I am trying to narrow down the possible causes for my rough-er than normal idle (the one where it makes you want to put it in neutral while you wait at a stoplight). Smooth in neutral, rough in drive, although only gets rough after having been stopped for about 5 seconds.

 

I thought/hoped it was the EGR valve, but I took it off and tested it and it seemed fine- not too much carbon buildup, diaphragm holds vacuum, holes to engine free of carbon. I did the Haynes recommended test, where I watched to see if the pin moved while I manually raised the throttle. It did, but it didn't stay up, it just went up then down.

 

Next place I looked was the EGR solenoid. It did the same thing. When I raised the throttle, it went from zero vacuum to a quick burst of about 14-18 inHg, then back to zero. Is this good, or is it supposed to stay until I lower the throttle?

 

I also tested the general engine vacuum, as detailed in Haynes chap. 2b5 vacuum test. I connected the gauge directly to the intake manifold, and it read a strong and steady 22 inHg in Park. Just to see what would happen, since my problem is when its in DRIVE, I positioned the gauge so I could see it through the windshield. I put it in drive, and it dipped down to about 16 or so, and remained steady until I put it back in P. Is this ok, or am I making progress?

 

Thanks,

Andrew

I'm not sure what to think on this Andrew. It kind of sounds to me that there may be a vacuum leak somewhere, possibly the transmission area. If you have any vacuum lines going to the transmission area try pinching them off to see if that makes any difference in the idle.

Check the egr coil with a meter. If it is out of spec, the cpu shuts down the #1 fuel injector.

 

Details are in http://endwrench.com/main.php?smPID=HTML::home.html

someplace.

 

A quick overall test is to saok the engine with a hose while the car is running. This will show up a vacume leak (as the water gets sucked in) or a leaky high voltage circuit.

 

nipper