87 still idling high

[Chrispbrown36]

I have been fighting this for a while now. I recently replaced my EGR valve after finding it leaked and thought I had it was fixed. I have fixed every vacuum leak I can find (starting fluid way), replaced the coolant temp sensor, idle air control valve, and the timing is set at zero. I have tried adjusting the idle down some and anything much below zero and the truck will die when I put it in reverse. It's driving me insane.....anyone have any ideas?

[Nick_R_23]

Assuming this is TBI since it's 87. Is it running lean? Good fuel pressure? Injectors and passages clean and injector microfilters and main fuel filter not clogged? Intake gaskets pulling air from crankcase?

[Chrispbrown36]

I put new gaskets and cleaned the entire throttle body about a year ago and the main fuel filter was changed about that time too. I changed the intake gaskets about two years ago. I have not checked the fuel pressure. Not sure on it running lean....how would I tell or check it?

[Nick_R_23]

May want to check those again, lots of wear, dirt, and water and accumulate in a years time. Best way to check would be with a wide and gauge, as it'll be the most accurate. You might be able to pull plugs and look at the color, but it may not pick up a minor air leak.

[foamypirate]

Could be worn throttle shaft bushings. They are notorious for wearing out and leaking, causing high idle and off-idle stumble issues.

[Chrispbrown36]

What did you mean by "wide and gauge"? I was considering replacing the intake gasket to see if that was the source of my vacuum leak, but since I thought I had that cleared up I had decided against it....may have to reconsider that.
I drove it into town today and it is now throwing the 32 code. " Fault in exhaust gas recirculation valve diagnostic switch" So now I am wondering if I shouldn't have ordered an AC Delco instead of getting an off brand from the local auto parts place. I am also wondering if it might be the egr solenoid.

[Chrispbrown36]

Ok....scratch the 32 code...let's just say it works better when you plug it up and leave it at that.....
The bushings seem solid to me...no wiggle to them that I can tell.

[Nick_R_23]

Originally Posted by Chrispbrown36

What did you mean by "wide and gauge"? I was considering replacing the intake gasket to see if that was the source of my vacuum leak, but since I thought I had that cleared up I had decided against it....may have to reconsider that.
I drove it into town today and it is now throwing the 32 code. " Fault in exhaust gas recirculation valve diagnostic switch" So now I am wondering if I shouldn't have ordered an AC Delco instead of getting an off brand from the local auto parts place. I am also wondering if it might be the egr solenoid.

Oops, that got autocorrected. Should be "wideband gauge", or wideband 02 sensor. That will tell you accurately just how rich or lean your engine is running. You might check out your EGR valve as well, as both a "negative vacuum" and "positive vacuum" version exists. If it's not the same as what came off your engine originally, it'll give you issues.

[Chrispbrown36]

Well, here is the deal....it has me scratching my head a bit. After finding the EGR solenoid unplugged and plugging it in I took it for a drive around the block...now mind you around the block here is about 4 miles....and no code thrown. A while later I had to run to the next town over....about 12 miles away...and about halfway there the light came on. Pulled the codes and it was 32 again. After shutting the truck down at the gas station started it back up to head home. The light didn't come on at all on the return 12 mile drive home. So what does this tell us?
As far as the wideband thing goes.....explain a bit to me. I think I have a general idea...and that idea means an investment of $150 give or take...and that isn't happening anytime soon.
Thanks for all the responses....keep em coming.

[Nick_R_23]

The reason you may only sometimes be getting a code is because the EGR will only activate under certain conditions. For example, engine must be warmed up to a certain temp, transmission may have to be in a certain gear, or cruise speed/engine rpm must be within a certain range. Basically, these conditions only get met when cruising at light throttle on the highway. Your truck is not seeing an issue with the EGR system until it commands it to operate, and is either not getting the proper reaction from the EGR valve/solenoid, or the PCM is not detecting the needed runability changes when the EGR activates properly.

Here is a great write up that should walk you right through troubleshooting your EGR system: http://www.chevytalk.org/fusionbb/sh...php?tid/258416

[cadillac_al]

Back in the 80's a clogged catalytic would give you EGR codes. As for the high idle, there is usually a detailed calibration of the idle control valve and tps in the service manual. Maybe someone will post it. It may be all in the tps but Cadillacs can calibrate the idle air control.

[Chrispbrown36]

No cat on the truck...that ten ton original cat went away as soon as I got it home.
Hopefully the rain will hold off and I will get some testing done today.

[foamypirate]

Originally Posted by Chrispbrown36

No cat on the truck...that ten ton original cat went away as soon as I got it home.
Hopefully the rain will hold off and I will get some testing done today.

Removal of the cat can cause the EGR code. The EGR valves on these trucks are VERY particular to exhaust back pressure, depending on the type. There were positive pressure valves, and negative pressure valves, depending on configuration. It's also possible you have the incorrect valve, especially if you are using a generic parts store valve. They often have the wrong orifice size for EGR flow.

In a nutshell, TBI trucks are very picky about EGR valves and ehxuast configuration.

[Chrispbrown36]

For electrical parts I have tried to stick with only AC Delco, but I assumed that for an EGR valve an off brand would be ok. There isn't much to them....you would think they would all be about the same. As far as negative and positive goes....I have read that there will be an N or a P at the end of the part number to tell you which one it is. My part has a D...I am wondering if it doesn't stand for dumba**...as in you're a dumba** for paying for this.

[Shady Rascal]

I've seen the EGR passages in the intake get fully plugged with carbon more than a few times. My current truck did this coincidentally. The EGR valve had a ruptured diaphragm for who-knows-how-long. The valve never opening over time allowed the carbon to clog the passages fully. Even with a new EGR valve the truck was throwing an EGR code. The fix was to pull the intake and blast the carbon out of the passages.



As far as the idle issue, your IAC sounds suspicious. When you put it in gear, the IAC should open and bump the idle.