, if that helps.
In summary, nothing's changed and the tremor still exists.

Going to make breakfast & veg out for awhile...been a long night.
Thank you for your time doing this. Talk to you again soon.

Photos of idle in Park and in Drive:

Idle in Park 05022024.jpg

Idle in Drive 05022024.jpg
 

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  • Live Data, Memory Location #2 - 05022024.pdf
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  • Idle in Drive 05022024.jpg
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Well, the PCM has a series of "adaptive learning" subroutines that allow it to compensate for inherent variations in manufactured components. For example, each MAF sensor registers slightly differently from one another, despite being a couple percent away from the design specification across the response curve (transfer function). Many components exhibit this.

The adaptive behavior stores the observed deviations from spec and shifts the baseline of the program by that amount. If you reset the PCM, all the saved values for the adaptive learning adjustments are cleared out and the factory spec programming is running.

What I'd really like to see is a graph or chart of values. It's really hard to read through those PDFs for any length of time and all but impossible to identify trends. It looks like the OBD-II interface you linked to can interface with more or less whatever software you want, like FORscan, which IIRC does chart data.

All the same, there's only so much out there that could cause an idle surge. Either spark isn't adjusting properly to fine tune idle speed, the idle air speed airflow is off, or the fueling is off. I'm focusing in on O2 sensors, MAF sensor, IAC valve, PCM. I suppose it's also possible that residual EGR is entering through a leaky EGR valve. What I'd really like to see is a graph of STFT, LTFT and F/R O2 sensor voltages to see if the MAF and O2s agree with one another across the range. This can be accomplished in a variety of ways, for example by logging from a stop in drive using manual 2, accelerating slowly up to maybe 40 or 50 MPH.
 
Ok...to provide the data & charts that you request, what scanner/software do you recommend I purchase, such as from Amazon?
I'm not well-versed in this stuff, since I've only piddled with the Autel, so any guidance you can give me is appreciated to ensure I get the correct scanner/software.
 
Update:
Link to video of engine idling on Google Drive: https://photos.app.goo.gl/oMznKY4NqA1jvsw39

After the fuse 15 pull yesterday morning, the slight RPM up & down 'breathing' or humming I described earlier has vanished, yet the tremor still exists when in gear.

It's the oddest thing...when idling in Park, as in the linked video, she seems perfect. But what perplexes me is the air-whooshing sound she's always had...sounds like Mad Max's Interceptor with the blower engaged. Don't know if that's normal now...but if it were a vac leak that large, she wouldn't be this smooth running/sounding. Yet, the damn tremor still exists when in gear.
 
When do you hear the whooshing?
 
The noises I hear are the injectors, the air thru the tb, and sometimes other assorted noises, after I break stuff. :)
Much like an ak-47 fired at you, both rod knock and valve smacking piston knock are clearly distinguishable.
 
When do you hear the whooshing?
All the time...just like you can hear in the video. Turn up the volume if you can't hear it.
You can hear the consistent rushing of air sound, like a giant vac leak...or is it a plentiful & normal amount of air running through the intake?

She's always sounded like this, but I honestly don't know if that's just a normal sound for this engine. This recent tremor issue has me looking at & noticing everything and wondering what's normal and what's not.

Also, during normal street driving, I can't hear the air sound in the cabin with the windows down...but whenever I pass by walls on the right, such as approaching my garage, the air-whooshing sound echoes off the walls and amplifies it and catches my attention. And for years, when turning off the car, there's a loud escape/hiss of air that happens every time for a few seconds, almost like she's exhaling. Again, I always thought this was normal, but I haven't worked on 4.6's besides my Bird's and the long-gone P71 Interceptor, so I have no comparison reference points.

I simply don't have the wealth of experience & knowledge to know what's normal on them, because this engine has been so trouble-free all these years, that all I've ever needed to do was regular maintenance. Until recent months.

And for extra-crispy fun, I've also had shitty gas mileage for years, simply thinking it was my spirited driving. But now I'm wondering if something else is amiss that's tied to the tremor & air sound.
 
I listened to the video and it does sound like a vacuum leak. Unless it's the mic picking up something else, I don't hear that constant hissing noise on my mostly stock 4.6.
You said it doesn't have any codes though, usually it will record a lean code when it's got a leak.
You said you replaced all the vac lines. Have you looked into the IAC valve? They can make strange noises when they go bad. The charcoal canister, and evap emissions sensor, and solenoid are in the area of the front passenger tire. If you can hear it more towards there it maybe worth going back and checking them.
 
