1994 Jimmy rough idle / trouble codes

Scenario: About 10 days ago I took my Jimmy out for a spin. Everything was ok. I stopped and put about 10 gas in; about 20 minutes later the Service Engine Soon light came on. I stopped at a service station, at which time the thing idled rough as hell. My first thought was water in the gas (from sitting, perhaps from the station I bought gas at [Tessoro]) so I put in a de-icer additive. The condition persisted throughout my

80 mile trip - rough idle, ran ok at higher RPM.

This morning, after learning how to obtain the error codes, I started it up. Same condition, rough idle, smooth at higher RPMs. After letting it warm up (about 15 minutes), the idle smoothed out and the Service Engine light went out. I went ahead to get the error codes:

32 (EGR) and 34 (MAPS). I then started it back up, Service Engine Soon light stayed off, idle remained smooth. I took it for a 5 mi test drive, got home and it remained smooth idle, light out.

Is it possible for water / ice in the fuel / fuel lines to cause this condition and throw these errors? What else would cause these symptoms and error codes, that would just "go away"? I am still thinking water in the fuel.

The vehicle is 94 Jimmy 4.3L V-6 Vortex series W

Thanks for your thoughts/opinions.

steve

Reply to
Steve
Loading thread data ...

The EGR on these is prone to clogging with carbon. Cleaning/replacing the EGR is a fix for this.

Another possible culprit, though the symptoms come >Scenario:

Reply to
Mike Levy

Carbon sticking the EGR open, Causes a BIG air leak and low vacuum, Which is why you get the 32 and 34 codes.

Best repair is to pull the EGR and put a

formatting link
EGRscreened gasket on it. I can Guarantee you IT WILL HAPPEN AGAIN. GM hasa revised program for the computer that opens the EGR and cycles it toclear it, but the hunks of carbon still jam it open. The gasket/screenunit keeps the crap out of the valve entirely and prevents it fromhappening. I made one out of a heli-coil for in my wifes because I gotsick of pulling the valve off to clear it out. Although I did get downto under 15 minutes to r&r and knock the carbon out.

Reply to
Steve W.

It WILL happen again, huh? nearly 60,000 miles after the EGR clogged the first time, it STILL hasn't clogged again. Clogged at 60,000 the first time. Had a GM dealer replace the valve and put in the updated PROM under terms of a TSB that allowed for free replacement due to being within time and mileage limits.

Steve, you did the CPI unit a while back, didn't you? How's that holding up for you? I did mine over a year ago, only put 14,000 on since I did it, but it's going strong...

Reply to
Mike Levy

MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.