2002 XKR Starts / Stalls
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Senior Member
Joined: Mar 2023
Posts: 155
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From: St Louis
During the above procedure, I removed all the plugs and did a compression test. I hadn't yet done that on this car.
So, I've discovered today, that the compression is bad, on bank ... well, whatever bank the driver's side is. B?
My understanding is the cylinder numbering from front to back is 5, 6, 7, 8 which corresponds to 305, 306, 307, and 308. Please correct me if I'm wrong.
By that numbering, cylinders 5, 6, 7, and 8 have 92, 25, 85, and 92 respectively. Cylinders 1, 2, 3, 4 have 100, 105, 103, 102.
So, cylinder 6 appears to be dead. I triple-checked it, and it never goes above 25. (Also, the engine audibly cranks easier when checking this cylinder, further indicating low - to - zero compression.) The oddity is that this is the only cylinder that *didn't* trigger a misfire code. But maybe I have the numbering wrong. This is the cylinder that is second-from-front on the driver's side.
A scope down the spark plug hole reveals a normal-looking piston crown, no sign of damage. The piston is moving as expected. I see no damage to the walls.
At this point, I'm suspecting a stuck-open valve or some other such cylinder head malfunction. I'll confirm tomorrow when it's light again and I can connect up the leak-down test kit, but, at this point I think I am facing a decision on whether to overhaul the head or not. I may also pop the valve cover and see if the valve stem is stuck-down as well.
I should have done a compression test to begin with, but honestly, this is the first vehicle I've inherited that actually had compression issues like this.
So thank you all for all the advice, as usual, but I believe I have found the smoking gun in this case. I suspect, that the ECU is detecting this heavy miss, and is disabling the engine to protect it from further damage.
So, I've discovered today, that the compression is bad, on bank ... well, whatever bank the driver's side is. B?
My understanding is the cylinder numbering from front to back is 5, 6, 7, 8 which corresponds to 305, 306, 307, and 308. Please correct me if I'm wrong.
By that numbering, cylinders 5, 6, 7, and 8 have 92, 25, 85, and 92 respectively. Cylinders 1, 2, 3, 4 have 100, 105, 103, 102.
So, cylinder 6 appears to be dead. I triple-checked it, and it never goes above 25. (Also, the engine audibly cranks easier when checking this cylinder, further indicating low - to - zero compression.) The oddity is that this is the only cylinder that *didn't* trigger a misfire code. But maybe I have the numbering wrong. This is the cylinder that is second-from-front on the driver's side.
A scope down the spark plug hole reveals a normal-looking piston crown, no sign of damage. The piston is moving as expected. I see no damage to the walls.
At this point, I'm suspecting a stuck-open valve or some other such cylinder head malfunction. I'll confirm tomorrow when it's light again and I can connect up the leak-down test kit, but, at this point I think I am facing a decision on whether to overhaul the head or not. I may also pop the valve cover and see if the valve stem is stuck-down as well.
I should have done a compression test to begin with, but honestly, this is the first vehicle I've inherited that actually had compression issues like this.
So thank you all for all the advice, as usual, but I believe I have found the smoking gun in this case. I suspect, that the ECU is detecting this heavy miss, and is disabling the engine to protect it from further damage.
Thread Starter
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Senior Member
Joined: Mar 2023
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Likes: 97
From: St Louis
In deciding the fate of this vehicle, I am considering a head swap. Has anyone done this head swap on the driver's side, and, is the job do-able with the engine remaining in-vehicle?
Alternatively, if anyone is near the St Louis, MO area and would be interested, I would consider selling the car to someone who has more time / space, and/or is interested in a parts car. It does run very well, even with a mostly-dead cylinder.
I'm 99% certain it's the intake cam lobe, since it has no signs of gas leakage into the crankcase, nor any signs of backfiring or any other valve leakage. I think the intake valve is just stuck closed.
Alternatively, if anyone is near the St Louis, MO area and would be interested, I would consider selling the car to someone who has more time / space, and/or is interested in a parts car. It does run very well, even with a mostly-dead cylinder.
I'm 99% certain it's the intake cam lobe, since it has no signs of gas leakage into the crankcase, nor any signs of backfiring or any other valve leakage. I think the intake valve is just stuck closed.
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Joined: Apr 2014
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From: Jersey, Channel Islands
I haven't been there, but it is doable with the engine in situ.
I'd certainly lift the cam cover on that side before condemning the car. The cam for that cylinder would have to be in some state for the valve not to open at all. The cover is pretty straightforward other than you'll have to fight the dipstick tube. A 1/4" drive set will help for the harder-to-access cover bolts.