I'll have to come out and see it this coming week. When you replaced all the hoses in the wheel well, did you follow the line that goes from the charcoal canister to the engine? There is another short piece of hose along the way that goes bad.
 
And for years, when turning off the car, there's a loud escape/hiss of air that happens every time for a few seconds, almost like she's exhaling.

This is the sound of air in the cylinders that was compressed prior to the combustion stroke bleeding out. Completely normal. :)
 
I'll have to come out and see it this coming week. When you replaced all the hoses in the wheel well, did you follow the line that goes from the charcoal canister to the engine? There is another short piece of hose along the way that goes bad.
Gordon, I appreciate you coming back out to look at things, but I'm willing to come to you if your on-site tools/resources will better equip you to resolve this tremor & the soft brakes issues. Your choice, just let me know what you want to do.

Any day is fine, except Thursday, 05/09/2024...having another surgery/procedure done on my back to hopefully relieve the constant agony. I'll be back home the same day if you want to visit, but won't be mobile enough to drive to you that day.

As for your question: Yes...in fact, I removed that long plastic tube from the engine bay to the canister to inspect it, then re-installed it while I was replacing all the rubber hoses in that chain of evap parts in the fender well, including the hoses that went to & from the plastic tube.

There's only a few rubber hoses that I haven't replaced, such as the one on the IAC, which was still good, pliable, and looked & felt like new with no detectable leaks. As far as I know, I replaced everything that needed to be replaced...but it's possible that I missed something, though others have said nothing shows up in the scanner readings to indicate that a large vac leak exists.

Also, I haven't yet changed the short emissions hose alongside the fuel tank, which I plan to do soon, when I lift the rear-end and drain & refill the gear lube in the differential. It's still the original oil in there, but since I've been on a mission to refresh/replace all the aged parts on The Car, figured may as well do that too.
 
I listened to the video and it does sound like a vacuum leak. Unless it's the mic picking up something else, I don't hear that constant hissing noise on my mostly stock 4.6.
You said it doesn't have any codes though, usually it will record a lean code when it's got a leak.
You said you replaced all the vac lines. Have you looked into the IAC valve? They can make strange noises when they go bad. The charcoal canister, and evap emissions sensor, and solenoid are in the area of the front passenger tire. If you can hear it more towards there it maybe worth going back and checking them.
It's not the mic phantom-ing the sound...standing over the engine as it runs, I hear it just the same as recorded.
I'm going to have to get my ears closer to various parts of the engine to see if I can track down where exactly the air noise is coming from. My initial listening sounded like it could be coming from anywhere or all over, because it's so pervasive & dominating over the other sounds from the engine. I even thought it might be serp belt noise, but never heard a sound like that coming from a belt. It really sounds like a giant air-sucking sound, almost like a jet engine intake, as you can hear in the video.
 
I'll have to come out and see it this coming week. When you replaced all the hoses in the wheel well, did you follow the line that goes from the charcoal canister to the engine? There is another short piece of hose along the way that goes bad.
Oh...I'm also going to order a FORScan cable from Amazon today, so I can use that app to chart & data-log what's going on better than what my simple Autel can do.
 
This is the sound of air in the cylinders that was compressed prior to the combustion stroke bleeding out. Completely normal. :)
Ahh...that does make sense.
Weird though, since I've never heard that from other cars I've owned, including a '74 Mark IV, '89 Bird, '05 P71 Crown Vic, and others.
That 'exhale' of air when turning off the engine always makes me think of Christine 8-)
 
This past week, I invested in the OBDLink EX connector & installed OBDwiz and FORScan, then tinkered with collecting data from both programs according to the instructions. Not sure if I'm doing it right or what files from FORScan to post for anyone to analyze, regarding the tremor issue my Bird is having.

Although I ran both programs, no codes show up...but I don't know how to interpret the other data, graphs/charts, etc, or if I tested correctly, so any help is appreciated and I can post any data files back to be eyeballed.

Thanx
 
I would say log front/rear O2 voltages, short and long term fuel trim on both banks, RPM, ISC Integrator (if you have it), ISC duty cycle, MAF counts, spark advance, spark source and fuel source.
 
And load, and rpm. If it stumbles, you should see rpm changes.
 
I would say log front/rear O2 voltages, short and long term fuel trim on both banks, RPM, ISC Integrator (if you have it), ISC duty cycle, MAF counts, spark advance, spark source and fuel source.
Thanks. After I collect that data, do I post the FORScan *.fsl files?
 

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