Hi,
im currently in a slow and long process of finding a issue with my V12 xjs. Especially with a cold engine it runs idle very inconsistent and when using the throttle while driving it sometimes feels like its dying before suddenly picking up. It also stutters a lot at that time. I've checked/replaced:
- checked all the vacuum lines (disconnected the fuel temp switch on rail)
- checked throttle valves on play and setup (installed the teflon spacer to clear play on throttle rods)
- replaced coils
- replaced fuel pump
- replaced ignition with rotor
- replaced leads and spark plus
- replaced fuel pressure regulators

Next stop is checking/cleaning all the injectors and replacing all connectors and hoses.

Anyone some more suggestions since the injectors will be my last option in resolving the issue.

Many thanks for any reply !!!

 

Have you tested the throttle position sensor (TPS)? That can lead to your issues. The TPS should vary resistance smoothly throughout its travel with no jumps or dead spots. It also needs to be adjusted properly for a smooth idle. There are some details on the process in Kirby Palm's BOOK.
Also test for vacuum leaks with a smoke machine. Vacuum leaks will play havoc with the fuel injection.

Jon

 

Hi Jon,
great tips, haven't looked at the TPS yet. But will definitly look into it first thing. Found the topic in Kirbys manual with the values as well. Many thanks.
not sure yet how testing the vacuum with smoke works but will also dive into that.
will post some updates soon.

 

I strongly suggest adding your location to your Sig.

These Marelli cars had different specs for different markets, although the basics stayed the same.

I would be more concerned with:
Spark plugs, age and gapped correctly
HT leads, all 14 of them.
Rotor integrity, bearing in mind the well known Marelli rotor issues.
TPS, already covered.

ALL, and ANY electrical connector. Unplug, CLEAN, replug.
Engine earth straps at and around the LH engine mount bracket. 2 straps involved here.

Injectoirs, nah, I have never had Injector issues on any Infected car, ever.

I wioy