Hello Gentlemen...

I could really use your brainpower on this one re: my 2001 VDP with 77k (I bought it at 76k.)

I've been dealing with a terrible idle and "Restricted Performance" messages for a while. My mechanic (a mobile mechanic who seems quite good and very knowledgeable) read the codes.

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Here's exactly what he did and found as he recounts it in his email to me:

• Plugged in the car for the first time and pulled the following codes: P0300: Random/Multiple Cylinder Misfire, P0307: Cylinder 7 misfire detected, P0308: Cylinder 8 misfire detected, and P0560: System Voltage

• Checked the primary and secondary resistance of the coil packs, all of which were good. We then checked the resistance of Spark Plugs 7 and 8, of which we found the resistance to be off, but you reconfirmed with the manufacturer that the plugs were okay for your vehicle.

• We then swapped coil packs 7 and 8 for 5 and 6 respectively, cleared the code and sent you driving.

• Upon our next appointment, we plugged in the car and received the following codes: P0300: Random/Multiple Cylinder Misfire, P0307: Cylinder 7 misfire detected, P0308: Cylinder 8 misfire detected

• We did a fuel system pressure test, verifying the fuel pump was within spec on pressure, even though it was on the extreme low end of the spec.

• We tested each fuel injector's resistance, of which all tested fine, and then swapped injectors 7 and 8 with 5 and 6 respectively.

• We then cleared the light and sent you driving again.

• Upon my next visit, the misfire codes were no longer present, but we did pull the following codes: P0102: Mass Air Flow Circuit Low Input and P0112: Intake Air temperature circuit low input.

• We tested the resistance on the Mass Air Flow Sensor and the Intake Air Temperature sensor, as well as both cam sensors.

• We then checked each wire from the PCM to the injectors and the coil packs to ensure their was no shorts anywhere in the wiring harness, all tested well.

• We worked on the battery issue a bit, then cleared your codes and sent you down the road.
(SIDE NOTE TO FORUM READERS: Jaguar dealer said I had a bad battery... replaced it... and also replaced 02 sensor. Both done to fix a parasitic battery drain which killed the battery within just 2 days of no driving. Both things replaced just yesterday.)

• When I came back, we plugged in again and downloaded the following codes: P0171: System too Lean (Bank 1), and P0300 - Random/Multiple Cylinder Misfire

• There were also a few pending codes, so I had you drive it more

• On my last trip to your place, I plugged in and pulled the following codes: P0171: System too Lean (Bank 1), P0300: Random/Multiple Cylinder Misfire, P0301: Cylinder 1 Misfire Detected, P0307: Cylinder 7 Misfire Detected, P0308: Cylinder 8 Misfire Detected, P1316: Throttle Position Sensor.

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At the conclusion of all this testing, my mechanic believes it's a bad fuel pump.

Since he's not able to do warranty work (he's not yet authorized by the warranty company), I took the car to the Jag dealer the other day. The Jag mechanic said, "It's not likely a fuel pump because the car would likely not start if it were... instead, it's probably a timing chain issue and we'll need to do a tear-down... check to see if the chain is jumping teeth... do a compression test... and leak-down test (whatever the heck that is)... $870 before doing any work."

My mobile mechanic said, "It does not take maximum fuel pressure to start the engine. Even though the car would run rough with a skipped timing chain, it would not create a lean misfire code unless it has skipped more than one tooth, and in that case you would have some internal engine damage due to the valves contacting a piston at some point."

Argh. My warranty states that it covers the timing chain... and I have "wear and tear" coverage that should cover any worn parts that need to be replaced. My concern--other than the warranty company finding a way to weasel out of paying the $870 tear down AND any repairs that they find are needed--is that something ELSE might be determined to be the cause that is NOT covered. Then I'd be out the tear down and not be able to recoup anything and be faced with a bill for non-warranty work if I chose to get it done.

Or... should I go to a shop recommended by my mobile mechanic and try to get the fuel pump replaced under the warranty (which is also covered). Question is, the warranty covers FAILED parts. How do you PROVE a fuel pump has failed?

Any suggestions by my fellow Jag friends would be greatly appreciated.

Many thanks,

SirJag

 

Has the fuel filter been changed? Also, I wonder if the throttle body might be involved. I'm sure one of the experts will be along shortly to offer real help.

But that Jag dealer scares me, and it isn't Halloween yet. They just want to throw money at the problem.

