EGR valve or vac problem

The code states it pretty clear..... EGR volts above closed limit..... sounds like an EGR valve that is stuck partially open.

With what you spent for the EP sensor, you could have sprung for a DMM and done some diagnostics.....

To be honest, if deciphering codes was cut and dried, I'd be collecting unemployment.

** Still working on a persistent problem... ** ** I cleared then ran new codes on my '92 5.0 and am getting a code 34 when on, ** running and continuous. My manual says that code means "EVP voltage above ** closed limit". I replaced the sensor (i.e. wasted money) and still have the ** idle problems and code. ** ** So, does "voltage above the closed limit" on a good sensor rule out (or ** support) a bad EGR valve or vacuum problem?

The problem is more likely a stuck EGR valve or a very dirty seat. You mentioned that you were looking for a vacuum leak - an EGR valve that is stuck open will create such a vacuum leak and make it difficult for the engine to idle properly.

Regards,

-JD

--------------------------------- JD's Locally-Famous Mustang Page: http:/207.13.104.8/users/jdadams---------------------------------

Ugh, it continues...

Today I took off the EGR and thoroughly cleaned it. The pin seems to be forming a good seal as it holds carb cleaner. Also, the diaphragm seems to be intact as I could suck on the vacuum end and draw up the pin. But I put it back together and still have the crappy idle and still show code 34.

Then I started looking up the line. When I pull the vacuum line off the EGR there is no vacuum present when hot, cold, whatever. I pulled the vacuum lines from the vacuum regulator and seem have a good vac for the source (I can hear it and it grabs my finger pretty good), but I never seem to get any vacuum on the side that goes to the EGR.

So, what conditions should I expect that vac regulator to actually allow vacuum to the EGR? And is there a way to test the regulator?

Many thanks Bud

An EGR valve with carbon build up on the valve seat and/or pintle can certainly trigger the CEL. If you have not removed and inspected the EGR valve, then do so.

I would also suspect possible harness connections. Check the EVP connecter C172 and upstream to connecters C118/C119. C118 links the EVP signal to the EEC. C119 links VREF and signal return to the EEC. An open circuit with any of these three wires can set off a fault code. You would need a volt/ohmmeter to diagnose this correctly. Visual only inspection won't cut it... Good Luck

-- Mike

93 Cobra

Just had this same problem start occurring to me recently. I pulled the vacuum line off of the little canister thing on the backside of the throttle body and my car idles perfect now.

Let me know if you want pics.

Don Manning

You did remember to clear the code, right (sorry, had to ask)? Also, are you retieving this code as and engine running self-test code or as a continuous memory code?

The EGR vacuum regulator is a duty cycle solenoid meaning the PCM will decide how much vacuum will get through - I would believe that it requires more than one or two inputs to operate. Like Mike suggests, time to check the integrity of the circuit - use your DMM to make sure that your (approx.)

5.0 volt reference voltage is present and to check the sensor ground is good. Wouldn't hurt to ohm the sensor to be sure that you didn't get a dud..... some of the repackaged off-shore sensors leave a little to be desired.

Since you state that the EGR valve doesn't appear to be leaking at the pintle, I would think that the poor idle may come from a different problem.

Jim Warman snipped-for-privacy@telusplanet.net

I did all of your suggestions except for the MAF element cleaning.

Both the EGR and ISC had a fair amount of carbon buildup. The EGR side of the throttle body was pretty nasty too. But I got everything cleaned up nice, cleared the codes and no changes. UGH!

I'm going to put in new fuel filter in tomorrow night to hopefully help the hard starting when cold. However, I'm starting to think that problem is a fuel pressure problem.

But this crazy idle thing has be baffled.

Thanks, Bud

Thanks Mike

I cleaned up the EGR and the ISC/throttle air bypass valve. I'll read up on testing connectors and give it a shot.

Thanks again Bud

I cleared the codes and still get the 34 when engine off, running, and pulling the continuous.

I'm not to sharp with a DMM, but I'll give it a shot.

Thanks, Bud