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Discussion Starter · #1 · (Edited)
Idle has managed to go high on my -98 lt, approx. 12-1500 rpm.
Has followed a bit of extra with the last time and it's after the engine has gotten hot and I've driven a few miles, and then it seems like it goes down to normal rpm when the car is standing still/wheels not turn. Otherwise it starts okay and normal, no cheating electricity The damper housing, lmm, idle engine is cleaned and tps "clicks".
Changed.
Idling valve
Air mass sesnor
Temp sensor for ecu
Throttle pos. switch
Vacum hoses on intake manifold
Fuel ecu
Crank sensor
Abs/speed sensor on rear axel
Cleaned up throttle house
Repalced the ecu with an used on with new ecotrim chip inside

When I shut og the engine and start it up again the problem is not there until the car has been shut of for aprox. 6-7 hours, depend of the outside temp. The problem seems to increase when outside temp is low from aprox. +5 C and lower. The problem comes after driving to the engine temp gauge shows about 1/4 warmed up.
In the winter time when I use the electric engine heater (230 V ac) and the engine i a little bit warmed up the idle is normal.
It is a very old thread on this forum were the car is acting exactly like mine.
Hope there is someone who can help with this irritating issue.
 

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Discussion Starter · #2 ·
Has begun to suspect that it is the Lambda probe that plays with me. Have ordered it now, it's probably the only relevant sensor I have not replaced.
 

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Discussion Starter · #3 ·
Have replaced oxygen sensor, but still the same problem.
Is there anyone who can tell me what task the relays beside the abs pump have?
 

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Old thread but did you ever solve the issue? I have the exact same issue and it drives me crazy.

Skickat från min SM-G950F via Tapatalk
 

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Discussion Starter · #5 ·
Hello.
I feel I have solved the problem approx. 90%. The last, and most successful, thing I have done was to replace the ptc nipple. It has original Volvo part number 1357352. I will not be near the car until 4-5 days, but I think I remember that it is on the hose between crankcase ventilation and hose between turbo and air flow meter. It cost no more than approx. $ 30 at Volvo dealer. The reason I changed it was that I suddenly discovered an electrical contact on it to become curious if it could have an effect on idle. I compared the ohm values ​​of the old and new nipples, and there was a marked difference. As mentioned, I only feel 90% successful, this is because if I start the engine and drive immediately, idling is 100% normal, but if I wait about 20 seconds to drive, after starting, idling can return to abnormal state again. The next thing I plan to do is replace the air flow meter. I did this at the beginning of the troubleshooting, without success, but that was before I was aware of the learning function on the LH 2.4 Jetronic, so I suspect that I did not give it enough time to adjust to the new air flow meter. Regardless: The new ptc nipple I put on had, in my experience, definitely an impact on the problem. I will try to keep in mind to update on this forum when I see the effect of the replacement of the air flow meter.
 
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