Hello, I'm new to the forum. Hopefully I can get some help and also help others. I posted the following on a different forum but it must be unique (or boring) enough to not generate a lot of input.
It is rather long so hopefully I don't lose you from boredom.
The problem:
My truck will sometimes feel like it is going to die and I have to pump the gas (or hold the pedal to the floor) for a few seconds to get it back to normal, usually when just pulling away, say once every 15 trips around town. If I am in park and try to keep the idle at 1000RPM I will get hesitation and surging between 900 to 1100 RPM. Also, if I try to keep it at 1000RPM and turn the wheel to add some load, the idle will drop to @600RPM and surge to@1200 RPM when I let go of the wheel. IF I am in drive and try to keep the idle at 1000 RPM, the RPM will fluctuate but not as much as if it is in park. No codes (using the key on-off 3 times and also the trip button while turning the key on methods) or from the Advanced Auto Parts scanner.
Here is what I have done to try to solve the problem (truck has 66,000 miles):
plugs
oxygen sensors
PCV
removed and cleans TB and IAC, neither of which struck me as being very dirty.
I have tried an Autozone TPS, didn't make a difference so I put back on the factory TPS.
I have tried an Autozone IAC but the truck wouldn't maintain an idle. I returned it as defective and put the factory IAC bac in.
Most of the posts I read say "replace the TPS" or "replace the IAC" without a whole lot of explanation behind the suggestion. To help with the investigation I did the following tests:
TPS unhooked
IAC unhooked
TPS and IAC unhooked
TPS and IAC both hooked up
Results:
TPS unhooked and IAC hooked up
Idles a little rough at 600 RPM
If I keep it at 1000RPM it stays pretty steady. If I turn the wheel it will drop to about 900 RPM and surge to @1100 RPM when I let go of the wheel.
TPS unhooked and IAC unhooked
Idles rough at about 400RPM
harder to start
If I keep it at 1000RPM is stays pretty steady . If I turn the wheel it will drop to about 900 RPM and surge to @1100 RPM when I let go of the wheel.
I just realized the results of the above two are pretty much the same except for the initial idle.
TPS hooked up and IAC unhooked
much harder to start, need to give some gas to keep it going initially.
If I keep the idle at 1000RPM it hesitates and surges between 900RPM and 1100RPM. If I turn the wheel it will drop to @600RPM and when I let the wheel go it surges back to @1200RPM and then back to 1000RPM.
Both hooked up
Starts fine and idles smooth at 600RPM.
If I try to keep it at 1000RM it fluctuates between @900 to @1050 RPM. If I keep it at 1000RPM and turn the wheel it drops to @600RPM and then surges back to @1200 RPM before returning to 1000RPM.
I just realized the results of the above two are pretty much the same except for the initial idle.
So, I am not sure what to make of all that. Anyone have any thoughts? And, thanks in advance
If you have gotten this far, thanks...
It is rather long so hopefully I don't lose you from boredom.
The problem:
My truck will sometimes feel like it is going to die and I have to pump the gas (or hold the pedal to the floor) for a few seconds to get it back to normal, usually when just pulling away, say once every 15 trips around town. If I am in park and try to keep the idle at 1000RPM I will get hesitation and surging between 900 to 1100 RPM. Also, if I try to keep it at 1000RPM and turn the wheel to add some load, the idle will drop to @600RPM and surge to@1200 RPM when I let go of the wheel. IF I am in drive and try to keep the idle at 1000 RPM, the RPM will fluctuate but not as much as if it is in park. No codes (using the key on-off 3 times and also the trip button while turning the key on methods) or from the Advanced Auto Parts scanner.
Here is what I have done to try to solve the problem (truck has 66,000 miles):
plugs
oxygen sensors
PCV
removed and cleans TB and IAC, neither of which struck me as being very dirty.
I have tried an Autozone TPS, didn't make a difference so I put back on the factory TPS.
I have tried an Autozone IAC but the truck wouldn't maintain an idle. I returned it as defective and put the factory IAC bac in.
Most of the posts I read say "replace the TPS" or "replace the IAC" without a whole lot of explanation behind the suggestion. To help with the investigation I did the following tests:
TPS unhooked
IAC unhooked
TPS and IAC unhooked
TPS and IAC both hooked up
Results:
TPS unhooked and IAC hooked up
Idles a little rough at 600 RPM
If I keep it at 1000RPM it stays pretty steady. If I turn the wheel it will drop to about 900 RPM and surge to @1100 RPM when I let go of the wheel.
TPS unhooked and IAC unhooked
Idles rough at about 400RPM
harder to start
If I keep it at 1000RPM is stays pretty steady . If I turn the wheel it will drop to about 900 RPM and surge to @1100 RPM when I let go of the wheel.
I just realized the results of the above two are pretty much the same except for the initial idle.
TPS hooked up and IAC unhooked
much harder to start, need to give some gas to keep it going initially.
If I keep the idle at 1000RPM it hesitates and surges between 900RPM and 1100RPM. If I turn the wheel it will drop to @600RPM and when I let the wheel go it surges back to @1200RPM and then back to 1000RPM.
Both hooked up
Starts fine and idles smooth at 600RPM.
If I try to keep it at 1000RM it fluctuates between @900 to @1050 RPM. If I keep it at 1000RPM and turn the wheel it drops to @600RPM and then surges back to @1200 RPM before returning to 1000RPM.
I just realized the results of the above two are pretty much the same except for the initial idle.
So, I am not sure what to make of all that. Anyone have any thoughts? And, thanks in advance
If you have gotten this far, thanks...