Engine Dropouts?
Thread Starter
Instructor
Joined: Jan 2006
Posts: 109
Likes: 0
From: Fremont CA
Engine Dropouts?
I get dropouts on my 93 between around 1000 and 2000 rpms with load and heat, like going up a hill in summer. It's tough to explain, but basically, it is as if the engine stops pulling. It gives me a 'thunk' that jerks the car, and the rpm's drop briefly.
I thought at first that this was a transmission problem, in that not engaging automatic overdrive seemed to help, but further testing showed me I could get it to happen in normal drive as well. Seems based on rpms and load, and is MUCH worse when it's hot.
Anyone experienced this before? My guess at this point is fuel, either filter or pump. Anyone had similar problems? What did the problem turn out to be?
I thought at first that this was a transmission problem, in that not engaging automatic overdrive seemed to help, but further testing showed me I could get it to happen in normal drive as well. Seems based on rpms and load, and is MUCH worse when it's hot.
Anyone experienced this before? My guess at this point is fuel, either filter or pump. Anyone had similar problems? What did the problem turn out to be?
Intermediate
Joined: Jun 2006
Posts: 30
Likes: 0
From: Orlando Florida
No joke!
I have an '89, but my cousin just bought a '93 with the same problem. We replaced the fule filter at someones suggestion, but still no luck. We are as baffled as you. Let us know if you find anything out and we'll do the same!
-É!
-É!
Safety Car
Joined: Jan 2006
Posts: 3,566
Likes: 4
From: Mt Laurel NJ
St. Jude Donor '06-'07
I hear you
I have a 90 coupe that just starting having the same problem; when I take my foot off the gas to slow down, if will sometimes buck and/or make a clunging sound. Last night, I was driving and the check engine light came on; When I got to were I was going, I turned the car off and restarted it, and no check engine light for the rest of the night.
I am going to change the fuel filter and try to get the code it set, and will report back.
Thanks, Randy
I am going to change the fuel filter and try to get the code it set, and will report back.
Thanks, Randy
Burning Brakes
Joined: Feb 1999
Posts: 1,157
Likes: 3
From: Encino CA
Do mean like a miss or buck? I had fought a problem like this on my 95. Symptoms were miss under load at low rpms and it would happen going up a hill in overdrive or sitting at idle with ac on. The first time around the dealer changed opti and wires but it came back after a while. Dealer then changed opti again and plugs but it came back after a year or so. I replaced the coil and the problem mostly disappeared. Then brought the car in to a local shop to install roller rockers. At the same time he changed wires and the fuel filter. Car has been better than new since then.
I'm willing to bet you get a bunch of responses telling you to change the opti but that seems to rarely be the solution. You can have several hours of enjoyable reading if you do a search on "missing" or "stumbling", etc. in the forum. There are some who ended up replacing everything but the kitchen sink and the problem was still there. Sometimes is is merely a bad connection.
Good luck in chasing down your problem.
Doug
I'm willing to bet you get a bunch of responses telling you to change the opti but that seems to rarely be the solution. You can have several hours of enjoyable reading if you do a search on "missing" or "stumbling", etc. in the forum. There are some who ended up replacing everything but the kitchen sink and the problem was still there. Sometimes is is merely a bad connection.
Good luck in chasing down your problem.
Doug
Pro
Joined: Jul 2005
Posts: 735
Likes: 0
From: Glasgow Va
Try new spark plugs.My 93 was doing the same thing.It would buck and jerk under a hard load or just going up hill with the ac on.I pulled the plugs and the gap had opened up to around .065.With new plugs it does great no problems with hard loads or hills.
Burning Brakes
Joined: Feb 1999
Posts: 1,157
Likes: 3
From: Encino CA
I should have mentioned that at the same time when I replaced the roller rockers, springs, fuel filter, and wires, I also had the guy repair an oil leak that was coming from the rear of the intake manifold. I had this leak for some time and this is apparently a chronic problem for LT1. I'm not all that engine-savvy but it could be that the leak was leading to poor performance (vacuum leak?).
Instructor
Joined: Aug 2002
Posts: 246
Likes: 18
From: Menlo Park CA
I had this same problem a couple of months ago and decided to clean my airfilter. I have a K&N filter and the filter box is cut out. I had been in a dusty area a couple of times and so thought that this might have something to do with the stumbling.
Well amazingly, it took care of the problem. I'm not sure if it was just coincidence or if the filter was just really dirty since I have the cut out airbox. You might try this a solution.
Good luck.
Well amazingly, it took care of the problem. I'm not sure if it was just coincidence or if the filter was just really dirty since I have the cut out airbox. You might try this a solution.
Good luck.
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Pro
Joined: Jul 2005
Posts: 735
Likes: 0
From: Glasgow Va
If the fuel filter does not do it I would pull a plug and check the gap.The AC Delco Platinum plugs are famous for the pucks falling off and opening the gap up.A lot of people here have had this happen and they were missing on about all of my plugs.I have heard of this happening on low milage cars as well.
