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This was the main symptom I was frustrated with, to say the least: I would try to cruise a parking lot or try to enjoy a scenic ride through a state park, and I could not do 5-10mph for the life of me. I'd lightly push the accelerator, and it'd take on up to 3K and want to do 15-20mph in 1st. Let off and it'd slow all the way down to idle (engine braking), try and do it again, jolt/jerk, takes off to 15mph. Hmmmm, this is pissing me off.....
There was also some rough engagements from stop to start and coast to reapplying throttle at higher speeds.
NO CODES.
I had cleaned the IAC when I first got the truck, and there was a new TPS, and newer "cleaned" MAF.
My main suspects were as follows:
1). TPS
2). IAC
3). Vacuum Leak
4). MAF
5). Fuel pressure regulator
I tested for simple things first, like vacuum leaks by spraying carb cleaner around vacuum lines, intake manifolds, injector o-rings, etc. No rpm change. Vacuum itself measured at 18-18.5 hg/in. at idle.
FPR held 20 hg/in of vacuum over a 10 minutes. Not leaking.
Throttle Position sensor checked out too. Resistance was as follows at sensor: 3.30 kohms at close, and .55kohms at WOT. The transition was very smooth. I also back probed it and actually read the signal voltage going to the PCM. It goes as follows: .72 v at idle, and 4.4v at WOT. Also a smooth climb.
MAF had 13.97v and was within spec on signal voltage at idle.
I even checked the HO2S's for the hell of it. They swing fairly rapid between .15-.935v. They also react and show lean (more towards .1 side) when i pull a vacuum line, and PCM adds fuel to even out mixture, and also showed rich ( more towards 1v) when I sprayed carb cleaner down the vacuum line, the PCM also adjusted here too.
Now to the IAC, measured resistance, measured at 10.6 ohms (spec is 7-13 ohms). I noticed however, that it didn't move between off, run, or running. The valve didn't adjust, or move. The PCM was changing the mV, but no movement. So, I happen to have an IAC off a 2.3 lying around. Slapped it on, reset computer, and I could do 5-10mph! Smoother acceleration, and no jolt when adding throttle from a coast.
I know it's not a permanent fix, but it'll do until I find a proper P/N IAC.
It seems these symptoms aren't commonly associated to the IAC valve, but I figured I'd offer up my experience for others.
Ryan
There was also some rough engagements from stop to start and coast to reapplying throttle at higher speeds.
NO CODES.
I had cleaned the IAC when I first got the truck, and there was a new TPS, and newer "cleaned" MAF.
My main suspects were as follows:
1). TPS
2). IAC
3). Vacuum Leak
4). MAF
5). Fuel pressure regulator
I tested for simple things first, like vacuum leaks by spraying carb cleaner around vacuum lines, intake manifolds, injector o-rings, etc. No rpm change. Vacuum itself measured at 18-18.5 hg/in. at idle.
FPR held 20 hg/in of vacuum over a 10 minutes. Not leaking.
Throttle Position sensor checked out too. Resistance was as follows at sensor: 3.30 kohms at close, and .55kohms at WOT. The transition was very smooth. I also back probed it and actually read the signal voltage going to the PCM. It goes as follows: .72 v at idle, and 4.4v at WOT. Also a smooth climb.
MAF had 13.97v and was within spec on signal voltage at idle.
I even checked the HO2S's for the hell of it. They swing fairly rapid between .15-.935v. They also react and show lean (more towards .1 side) when i pull a vacuum line, and PCM adds fuel to even out mixture, and also showed rich ( more towards 1v) when I sprayed carb cleaner down the vacuum line, the PCM also adjusted here too.
Now to the IAC, measured resistance, measured at 10.6 ohms (spec is 7-13 ohms). I noticed however, that it didn't move between off, run, or running. The valve didn't adjust, or move. The PCM was changing the mV, but no movement. So, I happen to have an IAC off a 2.3 lying around. Slapped it on, reset computer, and I could do 5-10mph! Smoother acceleration, and no jolt when adding throttle from a coast.
I know it's not a permanent fix, but it'll do until I find a proper P/N IAC.
It seems these symptoms aren't commonly associated to the IAC valve, but I figured I'd offer up my experience for others.
Ryan
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