rough idle

[Guest whitey]

Just verified my hot idle vacuum @ 17.8"hg in park with digital gauge. I believe this will vary somewhat with your location, vis-a-vis, altitude. I am at about 720ft. I would expect it to increase with a decrease in altitude, and vice-versa. Idle is not adjusted with TPS, which is only an indicator to the ECM of the throttle position. It functions somewhat like an accelerator pump on a carburetor as well as the angle of the throttle blade. It is desirable to have it operate in the expected range.

I checked my BLM for light 30 mph cruise, which is about 122-123 and rises to 133 or so when stopped in park. This is with 24# injectors and stock PROM, so I expect it to run somewhat low. The Integrator runs in the expected range around 128, so I consider this to be normal operation. These are variable numbers, and should be expected to operate over some range. If it didn't, it would lose the self-adjusting ability.

I sit at 1200 ft. so that may be part of what I'm seeing for vacuum. I am replacing the fuel pressure regulator and EGR gaskets this weekend. The FPR was not leaking but since my fuel pump rubber seals were totally disintegrating I expect the FPR diaphram to follow. One thing is apparent, seals that sit in gasoline and in the 100F + heat for extended periods go bad first. After this, replacing all the underhood vacuum lines will be the last thing left to do unless my ECM/MEM-CAL/connectors are faulty. I'm working on a back up. When I get done I will have a great parts car. Thanks for the update, it helps me know what is normal.

[Guest whitey]

So far it looks like I need to check for the FPR leakage and do a EGR gasket set replacement in an effort to find the vacuum leak. Thanks for the leads.

Replaced the FPR and EGR sensor but there was no improvement in the rough idle. Got some vacuum increase when I replaced the rubber grommet in the valve cover but still have rough idle . While searching for more vacuum leaks noticed that the fuel vapor canister's tank supply hose was looking weathered/ discolored so I will replace that when the part arrives. I have a question about the fuel vapor canister.....are you supposed to see a filter in the bottom of the canister when looking up into the air hole from underneath the car? I'm accustomed to seeing the filter at the bottom but I don't see anything there. If I should be able to see it then I have none and my canister is probably very dirty. Which leads to this next question... Does replacing the filter and removing the canister require pulling out the washer bottle or will it wiggle out once the 2 top canister bracket screws are removed?

[Guest whitey]

Thought I would wrap this up with some positive results. The rough idle is no longer. It was cause by a combination of problems. The fuel pump was going bad, the TPS was worn and needing replacement, the ICM was overheating and starting to cook the green. These things along with a couple of fixed minor vacuum leaks has it running like new. This car has only 32K miles on it but this shows that a lot can go wrong when they sit in hot storage. A sincere thank you for all the help. I could not have done it without you.

[Machiner 55]

Whitey,

I have a question about the fuel vapor canister..... are you supposed to see a filter in the bottom of the canister when looking up into the air hole from underneath the car? I'm accustomed to seeing the filter at the bottom but I don't see anything there.

There is, for lack of a better term, a false bottom inside the canister. So, when looking up into the hole at the bottom that is what you'll see. Not the bottom of the filter, whether it has one in it or not.

John F.