Hey guys, super new to posting here, been lurking for about a year. Bare with me as there is sort of a lot to this...
I bought a 98 TJ a little over a year ago, outside of some rust (that I've been painfully treating with POR-15) it had no issues. Its a manual 4.0 Sport.
Some months ago I was driving and it suddenly began to feel as though it was dropping torque. It never really happened at a specific RPM or speed/gear. It cleared up within about 20 seconds but caused some concern and I later read up on it. Initially I was sure it was fuel pressure related, and ordered a new pump. I got one pump DOA, so returned and got a second, problem persisted. I monitored fuel pressure at the rail several times, it always looked very healthy. I then cleaned the throttle body, IAC, and replaced the TPS.
I don't recall reading anything about this, but the ECM seemed to have to relearn the throttle values for about 20-30 minutes of driving around after the TPS replacement. In any case the problem came back some days later. It's worth noting that this problem is very intermittent, I've gone weeks without seeing it sometimes and often have thought I had fixed it.
At this point I'm shooting from the hip. I've replaced the fuel injectors with four ports. I did a reset on the ECM afterwards. I then drove it for something like a month with no issues.
Last evening I got back from holiday break and took the Jeep for a spin after putting new LED headlights in. Filled tank, and got back on the road. The intermittent torque problem was back, and I was in the middle of a busy intersection.
———
Before I go on, I should probably try to better describe what this problem feels like. I'm not sure that saying loss of torque is exact. It will feel like I can give it all the throttle in the world and it is of no consequence, except for short periods where it kicks in. Understand it's not like the engine is revving as I'm doing this, just nothing happens outside of small windows of burst power. I've also noticed several times that as it catches in those small windows I hear and feel a knock almost directly underneath the driver side seat undercarriage. My guess is somewhere along the driveshaft or T-Case. Everytime this has ever happened it clears out within about 20-30 seconds....though this last time it lasted for about two minutes. Ok back to yesterday.
———
I put hazards on and pulled into a vacant parking lot. If the Jeep is sitting during this, without me doing anything, it will slowly drop RPM to where it just about stalls out, and then revs up, rinse and repeats until it clears out. Sometimes when it clears out the idle will feel very rough after, though it looks solid at 650-750 RPM. As it was going on yesterday I plugged in OBDII reader and looked for any faults, none reported and all sensors read clean, vacuum was up and down, but seemed to coincide with RPM accordingly. After the problem remedied itself I turned it off and cranked it back up, everything seemed fine. I drove back to my neighborhood and noticed my dashboard seemed dim...not sure what that's all about and it may simply be not worth mentioning in the context of this issue. Turn signal also no longer worked, I'm wondering if the hazards being on and then off finally put that poor switch six feet under. Then, as I was a couple blocks from my house, the RPMs shot up to around ~1800. It happened as I was at a stop sign, foot completely off the throttle. It stayed like this to where I could even bring my foot off the clutch and it would drive. I got to my driveway, slight uphill and RPMs returned to normal, only to have the original issue happen again as I limped it up the driveway. Parked it, checked for faults again, nothing.
I have seen faults before off OBDII. The actual code I forget, but it basically pointed to the fuel pump relay. After looking over diagrams, looks like power is always present to fuel pump relay, and ECM provides ground for excitation. I haven't swapped the relay yet, only because it seems like I'd have larger problems if it were the relay, or I should say, more definitive problems.
I'm concerned the ECM is going bad? Or maybe how it's grounded? The loss of torque and subsequent pulsing of power reminds me of when I replaced the TPS and the ECM had to redefine fuel/air parameters.
Any help and/or guidance will be very appreciated, thanks for taking the time to read. I'm sure I've left our a lot of details, but this has been over several months.
Thanks again!
Sent from my SM-G950U using Tapatalk
I bought a 98 TJ a little over a year ago, outside of some rust (that I've been painfully treating with POR-15) it had no issues. Its a manual 4.0 Sport.
Some months ago I was driving and it suddenly began to feel as though it was dropping torque. It never really happened at a specific RPM or speed/gear. It cleared up within about 20 seconds but caused some concern and I later read up on it. Initially I was sure it was fuel pressure related, and ordered a new pump. I got one pump DOA, so returned and got a second, problem persisted. I monitored fuel pressure at the rail several times, it always looked very healthy. I then cleaned the throttle body, IAC, and replaced the TPS.
I don't recall reading anything about this, but the ECM seemed to have to relearn the throttle values for about 20-30 minutes of driving around after the TPS replacement. In any case the problem came back some days later. It's worth noting that this problem is very intermittent, I've gone weeks without seeing it sometimes and often have thought I had fixed it.
At this point I'm shooting from the hip. I've replaced the fuel injectors with four ports. I did a reset on the ECM afterwards. I then drove it for something like a month with no issues.
Last evening I got back from holiday break and took the Jeep for a spin after putting new LED headlights in. Filled tank, and got back on the road. The intermittent torque problem was back, and I was in the middle of a busy intersection.
———
Before I go on, I should probably try to better describe what this problem feels like. I'm not sure that saying loss of torque is exact. It will feel like I can give it all the throttle in the world and it is of no consequence, except for short periods where it kicks in. Understand it's not like the engine is revving as I'm doing this, just nothing happens outside of small windows of burst power. I've also noticed several times that as it catches in those small windows I hear and feel a knock almost directly underneath the driver side seat undercarriage. My guess is somewhere along the driveshaft or T-Case. Everytime this has ever happened it clears out within about 20-30 seconds....though this last time it lasted for about two minutes. Ok back to yesterday.
———
I put hazards on and pulled into a vacant parking lot. If the Jeep is sitting during this, without me doing anything, it will slowly drop RPM to where it just about stalls out, and then revs up, rinse and repeats until it clears out. Sometimes when it clears out the idle will feel very rough after, though it looks solid at 650-750 RPM. As it was going on yesterday I plugged in OBDII reader and looked for any faults, none reported and all sensors read clean, vacuum was up and down, but seemed to coincide with RPM accordingly. After the problem remedied itself I turned it off and cranked it back up, everything seemed fine. I drove back to my neighborhood and noticed my dashboard seemed dim...not sure what that's all about and it may simply be not worth mentioning in the context of this issue. Turn signal also no longer worked, I'm wondering if the hazards being on and then off finally put that poor switch six feet under. Then, as I was a couple blocks from my house, the RPMs shot up to around ~1800. It happened as I was at a stop sign, foot completely off the throttle. It stayed like this to where I could even bring my foot off the clutch and it would drive. I got to my driveway, slight uphill and RPMs returned to normal, only to have the original issue happen again as I limped it up the driveway. Parked it, checked for faults again, nothing.
I have seen faults before off OBDII. The actual code I forget, but it basically pointed to the fuel pump relay. After looking over diagrams, looks like power is always present to fuel pump relay, and ECM provides ground for excitation. I haven't swapped the relay yet, only because it seems like I'd have larger problems if it were the relay, or I should say, more definitive problems.
I'm concerned the ECM is going bad? Or maybe how it's grounded? The loss of torque and subsequent pulsing of power reminds me of when I replaced the TPS and the ECM had to redefine fuel/air parameters.
Any help and/or guidance will be very appreciated, thanks for taking the time to read. I'm sure I've left our a lot of details, but this has been over several months.
Thanks again!
Sent from my SM-G950U using Tapatalk
