skipc
NAXJA Forum User
- Location
- Georgia & points west and south
I like to think through a problem before I start taking things apart, rather than just replacing and seeing if that fixed it (like the stealerships). But, this one has me a bit baffled. This is a problem that has been going on for some time, and now getting worse, but still not failing, which makes it tougher...
If anyone has any ideas, please post. I'll list all the gory details below and will be accurate. I think each is an important symptom. It's an 89 XJ, 4.0L, auto, 4wd, PS, air.
Several months ago I got gas after days of rain (didn't drive in the rain though). About 70 miles into that tank (3/4 full or so) it started stumbling intermittently, so bad that it could stall. I could raise the idle, or accelerate hard, and it would run fine.
I thought it was bad gas.
So I added all sorts of additives, ran several tanks through, then it was fine.
A few weeks later I put in a half tank of the same brand gas, but from a different station (it closed down for some reason (ws a BP) since then BTW), and about 60 miles into it, same thing. I drained the tank right away (through the pump again) and put different gas in. All was fine.
Mysterious, but maybe bad gas brand...
A few weeks later, on the usual brand of gas, it started stumbling again. I put in some Marvel oil in the tank and it ran fine within a few minutes. For several weeks, and over 2000 miles, all was fine if I added the oil. I didn't add the oil one time and it had a little bit of a problem. Recently, it started to have an occassional problem with the oil too.
Maybe the bad gas ruined something...
I then started to think an injector was bad... It would try to cut out - a hard miss - when it would do it. I even changed the plugs, gapped and all. The old ones weren't bad though. No change. No plug fouling.
The Marvel oil seemed to take care of things...
Now, 2 days ago, I am down to 3 gal and stop, put in the oil, and fill up. Immediately upon starting, it stumbles. A rolling and cutting out kinda of stumbling. It was before any new gas or oil could've reached the fuel rail...
Now I'm not sure...
- all the electrical I can check is fine.
- plugs are good.
- seems to act up after a fill up (twice right after), or in the same driving period after a fillup.
- it's intermittent
- pump is noisy, but is always on and constant, although sometimes it's quiter
- Marvel oil in tank helped many times, but it's getting worse.
- it'll tend to right itself after a while if oil is in the tank (until now)
- no oil and it's very bad
- I jumpered the pump resistor to give it more oomph while stumbling and no change.
- I can disconnect the resistor while running and the engine will run for a couple seconds then stumble to a stall. Not an immediate cutoff, so elec connection to pump wouldn't do this.
- Always starts fine, even after a stall
- heavy accel or load is fine, it's idle and constant speed that it stumbles
- when it's real bad, even accel has a little stumble, but is still better than idle
- drained filter from inlet side and the gas looked fine.
- flow at the rail seems fine (I use the pump to drain the tank by jumpering it.
- banged on knock sensor and no effect
- disconnected EGR and no change
- when it runs fine, it's great and gets 21.5 mpg highway
- draining tank thorugh pump seemed to fix it twice
- Marvel oil in tank definitely fixed it all times but the last one.
- filter was new before this
- have run 'dry gas' and Berrymans through in case of water
I'd like not to be stalled and at the mercy of some shop if it goes - probably on a trip. Any ideas on what to test or what it could be? Some of the symptoms seem to contradict others. I've got a trip next week and would like to fix this. Detailed tests appreciated too. Maybe I'm not seeing a test that would help get at this intermittent problem.
Thanks in advance.
-Skip
If anyone has any ideas, please post. I'll list all the gory details below and will be accurate. I think each is an important symptom. It's an 89 XJ, 4.0L, auto, 4wd, PS, air.
Several months ago I got gas after days of rain (didn't drive in the rain though). About 70 miles into that tank (3/4 full or so) it started stumbling intermittently, so bad that it could stall. I could raise the idle, or accelerate hard, and it would run fine.
I thought it was bad gas.
So I added all sorts of additives, ran several tanks through, then it was fine.
A few weeks later I put in a half tank of the same brand gas, but from a different station (it closed down for some reason (ws a BP) since then BTW), and about 60 miles into it, same thing. I drained the tank right away (through the pump again) and put different gas in. All was fine.
Mysterious, but maybe bad gas brand...
A few weeks later, on the usual brand of gas, it started stumbling again. I put in some Marvel oil in the tank and it ran fine within a few minutes. For several weeks, and over 2000 miles, all was fine if I added the oil. I didn't add the oil one time and it had a little bit of a problem. Recently, it started to have an occassional problem with the oil too.
Maybe the bad gas ruined something...
I then started to think an injector was bad... It would try to cut out - a hard miss - when it would do it. I even changed the plugs, gapped and all. The old ones weren't bad though. No change. No plug fouling.
The Marvel oil seemed to take care of things...
Now, 2 days ago, I am down to 3 gal and stop, put in the oil, and fill up. Immediately upon starting, it stumbles. A rolling and cutting out kinda of stumbling. It was before any new gas or oil could've reached the fuel rail...
Now I'm not sure...
- all the electrical I can check is fine.
- plugs are good.
- seems to act up after a fill up (twice right after), or in the same driving period after a fillup.
- it's intermittent
- pump is noisy, but is always on and constant, although sometimes it's quiter
- Marvel oil in tank helped many times, but it's getting worse.
- it'll tend to right itself after a while if oil is in the tank (until now)
- no oil and it's very bad
- I jumpered the pump resistor to give it more oomph while stumbling and no change.
- I can disconnect the resistor while running and the engine will run for a couple seconds then stumble to a stall. Not an immediate cutoff, so elec connection to pump wouldn't do this.
- Always starts fine, even after a stall
- heavy accel or load is fine, it's idle and constant speed that it stumbles
- when it's real bad, even accel has a little stumble, but is still better than idle
- drained filter from inlet side and the gas looked fine.
- flow at the rail seems fine (I use the pump to drain the tank by jumpering it.
- banged on knock sensor and no effect
- disconnected EGR and no change
- when it runs fine, it's great and gets 21.5 mpg highway
- draining tank thorugh pump seemed to fix it twice
- Marvel oil in tank definitely fixed it all times but the last one.
- filter was new before this
- have run 'dry gas' and Berrymans through in case of water
I'd like not to be stalled and at the mercy of some shop if it goes - probably on a trip. Any ideas on what to test or what it could be? Some of the symptoms seem to contradict others. I've got a trip next week and would like to fix this. Detailed tests appreciated too. Maybe I'm not seeing a test that would help get at this intermittent problem.
Thanks in advance.
-Skip