Hey community. I love my 2001 xj8 a lot. 300kkm.. Engine has about 180k..
Now we have some problems.
It started 2 years ago with tps sensor error and oxygen errors. I Googled a lot and cleaned the throttle body and contacts. Went away and she ran smoothly for years and km.. I knew the oxygen sensors were bad. The exhaust was off and they thru errors. She drove perfectly tho and milage was good.
Then first the idling became a bit rougher.. Then sometimes she stalled when going steady at around 100km pH.. Then it got worse and when I went 180km pH once and turned off the ac she went into restricted engine program. Turned off reset and went again.
Idling reaming bad I let the ship change the o2 sensors. And got approved tüv.. MOT..
Now when idles wuum wuum. Like a sinus curve. And when I accelerate slowly it's smooth.
As soon as I give more.. She goes up and down....

Any ideas? I just changed the tps.. Thought that can help and I had one spare ever since.
Same.

Thnx

 

Any codes in ecm after o2 sensor replace? Sounds like its running lean.

 

No codes at all. That's the thing. Drove a few hundred miles. Maybe a vacuum leak? It might rather run rich. Have the feeling she needs a bit more fuel..

 

to my mind a sine wave-like idle is caused by an air leak or lack of steady fuel. Try changing the fuel filter, check the fuel pressure at the rail (may be a bad fuel pump), clean the throttle bore and plate, check all hoses for tightness, run a good brand of fuel system cleaner through a tank . . .

 

Worth looking at the fuel trims if you can, especially at idle. Should be steady and close to zero.

Also check it's running CL (closed loop), of course.

And that all the OBD monitors are set. Each one not set will mean many codes cannot flag.

 

Thanks for the input.
Can you please help me on what you mean by checking fuel trim?
Is this an obd reading? Same CL?

I had replaced the tps and now the air sensor as well. It feels like it's having an impact but still misbehaving. But not constantly. Worst idle is when the car is warm and was sitting off for a bit. Then restart. Very umm umm. Cold start with a bit of choke it feels good. Also sometimes in between after a highway tour it feels better..

Thnx
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Fuel trims - use OBD live data (& web searches!).

CL = closed loop as I put

C'mon I don't expect to google things for people!!
https://en.wikipedia.org/wiki/Closed_loop