1991 5.0 - fires up every time, idles perfectly, but once it’s warm it won’t idle for more than 15 seconds
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For what it’s worth, I just spent about 20 minutes closely checking all the vacuum lines and electrical connectors (just visually). Everything looks brand new.
I may have reached the end of my competency here. I plan on having it towed to a shop next weekend. Otherwise I’m just gonna be throwing parts at it.
I may have reached the end of my competency here. I plan on having it towed to a shop next weekend. Otherwise I’m just gonna be throwing parts at it.
Have you tried to pull and clean the IAC? I would do that first. Certainly wont hurt. You can also look to see what its doing(or not) with it taken off and plugged in by turning the key fwd but not starting.
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Which screw is it and which way do i turn it?
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I do have a new in box IAC here. I may just swap it out and see where I end up. Couldn’t hurt.
The previous owner swapped in a new IAC (and IAT and TPS)about 5k miles ago
screws go in when u turn them to the right. should have a spring on it. ford used to sell a little plate with bypass set screws so you can increase idle airflow. not sure if its still around. without fancy dancy binary hacking, itll probably help. if thats even the issue. im probably making someones eyes bleed...
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I'm not going to go back and reread all of this.
If I remember correctly, it idles when cold? If so, the iac itself is not the issue. Engine needs more air when cold.
If I remember correctly, it idles when cold? If so, the iac itself is not the issue. Engine needs more air when cold.
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What is the coolant temp sensor and the narrow bands doing?
I posted a picture in this thread. Turn it clockwise a half turn, then restart the engine. If you need more, you have to shut the engine off and restart or engine will think it's at part throttle. You can back off while it's running if the idle is too high. You're just trying to give it enough air to let it idle without stalling.
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visual test can only go so far, actual smoke and meters will be needed
if you can keep the car running, with the pedal,
you could be able to turn a screw, that has been laid out for ya clearly by cougar…..
ensure you do not exceed 1.15v TPS, or at least measure before voltage and after
so if you need to g back, you have a reference
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Ok guys I'm back. Did a little digging.
First, I replaced the IAC with a brand new Motorcraft unit. I reused the gasket, it appeared to be in good shape. I dropped one of the bolts on the ground and cleaned it off thoroughly, but now I'm worried I had a tiny bit of residual dirt/sand on my hands from leaning down when I installed the IAC. I don't think I did, but I worry about everything and I'm worried it'll get into the intake.
ANYWAY
The car seems to idle slightly better now, but still dies. It does run for longer before dying. But it still cuts off after idling for a bit.
So, I ran the KOER codes.
When I began the test, the engine RPM's immediately went up to 1600 RPM. Really threw me off, but I let the code reader do its thing. When the test finished, I shut off the code reader as indicated in the instructions, and the engine idle went back down to normal.
CODES PULLED:
91: HEGO (HO2S) sensor signal out of range/always lean
33: EGR valve not opening properly
First, I replaced the IAC with a brand new Motorcraft unit. I reused the gasket, it appeared to be in good shape. I dropped one of the bolts on the ground and cleaned it off thoroughly, but now I'm worried I had a tiny bit of residual dirt/sand on my hands from leaning down when I installed the IAC. I don't think I did, but I worry about everything and I'm worried it'll get into the intake.
ANYWAY
The car seems to idle slightly better now, but still dies. It does run for longer before dying. But it still cuts off after idling for a bit.
So, I ran the KOER codes.
When I began the test, the engine RPM's immediately went up to 1600 RPM. Really threw me off, but I let the code reader do its thing. When the test finished, I shut off the code reader as indicated in the instructions, and the engine idle went back down to normal.
CODES PULLED:
91: HEGO (HO2S) sensor signal out of range/always lean
33: EGR valve not opening properly
You should probably do a cylinder balance test (throttle blip and end of KOER test? I forget) to see if you have any cylinders not firing properly. 91 is drivers side O2 sensor always lean. There's a bunch of troubleshooting for this code. Check for proper oxygen sensor ground, O2 function test (forcing rich condition while looking at O2 voltage) etc. EGR isn't there, correct?
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I read about the throttle blip test but the manual said that if this was applicable to my car, the code reader would prompt me to do this by displaying a "10", and it never did that throughout the test.
EGR isn't there as far as I'm aware. I honestly don't know how to do an 02 function test, I don't know how to force a rich condition while looking at O2 voltage
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I replaced it because I had a new one in the box sitting around and I spoke to a shop and they advised me to do so. Took me 5 minutes to do.
I'm guessing replace the driver's side o2 sensor? Not sure if that's something I can do in my driveway without a lift
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Ok, what do you suggest?
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