RJ____________
95 XJ6 120K mi
97 XK8 86K mi

 

Bit of a ragbag of codes.
I know you've got a new battery but I'd still check the voltage at the posts and under the bonnet with the ignition on.
I'd also reset things (pull off batt ground lead and touch lead to +ve post for a few seconds).
Have you looked at plugs 7 +8 ?
There are two problems which may be causing this - your mechanic said fuel pressure was borderline low - you need to check that with the engine at 2500 rpm.
Also check for leaks/cracks downstream of the MAF sensor.

 

I would vote for removing the cam covers only (not the front timing cover). I would hardly label this a teardown. You can then immediately see if the cam flats are aligned and whether the secondary chain has jumped a tooth.

Even if the chain has not jumped a tooth, the old secondary tensioners should absolutely be upgraded to the new metal type while the cam covers are off. If it did jump a tooth, the cams can be realigned at the same time.

If you did jump timing, the dealer would no doubt want to do a complete timing overhaul. If the warranty covers it..well great.

If you have reason to not trust the coverage of your warranty, if there is no obvious damage other than bad secondary tensioners, you probably can get away with just replacing them and resetting the secondary timing and your mobile guy sounds like he knows enough to do the work.

 

I agree with WhiteXKR. Pull the cam covers and have a look, especially the one on the LH side with cylinders 7 & 8 under it. Also +1 on looking at those plugs and checking for oil in those plug wells - if this hasn't been done already.

 

How long has it been lumpy? did it just appear one day, does it come and go or is it every start?
I'd echo the suggestions above and check oil in the plug well, it only needs a drop for a short and missfire, but this usually isn't logged as an OBD code.

The main thing is the timing - it's a half hour job to check. Maybe point your tech onto this forum for guidance on the zip-tie method

I would not start the car until the timing is confirmed.

 

Yes, indeed... the fuel filter was changed recently. Yeah... nice pre-holiday scare, alright. It's no treat... maybe just a trick and I don't want to be its victim! ;-)

 

Yes, actually ALL the plugs were recently replaced. I'll add it to the list of things to check.

SirJag

 

It's been this way for a long time and it runs like this all the time. It's fine while accelerating... horrible when idling.

Thanks for the info and suggestions!

SirJag

 

Steve (WhiteXKR) tends to be right most times but I'll stick my neck out here and say I don't think it is the timing.
However unless you're 100 % sure the secondary tensioners have been replaced they will need doing.

 

Well since you asked me Ill answer. first I too would pull the covers and look at tensioners and flats. It will give a rough idle if jumped and if theyre plastic the EW company will (should) cover for cracks down the side. I think you just have multiple issues. I think the MAFS if screwing the AFRS hense p0171 if the air intake tube doesnt have cracks. Also the P0112 will only show if someone had the key on and MAFS unplugged or if its bad.
My work would be exactly what the dealer recommended and its not throwing money at it. Based on what youve said has been done I would want to also look at compression, but more so leak down especially for 7,8. My thoughts are, did it jump time(you stated always rough idle) and tweek ever so slightly valves in those cylinders? Or are they just carboned up enough to cause leakage. Dont laugh my 70k Nissan truck did it. Not to the point of problems, but when I had the engine out and rebuilt the heads. there was enough carbon on the valves to let liquid leak out of the chambers when checked and alot on some. After I cleaned and lapped them back in they all sealed fine.
I dont think its the fuel pump either. but I would look at the bigger issue which is cylinder health and chains, all the rest is small money and issues and should be taken as a second or seperate repair AFTER doing what the dealer said. Doing anything else IMO would be like putting new tires on a car that doesnt run

 

Well put and to the point.

The point on the secondary tensioners is especially good because unless they have been replaced in the past, they will almost certainly have at least cracks in the usual spot. Once cracked, warranty coverage kicks in and regardless of whether the chain has skipped the cost is covered to get to the point of viewing the timing.

 

I'm with the crowd on checking the valve train. A compression / leakdown test should not be too expensive from the mobile mechanic. If the fuel pressure is within spec,(you dodn't say what the pressure was), then its within spec and certainly isn't causing such major problems. Misfires can cause the lean readings on the OBD, so I'm betting something seroius in the 7 -8 cylinders and valves.

 

I'm on the band wagon for the compression test and leak down test. I was taught a long time ago to check compression when you have the spark plugs out if you're chasing a problem and even on a tune-up. It's one of the essential tests for an initial assesment of an engine. You could end up putting a lot of time and money into an engine that has low compression on two cylinders and still have a rough idle and misfire codes.