EGR Valve. Thought it was the problem.

[Matt]

3/12/05-12:30 PM-- I had a problem with what felt like engine missing at constant RPM on the hi way. I felt it was not a miss and did some checking. I found the EGR valve would not hold any vacume when pumping the trigger on my vacume test guage, not a bit. Today I replaced it and now the engine stammering wile running steady on the hi way has gone away. Wow, what a relief!! I still feel that I have a few dirty injectors, this stuff called " Lucas Injector Cleaner" was supposed to be good so I put that in with a tank of Gulf Hi test. Time will tell now. I feel a bit of a rough idle sometimes { more often } when I do not use Mobile Hi Test. Mobil makes the car idle great for some reason. I have only one Mobile station far away and the guy is not nice to me so I used Gulf. ( this guy at the Gulf speaks english and does not say things to you in another language when you drop a pen or ask him not to spill gas on the side of the car) I may have to go back to Mobil again since it is not idleing good again with the Gulf in it. So what does the EGR do?? How does it work. Thanks. Matt P/S I'd love to post a pic but it keeps saying file not excepted. Maybe someone has a tip on that to. >>>>>3/12/05-7:30PM-- WELL WELL WELL, I spoke to fast. Nothing is better,in fact it's worse !!! After I replaced the valve it was a twenty min ride home and all was bliss. I just got back from a 45 min ride. After 20 min things went down hill. The same problem came back. The engine kicks and bucks and hesitates very bad. It starts out like this. Engine start up and coolent is at 70 deg F. A few min and 135 deg.F. and it smoths out and is ready to go. A few min more and average runing temps of 208 to 214 F. are seen. The engine is smooth and very fast, idle is good at lights and take offs are rocket ship if I want. About 25 min out and I notice a little bucking wile runing even speeds on the hi way. Then it gets worse, more bucking and then take offs from lights are full of hesitation. Idle at lights are nothing but up and down RPM, acting like it wants to stall. Pulling a way it's about 4 or 500 RPM drop offs and big time hesitation at times.. If you boot it, it's like on and off power. How in the world can it be good for 20 min and then change like that???? I'm going to post this same message a few times if need be till some of the regulars that have helped me in the past see it. Please do not get mad guys but my ride is sick and she needs help. Bare with me. Thanks . Matt

[Ranger]

I am not sure what your problem is but, read this. Do you see any similarities here? Just a guess.

http://www.cadillacforums.com/forums/showthread.php?t=34004

[Matt]

Thanks Ranger. It does not quite fit what is going on here though. I'm waiting to see what Scotty has to say about all of this. I hope he sees this problem of mine. I not going to sleep good tonight!!!!

[Scotty]

Matt, I did not get a chance to fully read your post yet, but I will. However I learned an important lesson from bbobynski in September 2004 about testing the diaphram on and EGR valve. They don't work like they did when we were kids...LOL. Review this thread and pay particular attention to my post about vacuum testing the EGR and bbobynski's reply about how my thinking was dead wrong...

http://caddyinfo.ipbhost.com/index.php?sho...=15entry24487

So its possible that you replaced the EGR and it was OK, and that is why your problem did not improve.. Check for codes, it sounds like TPS to me, let me think about this one

[Scotty]

Matt let me offer some advice, your post is TOO congested, stay on the point, tell us the important points, use paragraphs this post is to difficult to read in detail.

If you did not replace the EGR with an OEM EGR clean the old one and put it back. This problem could be related to so many things as a matter of fact someone else here is experiencing the same symptoms (problems when warmed up), read this post and post your codes:

http://caddyinfo.ipbhost.com/index.php?showtopic=5349