my 1985 xj6 is getting way too much gas. went out to it one morning to find it smoking badly and not having any power. plugs were black and dripping. i cleaned plugs up depressurised fuel system and ran sea foam through system and can drive around but do get a choking at higher speeds and idles about 1800. from reading and conversations i understand there are numerous possible causes where should i start looking and how do i test various sensors, relays, afm, etc. any help and advice would be gratefully appreciated as i have limited funds and time

cheers

 

Here's some basics infor
XJ6 Series - EFI Rich Mixture

If the problem occurs primarily on a cold engine....
XJ 6 Series III 4.2 - Cold Start EFI Overfuelling


Post back with any questions

Cheers
DD

 

overfueling could also be caused by a faulty fuel pressure regulator or broken diaphram inside the regulator (the metal canister bolted at the end of the fuel rail). at 50-70$ it's not a terribly expensive component to replace. I'm not sure if that would cause the hesitation at certain RPMs which you are having but I know it's at least a proximate cause of overfueling in some cars and my engine smoothness at all acceleration levels (especially at idle and the shift from 2nd to 3rd) improved substantially upon replacement.

However, You said you came out one morning at it had this problem which might imply Doug is on the right track (no shock there) in posting the link to the Cold Start diagnosis since it seems to be controlled by the time of day/temperature more than by any performing variables or recent engine changes.

 

firstly thank you for the input. i have tested the coolant temp sensor not sure how accurate my results would be, but indicate that the sensor is not working correctly, at about 32f i got reading of 6.1 and ohm values were consistently higher than should be according to the table, at 212f i got a reading of 0.38

 

ok i know this is slow progress but very little time lol! first thing i did was replace the oxygen sensor, wow what a difference it bought the idle speed down about 500 rpm and got rid of any fluctuations, now all i had to do was wait patiently on my ordered temp sensor to come in, and wait and wait and wait. when it eventually came in i was like a kid in a candy store immediately putting it in, oh no my revs are back up, so now what? has something else come into play? the temp sensor is good as i have since bench tested it.