Annoying gremlin with the engine management 4.0 v8

[vitasik]

Merry Christmas to you all brave souls owning Jaguar. 

I have been Jaguar owner for not long. Its a temporary car that is going to be in the family later until its scrapped hopefully in many many years in the future. But saying that I have some problems .....

 

Main problem absolutely brain exploding issue - since 10 days my fuel economy went from 14-16MPG around town to .....8. It has 8 brand new spark plugs. When you trash it at some point in RPM range ( around 3500rpm mark) engine MIL lamp will start blinking ( not light ON, but blink). After 20-30 seconds will go off. Tried several different diagnostics some very high end and only on first hook up it was showing several problems that when cleared wouldn't reappear. I have been running like that for over week now and no new errors were recorded. I am trashing it from time to time hoping this error to be recorded.  And it will not come back whatever it is. 

Initial errors were:

P0171, P0174 ( System too lean on both banks - that is my fault when adjusting LPG on it )

P0303 Missfire on cylinder 3.  (tomorrow will remove 2 spark plugs - one  of them on this cylinder and check are they burning equally)

P11B6 - Unknown

P11C1 - Unknown

P1000 - Something about incomplete system check

I can monitor live data so its not connectivity to ECU. I was driving car and made it blinking MIL and tried reading error codes during that 20 seconds that MIL is blinking.. No error codes detected. 

Another thing I have noticed is a engine juddering between 1500 and 2200 rpm, mainly at higher loads ( line in last 2 gears). That has been becoming quite more evident in the last week driving it. 

 

Any Ideas regarding this subject would be much appreciated. 

[vitasik]

Replying to my own question - today had a play. Spark 3 was drowned in fuel and I compared condition to spark 1. On cylinder 1 used old spark plug ( they were running ok and gap was within spec - 1.3mm) and on cylinder 3 used spark plug from cyl.1. I did resistance test on coils and guess what - coil on cylinder 3 was different to all others. Its design is different slightly as well. On secondary winding it had around 3.6kOhm, when all other coils on that head were with 5.5-5.9kOhms. Seeing its slightly different design fitted that coil on cylinder 1 and tested car - same symptoms  - checked condition of spark plug on cylinder 1 and 3  - now 1 is drowned in fuel, 3 is with normal signs of combustion. 

Verdict -  knackered coil... will see what my local parts suppliers can give me off the shelf as I have 2 cars to pick up with trailer tomorrow from 70m one way. So will need to change coil in the morning, adjust my LPG system accordingly, hook up the trailer and head  on road.

 

Which coil manufacturers you would say will do the job and which are nothing but trouble as there are quite a few on market?

[vitasik]

Hi again

It was indeed coil problem. I got my economy back( if you can call it like that on a v8). Its not juddering any more. As for make got some thing I have never heard before, but it was on a shelf. 

Happy days.