high idle after lim & uim change! HELP!!!

[55trucker]

The power steering assist sensor usually won't cause a high idle situation, if the vehicle is stationary there is a load put on the engine at idle if you try to turn the wheels, so the switch closes under this high oil pressure which causes the ECM to raise engine rpm just a small amount to overcome the additional load on the engine until the wheels are stopped from turning. This switch is also tied into the A/C circuit and under the same load circumstances cuts out the A/C until the engine load is reduced. But.....there's no reason why you can't test it.....just disconnect the harness from the switch and note if there is any change in engine idle rpm, if the switch IS stuck closed then the ECM will see that and will constantly keep the rpm raised a small amount.

[lvbroham1]

i'm going to go back and visually inspect every aspect of the vacuum system tomorrow for anything i might have missed. I replaced the TPS and the idle seemed ok for the first few seconds after I installed it, then the idle increased gradually to 2-3000rpms. I'm about to throw in the towel and take it to a local shop.

[55trucker]

The engine rpm is still climbing to 3grand?....in Park/Neutral?..that is definitely going to set a code....is the rpm limiter cutting in at 3g's?.....I'm not too sure on the later models but on the early DOHC's there is a 3 grand rev limiter programmed in as a safety feature, the rpm will climb to 3G then drop off then repeat the cycle. Perhaps it's time to purchase an inexpensive hand held propane bottle (with the nozzle) and do a *leak test* ....search for vacuum leaks with the bottle all around the intake assembly. Anywhere there is a leak the propane will be sucked in and you'll immediately hear an rpm change. You're absolutely sure there's no air getting by the throttle body.

[lvbroham1]

yea, it's still climbing to 3,000rpms, i'm going to take your advice and purchase a propane bottle and perform a leak test. I'd much rather fix this myself than have some mechanic rip me off for a simple fix I could've done myself.

[lvbroham1]

alright guys here's an update. looked everywhere for a vacuum leak and finally broke down and took it to a mechanic at a well know shop out here. They took a look at it and said they know it's a vacuum leak, but cannot find it, they said they won't even charge me for looking at it because they can't find the problem with it. I'm at a loss right now. Anyone else have this problem before?

[55trucker]

Can't say that I've had this sort of annoyance.....did you try the propane test?...did the shop attempt any sort of *leak* test to find the vacuum leak?...while they had the car did they run the ECM scan and test the IAC, TPS, various other sensor tests for operation?

[ratrodder]

you might want to check the injector o-rings, they will easily rip, did you lube the o-rings before installing the rail?

[lvbroham1]

they checked all the diagnostics and it all checked out fine, no ses light. yep, tried the propane test, found nothing. I lubed the o rings with some new oil before reinstall. I'm thinking maybe the coolant temp sensor. I heard that sometimes if this goes bad it won't mess with the temp gauge inside the car, but will trick the car into thinking it's always cold, thun increasing the idle to warm it up. I guess it couldn't hurt to change it, and if it doesn't solve the problem $11 isn't that much of a loss.

[55trucker]

Something that strikes me as odd is....why isn't the ECM setting a high idle code?...if the engine rpm in park/neutral is rising to near 3g's (almost rev limiter rpm) the ECM should set a code as it wouldn't understand why at that rpm the car isn't moving. The ECM should be getting a signal from the Park/Neutral switch that the trans is indeed in either Park or Neutral, the EGR circuit will be open (no EGR), the IAC circuit will be engaged, if the rpm climbs above approx 1800 and stays up there without coming down for more than 20 secs the ECM should set a code and your SES light will flash on.

[lvbroham1]

i'm confused too as to why it wouldn't be throwing a code. At least if it were throwing one, i'd know what direction to go in instead of throwing parts at it. If the temp sensor thing doesn't help i guess it's back to the drawing board. That or 3800 supercharged swap time lol.

[55trucker]

I might suggest taking a closer look at the Park/Neutral Safety Switch....if it is electrically out of adjustment that could explain why the ECM is perhaps not seeing a grounded circuit from it when in Park or Neutral and in turn the idle circuit is not actually engaged when you are in either Park or Neutral, the Safety switch circuit is not part of the Emission control devices so if it is not adjusted properly the ECM won't set a code. There are a pair of *notches*...one in the inner housing (that moves with the shift lever) and one in the outer housing that are supposed to be lined up when the trans is in park, have a close look to see if they are.

[pocket-rocket]

If the ECM is telling the engine to idle at 3k, it's not going to be setting a high idle code because the engine is doing what the ECM is telling it to. Where are you located lvbroham1? Maybe someone on the board is close to you that has the equipment and know-how to throw a laptop on your car and see what the ECM is doing to help find the problem.

[lvbroham1]

I might suggest taking a closer look at the Park/Neutral Safety Switch....if it is electrically out of adjustment that could explain why the ECM is perhaps not seeing a grounded circuit from it when in Park or Neutral and in turn the idle circuit is not actually engaged when you are in either Park or Neutral, the Safety switch circuit is not part of the Emission control devices so if it is not adjusted properly the ECM won't set a code. There are a pair of *notches*...one in the inner housing (that moves with the shift lever) and one in the outer housing that are supposed to be lined up when the trans is in park, have a close look to see if they are.

I will take a look at this as soon as the weather gets a little warmer. It's about 15 outside right now.

If the ECM is telling the engine to idle at 3k, it's not going to be setting a high idle code because the engine is doing what the ECM is telling it to. Where are you located lvbroham1? Maybe someone on the board is close to you that has the equipment and know-how to throw a laptop on your car and see what the ECM is doing to help find the problem.

I'm in Saint Joseph, Missouri. What program would you have to have in order to do this?

[pocket-rocket]

For 95, I am not sure. I just went back and saw what year you have and should have done it the first time around. Hopefully someone else can chime in on this information and help you out.