View Full Version : Rough Idle in Gear
Hello I have a stock 87/5.7 truck has been sitting for a while but started and driven once in a while before i picked it up but i am at the end of my knowledge new plugs, fuel filter, air filter new coolant sensor new ign. module and it will idle in park most of the time just fine and in gear for just a few seconds then it will stumble will not die but it is loading up with fuel very bad will not die though i have checked codes and only got 45 and that makes sense with it loaded up so bad the service manual said to replace the o2 sensor seems to me its working it picked up the rich mixture. i have checked all the vacume lines and have not found a leak or cloged line or anything . I neeed some help i want to use my new/used truck..
05-21-2004, 07:01 PM
I would check/clean the idle air control valve on the EFI. It might be worn, dirty or malfunctioning. If I remember correctly, it's on the passenger side rear of the EFI, and it controls the fuel mixture at idle by controlling the amount of air coming in.
They get pretty crudded up, and the passage it dumps into as well.
Once you clean it, it will idle high on the first start, then shut it off and restart, and it calibrates itself after that. Hopefully, that will help, if not, I would change out that O2 sensor if you are getting any 02 codes.
If that doesn't do it, check your injectors and see if there is a mist coming out or a dribble or uneven pattern. Could be clogged injector(s) (or weak fuel pump -or intake gasket leak check as a last resort) ..but I think I would start with that IAC valve and some good carb cleaner, both on the IAC setup, and on the injectors and in the gas tank, just to try and rule that out. I like the Chevron Techron. IMO, works better than most cleaners.
I left off that it has a new fuel pump and tank the guy that sold it to me put it in a year or so ago. i will try the IAC and i am goint to install some new injectors tomorrow after work. thanks i hope it works out
Any Ideas? Today I installed a new IAC, o2 sensor and both injectors and STILL it has very bad idle in gear only loading up almost to the point of dying it does it hot or cold. Which way do I go now??
05-23-2004, 03:28 AM
Check the spark timing and do a full tune up, or at least a cap and rotor replacement and check the pcv valve isn't sticking causing a vaccum leak through it. It could also be a bad base gasket on the EFI if all the rest of the vacuum lines look good. Maybe throw a vacuum gauge on it and see what's up. Could be an intake valve not sealing etc.
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