Injector Issue - Help Needed

Stanley

Stanley

4th Gear Poster
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Canada
Vehicle Details
1997 Thunderbird 4.6L V8
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Apologies if this is vague, but I'm relaying what my mechanic told me so I'm probably not going to be able to add much.

My car died a couple of days ago. I drove it a couple of hours down the highway, parked it for an hour, and when I came back it would turn over but not start. I tried again, and it started, then died after a foot. Then it would not start again. I had it towed to a local mechanic, who has just called me back.

I suspected the fuel pump, but he says that's not the issue. The problem, he says, lies with the injectors: they're simply not properly providing fuel properly. But he's not familiar with this car, and there's no codes being thrown so any OBD reader isn't going to be useful. He's saying that broadly he thinks the issue is with the main computer controlling the injector operation, though he wasn't sure or specific, and he of course has no extras for a 97 Bird lying around. So he called to let me know the situation, and I said I'd check with some people--namely, you all.

I'd greatly appreciate some insight, even of a general sort, as to what might be happening and what I should do next. I'm on a timeline as I sit with a rental and the car taking up space on his lot.
 
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I guess I'd be curious to know what all led to his diagnosis. The engine shutting off could be caused by all kinds of things; what points to fuel specifically?

In typing this, I'm thinking that if you had more information, you would have provided it...

Limited to what we know, you could get a junkyard PCM, plug it in, and see if that improves anything. But frankly, if the PCM is indeed the issue, I find it odd that there aren't any codes. I would be more inclined to check hardware. What about the IAC valve? Coilpack? Those are things that left me stranded in the past.
 
Yeah, definitely a case of I'm playing telephone relaying what he said, which was vague, and wishing I had more to go on. I believe he said he had some kind of instrument that led him to narrow things down to the injectors. But he did say for sure that there were no codes.

I need to call this guy back tomorrow with some kind of game plan, so while this is vague I'm hoping someone here can provide advice.
 
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While I'm still looking for information from you all, I figure I should check on this now: does the calibration on the ECM matter? I have 7-18B, and I see a 7-18P for sale and still listed as compatible. If I get a new one, should I stick to what my car came with, or does it matter as long as it's broadly compatible?
 
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"P" is for a California calibration. We had this conversation on here when I changed PCMs, and I was concerned about that. Check my thread about the crank sensor code. Everyone here said that it made no difference.

Definitely only buy if you have a return option. You don't want to pay for a PCM that may not be the cause of the issue.
 
Borrow a set of solenoid lights from autozone. check the injector outputs. this is not a typical fail for a 97.
 
While not impossible my first conclusion is that I doubt it's anything to do with the injectors. IMO it's probably the IAC. First thing I'd do is rule out the IAC by cranking it with my foot on the pedal about 1/4" or so.

Remember what makes the car run: fuel, air, spark. If fuel rockets out of rail rail schrader valve when depressed, the pump is working (if not it could also be a bad FPR). If the plugs are wet with fuel after you try to crank and it fails to turn over, the injectors are pulsing properly. If the plugs are firing the crank sensor and coils and drivers are working. If the MAF is bad it will still start (albeit run poorly); if the IAC is bad it will start then die almost immediately; hold your foot on the throttle to let in just a little air. If it's none of these things a short in the harness can cause all sorts of weirdness.
 
The idle air control (IAC) sensor will cause that issue when it's failing. I've had that happen to me. I'd look at replacing that. It sits up on the throttle body and, as I recall, is pretty easy to get to. Couple of screws, unplug the old one, screw the new one on and reconnect. Good to go.
 
1997ThunderbirdLXV6 said:
The only argument against the IAC: the car is with a mechanic. Seems like the first thing they would have ruled out.
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You give some mechanics too much credit. My 💰 is on the IAC.

It'll be interesting to see what the issue turns out to be.
 
Beautiful, guys: thanks for the quick responses. One question on the IAC: is it a sensor we're talking about, or a separate part, or is the sensor integrated into the part? I see both valve and valve sensor mentioned above.

Also, there's a lot of different brands of IACs still available for the 97. Any one in particular recommended?
 
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It's a V8. Here's what Rockauto shows me (bearing in mind I'm in Canada):

Clipboard_08-26-2025_01.png
 
Interesting thing for the V6: Rockauto does not show the Motorcraft one for Thunderbird; however, it does show it for '99 E-150 4.2 V6, which is the exact same IAC, and which is what's on my car. I never looked for the V8 IAC, but I wouldn't be surprised if you found the Motorcraft one elsewhere on Rockauto.
 
1997ThunderbirdLXV6 said:
Interesting thing for the V6: Rockauto does not show the Motorcraft one for Thunderbird; however, it does show it for '99 E-150 4.2 V6, which is the exact same IAC, and which is what's on my car. I never looked for the V8 IAC, but I wouldn't be surprised if you found the Motorcraft one elsewhere on Rockauto.
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Perhaps, but without some kind of part number or something like your post to confirm for the V8 instead I'd never know for certain. Looks like the original was F6AZ9F715EB, Motorcraft part CX1648. But they're gone.

EDIT: There's actually some indication that the 96-99 Town Car, 96-01 Mustang, and 96-02 Grand Marquis and Crown Victoria used a compatible IAC. I'll check further.
 
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So, I'm in an awkward spot with the car being stuck out of town hours away. I don't want to do the usual change one part, wait and see if it's right, if not then change another, etc.

Right now I'm thinking of asking him to change the fuel pressure regulator, fuel filter, spark plugs, and idle air control valve. As I understand it, all are relatively easy to do, and I don't mind doing a bit of overkill to lessen the chance of needing to keep waiting (and keep renting a car while I wait).

