Idle speed.

[Pat]

Does the transmission have anything to do with idle speed? I would'nt think so but with the electronic interaction among components, never say never.

The probllem began just a couple of weeks ago. The idle hovers around 1500 RPM when driving (no throttle) or at idle (car stopped). This condition is intermittent, after a moment or two the idle drops to 800 RPM like it's supposed to, but sometimes doesn't.

Perplexing, the idle air controller is fairly new (changed last year for wandering idle speeds, not same problem as now).

Maf has been cleaned, maybe a vacumn leak?

The idle will usually return to normal after a while, but not while driving under no throttle.

Thanks,

Pat

[RacerX]

get to a point where it has a stable high rpm and blip the throttle real quick. Does it go down after? If so, could be a sticking throttle blade.

[fastblackmerc]

I'd say it's a sticking TB also.

[Pat]

I did the procedure you asked, RacerX, and the results were more failed return to normal idle than not.

I'll be looking into the TB.

Thanks,

Pat

[Green96]

If the TB is sticking you should be able to disconnect the IAC connector and the idle should stay high. If it dies, your idle is high because something is commanding your IAC open.

[Shaijack]

The Blue did the same thing after M-Ville 9 It went away on its own. I figured it was because we were under water the hole time.

[BODYMAN]

Id agree sounds like something in TB/IAC function.

[Pat]

An update on this idle problem. I consulted Zack and he determined that I have a vacuum leak. He recommended checking all the lines in the engine bay, particular attention to the ones around the EGR valve. He also mentioned the by-pass valve. I determined the by pass-valve was good and I didn't find any broken, disconnected or torn vacuum lines. Zack was very helpful and quick to respond to my call for help.
I'm on the right track now.

So, I'm still searching, my IAC is working properly, TB has new gasket and cleaned, blades are closing OK. Car is pulling 16 inches of vacuum at idle. Idle speed is 900 rpm.

This is gonna be a toughie, suggestions welcomed.

[justbob]

16 is too low Pat. In park she should be around 19-22. Did you check the injector o-rings for unmetered air? Good way to check is with a propane bottle (unlit...)

[Pat]

That's a place to start, Thanks.

[RacerX]

16 is too low Pat. In park she should be around 19-22. Did you check the injector o-rings for unmetered air? Good way to check is with a propane bottle (unlit...)
Yup! Mine is a hair over 20in. When I installed my 39lb injectors and started her up, my idle was high and I could hear air whistling in around the lower injector O-ring on cylinder #1. Hope it's an easy fix!

[justbob]

Other out of the norm places to check would be the boost line from engine to gauge, brake booster, even the vacuum storage box on the fender well. You have a BAP? Check the hobbs switch that controls it if it isn't bypassed like some people do. That's all I got for now.

[Pat]

Just Bob, you speak of a vacuum storage box on the fender well. I can't seem to locate such a component. Can you be more specific.

There is another question you may be able to help me with, to the left side and next to the OBDII port is a white vacuum line that, on my car, is not connected to anything. I couldn't find another loose end. My GM uses that same line to connect to other components under the dash.

I plugged the line but it didn't help any. It may not be used in the Marauder.
Would you be so kind as to look in your car, locate the line and tell me if its connected to something.

Thanks,

Pat

[justbob]

The vacuum box is the plastic square box that sits directly in front of the Cruise control unit. It has a single vacuum line going to it.

That line you speak of isn't used on marauders, there is another one like it at the vacuum manifold bolted on the firewall center behind the engine. Once again, not used.

[Pat]

I checked the line to the vacuum box and the lines to firewall manifold box, all seem OK.

I did the propane gas wave and nothing changed idle speed.

I did find a funny I'll share. Thought it could be my problem but it wasn't. So, I lowered the glove box door to check the vacuum lines that run behind it and found a pair of sunglasses mashed up against the white vacuum line. Removed the glasses, freed up the line but it wasn't broken or torn just mashed. Didn't fix the problem but it was odd how the glasses got there. Probably one of the grandkids stuffed the box with stuff and forced the glasses over the back wall of the glove box, then after repeated openings and closings the glasses migrated to the vacuum line where they got stuck.

Car's on ramps now while I inspect underneath. I'll also look at the gas tank area.

Wonder if a car repair shop would be able to find it? I would want to watch otherwise I might pay for a three hour "wall job".

[RacerX]

but it was odd how the glasses got there.
A 9g brake check might do it! :D

[Pat]

Zack found the vacumn leak in short order. The plastic hose from the engine to the vacuum/boost guage was torn behind the guage. Reads 20 now.

Thanks to all.

http://i307.photobucket.com/albums/nn306/Marauder-Z/Marauder%20Repairs/2012-04-15_09-46-59_121.jpg