Hi.
I've had this issue for almost a year now. Went to 3 or 4 shops and they found nothing.
When downshifting manual gearbox, mostly at turns or red lights, sometimes rpm drops way low to 400 rpm or even stalls the engine while the car is moving. Here is a video going downhill in serpentines, down shift from 4th gear:
A significant change occured 2 months back, when I used throttle body cleaner from Liqui Moly. Now problem occurs mostly when downshifting mutiple times in short order while decelerating.
Before that the issue was significantly larger: rough starting, rough idle, stalled very often while driving.
What I did in the last 9 months:
cleaned MAP sensor and later replaced it
cleaned IAC valve and later replaced it
new air intake temperature sensor.
new rocket cover gasket, intake body gasket, 4x intake seals.
Fuel injector cleaner from Liqui Moly
disassembled injectors, tested resistance (fine), tried water splash for leaks in the area of injectors and intake seals while the car was idling
I used the screwdriver test on injectors to hear them open and close, all 4 performed the same way
The car only has OBD1.5 that tells you very little. But nothing on any diagnostics in any of the shops.
1.5 years ago I changed all filters, engine oil, coolant, brake fluid. Last year I partially changed power steering fluid (sucked/filled reservoir, no noises from there, I did it for maintenance only after 20 years)
Other symptoms:
rpm drops only happen with hot engine
with cold engine the car feels stronger in terms of powersteering (it's 20 yo 55kW engine so it sometimes struggles while steering)
when the car idles (stationary), it idles steadily.
when driving, the car behaves normally but I feel like in the last year it lost some power especially in hills climbing
There are some oil spots in transmission area, but no dripping
I can't hear any wierd noises from the engine bay
Any ideas?
