2000 EXP. no idle at cold start-up

[HighSierra49er]

Every couple of weeks my Exp. will not idle at a morning start up. Starts super quick, as usual, then the rpm just dies off until the engine quits. Only happens in the morning. The only way to keep it running is to keep the rpms up with the accelerator peddle. No high-idle at all. If I disconnect the battery, which I believe resets the computer, then reconnect, the engine will again immediately start up and the fast idle and normal idle is reset and works great for another couple of weeks.

The engine runs super smooth otherwise. I bought my Exp. new in 2000, and with 264,000 miles on the truck, have only had to replace the fuel pump and alternator. Has yet to burn any oil, but I do a pretty good job at following prescribed maintenance. Best vehicle I have ever owned.

Thanks for any input you can provide.

 

[toms89]

I would first recommend cleaning your IAC valve and check throttle body for buildup around the throttle plate. If it has buildup clean it as well. With the pcv system a lot of oil gets circulated into the intake and it gums up these areas which can affect idle.

 

[SWAGGA]

I would first recommend cleaning your IAC valve and check throttle body for buildup around the throttle plate. If it has buildup clean it as well. With the pcv system a lot of oil gets circulated into the intake and it gums up these areas which can affect idle.

Cosigned with what toms89 said... I'd recommend that if this does end up being the issue, seafoam the top of the motor. (unhook cable from the brake booster, have someone keep the motor forcibly running around 1k-2krpms and suck a can of seafoam into the top of the motor, let it sit for 10 minutes, and enjoy the smoke show.)

 

[HighSierra49er]

Thanks for the input. What a break if it is the IAC valve. I will get the valve cleaned up over the weekend and post the results. I was thinking in a completely different direction, but the issues with dirty IAC valves and my symptoms make the valve fit the problem perfectly. Appreciate being pointed in the right direction.

 

[HighSierra49er]

Cleaning up the IAC valve..

Prior to this week the Exp. would fire up and idle most days, with the occasional quirk where it wouldn't idle at cold start up. This week the morning weather was in the 20's and no idle all week for the truck. When I drove the truck for about 15-20 minutes the idle would start to work again, but every time it sat for a while and got cold, the idle disappeared. I was anxious for Saturday to arrive so I could tackle the problem.

Getting to the IAC valve wasn't too bad. The valve was definitely dirty, but easily cleaned up. The throttle plate area needed cleaning, too. 264K miles took its toll on the assembly.

After putting everything back together the truck immediately fired up with high idle, and then dropped back to normal idle when appropriate, perfect. This morning, Sunday, was the coldest morning of the week, so a good test. Truck immediately fired up with a high speed idle. I went to Truckee, CA., early today and the truck sat in 18 degree temps. most of the day. Fired right up again from a very cold start and with perfect idle performance. The truck even seemed to start quicker than normal, but maybe that was just my joy at having it start up and idle as it should.

For the past couple of months it seemed the engine "hunted" a bit for rpm levels, sometimes starting up at fast idle a hundred or so rpm below normal, and even warm idle was at times a bit up or down. Not any more.

Thanks very much for the valuable and accurate information that allowed me to resolve this problem the first time around.. Can't believe it was done with the only out of pocket expense of a new gasket for the IAC valve.

As the truck approaches 265,000 miles and beyond it will be interesting what other issues pop up with age.

Thanks again!!!!!!!!

 

[hammerg26]

Congrats HighSierra... I have to admit, seeing posts like this give me great hope that I made a good choice when I got my Expy... having to do a few things here and there, but praying that those little "odd and ends" are the norm... nothing major - praying!