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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
 
#38 ·
Okay here goes. This morning I removed the intake manifold. Cleaned the mating surfaces and installed new gaskets. Replace the plenum. Replaced both knock sensors, the crankshaft position sensor, the camshaft positiin sensor, replaced the wiring harness for these sensors and thoroughly cleaned the throttle body. Problem solved. Hopefully this isuue doesn't return.

Don
 
#40 ·
So this morning I am driving to breakfast and I notice my issue is still there. But it is way less than before. Before it would "surge" about every ten seconds or so. Now it is sporadic at best. When I say surge I mean a drivetrain surge not an engine surge. The RPM's do not raise when this is happening. If anything the RPM's might be dropping a little. But it isn't visual on the tach. So I decided to clean the MAF since I hadn't done that. After cleaning still no change. So the only thing I am left with is maybe an injector issue or maybe a transmission issue. I might just bring the car to my local $$$$dealer$$$$ to get a diagnosis done.

Don
 
#42 ·
Don

Can your scanner do IAC counts, throttle angle? Check the IAC counts, throttle angle and map cold and hot. Match them up.
If the IAC counts and map are high or throttle angle is open excessively in comparison this may be a result of high engine load
and a torque converter and or stator support shaft may be a problem.

Can your scanner read trans temp. The trans oil cooler outlet line (the upper one to the rad cooler)
Is it real hot also do you loss of power when it happens?

One other thing have you done a Crankshaft Position Variation Learn?
 
#43 ·
Unfortunately my scanner doesn't cover those. I read up on the crankshaft position sensor learn procedure and it basically said to let the car idle for a bit, wide open throttle it until the cut off kicks in, and let it idle a bit before turning the engine off. I did this with my '02 Seville a long time ago and never had an issue with the sensors. So I assume all is well with that. I hate to do it but I think the dealer is my only hope. I would buy new injectors and see if they fix it but the cheapest price I found was about $30 apiece. If it is an injector I would assume the dealer will be able to pinpoint which one it is. Plus I guess they can make the Tech 2 force the sensors to do what they do. And if that doesn't work then I guess it would be a bad part. I will sleep on this and figure out what action I should take. I definitely will not be taking the car to the dealer before Saturday

Don

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Oh and I do not lose power at all. Aside from the issue the car runs as it should. The issue is only at idle. Once the throttle is pressed all is well again. Even when I am driving at speed and I lift off the throttle I do not feel any issue

Don
 
#45 ·
I have changed everything but the throttle body gasket. The throttle body is mounted to the crossover. Does coolant run through the throttle body? Is there a possibility that the gasket is shot and allowing some coolant into the engine? Just a thought

Don

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Okay after seeing the throttle body gasket my idea seems ridiculous. But I guess that changing the gasket may not be a bad idea. It just might be the cheap thing that has been causing the issue. I always seem to forget the cheap simple things. I will update after the install

Don
 
#46 ·
For the price of one hour diagnostics I decided to purchase 4 injectors and a throttle body gasket. With the previous cash spent on parts so far I think I am still ahead of the game. Remember reading someone paid $500 for a plenum install. I did that and a whole lot more and I am not even close to that yet. So hoping once again that this will gitterdun

Don
 
#51 ·
So I changed the throttle body gasket. No change. I then changed the four right side (rear) fuel injectors. So far so good. But like once before I will hold elation until I drive it awhile. Happened before that I thought I was golden only to be disappointed a morning later. I will update tomorrow.

Does anyone know if it is possible to bench test the injectors? Would like to know if they are malfunctioning or just needing cleaning

Don
 
#53 ·
My issue never affected RPM's. They always stayed constant. It happened cold or hot didn't matter. But by changing the 4 injectors I seemed to knock my problem down by 90%. So I think I am going to change the other 4. I still feel the "lurching" but nowhere near as often and it feels like a 10 year old is pushing the car instead of Goliath. I tested the 4 injectors I replaced and it seems that one of them tests out of spec. So since I have the problem still, albeit only slightly, I think I may have another injector starting to get out of spec.

Don
 
#54 ·
Received and changed out the remaining 4 injectors. I will find out on the drive to work tomorrow morning if the issue is gone. I checked the old injectors and found them all to be in spec. But one seemed quite a bit dirtier than the others. So if the issue is indeed repaired I will blame one bad injector and a dirty fuel system. If it isn't repaired I am well on my way of having a lot of new parts on my engine that still is acting up

Don
 
#55 ·
Update: My problem persists. But it seems to only happen on a cold engine. So I decided to do a computer reset. I disconnected the negative and positive battery cable. I touched the two cable ends together for half a minute. Left the cables disconnected for 30+ minutes. I will see how things go when I drive to work in the morning. Another strange thing. When I started the car after the battery disconnect my stereo still had memory. My stations still were there and the time was still accurate. Also my memory seat was still set. Is this stuff that is downloaded into the computer or is there some secondary memory battery somewhere? Never had that happen before

Don
 
#56 ·
After installing a new battery my station pre-sets were still there but the time had to be re-set. Service tire pressure monitor came on but re-set itself the next day. Drivers window express up is gone. Down & passenger down & up still works. Haven't gone in the book to figure that out yet.
Norm
 
#58 ·
UPDATE: Changed the MAF yesterday with no change. Then I installed a new EGR this afternoon. So far so good. Have taken three "run around" trips and have yet to feel the issue. There was lots of stop and idle in these trips and seems to be repaired. I will update again in a week if all goes well. I will update sooner if the issue is still there.

Don
 
#63 ·
Not to be nasty, but by now have you spent enough time (at whatever dollar-amount you rate your time worth) and money on parts (sounds like a bunch) for it to have been worth a trip to your dealer to get the codes read in the first place?

I'm the type that once they started putting plastic covers over the engines said "enough already" and paid to get it done. Not that I didn't know then (I took the cylinder head off a straight-6 - decoked it - and it started first time) but I sure know now that if I can afford a Caddy, I can afford to get it fixed by folks that have all the diagnostic and restorative tools...
 
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