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Weird problem

19K views 86 replies 17 participants last post by  TulsaVic 
#1 ·
So on Thursday morning I was heading to get mt car state inspected. It started running strange almost like it is misfiring. The car is not throwing any codes. When at a stop light the car seemed to want to go. It was lurching forward even though my foot was firmly on the brakes and the throttle was closed. This same thing happened to my '02 Seville and it was the intake plenum. So yesterday I went by the dealer and picked up a plenum. This morning I removed the intake manifold to find the plenum in good condition. No tears and seemed to snug up nicely. So I figure it might be a cracked spark plug as that has happened to this car once before. So I change out all 8 spark plugs with AC Delco 41-987's. Problem is still there. Then I decided to clean the throttle body as I had cleaner within arms reach. The problem is still there.

Since I am not getting any codes I am at a loss as to where to check next. Does anyone have any ideas? I could start throwing parts at this thing and eventually I will get it fixed. But that will be expensive. Any input is greatly appreciated

Don
 
#64 ·
Went to the dealer today. They said they scanned it and found nothing that would cause this problem. So I would assume that it isn't an electrical issue. They said the first step for them was to check the fuel pressure. My car should be 60 psi. They found 42-45 psi. Diagnosis tree says to change the fuel pump. So I ordered one from Rock Auto and will install when it arrives. I will update when it is in. I will see this thread through to the end. To help anyone in the future that may have this same issue

Don
 
#67 ·
$125 for diagnostics. I paid $220 for fuel pump and installed myself. Problem is now more pronounced since the engine is getting full fuel pressure. The dealer has the car and will do more diagnostics tomorrow. I told them to drive it before working on it as the problem is worse on a cold engine. I feel it is a transmission issue. I guess we will see tomorrow.

Don
 
#70 ·
Don,

You are my hero!!! I love your persistent and I hope your perseverance is paid off to your satisfaction soon. One would think that the Cadillac dealership should be able to get to the bottom of the problem and fix your vehicle. One could ONLY hope for a satisfactory solution from the manufacturer's authorized representative.
 
#71 ·
Well I think we got somewhere today. They did more diagnostics and hooked it up to the machine. Found a consistent misfire on cylinder 8. Mechanic installed a known good used coil and the misfire went away. Told me to drive it for a week and let him know. The charged me $155 for diagnostics. Did not charge me for the coil. I told the mechanic that if the problem stays away I will buy a new coil and return the used coil back to him. So far so good. Drove the car three times and felt nothing. But the real test is in the morning when the engine is cold. That is when it is always present. But I feel good about it this time

Don
 
#75 ·
So I drove the car today and it seems to be almost corrected. The tech told me that he saw a severe misfire on cylinder 8 and a really slight misfire on cylinder 1. So he put the used coil in number 8 and it made the issue go away. He didn't address number 1. So I bought two coils today through Amazon. When they get here I will change out 8 and 1. That should get me to perfect again.

Don
 
#76 ·
Don, You mentioned in Post #64 that you went to the dealer today. They said they scanned it and found nothing that would cause this problem. Then in Post #71, you said well I think we got somewhere today. They did more diagnostics and hooked it up to the machine……... So is this continuation of Post #64 or is this a different dealership? I hope you got it fixed finally.

Don, couple of questions; 1) did your scanner or on-board diagnostics (OBD II) computer pull any codes at all?, 2) Shouldn’t you be looking @ replacing all eight coils instead of just two (I don’t remember that you mentioned the odometer readings on your vehicle)?
 
#77 ·
First diagnosis was with the Tech2 scanner. There was no fault codes using the Tech2. So they went to general diagnostics and started with fuel pressure. After that there was some other machine that I guess graphs ignition. Don't ask me what it is because I haven't seen it. But the tech said it was graphing all crazy with a misfire. So that's when he changed the coil and it quieted the graph down. My car has 65,000 miles on it and I am not yet ready to replace 8 coils at $50 a pop just yet. If they were half that I would do it. Also my scanner showed no codes. It only reads emission codes that would trip the CEL. And the CEL never came on so my scanner said all things were good. Oh and it was the same dealer.

Don
 
#78 ·
I have a little over 130,000 on mine and I guess I have been lucky.
Except for a half case leak that was fixed under warranty it has been pretty much trouble free.
Other than that, it has never had a wrench on the engine or transmission.
No ignition problems or fuel problems ... at least not yet.
It still has the original plugs in it... I probably need to change them...

Jim
 
#82 ·
It varied in intensity. The major symptom was a feeling of the car wanting to drive while my foot was on the brake. Quick misfires in rapid succession. When the engine was fully up to temperature the frequency and intensity died down significantly.

I drovebto work this morning to a butter smooth engine. Issue is completely gone.

Don
 
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