SL/R129: 91' SL500 revs up and down periodically
05-03-2023, 03:56 AM
#26
Great new indeed. Thanks for feeding back the solution. These engines can take a lot of fine tuning before they get back to perfect. A good specialist is important. The guy I use when I get stuck spends most of his time on R129's. Experience is key.
The other area that causes niggling idle problems is the breather hoses. I replaced mine recently - easy DIY job and it made a big difference. Next job is to replace all 8 fuel injectors and related seals, which are leaking air also (I did a smoke test) and I believe the injectors are leaking fuel causing warm start struggles...
The other area that causes niggling idle problems is the breather hoses. I replaced mine recently - easy DIY job and it made a big difference. Next job is to replace all 8 fuel injectors and related seals, which are leaking air also (I did a smoke test) and I believe the injectors are leaking fuel causing warm start struggles...
Last edited by darraghn; 05-05-2023 at 04:32 AM. Reason: typo
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dolucasi (05-03-2023)
05-11-2023, 05:01 PM
#27
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Hello together,
Issue FIXED.
So the ECU was definetly failed, it was a good choice to change it, but after there was still a long way to go with this high idle issue in P and N, but at the end it was resolved.
Basically after, reading endless forums and trying out various things I decided to take it to a high reputation mechanic specilazied for old cars, with experience in KE jet since the begininngs.
According to his explanation various reasons led to the behavior:
So for us there was one big takeaway from the story, we were really suspecting the mixture screw from the begining and also there was at the end(after changes) no more failed component left in the system. But we were still unable to resolve the issue without proper equipment and knowing the values, it is very very difficult.
Now the car has a very good idle 600 rpm and just sightly increases while in P and N (~700rpm). Drivin, testing very good behaviour. Also the mechanic told it is basically perfect as new. Hope he wont be wromg on the long run
I m still greatful for the answers here we proceeded a lot.
I saw a lot of other threads around and I believe this can be a good hint, to look out for a diagnostics specialist because the issues might be just fine tuning, but still quite hard to resolve without proper equipments.
Hope it helps someone in the future, and I m looking forward for the summer to drive the car.
G
Issue FIXED.
So the ECU was definetly failed, it was a good choice to change it, but after there was still a long way to go with this high idle issue in P and N, but at the end it was resolved.
Basically after, reading endless forums and trying out various things I decided to take it to a high reputation mechanic specilazied for old cars, with experience in KE jet since the begininngs.
According to his explanation various reasons led to the behavior:
- Someone messed with mixture screw --> mixture was lean
- After changing the ICV, it needed to be fine tuned. It happens a lot in his experience. Even sometimes with MB parts.
- Added 3dl transmission oil
- Transmission cable needed to be fine tuned with some centimeters, was a little loose.
- There was one tube stucked, but I did not catch which one unfortunetly.
So for us there was one big takeaway from the story, we were really suspecting the mixture screw from the begining and also there was at the end(after changes) no more failed component left in the system. But we were still unable to resolve the issue without proper equipment and knowing the values, it is very very difficult.
Now the car has a very good idle 600 rpm and just sightly increases while in P and N (~700rpm). Drivin, testing very good behaviour. Also the mechanic told it is basically perfect as new. Hope he wont be wromg on the long run
I m still greatful for the answers here we proceeded a lot.
I saw a lot of other threads around and I believe this can be a good hint, to look out for a diagnostics specialist because the issues might be just fine tuning, but still quite hard to resolve without proper equipments.
Hope it helps someone in the future, and I m looking forward for the summer to drive the car.
G