If there's anything else simple and somewhat possibly the culprit behind my problem, or just worth doing while they're at the above, please list it and I'll swap that out too. I'm going to check in on the thread tomorrow morning, see what's been mentioned, then call up the guy and give him his marching orders.
 
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It pains me to see you throw all these parts at the car. But I understand your predicament.

I would not do plugs or anything that comes in one per cylinder, because those things don't all fail at the same time, and one failing may cause a poorly running engine, but not one that dies altogether. I suggest only doing parts of which there's only one.
 
I know you won't get the answer, but I'd be real curious to hear what steps he took to determine the injectors were not providing fuel properly. As noted, a noid light can help determine if the signal is getting to the injector to fire it. I understand he maybe hasn't worked on a Thunderbird lately, but this isn't that much different than any other late model OBD-II (or internal combustion engine for that matter) car for diagnosis.

I'd probably go with the Hitachi or Standard (not T-Series) IAC if you do replace it. I would think he would be able to limp the car along to determine if that were the cause though.
 
1997ThunderbirdLXV6 said:
Interesting thing for the V6: Rockauto does not show the Motorcraft one for Thunderbird; however, it does show it for '99 E-150 4.2 V6, which is the exact same IAC, and which is what's on my car. I never looked for the V8 IAC, but I wouldn't be surprised if you found the Motorcraft one elsewhere on Rockauto.
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I was told by a RockAuto rep that they only stock what they are told they are getting from the vendor, they do not deduce what it may or may not fit. That is why yuo see various parts that you KNOW do not fit your car, but are listed for it.

Did the mechanic do a fuel pressure test? See if fuel is even getting to the rail and what the pressure is?
 
I have no idea what they did. I'm not a mechanic myself, so I can't ask them questions beyond "what do I do next?"
 
Why can't mechanic tell you what your fuel pressure is? No pressure then check relay output. Spray some carb cleaner in the intake tube to verify lack of fuel. A bad IAC is a very good guess. I pull used ones at jy from f150 or others just to have spare. Next use a oscilloscope to verify crank signal output. Not much else to diagnose.
 
It's not so much that he can't tell me what my fuel pressure is so much as I know literally nothing about auto mechanics besides what I research here over the course of weeks at a time. So, I can't be calling him up every time someone suggests something here, then hoping he doesn't ask me for more detail or some other follow on point that I can't answer, and if so returning here to ask for clarifications, and then calling him back, etc. He's got my car: I'm not interested in pissing him off with back-seat driving.

At a certain point I just have to trust a professional and assume he knows what he's doing. Maybe he's a hack, but I'm in no position to judge myself. If we wind up in another conversation after the first set of fixes I've settled on don't work, I'll try to get some more detail out of him to pass on to the thread here.

However, I did go with the IAC as the suggested number one culprit and asked him to tackle that first, thanks to the feedback here, so here's hoping. I'll likely know something by Saturday, and I'll post back here with what the problem was when they at last figure it out.
 
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I highly doubt there is anything wrong with your computer or injectors. Neither of those components frequently fail, and there is no way all 8 injectors are going to fail at once. If a single injector failed and stuck open, it would run extremely rich, but it would run. As has been stated, if the IAC failed and stuck closed, it would run with a little input from the gas pedal, which I would hope the mechanic would have tried. If the injectors “aren’t providing fuel properly”, the only way that could happen is a failed computer, or a problem with the fuel pump. The way that you described how the car started then stalled, then wouldn’t restart, makes me think it is a fuel issue. If the computer failed, it wouldn’t have restarted at all. But if there was some pressure left in the lines, but the pump wasn’t running, it would do exactly as you described. At this point, the first thing I would want to know is if he checked the fuel pressure, and if so, what is the pressure with the key on, and when cranking. Key on pressure should be between 39-45lbs, and cranking should drop slightly. If there is no fuel pressure, then first check that the inertia switch wasn’t tripped, and if that is good, then next would be to pull the fuel pump relay to test each leg of the circuit. If fuel pressure is good, then the next thing to check is whether you have spark. If no spark, then I would suspect a crank sensor, but again, those rarely go bad on the 4.6. If you have fuel pressure, and you have spark, then, and only then, should you check for injector pulse. This can be done either with a noid light, which is specifically calibrated to mimic the resistance of an injector, or more simply, just listen to the injectors with a stethoscope while someone cranks the engine. If you have spark, but no injector pulse, then a failed computer is possible, but again this is highly unlikely for these cars.

Feel free to copy this post and send it to the mechanic and have him reply with his findings. If he has trouble performing any of these tests, then he is incompetent as a mechanic, and you need to tow the car out of there to someone who knows how to work on them.

Whatever you do, do not start throwing parts at it. First off, this is not likely to fix the problem. Secondly, this wastes your money and the mechanic’s time, and the only result will be both you and he will be upset with one another, your car still won’t be fixed, and it will be stuck on his lot with him trying to get paid for changing parts that you provided. This is the worst of all options. Have him perform the above basic tests. If he can’t perform them, tow it out of there to someone who can. If he can’t interpret the results of those tests, then have him reply with his findings and post them here for us to figure out. But don’t go firing the parts cannon at it!
 
Beautiful, thanks. If we don't get anywhere with the IAC fix, which is already booked in, I'll try and get a lot more detail out of him and put your reply to him as well.
 
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My IAC went out one day after work. I went to warm it up and it died pretty quick. I thwacked the IAC with a screwdriver and it ran. Drove her home just fine, then replaced it.
 
massacre said:
IAC should be like a 5 minute install. 2 bolts and 1 connector.
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Yeah, that fact and all the responses indicating that it was the best first step is why I decided to go ahead with it no matter what. Here's hoping.
 
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