Want to leave a note here that this issue has been since SOLVED.
Since my last post, I figured the only remaining variable was an aftermarket airflow sensor that both myself and the LR shop effectively overlooked (to be fair, they didn’t overlook it necessarily, they said up front they refused to diagnose the performance of a non-LR/Lucas part). After replacing the Air-flow sensor (MAF or Air Meter), the engine has been running mint and my OBD2 computer has reported all sensors are working properly. Thanks to everyone who helped out and offered advice. Hopefully this thread will help someone else troubleshooting the same or similar issue!

Hi all,

I have been gradually working my way through a D1 4.0 V8 with about 187k miles. Big & small repairs here and there, and driving it weekly for just over a year. This is the first repair issue that, for the moment, has me totally stumped.

3 times in the last 2 months, after the engine reaches operating temp (190-200) and usually after some time in traffic, stop & go or slow speeds, it seems to enter a state that any load on the engine causes it to sputter, backfire, lose power & eventually stall out completely. Idles happily, revs as high as you like in Neutral or Park, but try to move and it puts on the dramatics. First time it happened I was able to limp home at like 10mph, second time it had even less power and couldn’t make it home, and today the engine completely died in the road and I had to leave it there. Each time it starts easily while hot, idles and revs all you like, but can’t sustain any engine power or revs while in gear. The next morning it will be back to normal.

As far as recent work: I replaced the MAF this morning to address a low input code and that went well. Fresh engine oil, air filter, transmission fluid and coolant. The second episode it threw a cam position sensor code but it went away and hasn’t returned. The fuel pump primes when the key cycles and builds pressure (I haven’t put a gauge on it, but it’s got pressure at the rail). I checked for fuel leaks, and vacuum leaks (by spraying starter fluid around the vacuum connections and fuel injectors). Everything looks good. I have new plugs and wires in a box but these have been replaced within 30k miles.

Does this sound familiar to anyone? Anything else I should be looking at to rule things out? I’ve searched the forums for weeks and haven’t found a situation exactly like mine, but I’ve seen posts about everything from brake pedal sensors to overheating distro caps (don’t have one), vacuum timing advance…

My impression is that there is either an electronic issue related to an overheated sensor or wire harness, as it doesn’t show when the engine is cold and I’ve driven hours on the freeway with no problem (so I suspect engine bay temps). Otherwise a fuel delivery issue with the pump, as it feels like fuel starvation and is related to the amount of throttle & engine load. Or maybe less likely, it could be the transmission? As the engine doesn’t stumble or stall if I’m in Neutral.

Thanks in advance for reading through and for anyone willing to pay their 2 cents. Looking forward to tackling this one.


P.S. Worth mentioning I have no CEL and no pending codes. Going to try and test the fuel pump pressure professionally tomorrow.

 

I would truly inspect the wiring & connector at the CPS. Also does your CPS still have the little cover or is just out exposed? I've seen em and exposed and they'll work, but their service life is greatly reduced due to heat. The OEM CPS wiring can get brittle over time and cause plenty of crazy issues. CPS itself is like a 35.00 part and not that hard to swap out.

 

Thanks for your reply, you’re referring to the Crankshaft Position Sensor? I will take a close look. Do you think it would cause problems without offering a code or preventing the engine from starting?

 

Yes. It generally is at its worst when it gets hot. Pouring cold water on it may actually help.

 

I've had em throw codes & then I've had em not throw codes. But the wiring is the #1 thing I check. My friend was lucky and bought 2 super clean D1's (both white which was funny) for 500.00 each. One had a new CPS, but the wiring was basically twisted together like a DNA strand. Once we fixed that harness truck ran like a beast with zero issues. Second one was towed home, he hooked up the Lynx and it showed a P0340 code. I crawled under it to find the darn CPS not plugged in.... Fired right up after that with once again zero issues mechanically after that. Best 1k my friend ever spent no doubt!

 

if not the CPS I would try unplugging the VSS at the transmission and see if it runs okay, You will lose the speedometer function, but will know if that is the culprit.

https://landroverforums.com/forum/di...cut-off-45273/

 

Thanks reboot, for the recommendation and link. I had basically ruled out the VSS because I hadn’t seen any inconsistencies in my Speedo on the dash or UG (but didn’t know about the speed buffer circuit until now), but I read that other thread and am happy to have something else to try if the gremlin persists.

 

Something interesting I wanted to add, I took a close look at the CKP and it looks like the PO has wrapped the cover in fiberglass resulting in an oil-soaked, hairy mess.
Hard to find the 7mm fixing bolts with all the muck and debris, but gives me confidence that it is causing a problem if someone felt the need to tamper with it.

I'll write back if I find anything interesting assuming I can get it out.

 

Will over at www.discoweb.org can probably get you an original cover for the CPS.

 

mine was a oil soaked 'hairy' mess also, so I removed it and the wire was frayed, insulation off in some spots. I replaced a segment of the wire , about a foot and the connector to the CPS, and put a large piece of heat resistance wire loom over it that covers the wire and the connector. No problems, since. That's been almost two years.
When that started, it ran fine, just would not crank unless I got under the vehicle and wiggled the wire . I soaked it a few times with electrical spray, but that stuff tends to weaken plastic.