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1994 K1500 dtc 32, EGR system

This is a discussion on 1994 K1500 dtc 32, EGR system within the Technical / Maintenance forums, part of the General Discussion category; My '94 K1500 4wd auto P/U with 5.7L V8... "Service Engine soon" light comes on after driving 20 - 30 ...

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    Cool 1994 K1500 dtc 32, EGR system


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    My '94 K1500 4wd auto P/U with 5.7L V8... "Service Engine soon" light comes on after driving 20 - 30 miles and stays on. If I stop, turn off the ignition for a couple of minutes and restart, the SES light comes back on... however, if I turn off the ignition, open the gas cap momentarily, then restart the engine the SES light doesn't come back on and stays off for 5 miles or more but then comes back on. It has done this for some time now but performance doesn't seem to be affected, but perhaps it only seems that way because it has gradually gotten worse. Today I checked the trouble codes... it reads 32, EGR system problem. So far I haven't done anything but research the problem... any suggestions? Thanks in advance.

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    Re: 1994 K1500 dtc 32, EGR system

    i get code 32 on the highway all the time since I put headers on....

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    Re: 1994 K1500 dtc 32, EGR system

    Code 32 happens for lots of reasons other than an EGR problem. I've had code 32's for bad vacuum lines and another time for a bad fuel pump. It makes me wonder if something's up with the vapor recovery system. I'd check on that first before messing with anything more expensive.

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    Re: 1994 K1500 dtc 32, EGR system

    is it the original egr valve?
    O2 GMC RCSB 4.8L V8 AUTO 3.73's
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    Re: 1994 K1500 dtc 32, EGR system

    Quote Originally Posted by smaurno View Post
    Code 32 happens for lots of reasons other than an EGR problem. I've had code 32's for bad vacuum lines and another time for a bad fuel pump. It makes me wonder if something's up with the vapor recovery system. I'd check on that first before messing with anything more expensive.
    Thanks... I've been looking at the vapor recovery system before checking the trouble code. It seems to fit with the symptoms. I may have multiple problems as I checked the smog test records back to 2004 and there has been a steady increase in NOX. This time, in January, it barely passed. The truck has 240,000 miles on it and burns no oil. I bought it from a friend who bought it new and babied it.

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    Re: 1994 K1500 dtc 32, EGR system

    Quote Originally Posted by NEUMANNZZ View Post
    is it the original egr valve?
    So far as I know it is the original. I've had the truck since 11/04 and it has 240,000 miles on it now. The California smog inspections have shown an increase in NOX reading over the years... I may have more than one problem. I've been diagnosing the problems with the aid of a Chilton manual... not the best I've ever used.

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    Re: 1994 K1500 dtc 32, EGR system

    You almost certainly have a bad EGR valve. Don't confuse your troubleshooting by looking towards the evap system as it is pretty much unrelated. The conditions for code 32 to be met are pretty straightforward; the reason the light doesn't come back on immediately is because the conditions haven't been met. Each time you turn the key off, you have momentarily cleared the light, but it will come back next time conditions are met for the EGR test to be run. Has to be in closed loop operation (warmed up), traveling for X amount of time with less than X % throttle variation, I forget all the specifics but in other words - cruising at a fairly steady state on the highway. The reason for the cruise condition is because the EGR position will change based on throttle input, so it's waiting to see that there has been little change in it for a while. Then the PCM will momentarily command the EGR valve open as a test. It looks to the O2 sensor to see if there was a dramatic change in reading. If not, it assumes the EGR is bad because it was unable to produce a notable change in the exhausts' O2 content. Usually, this is because the valve is bad. Sometimes the solenoid that controls it is bad.

    Don't depend on the "push the diaphragm with your fingers - engine stumbles" method of testing. All this proves is that the passage in the intake is not clogged, which isn't generally a problem on the V8's anyway (though some of the V6's are bad about carbon blocking in the passage.)

    If you have access to a vacuum test kit (Mityvac) - you can test the valve. Engine OFF, hook the tester directly to the valve. Pull vacuum on it. It should have no problem holding vacuum until you release it. Pull vacuum on it again and then start the engine. Vacuum should bleed off immediately as the engine starts. While you're in there you could check to be sure there's vacuum present at the source. Check the line that feeds from the TBI unit to the EGR solenoid. It should have vacuum present at all times while engine is running. Check hose routing on the EGR solenoid. The side of it that has what appear to be two connections is the side that connects to the EGR valve. One of those connections is actually not a connection at all, but a vent. It's easy to tell them apart - one has a barb for retaining a hose; that's the one that hooks to the EGR valve. The smooth one is the vent and needs to stay open. Sometimes there's a little foam filter on it, but usually this is missing.

    Your increase in NOX can easily be a symptom of a bad valve, too. The EGR valve's job is to introduce inert gas (exhaust) to the combustion chamber in order to keep the temperature down in there, which helps prevent spark knock (detonation/ping.) To oversimplify things, lower combustion chamber temperatures means less NOX. The PCM can command proper spark advance without ping, using regular grade gasoline, with a properly functioning EGR.

    It bears repeating - if you go to replace your EGR valve, please, get one from the dealer only - using your VIN as a reference - or get a Delphi brand one from a good parts house. The lesser, cheaper one-size-fits-many valves can be very problematic on TBI engines. Some people have had luck with them but many have had lots of trouble.

    Richard
    Last edited by someotherguy; 08-09-2010 at 08:07 AM.

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    Re: 1994 K1500 dtc 32, EGR system

    Richard... thanks for the easy to follow, detailed info. My Chilton manual should be so straightforward. I'll pick up a vacuum test kit today... it wouldn't hurt to have on hand anyway and the cost is a lot less than taking my Chevy to the shop. In addition to the SES light coming on I have noticed a bit of a decline in gas mileage, from around 15 mpg to around 13 mpg for similar driving conditions. Thanks again.

    Ken

 

 

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