Another XJR8 misfire thread...
Discussion
Oh dear!
I bought my XJR8 with rattly cam tensioners and a lambda sensor error on the OBD scan.
Sent it to the garage and had them replace the top tensioners and it went well, if perhaps a little sluggish from standstill, but most of the autos I've driven can be a bit like that so wasn't too worried.
Had it for a couple of weeks and booked it in to have the Lambda sensor error 'fixed'...
I'd done easily 1k miles in between times and it'd served me well, but a few days before the 'date' I pulled off the A1 after about 120 non stop miles and I got the dreaded 'misfire on idle'...
So...
Checked the throttle body and MAF sensor and gave them a fair dose of carb cleaner and sealed a potential induction leak and that just made it worse, so left it until the 'date.
Took it to the garage, (a good one!), and they said that it was running ridiculously lean. So much so that when they tested it, the exhaust manifolds were glowing red. So they reckonned fuel starvation as they couldn't find an induction leak...
So far they've replaced the fuel pumps, (didn't realise there were two!! DOH!), plugs and reattached the FPR vacuum hose which turned out to be loose. They've also checked the coils and they're OK and have hitched it up to all manner of metering doohickeys, (it looks like it's in intensive care!!), and they're stumped.
So according to their metering devices it's running on a good mixture but the ECU's showing misfire on all but #5 cylinder and runs lumpy on low, (-2k), RPM but, (as appears to be usual), works great above that.
Now both 'upstream' lambdas are showing errors now.
Throw me a bone guys please!!!
TIA
I bought my XJR8 with rattly cam tensioners and a lambda sensor error on the OBD scan.
Sent it to the garage and had them replace the top tensioners and it went well, if perhaps a little sluggish from standstill, but most of the autos I've driven can be a bit like that so wasn't too worried.
Had it for a couple of weeks and booked it in to have the Lambda sensor error 'fixed'...
I'd done easily 1k miles in between times and it'd served me well, but a few days before the 'date' I pulled off the A1 after about 120 non stop miles and I got the dreaded 'misfire on idle'...
So...
Checked the throttle body and MAF sensor and gave them a fair dose of carb cleaner and sealed a potential induction leak and that just made it worse, so left it until the 'date.
Took it to the garage, (a good one!), and they said that it was running ridiculously lean. So much so that when they tested it, the exhaust manifolds were glowing red. So they reckonned fuel starvation as they couldn't find an induction leak...
So far they've replaced the fuel pumps, (didn't realise there were two!! DOH!), plugs and reattached the FPR vacuum hose which turned out to be loose. They've also checked the coils and they're OK and have hitched it up to all manner of metering doohickeys, (it looks like it's in intensive care!!), and they're stumped.
So according to their metering devices it's running on a good mixture but the ECU's showing misfire on all but #5 cylinder and runs lumpy on low, (-2k), RPM but, (as appears to be usual), works great above that.
Now both 'upstream' lambdas are showing errors now.
Throw me a bone guys please!!!
TIA
I see you are in Fife. Try Prestige Jaguar in Paisley. I just put my new to me XJR8 into them for upper and lower tensioners, transmission fluid, suspension stuff and fitting an upgraded supercharger pulley.
Dougie there was a Jaguar mechanic for 22 years and really knows his stuff, is enthusiastic and uses his noggin. Great value too.
As an example, mine was making a slight noise from the back. Looking at the history, the main dealer and another couple of specialists thought it might be this and it might be that. Dougie had a quick listen and immediately (and correctly) diagnosed it as lower rear shock absorber bushes.
Dougie there was a Jaguar mechanic for 22 years and really knows his stuff, is enthusiastic and uses his noggin. Great value too.
As an example, mine was making a slight noise from the back. Looking at the history, the main dealer and another couple of specialists thought it might be this and it might be that. Dougie had a quick listen and immediately (and correctly) diagnosed it as lower rear shock absorber bushes.
Just a thought.
Glowing red exhausts can mean that the fuel is still burning as it leaves the exhaust valve.
If you say the mixture is now correct.
This could be either severly retarded ignition timing, or possibly when they did the cam chains the valve timing itself is now out, exhaust valves opening too soon.
As I say just a thought, but a retarded ignition (hear a ticking noise) will overheat the engine more than an over advanced one which you can hear pinking.
Glowing red exhausts can mean that the fuel is still burning as it leaves the exhaust valve.
If you say the mixture is now correct.
This could be either severly retarded ignition timing, or possibly when they did the cam chains the valve timing itself is now out, exhaust valves opening too soon.
As I say just a thought, but a retarded ignition (hear a ticking noise) will overheat the engine more than an over advanced one which you can hear pinking.
I've been wondering about that to be honest Jaged and mentioned it to the mechanic a couple of times. I mean I'm not blaming them for doing it wrong, but I'm wondering if the timing was good before I took it to them. All they did was whip the old tensioner out and put the new one in withouit taking the chains off the gears so if it was out before it'll still be out.
He said categorically that it was seriously underfuelling and the fuel pumps fixed that.
Do I believe him?
He said categorically that it was seriously underfuelling and the fuel pumps fixed that.
Do I believe him?
Just to add that on my A4 FSI there is a design fault in that the fuel pump pick up has too fine a mesh filter.
This filter get blocked (due to the way the FSI pump returns fuel to tank) and the pump sucks the filter in and it collapses blocking the inlet.
This causes the fuel pressure to drop and all sorts of other fault codes and problems result, with EPC light coming on and loosing all power on ovetaking! NOT NICE!!
I've fixed that, but I wonder if you car has been running so very weak, have the plugs overheated and "glazed"??
Have you changed the plugs?? Might just be that simple and worth a try I'd suggest.
This filter get blocked (due to the way the FSI pump returns fuel to tank) and the pump sucks the filter in and it collapses blocking the inlet.
This causes the fuel pressure to drop and all sorts of other fault codes and problems result, with EPC light coming on and loosing all power on ovetaking! NOT NICE!!
I've fixed that, but I wonder if you car has been running so very weak, have the plugs overheated and "glazed"??
Have you changed the plugs?? Might just be that simple and worth a try I'd suggest.
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