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EGR


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Guys, I require your assistance. A couple of months ago, I had intermittent stumbling at idle, and eventually a shudder under light acceleration at highway speeds. Both EGR symptoms. I also eventually threw a code, P036, pintle out of range, as we are all familiar with. I proceeded to remove the valve, clean it with solvent right side up with a gun cleaning brush, per caddyinfo instructions. I tried this several times, thinking I had not cleaned it enough. The valve did appear to be sticking, until I finally let the bottom of the valve soak in solvent in a closed container. After the final cleaning, the valve could easily be moved with my finger open and closed. After putting it back on, I still had the same symptoms, and the same code. So, thinking maybe the valve was actually defective, I got another one. Installed it, now I have no more P036 code, but I still have the same symptoms. I have the Caddy service manuals, so I performed the diagnostic chart using the PCM on-board system. I arrived at the bottom of the chart with only one possibility: An open or short to ground in two particular circuits in the wiring harness. This doesn't make any sense, since the wires are pretty much protected all the way to the PCM. I got my Dad to check for shorts and/or open circuit and he detected no fault with the wiring. Any ideas on where I go from here?

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Sounds like your old valve was always open. Did yo try to disable the EGR to have the valve al time close? It should eliminate the problems with idle and light acceeration. Unfortunately, I am not familiar with EGR operation on Northstars just know it is completely different from one on 4.9 I have.

The saddest thing in life is wasted talent

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Did you clean the EGR "tunnel" system, and the opening to each intake port?

See attachment of a dirty EGR runner system.

This is a 93 engine, I think yours is the same.

.The mouse holes at the end must be clear, use a drill bit turned by hand.

.Each small slot from the runner, to each port must be clear.

.Use a vacuum cleaner to pick up all of the debris as you work.

-George

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Drive'em like you own 'em. - ....................04 DTS............................

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Thanks for the help, guys. I did spray some intake cleaner into the intake tube while the engine was running, with the egr valve off. But, I did not actually scrape the inside of the tube or anything. Will I have to remove the tube to do that? Or can I use some kind of pipe cleaner device? Also, I don't think it could be anything else, like a fuel problem or spark problem, as it is intermittent. One minute you stop at a light, and the car purrs, the next time you stop, the whole car shudders.

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Thanks for the help, guys. I did spray some intake cleaner into the intake tube while the engine was running, with the egr valve off. But, I did not actually scrape the inside of the tube or anything. Will I have to remove the tube to do that? Or can I use some kind of pipe cleaner device? Also, I don't think it could be anything else, like a fuel problem or spark problem, as it is intermittent. One minute you stop at a light, and the car purrs, the next time you stop, the whole car shudders.

I would just block the EGR off to make sure it is EGR related....

The saddest thing in life is wasted talent

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If I were to block off the EGR valve, I don't see what purpose that would serve in diagnosis. If I were to block the valve and leave the egr plugged into the PCM, then surely it would throw a code, and surely it would behave as it is behaving now. darn, am I making any sense?

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If I were to block the valve and leave the egr plugged into the PCM, then surely it would throw a code, and surely it would behave as it is behaving now.

Throwing a code would not make the car behave differentl. But if idle improves (say, at stops) you would know it is definitely EGR related.

The saddest thing in life is wasted talent

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If I were to block the passages, which is what I think you're saying, then the car would definitely not run correctly, because it wouldn't be getting proper egr flow to the intake manifold, and the computer would think that it is. I don't see how it would run correctly. In other words, the PCM would be adjusting fuel and spark for a certain amount of egr air that is supposed to coming in, but would not be. I would think this would lead to the same problem I have right now, and not help with diagnosis. Maybe I'm missing something.

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Hey guys, I have a new observation. Now that's it getting hot around here, I've been using the AC. Whenever I turn on the AC, the idle gets extremely rough, RPM's jumping all over the range from 400-1000. When I turn it off, it gets instantly better. Does this change anyone's opinion, or is it just still the EGR valve/EGR pipe? Any ideas?

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