This thread from the archive should be helpful:
I have just picked up my XJ8 from the workshop. I have been chasing similar high revs on start up and rough running until warmed up. It ran perfectly after warming up. Problem has turned out to be Capacitors leaking in the ECU. Maybe something similar on yours.
Regards
Kirweekid.
How did it run after you warmed it up for 30min, turned the car off and then started it again? Because my car alwways ran rough, even after if was warmed up. Oh and where is the ECU located and can it easily be opened to inspect the PCB for obvious damage? I just wanna check mine in the future.
Thanks MIke_Stone. I ordered a new MAF, luckily they arent expensive (65 Euros). 5v and 12v definitely are present at the connector. And i couldnt indicate a loose connection in the wireā¦
I will update you all when it arrivesā¦
Car ran fine after warmed up. Started fine all the time afterwards. ECU on the xj8 is fitted under toolkit panel. It had to go to a specialist to repair.
hmm seems like a different issue like I had then, cause it always idled badly for 30-60seconds even after it ran for 1 hour.
Hmm now where is the toolkit panel xD
XJ8 has nothing in common with your XJ40 other than four wheels.
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If you have the xj40 (I have an x308) Iām not sure where your ecu is fitted. Maybe someone else on the forum may be able to help with that.
LOL and IIRC even those are different sizes
Marmo ā¦
Hereās a picture of the ECU that I grabbed off the internet (it looks a bit beaten up).
On my '89 itās located under the dash just to the right of the console ā¦ and hereās a video on removing it (OK not in English but youāll get the general idea).
Thanks Grooveman the ecu looks pretty sealed, so i will probably leave it be in peace
I just checked the connections again for looseness and checked the voltages while the car ran at idle (runs great now, just really rich because of the bad MAF)
With the MAF connected and the car running i hadā¦ (it starts pretty good now btw after installing the IACV new. the old seems to have had a loose bearing or too much wiggle roomā¦)
14v at pin 9 ā should be ok
2.2v at pin 12 ā should be ok
0.2v at pin 7 ā problem, right?
I really hope the new MAF comes soon and fixes the problem.
DO you think cleaning the old maf would help with this pin 7 situation? What has to go wrong in the MAF so that pin 7 wont put out the correct voltages? I cant see any damage at all. also opened the 2 screws where the connector connects and i could not see ANY corrosionā¦
Cheers Marmo
The new MAF from china via Aliexpress just arrived (took just 10 days)
It looked really the same like the one installed.
I swapped it out and voila, after so much pain the car idles good and doesnt gulp down fuel anymore. There is no CEL anymore!
So it seems like my issues were: bad MAF, bad IACV, rotten fuel rail.
What is weird is that the old maf had a DIY wire attached to the metal housing and going into the wiring harness nearby. is probably was a ground the previous owner attached. i just connected the new maf without this wire attached to the metal body and it worked.
why would the previous owner do such a thing?
Did you try disconnecting that wire from the old MAF to see what happened?
actually im NOT sure if i did that, cause it ran for 4 months with that wire onā¦
maybe i will see if the old one works without the wire.
but the new maf was only 50$ anyways and it looks waaaay better now since it all new and shiny
Any idea why such a wire would be there tho?
No idea. If it was attached to only the body my guess would be (as you did) it was intended to serve as a ground. Dunno.
weird. well i hope the new maf keeps working as intended. gotta adjust the idle speed again with the screw as it was rather low after the fix.
but now im back at 10liters/100km or 23-24mpg instead of the 14-15 liters/100km
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