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Joeyblaze
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I have a 1995 GMC k1500 4x4 with the 5.7L TBI engine in it. I just bought the truck and as it is about 24 years old, it only needs to pass one more emisions test before It is grandfathered and therefore immune to e-checks (I live in northern Ohio) and also before I can get plates for it. The problem is, I've failed e check 3 times. A code 32 pops up every time I test it (on my own with a reader) and when I got the emissions test, high nox is the reason it fails. This would make sense, as code 32 is an egr error, and the egr being faulty would definitely trigger high nox, however:

The egr valve has been replaced (yes, a negative one) 

The egr vacuum solenoid has been replaced 

Map sensor replaced 

Spark plugs, cap, rotor, wires. Replaced

Even went as far as to replace the oxygen sensor.  

There doesn't seem to be any vacuum leaks and every test I've done on any part of the egr system points to it all running correctly. 

 

The kicker is: the truck runs great! No loss in power. Idles great. Super clean and well kept truck. 

 

Notes : it does have a Flowmaster super 10 dual exhaust on it, but it isn't a true dual as only one pipe comes from the catalytic into the exhaust, Then two come out. 

 

Also, high nox seems to be caused by high engine Temps, however, my engine temp on my dash shows that it never gets above about 165 or 170*. Idk if this is relevant but it seemed strange. 

 

Any help is greatly appreciated. I'm really at a loss and I'm running out of time before I need to buy another temporary tag. 

Thanks again - Joe 

Edited by Joeyblaze
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41 minutes ago, riverbanks said:

32 is no change seen by map and 02,could the port be clogged?if you suck on the vacuum line,can you get it to stumble?

There's no buildup inside the egr port and yes, when you suck on the line or when u just push the egr interior with your finger you can get it to stumble quite easily 

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My next thought is to get a new egr valve again, particularly a Delphi or oem one, Bc the one that is in there now, while new, was only thirty bucks on rock auto. I don't want to be blindly throwing money at it, but maybe a more expensive egr valve will work. Any thoughts? Thanks again

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4 minutes ago, riverbanks said:

Argh,did some searching,chevytalk.org,post#2053697,it's got it all in one spot

And ya, I read up on that post earlier. It seems to confirm everything I knew. Like I said tho, I replaced about every part in the egr system, I just can't figure out why it's still throwing a code and failing e check. 

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I'd just throw a cooler thermostat in it to get the head and combustion chamber temps down enough to pass. Only one more year - I wouldn't spend another nickel on useless emission crap.

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5 minutes ago, riverbanks said:

One item is to put a vacuum gauge on there,see where you're starting from,18 at idle,and back to temp.question, combustion temp. not thermostat,and you have or not,any pinging?

No pinging. The motor runs flawlessly. Idles great. Good acceleration. I don't have the combustion temp, but I pointed a laser thermometer on the exhaust manifold(228*f), valve cover(145*), and the Catylitic converter(290) and they seemed to be in a normal range. 

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High Nox = high combustion temperatures. Higher the temp the worse it gets. There's probably something wrong with the EGR system, but as a CHEAP bandaid, I'd go with a cooler T-stat just to get your sticker. Once that's done, you're home free.

Edited by Jsdirt
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8 minutes ago, Jsdirt said:

I'd just throw a cooler thermostat in it to get the head and combustion chamber temps down enough to pass. Only one more year - I wouldn't spend another nickel on useless emission crap.

With what I just said about the laser Temps, would you still do that. Like I said, the thermostat reading on my dash is showing its not that hot at all. 

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I'll try what you guys are saying. I'll put a new thermostat in it, just really wondering if a differently calibrated egr valve would solve the problem. I need to get it fixed asap like I said but I'd really enjoy it if the check engine light didn't pop on every time I took her on the highway too. Crossing my fingers for possibly better gas mileage with less emissions too. Thanks again. I'll post if I ever figure it out 

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I'd try a 180° t-stat, then, if you have more than a half tank in the truck, or are planning to fill it, throw in a bottle or 2 of gas line antifreeze - that will ensure the cooler t-stat doesn't cause high hydrocarbon emissions during the test.

 

It's ridiculous how some states test for emissions on something over 20 years old. "Moronic" would probably be a better word for it ...

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5 minutes ago, riverbanks said:

Yep,stinks,no pun intended,you went by the book for repair,and still a issue,but,you verified power at solenoid,and followed the ecm ground for a problem?so close,man

Didn't follow the ecm ground but I had power to the solenoid 

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