mrboyertown

I have a 94 Pickup SR5 V6 Automatic 200k miles. Iv'e been trying to diagnose a idle problem and excessive fuel consumption on my truck. At idle the engine has a slight lope to it. Sometimes it's worse than others but in either case its not a horrible lope. It holds a steady rpm at idle but the engine seems to shimmy. I tried raising the idle a little bit (it's already close to where it should be but figured raising it a little would help) but when i tried to increase the idle speed by turning the idle set screw i really didn't get much of an increase. I turned the idle screw all the way out and I couldn't get the idle to go any higher than 750rpm's in neutral and when the truck is in drive it's at about 650 to 700 rpm which makes the engine lope a little worse. Any idea why i cant get the idle speed any higher? Since I got the truck about 2 months ago I have had a few trouble codes but cant seem to figure out what would be throwing the codes and if it has anything to do with the engine lope and poor fuel economy. About 10-12mpg. First code thrown was 2-6(engine running rich) I figured it was the O2 sensor so i replaced it and reset the ECU. Started the truck up and the idle lope was still there and not but 100 miles later and engine light comes on again. The second time the light came on it was on for a day or two then went out for a while then came on again so I checked the codes again and this time I got a 2-5 and 2-6 (engine running lean, engine running rich?) now I am scratching my head. Running rich for a little than running lean? what could be making it throw both codes? O2 sensor new, MAF is working within parameters resistance wise, plugs-wires-cap-rotor all new and I have run all sorts of injector cleaner through it. Thinking maybe its the coolant temp sensor? Could that be throwing the codes? I reset the ECU to see if the light would come on again and it didn't for a week than it came on again. I checked the codes again and this time no 2-5 or 2-6 but now its 7-1(EGR valve exhaust temp not correct) what does that mean and do think that could be the problem thats making the engine run funny? In my FSM it says the 7-1 code is for California models only.....I live in PA but I guess I have a california model truck. Is that a good thing or bad? Overall the truck runs great, when going down the road you dont notice the engine lope and it doesn't hesitate at all. I do notice when I first start it in the morning you can smell the exhaust smells rich but no black smoke even when revving the engine at high rpm's. Im am lost as to where to go next and any bit of help would be appreciated. I dont want to just start replacing parts if I can help it. Sorry for such a long thread.

MudHippy

My first geuss will be clogged catalytic converter. Slightly loping @ idle can be a stretched out timing belt or tensioner spring.

gametom

maybe a stuck egr valve

TNRabbit

If your idle screw is not making much difference, it's one of two things:

1. A vacuum leak. Run an UNLIT propane torch around all the vacuum hoses; if it idles up a little bit, you have a leak there. If it idles up a lot, you have a REALLY BIG leak there! A vaccum leak can cause the lean/rich swing you've experienced.

2. The throttle body butterfly valve is not closing all the way due to an obstruction, usually carbon/gunk build-up around the butterfly which holds it slightly open at idle.

Good Luck & let us know what you find out.

chopitrakeit

89 3.0 auto 4 runner. Same exact symptoms without trouble codes. I suspect air leak as well as it came instantly and does not affect running above idle. Will keep watching your thread, let you know what I find. Mike

chopitrakeit

Bump...Any luck yet? Mines idling like a V8 with big cams, wifes got it today, hope it dont break down on her, love those calls at work.

mrboyertown

Hey guys dont plan on really going over the truck for a couple of weeks yet but when I do I will surely let you know. I will FIND and FIX the problem. I hate when my motor doesn't run perfect. Anyone heard of a bad coolant temp sensor ever throwing those codes?

timebandit

I have had bad evap can valves cause the rich/lean code C.F. you are describing. The engine will rich at idle and lean on cruise if the evap system is stuck on purge at all times. The Toyota EFI EVAP system is very simple at least on the 22R. The charcoal can has a system of check valves inside of it. Cap it off where it ties in the intake.