br1anstorm
NAXJA Forum User
- Location
- United Kingdom
My 1993 (so not a Renix) XJ 4.0 auto is now 21 years old, 145k miles. Like the owner, it's beginning to show its age - it creaks, and it leaks, and it doesn't like the damp and cold!
I'll skip the catalogue of ailments (mine and the Jeep's!) and focus on just one. A search of the forum suggests it's a very common problem and like so many, could have any one of numerous causes. So I apologise for posting a thread on an issue which has been raised many times before. But here goes with the symptoms:
- 98% of the time it starts and runs fine;
- but occasionally when trying to start (sometimes first-off, other times when stopped after a run) it won't fire instantly. Needs a bit of cranking with gas pedal flat to the floor, and after 5-10 secs it fires up and runs, sometimes after a brief stutter;
- now just recently, it has begun a different misbehaviour, which may or may not be related;
- after being stopped at junction or lights (engine idling), when I accelerate to pull away, engine briefly almost dies, as if to stall, but then picks up and runs normally. It feels either like sudden fuel starvation or an ignition problem, and only happens out on the road when I press the gas pedal quite hard from low-revs/idling . In traffic this can be a tad disconcerting!
- I can't get the problem to show when sitting on the drive in neutral (ie no load): the engine revs cleanly from idle. It also picks up cleanly under hard acceleration in any gear on the road.
- it's wintertime now, damp and cold. I don't know if the problem will happen in summer (we'll have to wait and see).
Meanwhile I'm trying to narrow down the possible sources of the problem. Fuel pressure at rail is fine, and I don't think it's dirty fuel. My nonexpert guess is that it is more likely to be an ignition (or electronic sensor signal?) issue. The ignition coil was replaced less than a year ago after the original failed (at that time suspicion fell first on the CPS which we swapped out, only to find that the original CPS was OK). It had new spark plugs a month or two ago. Plug wires are original but clean.The Optima battery is fine. Last week it passed the UK emissions test well within limits so it isn't running rich or misfiring.
I tried looking at the 'Check engine' flashing-light diagnostic codes (OBD-1 is all I have on the 93 model) and - if I read the codes right - it seemed to flash 12 (=battery previously disconnected, which will have been true many times), and 17 (=engine running cool, perhaps not surprising in winter though the gauge usually gets up to normal temp pretty quickly). I know codes aren't a guaranteed clue, but this suggests that there's no other major sensor-type failure.
Now I don't want to push the parallels with the owner too far. I too occasionally have problems getting started in the mornings, and have been known to stumble when out on the road. But what do I look at next.... on the Jeep?
I'll skip the catalogue of ailments (mine and the Jeep's!) and focus on just one. A search of the forum suggests it's a very common problem and like so many, could have any one of numerous causes. So I apologise for posting a thread on an issue which has been raised many times before. But here goes with the symptoms:
- 98% of the time it starts and runs fine;
- but occasionally when trying to start (sometimes first-off, other times when stopped after a run) it won't fire instantly. Needs a bit of cranking with gas pedal flat to the floor, and after 5-10 secs it fires up and runs, sometimes after a brief stutter;
- now just recently, it has begun a different misbehaviour, which may or may not be related;
- after being stopped at junction or lights (engine idling), when I accelerate to pull away, engine briefly almost dies, as if to stall, but then picks up and runs normally. It feels either like sudden fuel starvation or an ignition problem, and only happens out on the road when I press the gas pedal quite hard from low-revs/idling . In traffic this can be a tad disconcerting!
- I can't get the problem to show when sitting on the drive in neutral (ie no load): the engine revs cleanly from idle. It also picks up cleanly under hard acceleration in any gear on the road.
- it's wintertime now, damp and cold. I don't know if the problem will happen in summer (we'll have to wait and see).
Meanwhile I'm trying to narrow down the possible sources of the problem. Fuel pressure at rail is fine, and I don't think it's dirty fuel. My nonexpert guess is that it is more likely to be an ignition (or electronic sensor signal?) issue. The ignition coil was replaced less than a year ago after the original failed (at that time suspicion fell first on the CPS which we swapped out, only to find that the original CPS was OK). It had new spark plugs a month or two ago. Plug wires are original but clean.The Optima battery is fine. Last week it passed the UK emissions test well within limits so it isn't running rich or misfiring.
I tried looking at the 'Check engine' flashing-light diagnostic codes (OBD-1 is all I have on the 93 model) and - if I read the codes right - it seemed to flash 12 (=battery previously disconnected, which will have been true many times), and 17 (=engine running cool, perhaps not surprising in winter though the gauge usually gets up to normal temp pretty quickly). I know codes aren't a guaranteed clue, but this suggests that there's no other major sensor-type failure.
Now I don't want to push the parallels with the owner too far. I too occasionally have problems getting started in the mornings, and have been known to stumble when out on the road. But what do I look at next.... on the Jeep?
