crappy idle on 91 astro

[Gordon]

My 91 astro awd has a crappy rough idle.

So far i've changed the o2 sensor, plugs, cap, rotor, temp sensor, plug wires test good for resistance...

That's all i've changed but it still has a crappy idle.

Has anyone got any other ideas?

[Jim in Indy]

Check for a vacuum leak by pulling & capping a section at a time of all vacuum lines attached to the intake.

Look at the spray pattern of the injectors... are they both in a nice 'cone' shape with no drips/dribbles.


Is it popping a Code 32? Even if it isn't, I'd still check for a inop EGR valve, or plugged EGR passages on the intake.

[Gordon]

checked for vac leaks.... none that i can find

no codes at all... the egr is moving as it should through the rev range

the injectors are spraying a nice even cone... no dribbles

gonna test the fuel pressure tomorrow

[Gordon]

i forgot to mention the idle gets rougher as the engine heats up to operating temp.... no idea why??

[Jim in Indy]

I'd be tempted to say Coolant Temp Sensor, (CTS), but you already went there....

OK, all you brain-surgeons.... jump in here....

[GEJ]

Percentages lead to EGR valve.A screen gasket should be used as a replacement.I studded the bolt holes to make any work in the future easier.I recently found the diagram for the cruise control had a hole in it and created a leak there.Wasn't easy to find that one.We sprayed with carb cleaner and didn't find that leak.Just a chance happening that we found it.

[kings-x59]

Here's one other thought: how's your pcv valve? and, are you getting good vacuum on the pcv hose?
The idle on my '89 would get worse the longer I drove until I rebuilt the throttle body and cleaned the pcv port.

[peppy]

What is a screened gasket?

Thanks all!

peppy

[kings-x59]

Its a replacement gasket for your EGR valve.
looks like this:
http://bbb-carb.com/Klean_Screen/buynow/2-1357.htm

looks like they are carrying them for models only as far back as '92 now. I knew I should have bought one of these when I first heard about them. ya snooze ya lose.

[kings-x59]

Here's one last thought related to vacuum. Start the engine up and pull the hose off the pcv valve. put your thumb over it, are you getting strong vacuum there? at idle it should feel like it's trying to suck your thumb down the hose. The hoses and fittings may be just fine. If the hose ports on the throttle body are clogged up it will make the engine idle like crud. The pcv port gets very impacted with carbon.