Guess what? I have a RENIX XJ with a rough idle and misfires!
01-22-2012, 11:45 AM
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Guess what? I have a RENIX XJ with a rough idle and misfires!
Hey everyone,
I want to start by saying this forum has already been a great help. I picked up an '89 XJ 4.0 (4WD, auto) with 189k miles for $500 last week. Get ready for this... I know you're surprised... it has a rough idle, misfires, and gets like 3MPG. I know, weird, right?!
After reading I learned about the RENIX setup and how hard this is to troubleshoot. I was hoping you guys could just help me go down the list of things to check.
SYMPTOMS:
- Cranks about 5-6 times before finally starting.
- Rough idle, almost sounds like it's cammed.
- Slight hesitation when starting from a stop.
- Accelerates up to speed (relatively) smoothly with no backfiring.
- If I slow down, then speed up again, there is major hesitation, slight bucking, and popping noises coming from the driver's side of the engine bay (backfiring?).
- Idle will eventually settle to about 350-450rpm but will go as high as 2,000rpm after turning off A/C. Sometimes stalls when finally putting it in park.
- Exhaust smells extremely rich.
Here are the things I've already checked:
- Plug wires are in the correct order, however the cap looks to be replaced and the distributor may be as well, and I have not manually re-checked the timing.
- Vacuum sits at about 5-10 inches at idle, and will go as low as 35 inches with the engine at about 3500rpm.
- Fuel pressure is 35psi.
Other observations:
- TPS looks to be new.
- Oxygen sensor looks to be new.
- No obvious vacuum leaks from up top.
I've already ordered a new MAP sensor, O2 sensor, and IACV. I hate the idea of just throwing parts at this thing, so any help is appreciated.
Thanks again!
--Andy
Annapolis, MD
I want to start by saying this forum has already been a great help. I picked up an '89 XJ 4.0 (4WD, auto) with 189k miles for $500 last week. Get ready for this... I know you're surprised... it has a rough idle, misfires, and gets like 3MPG. I know, weird, right?!
After reading I learned about the RENIX setup and how hard this is to troubleshoot. I was hoping you guys could just help me go down the list of things to check.
SYMPTOMS:
- Cranks about 5-6 times before finally starting.
- Rough idle, almost sounds like it's cammed.
- Slight hesitation when starting from a stop.
- Accelerates up to speed (relatively) smoothly with no backfiring.
- If I slow down, then speed up again, there is major hesitation, slight bucking, and popping noises coming from the driver's side of the engine bay (backfiring?).
- Idle will eventually settle to about 350-450rpm but will go as high as 2,000rpm after turning off A/C. Sometimes stalls when finally putting it in park.
- Exhaust smells extremely rich.
Here are the things I've already checked:
- Plug wires are in the correct order, however the cap looks to be replaced and the distributor may be as well, and I have not manually re-checked the timing.
- Vacuum sits at about 5-10 inches at idle, and will go as low as 35 inches with the engine at about 3500rpm.
- Fuel pressure is 35psi.
Other observations:
- TPS looks to be new.
- Oxygen sensor looks to be new.
- No obvious vacuum leaks from up top.
I've already ordered a new MAP sensor, O2 sensor, and IACV. I hate the idea of just throwing parts at this thing, so any help is appreciated.
Thanks again!
--Andy
Annapolis, MD
02-15-2017, 11:21 AM
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Year: 1989
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My jeep is acting that way and I just put a new engine in it with a crap ton of new parts, and still acting that way, oil pressure Ian great, fuel pressure is also, have spark fuel and compression
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02-15-2017, 04:02 PM
#8
CF Veteran
@OP
Check for vacuum leaks, and check cruiser's tips https://www.cherokeeforum.com/f51/cr...x-tips-153657/
02-15-2017, 05:20 PM
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02-16-2017, 07:42 AM
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Year: 1990
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02-16-2017, 08:27 AM
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Not banned... Just busy I guess. Shame on me for breaking forum code of conduct and posting my solution.
This problem was solved. The issue was a failed EGR valve. I borrowed an ancient Snap On scan tool and would watch the duty cycle of the EGR... the computer would call for it to close at idle and low RPM/engine loads. It would not, but the computer would pull fuel and open the idle valve. If I held the valve shut with a pair of needle nose pliers, it idled beautifully. So I effectively had a huge intermittent vacuum leak.
I replaced the EGR valve and the thing never ran better! Then I sold it
This problem was solved. The issue was a failed EGR valve. I borrowed an ancient Snap On scan tool and would watch the duty cycle of the EGR... the computer would call for it to close at idle and low RPM/engine loads. It would not, but the computer would pull fuel and open the idle valve. If I held the valve shut with a pair of needle nose pliers, it idled beautifully. So I effectively had a huge intermittent vacuum leak.
I replaced the EGR valve and the thing never ran better! Then I sold it
02-16-2017, 05:15 PM
#15
CF Veteran
Thank for posting the solution.
Renix XJs are getting long in the tooth & any help is appreciated in trying to fix them.
Renix XJs are getting long in the tooth & any help is appreciated in trying to fix them.