Vacuum leak on my 04 XJ8, was those eight pesky gaskets, in the intake manifold.
No issues except the C E light would come on.

 

So the car kept going into restricted performance mode still when started from cold. I've been checking for fault codes and there was nothing showing - not even pending codes. However yesterday morning when it went into RP on starting it was running even rougher than before. I checked for fault codes and it had P0207 as pending. I've cleared the pending code and it now keeps throwing P0207 as pending every time I start the car from cold. If I drive the car for a while with RP and then stop and start the car the codes seem to clear and RP disappears which I find strange. I took it for a long drive yesterday and after a long amount of driving it did go back into RP and then actually threw a registered fault code - again P0207. I've started the car this morning and it has once again gone into RP with the pending fault of P0207. I drove the car to work, filled up with fuel oh the way and then started the car and no RP - it had gone. I drove the next 50 miles with no RP and the car drove perfectly (apart from the engine vibration still at about 1400 RPM).

Since cleaning the MAF, when the RP is off, the car does drive so much better. It does not seem to hesitate on acceleration, it no longer lurches in cruise control and the engine at idle is now almost silent and with almost no vibration.

Just now got to get out the multimeter and test that injector and harness. I had an injector fail a while ago, the one next to this one in fact, injector number 5. When that went it was an open circuit but displayed the fault code all the time. This problem seems to go away when warm possibly so it could be the injector starting to fail.

If it is a failed injector then it would not explain the rich running on the other bank but I'll deal with this first and then look at possibly replacing those intake gaskets. I might do them at the same time, it's just if I have enough time to spare to do it all at the moment.

Thanks,

Chris

 

Hi Chris,

Here are the definition and listed possible causes of P0207 from the 2003.5 DTC Summaries:




Based on the above, you might start by checking the electrical connector and wiring to the injector at cylinder 7. If you have a noid light or if your meter has a duty cycle setting you could check for a plausible drive signal at the injector connector while the engine is running. If that looks good, you could check the DC resistance across the injector pins and compare it to other injectors on that bank.

Cheers,

Don

 

Hi Don,

Thanks for this. Yes I'm going to start with checking resistance on the injector itself. I did this last time when I had an open circuit on injector 5. I still have the OHM readings from then for the other injectors so I know what to expect. I think they were 14.7 or 14.8.

If the injector resistance is ok then I'll start checking the connector and the harness itself.

Hopefully it's just the injector. If it is then I'll check the cabling further when I'm in there replacing it just in case there is some short occurring in the harness.

Thanks,

Chris

 

Hi all,

The problem is definitely injector 7 is open circuit (no resistance across it). The fault code p0207 is now present all the time and the RP is on all the time now. I think the injector has been partially working and starting to fail which is why the faults and the RP were intermittent. Just ordered a new injector and spare o-rings for the other injectors. I replaced injector 5 on the same bank last year so at least I know how to replace number 7 and what to expect. Interestingly, I have been driving the car with the faulty injector and I have not had any rich fault codes yet at all on either banks since cleaning the MAF.

I'll keep you all updated once done and let you know if it clears the RP issues.

Thanks,

Chris

 

Hi all,

Success

I replaced the injector #7 at the weekend and the car now runs without any fault codes. RP and EML are off and I took the car for a drive for it's MoT which it passed. The car now drives brilliant and there are no rich fault codes anymore either. The car starts great, first time and does not rough idle anymore either.

I'm going to take it for a long run tomorrow to work so hopefully all will be good and I'll get a chance for it to stretch it's legs.

Hopefully my MPG will also be better as well now that the rich codes are gone and that the car is not running in RP anymore.

I'm not sure if this was the cause of the rough idle or if cleaning the MAF helped with that.

Thanks for all the support with this guys.

Cheers,

Chris

 

Hi all,

Well my rough idle is back when the car is started from cold and the engine vibration at about 1400 to 1800 RPM is also back. It's odd because the car ran great for over a week after replacing the faulty injector.

I've got no fault codes or rich codes registered but there is clearly some reason for this problem to return.

I'll check fuel trims to see if there is any difference from before the injector was faulty.

Looking like it might be the manifold gaskets as these are pretty much the only thing I haven't replaced.

Thanks,

Chris

 

Mine still ran fine, but the check engine light kept coming on.

Replace something hoping for the best, all parts are suspect turn light off.

Drive a hundred miles or more sometimes, a few blocks till on again it went.

Runs the same after finally fixing it, but no more light, & it passed the emissions test.