I've attached the JTIS procedure. It's for MY2000 but it will give you a feel for what needs to be done. I'd also recommend downloading the 2nd edition workshop manual from the stickies as the attached snip refers to other sections.
I'd certainly lift the cam cover on that side before condemning the car. The cam for that cylinder would have to be in some state for the valve not to open at all. The cover is pretty straightforward other than you'll have to fight the dipstick tube. A 1/4" drive set will help for the harder-to-access cover bolts.
I've attached the JTIS procedure. It's for MY2000 but it will give you a feel for what needs to be done. I'd also recommend downloading the 2nd edition workshop manual from the stickies as the attached snip refers to other sections.
Veteran Member
Joined: Oct 2010
Posts: 2,012
Likes: 960
From: Spain
While you have the cam cover off check the timing is correct - whether slightly off timing would give you the symptoms you report I don't know, but worth checking before deciding an engine rebuild is needed - ,maybe someone else has an insight?
Thread Starter
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Senior Member
Joined: Mar 2023
Posts: 155
Likes: 97
From: St Louis
I removed the cam cover today, the cams on that cylinder look healthy. I can't fit my caliper for precision measurements, but the lobes should definitely be opening and closing those valves. So I am certain it is not the cam.
The valve caps look OK, but obvs. I cannot see underneath them.
I'll look for the timing procedure (thank you for the suggestion @dibbit ,) and also connect a leak-down kit if I can get my air compressor working.
I see several cylinder inspection tools on Amazon, but I am skeptical of their quality. I need something with a mirror, or something that can curl back to look at the valves.
In any case, it seems if the timing checks out correct, then all signs seem to indicate a necessary head removal at this point.
And knowing myself, I will not be able to refuse the challenge...
The valve caps look OK, but obvs. I cannot see underneath them.
I'll look for the timing procedure (thank you for the suggestion @dibbit ,) and also connect a leak-down kit if I can get my air compressor working.
I see several cylinder inspection tools on Amazon, but I am skeptical of their quality. I need something with a mirror, or something that can curl back to look at the valves.
In any case, it seems if the timing checks out correct, then all signs seem to indicate a necessary head removal at this point.
And knowing myself, I will not be able to refuse the challenge...
Junior Member
Joined: Apr 2024
Posts: 1
Likes: 0
Hi all, it's been awhile!
My 2002 XKR (convertible) which I saved from the scrapyard, and has been running quite well, suddenly began intermittently stalling after start for no apparent reason.
Sometimes it will start and run fine (for hours if I continue driving) but sometimes it will start fine but stall after 1-2 seconds. It runs great for a second, then stumbles and dies. It definitely feels like fuel cut-off, but I have been unable to confirm this with a pressure gauge yet.
Again, this is intermittent, so it doesn't seem likely to be a mechanical pump failure (I just replaced both pumps last summer, also.)
Yesterday I managed to fit a pigtail onto the fuel rail Schrader valve, but of course, this became a day which the car refused to exhibit the problem.
Vehicle detail:
- 2002 XKR supercharged 4.0L
- Later engine model with the proper timing chain tensioners
- Runs quite smoothly (when not exhibiting this issue)
- 95,000 miles
- Relatively new battery (last summer)
- Drives great, plenty of power
- Both fuel pumps replaced last summer
Problem detail:
- Starts fine (initial rush of fuel)
- Stumbles and dies after anywhere from 1-3 seconds (definitely feels like fuel starvation)
- This can happen whether hot or cold (happened in the AM with a cold engine, also happened after a day drive, after filling the tank at a station)
- There appear to be no DTC's triggering when this happens
Things I have done:
- Checked fuel pump relays for #1 and #2 (both are good)
- Opened the ECU and checked for any damaged / leaky capacitors (no damage found, looks to be in mint condition - though I realize there could still be bad caps, I'd like to further isolate the issue before jumping to this conclusion)
- Found, and then plastic-welded, numerous cracks in the air intake hose (it's not ideal, but functional) I do not think this leak would have been bad enough to cause such a hard stall, anyway.
- Checked DTC's, there are none (I cleared a random misfire code which hasn't come back)
- Attached a fuel pressure gauge, but have yet to recreate the issue (I'll try again later this evening.)
My theory tells me that the computer is deciding to cut off fuel for some reason, perhaps a bad signal from the MAF? But before going further, I want to confirm this by checking voltage at the pump connector above the tank, I expect I will find that pump #1 is priming the system, but pump #2 is failing to carry the fuel pressure after startup. A drop in fuel pressure plus no voltage to the pumps would confirm this, I believe.
