Misfire help ASAP
#21
Join Date: Mar 2008
Location: Pacific Northwest USA
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FWIW....
IMHO this (and most others used XJSs out there, really) would be a prime candidate for "cleaning the vee". Remove everything in the Vee, clean it, repair/replace all wires and vacuum hoses, new fuel hoses, new FI harness, new plugs-plug wires-dist cap-rotor, repair distrubutor vacuum advance and mechanical advance, reseal cruise control bellows, new intake and cam cover gaskets, clean throttle bodies, new throttle businhgs, synchronize throttle linakges, etc. Get it all in one big shot.
Cheers
DD
IMHO this (and most others used XJSs out there, really) would be a prime candidate for "cleaning the vee". Remove everything in the Vee, clean it, repair/replace all wires and vacuum hoses, new fuel hoses, new FI harness, new plugs-plug wires-dist cap-rotor, repair distrubutor vacuum advance and mechanical advance, reseal cruise control bellows, new intake and cam cover gaskets, clean throttle bodies, new throttle businhgs, synchronize throttle linakges, etc. Get it all in one big shot.
Cheers
DD
#23
#24
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That's not too far off.
You can adjust the timing with the cam-screw on the side, but if you take the cap, rotor, dustcap off you will see 3 allen screws that hold the dist in place and there is some adjustment there as well.
Before you mess too much with it, do yourself a favor and fix the wires first! I thought my timing was messed up and screwed with it for quite a while before I found it was in the wiring!
You can adjust the timing with the cam-screw on the side, but if you take the cap, rotor, dustcap off you will see 3 allen screws that hold the dist in place and there is some adjustment there as well.
Before you mess too much with it, do yourself a favor and fix the wires first! I thought my timing was messed up and screwed with it for quite a while before I found it was in the wiring!
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M90power (03-19-2012)
#25
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If you have an XJS, this is the book to have, should give you a lot of help with your car.
Hope you like reading, it is 700 pages, and is an incredible project to help Jaguar owners.
Free download
Kirby Palm's Jaguar XJ-S Help Book
good luck
Pete
Hope you like reading, it is 700 pages, and is an incredible project to help Jaguar owners.
Free download
Kirby Palm's Jaguar XJ-S Help Book
good luck
Pete
#26
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#28
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On the other hand, it is very easy to get a plug wire wrong, or forget they go anti-clockwise!
Greg
#30
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Welp, thanks to Mish ive got the new injector in for 2a and the Jag is officially running on all 12. its idling a little bit smoother and runs about 8.3% stronger.
its still running REALLY rich and it cuts out if you give it too much throttle. its much worse if you reconnect the Vacuum ECU hose. so no improvement outside of the small performance increase the 12th cylinder makes.
its still running REALLY rich and it cuts out if you give it too much throttle. its much worse if you reconnect the Vacuum ECU hose. so no improvement outside of the small performance increase the 12th cylinder makes.
#31
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This really sounds just like the symptoms I had with mine. No matter what I did I could not get it to run any leaner. Once I replaced the brittle wires it was like a totally different car. Considering how the wires to the ATS and CTS in your picture look like they've been messed with, I'd suggest starting with those and replace them back to where they come out of the fender.
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M90power (03-21-2012)
#33
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#38
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Another thing you should really need to check is the TPS under the throttle "capstain". They're known to go bad and if yours is telling the ECU that the throttle is wide open at idle, it could be running rich for that reason!
Check TPS voltage at the square 3-wire connector where it come out from under the capstain. Unplug it just a tiny bit so you can see the metal connectors and with the key on, engine NOT running, probe the red and yellow wires. It should read about .32-.35v at idle position and 4.8-5.0v at full throttle position. Voltage should increase smoothly as you open throttle.
I'd like to take credit for all this info, but honestly it's all gleaned from Grant and Doug!
Check TPS voltage at the square 3-wire connector where it come out from under the capstain. Unplug it just a tiny bit so you can see the metal connectors and with the key on, engine NOT running, probe the red and yellow wires. It should read about .32-.35v at idle position and 4.8-5.0v at full throttle position. Voltage should increase smoothly as you open throttle.
I'd like to take credit for all this info, but honestly it's all gleaned from Grant and Doug!
#39
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the original owner told me the TPS was the only thing he hadnt replaced. not only had he not replaced it but he removed it from the throttle capstain and laid it aside. it does have a small effect on the idle when opened or closed and when i put it back on the throttle capstain it didnt seem to run any better. its also missing a wire that should be going to the middle pin.
also i have to let off the throttle for the transmission to upshift. if this was on either of my Grand Prixs there would be no doubt in my mind that it was a TPS issue. however, i have no idea if the V12 TPS controls shift points.
also i have to let off the throttle for the transmission to upshift. if this was on either of my Grand Prixs there would be no doubt in my mind that it was a TPS issue. however, i have no idea if the V12 TPS controls shift points.
#40