Your MAF is to high. Should be about 1 gram/sec per liter at idle. Yours should be around 5 to 6 gs/sec at idle. Your ldle is high also but your pounds convert to 11.78 grams/sec. Look at he commanded idle. I don't think you IAC is the problem.
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1997 ford van 5.4 Runs rough dies out
- Thread starter jigfeett
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jigfeett
Hero Member
Thank you,
So you don't think the IAC is high or do you think it is caused by the MAF reading?
Do you think the MAF should be replaced?
I don't have the resources to swap parts if I'm not sure the part is defective.
I think I'll monitor short term fuel trim (STFT) and long-term fuel trim (LTFT), engine temperature, BARO, calculated load, rpm, MAP or MAF and the O2/AF sensors and see what shows.
So you don't think the IAC is high or do you think it is caused by the MAF reading?
Do you think the MAF should be replaced?
I don't have the resources to swap parts if I'm not sure the part is defective.
I think I'll monitor short term fuel trim (STFT) and long-term fuel trim (LTFT), engine temperature, BARO, calculated load, rpm, MAP or MAF and the O2/AF sensors and see what shows.
Want a long-shot? Just a guess but easy to check and easy to fix.
Look under the "chin" of the TB. Is there a rubber 90-deg. elbow there, connecting the underside of the TB to the intake manifold? If so, I ran into one that cracked and caused some weird idle problems. It was difficult to see, had to pull it off before it was obvious. It is about the size/shape of a right-angle spark-lug boot on a pre-HEI M dizzy. That's what I used to replace it.
Look under the "chin" of the TB. Is there a rubber 90-deg. elbow there, connecting the underside of the TB to the intake manifold? If so, I ran into one that cracked and caused some weird idle problems. It was difficult to see, had to pull it off before it was obvious. It is about the size/shape of a right-angle spark-lug boot on a pre-HEI M dizzy. That's what I used to replace it.
jigfeett
Hero Member
I think this is the tube that was mentioned and it looks ok.
I also swapped out to a known good MAF and didn't get any change. If I get time this weekend I will pull all the coils and plugs and run a compression check on all cylinders
I also swapped out to a known good MAF and didn't get any change. If I get time this weekend I will pull all the coils and plugs and run a compression check on all cylinders
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jigfeett
Hero Member
The TPS has not been adjusted as far as I know.
thewrightman
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I had a 97 F150, 5.4. It doesn't take much of a leak in the idle circuit to cause rough idle. Had a time finding my root cause - it was the rubber elbow to the solenoid and it only leaked while running. I don't think this is your only problem, but it could be one. Good luck.
jigfeett
Hero Member
Ok will do. Than you
Just to be clear this engine starts when cold and only runs for a short time before running terrible and dies.
Also when I try to restart after dying, it takes part open to wot to get it to start and it just runs horribly bad and if I place the transmission in any gear it dies immediately unless I throttle it and even then it dies within a few seconds
Just to be clear this engine starts when cold and only runs for a short time before running terrible and dies.
Also when I try to restart after dying, it takes part open to wot to get it to start and it just runs horribly bad and if I place the transmission in any gear it dies immediately unless I throttle it and even then it dies within a few seconds
jigfeett
Hero Member
I adjusted the clamp that is not seated in position, the hose on the right shows heat wear but seems ok but I'll replace it.
jigfeett
Hero Member
I might have mentioned this but when I am running the engine and at engine shut down I hear a hollow sound, sorry it is hard to describe.
There are just two wires to the IAC valve, correct? I think that is a PWM system, at about 300Hz. You should be able to get a meaningful DC voltage reading across those wires. Compare what it is doing when it first starts and runs as opposed to when it begins to run rough; we may get some hints from that.
I went back and browsed this thread. Was the "high MAP" issue ever resolved? What about other things like moisture in the manifold? I was really looking to review live-data, but the photos of your scanner screens just were too small/blurry for me to want to bother with.
I, too, suspect this isn't a problem with the IAC itself, but is a problem with some other sensor that the PCM uses to conclude there should even be an attempt to control idle. MAF/MAP, VSS, TP, ECT, trans gear, and RPM are all generally used to determine if the engine is at "idle".
If the IAC drive signal goes away, or stops varying, when the engine starts running rough, that is a hint the PCM is not invoking idle control.
Please recap what the present symptoms are; as well as compression and FP readings.
I would also put a timing light on it, see if timing is dancing around differently when the engine is idling good/bad. And put the light on each plug, see if any are winking out.
Have you checked the injectors for flow-rate and spray pattern? At least, check that they are all the same (correct!) P/N.
My perception is this beast came to you with a lot of "unknowns", so I guess I am saying that we should "regroup" here...
I went back and browsed this thread. Was the "high MAP" issue ever resolved? What about other things like moisture in the manifold? I was really looking to review live-data, but the photos of your scanner screens just were too small/blurry for me to want to bother with.
I, too, suspect this isn't a problem with the IAC itself, but is a problem with some other sensor that the PCM uses to conclude there should even be an attempt to control idle. MAF/MAP, VSS, TP, ECT, trans gear, and RPM are all generally used to determine if the engine is at "idle".
If the IAC drive signal goes away, or stops varying, when the engine starts running rough, that is a hint the PCM is not invoking idle control.
Please recap what the present symptoms are; as well as compression and FP readings.
I would also put a timing light on it, see if timing is dancing around differently when the engine is idling good/bad. And put the light on each plug, see if any are winking out.
Have you checked the injectors for flow-rate and spray pattern? At least, check that they are all the same (correct!) P/N.
My perception is this beast came to you with a lot of "unknowns", so I guess I am saying that we should "regroup" here...
jigfeett
Hero Member
Yes two wire,
It had new plugs, new coils, new injectors when the intake was replaced by (not me)
I can tell you vss should be 0 because I can't even drive it 20 feet be fore it dies and that is with a lot of throttling.
I will recap asap
I intend to pull plugs to verify original coolant in plug hole is not involved.
It had new plugs, new coils, new injectors when the intake was replaced by (not me)
I can tell you vss should be 0 because I can't even drive it 20 feet be fore it dies and that is with a lot of throttling.
I will recap asap
I intend to pull plugs to verify original coolant in plug hole is not involved.