I'll post findings once I am able to recreate the issue, hopefully this evening, and get more data.
As always, I appreciate any / all input!
My 2002 XKR (convertible) which I saved from the scrapyard, and has been running quite well, suddenly began intermittently stalling after start for no apparent reason.
Sometimes it will start and run fine (for hours if I continue driving) but sometimes it will start fine but stall after 1-2 seconds. It runs great for a second, then stumbles and dies. It definitely feels like fuel cut-off, but I have been unable to confirm this with a pressure gauge yet.
Again, this is intermittent, so it doesn't seem likely to be a mechanical pump failure (I just replaced both pumps last summer, also.)
Yesterday I managed to fit a pigtail onto the fuel rail Schrader valve, but of course, this became a day which the car refused to exhibit the problem.
Vehicle detail:
- 2002 XKR supercharged 4.0L
- Later engine model with the proper timing chain tensioners
- Runs quite smoothly (when not exhibiting this issue)
- 95,000 miles
- Relatively new battery (last summer)
- Drives great, plenty of power
- Both fuel pumps replaced last summer
Problem detail:
- Starts fine (initial rush of fuel)
- Stumbles and dies after anywhere from 1-3 seconds (definitely feels like fuel starvation)
- This can happen whether hot or cold (happened in the AM with a cold engine, also happened after a day drive, after filling the tank at a station)
- There appear to be no DTC's triggering when this happens
Things I have done:
- Checked fuel pump relays for #1 and #2 (both are good)
- Opened the ECU and checked for any damaged / leaky capacitors (no damage found, looks to be in mint condition - though I realize there could still be bad caps, I'd like to further isolate the issue before jumping to this conclusion)
- Found, and then plastic-welded, numerous cracks in the air intake hose (it's not ideal, but functional) I do not think this leak would have been bad enough to cause such a hard stall, anyway.
- Checked DTC's, there are none (I cleared a random misfire code which hasn't come back)
- Attached a fuel pressure gauge, but have yet to recreate the issue (I'll try again later this evening.)
My theory tells me that the computer is deciding to cut off fuel for some reason, perhaps a bad signal from the MAF? But before going further, I want to confirm this by checking voltage at the pump connector above the tank, I expect I will find that pump #1 is priming the system, but pump #2 is failing to carry the fuel pressure after startup. A drop in fuel pressure plus no voltage to the pumps would confirm this, I believe.
I'll post findings once I am able to recreate the issue, hopefully this evening, and get more data.
As always, I appreciate any / all input!
Thread Starter
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Senior Member
Joined: Mar 2023
Posts: 155
Likes: 97
From: St Louis
For your case, I'd recommend checking the basics first, including a compression check. I wish I had done that before diving into all the other fixes.
Member
Joined: Aug 2011
Posts: 84
Likes: 32
From: Soquel, CA
Your leak-down test will tell you more. A stethoscope (or any small flexible tube) into the various destinations of the leaking air will tell you for certain whether the leak is into the crankcase, (rings) coolant, (head gasket) fuel injector, (intake valve) or O2 sensor (exhaust valve). Also, if your inspection camera can fit into the injector hole, you may be able to see any unusual intake valve issues.
Last edited by twinsemi; Sep 4, 2025 at 01:43 PM.
Member
Joined: Aug 2011
Posts: 84
Likes: 32
From: Soquel, CA
For this parallel issue of GDan, I have one question that does not seem to be answered in your description of events.
What is your right foot doing while all of this is going on?
To explain this question, we must understand that there are two fuel pumps that have separate electrical circuits and control logic. If you apply pressure to the throttle pedal at any time during the starting sequence, you may well trigger input that causes the secondary fuel pump to power on. Releasing pressure on the throttle pedal will remove this input to the ECU and cause the secondary pump to shut off.
With one post from GDan, I may just be whistling into the wind, Ehh?
What is your right foot doing while all of this is going on?
To explain this question, we must understand that there are two fuel pumps that have separate electrical circuits and control logic. If you apply pressure to the throttle pedal at any time during the starting sequence, you may well trigger input that causes the secondary fuel pump to power on. Releasing pressure on the throttle pedal will remove this input to the ECU and cause the secondary pump to shut off.
With one post from GDan, I may just be whistling into the wind, Ehh?
Last edited by twinsemi; Sep 6, 2025 at 09:00 PM. Reason: adding info
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