1990 L98 Vibration
Thread Starter
Advanced
Joined: Nov 2016
Posts: 50
Likes: 7
1990 L98 Vibration
HI,
Car has 84,000 miles on it. Just this week the car has shown a new issue. The engine starts normally, idles well and goes into gear normally. While still cold it will drive normally. Once it is warm, if you try to accelerate much beyond 1/4 pedal, the car bucks or vibrates if you will. The car will continue to accelerate but it sure is not normal. Once you hit the desired speed and back off the accelerator, it smooths out. No check engine light.It does not feel like an ignition issue, although I have not ruled that out. Is the cat starting to fail, restricting the exhaust once it is warm? Drivetrain, although again I do not feel as if that is it.
Any recommendations on how to proceed diagnosing this issue?
Thanks in advance,
B
Car has 84,000 miles on it. Just this week the car has shown a new issue. The engine starts normally, idles well and goes into gear normally. While still cold it will drive normally. Once it is warm, if you try to accelerate much beyond 1/4 pedal, the car bucks or vibrates if you will. The car will continue to accelerate but it sure is not normal. Once you hit the desired speed and back off the accelerator, it smooths out. No check engine light.It does not feel like an ignition issue, although I have not ruled that out. Is the cat starting to fail, restricting the exhaust once it is warm? Drivetrain, although again I do not feel as if that is it.
Any recommendations on how to proceed diagnosing this issue?
Thanks in advance,
B
Melting Slicks
Joined: May 2019
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From: Mid-Atlantic
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My '90 has been kind of doing the same thing. I just now, around an hour ago, put a bottle of Cataclean in a quarter tank of gas and ran it almost dry, then refilled the tank. Seemed to stop doing it, for the most part. Still have a bit of a miss every 5 seconds or so, feels like a miss, not sure if it's actually a miss, but very noticable improvement just in that hour. I was getting very responsive acceleration in about twenty minutes, and that was prior to refilling. Gonna check plugs, plug wires and sensors tomorrow.
Last edited by Natty C; Oct 29, 2019 at 04:59 PM.
Melting Slicks
Joined: May 2019
Posts: 3,237
Likes: 1,403
From: Mid-Atlantic
2025 C4 of the Year Finalist - Unmodified
2023 C4 of the Year Finalist - Unmodified
2022 C4 of the Year Finalist - Unmodified
2021 C4 of the Year - Unmodified Finalist
My '90 has been kind of doing the same thing. I just now, around an hour ago, put a bottle of Cataclean in a quarter tank of gas and ran it almost dry, then refilled the tank. Seemed to stop doing it, for the most part. Still have a bit of a miss every 5 seconds or so, feels like a miss, not sure if it's actually a miss, but very noticable improvement just in that hour. I was getting very responsive acceleration in about twenty minutes, and that was prior to refilling. Gonna check plugs, plug wires and sensors tomorrow.
Le Mans Master
Joined: Dec 2005
Posts: 8,574
Likes: 961
From: Communist Colorado
HI,
Car has 84,000 miles on it. Just this week the car has shown a new issue. The engine starts normally, idles well and goes into gear normally. While still cold it will drive normally. Once it is warm, if you try to accelerate much beyond 1/4 pedal, the car bucks or vibrates if you will. The car will continue to accelerate but it sure is not normal. Once you hit the desired speed and back off the accelerator, it smooths out. No check engine light.It does not feel like an ignition issue, although I have not ruled that out. Is the cat starting to fail, restricting the exhaust once it is warm? Drivetrain, although again I do not feel as if that is it.
Any recommendations on how to proceed diagnosing this issue?
Thanks in advance,
B
Car has 84,000 miles on it. Just this week the car has shown a new issue. The engine starts normally, idles well and goes into gear normally. While still cold it will drive normally. Once it is warm, if you try to accelerate much beyond 1/4 pedal, the car bucks or vibrates if you will. The car will continue to accelerate but it sure is not normal. Once you hit the desired speed and back off the accelerator, it smooths out. No check engine light.It does not feel like an ignition issue, although I have not ruled that out. Is the cat starting to fail, restricting the exhaust once it is warm? Drivetrain, although again I do not feel as if that is it.
Any recommendations on how to proceed diagnosing this issue?
Thanks in advance,
B
Thread Starter
Advanced
Joined: Nov 2016
Posts: 50
Likes: 7
Hi,
As far as I know they are the original injectors. I am planning to do a full "tune-up" this weekend to start with, including a new fuel filter. I have only had the car for a year, so I do not have much history on it.
As far as I know they are the original injectors. I am planning to do a full "tune-up" this weekend to start with, including a new fuel filter. I have only had the car for a year, so I do not have much history on it.
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Thread Starter
Advanced
Joined: Nov 2016
Posts: 50
Likes: 7
Update:
HI,
Car has 84,000 miles on it. Just this week the car has shown a new issue. The engine starts normally, idles well and goes into gear normally. While still cold it will drive normally. Once it is warm, if you try to accelerate much beyond 1/4 pedal, the car bucks or vibrates if you will. The car will continue to accelerate but it sure is not normal. Once you hit the desired speed and back off the accelerator, it smooths out. No check engine light.It does not feel like an ignition issue, although I have not ruled that out. Is the cat starting to fail, restricting the exhaust once it is warm? Drivetrain, although again I do not feel as if that is it.
Any recommendations on how to proceed diagnosing this issue?
Thanks in advance,
B
Car has 84,000 miles on it. Just this week the car has shown a new issue. The engine starts normally, idles well and goes into gear normally. While still cold it will drive normally. Once it is warm, if you try to accelerate much beyond 1/4 pedal, the car bucks or vibrates if you will. The car will continue to accelerate but it sure is not normal. Once you hit the desired speed and back off the accelerator, it smooths out. No check engine light.It does not feel like an ignition issue, although I have not ruled that out. Is the cat starting to fail, restricting the exhaust once it is warm? Drivetrain, although again I do not feel as if that is it.
Any recommendations on how to proceed diagnosing this issue?
Thanks in advance,
B
Since it looked to be running lean, I decided to go further, removing intake plenum and runners. Someone before me had obviously been in there, several fasteners were loose, resulting in air intake leaks that could explain the lean condition. Cleaning everything, installing new gaskets for runners and the throttle body. Last but not least I will change the fuel filter as well.
Hope to have it all back together in 2 weeks and running better.
Anything else I should check at this point?