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RepBolt 06-29-2019 06:08 PM

ZJ Dies When Idle
 
I just got my 97 ZJ 5.2L with 166k miles back from the auto shop after doing a full tune up and replaced a bunch of parts. My mechanic told me I have bad shocks and a bad transfer case. I knew about both and already had plans to do a 4.5" lift and get a new VC for my 249 (don't want to swap TC). I drove my ZJ for about 15 miles after I picked it up, and it would die on me when I was idle either at a stop sign or stop light. It died about 7x throughout my drive, and I'd say about 75% of the time I came to a stop it died on me. I went back to my mechanic and told him about the issue, and he said it was due to the bad transfer case. However, prior to me bringing my ZJ to the shop to get repaired, I didn't experience my ZJ dying on me when I came to a stop at all. I hardly drove it, but even then it never died on me and I certainly drove it more than 15 miles before I dropped it off to my mechanic. It only died when I got it back from the shop.

Here is a list of parts I got installed:
  • Oil Pan
  • Water Pump Stud Kit
  • Oil Pan Gasket
  • Valve Cover Gasket
  • Water Pump Gasket
  • Water Pump
  • Belt
  • Idler Pulley
  • Belt Tensioner
  • Radiator Fan Clutch
  • Oil Pump
  • Oil Filter
  • Crankshaft Seal (Rear)
  • Crankshaft Seal (Front)
  • Transmission Mount
  • Motor Mount
  • Plenum Kit
  • Timing Chain Kit
  • Heater Hose
  • Thermostat
  • Water Flange Gasket
  • Timing Cover Gasket

That said, can a bad TC cause your ZJ to die when idle or is this an issue that was caused by one of the parts being installed? I also noticed a hose hanging down underneath my engine and my mechanic said that was for the shocks to let air in. I'm not at all a mechanic so I went with whatever my mechanic told me because I've been going to him for quite some time now and I trust him. I just want another opinion from actual people who know the ZJ.

FlamingRain 06-29-2019 08:04 PM

Check battery terminals and especially grounds. Any vehicle, if the grounds are even a little dirty can cause some random BS to start happening, including stalling when idle.

riverzj 06-30-2019 10:18 AM

Does it studder and die or just die like you shut if off. If it studders itís something like IAC or FPR or fuel pump/filter. Otherwise probably electrical and wouldnít be suprised if it was the crankpositionsensor thatís what was bad on mine and I had that happen where it would just shut off.


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firebane 06-30-2019 10:32 AM

Quote:

Originally Posted by RepBolt (Post 40662965)
I just got my 97 ZJ 5.2L with 166k miles back from the auto shop after doing a full tune up and replaced a bunch of parts. My mechanic told me I have bad shocks and a bad transfer case. I knew about both and already had plans to do a 4.5" lift and get a new VC for my 249 (don't want to swap TC). I drove my ZJ for about 15 miles after I picked it up, and it would die on me when I was idle either at a stop sign or stop light. It died about 7x throughout my drive, and I'd say about 75% of the time I came to a stop it died on me. I went back to my mechanic and told him about the issue, and he said it was due to the bad transfer case. However, prior to me bringing my ZJ to the shop to get repaired, I didn't experience my ZJ dying on me when I came to a stop at all. I hardly drove it, but even then it never died on me and I certainly drove it more than 15 miles before I dropped it off to my mechanic. It only died when I got it back from the shop.

Here is a list of parts I got installed:
  • Oil Pan
  • Water Pump Stud Kit
  • Oil Pan Gasket
  • Valve Cover Gasket
  • Water Pump Gasket
  • Water Pump
  • Belt
  • Idler Pulley
  • Belt Tensioner
  • Radiator Fan Clutch
  • Oil Pump
  • Oil Filter
  • Crankshaft Seal (Rear)
  • Crankshaft Seal (Front)
  • Transmission Mount
  • Motor Mount
  • Plenum Kit
  • Timing Chain Kit
  • Heater Hose
  • Thermostat
  • Water Flange Gasket
  • Timing Cover Gasket

That said, can a bad TC cause your ZJ to die when idle or is this an issue that was caused by one of the parts being installed? I also noticed a hose hanging down underneath my engine and my mechanic said that was for the shocks to let air in. I'm not at all a mechanic so I went with whatever my mechanic told me because I've been going to him for quite some time now and I trust him. I just want another opinion from actual people who know the ZJ.


When I have was having idle issues and idle issues to the point it would stall.. I replaced the map sensor and all issues went away.

Roadtripguy 06-30-2019 11:13 AM

If I had an issue like this, ESPECIALLY right after having a bunch of stuff replaced at the shop, the very first thing I would check would be the vacuum lines, and I'd go over all of them with a fine tooth comb.

V8GCZJ 06-30-2019 11:30 AM

The mechanic probably disconnected the battery cable. When doing so it clears the memory in the pcm. After reconnection the pcm needs to relearn the sensors(and the IAC/idle). Does it stall when in park after you start it/rev it? Wouldn't hurt to clean the throttle body and IAC port. Carbon builds up in there and can cause idle issues.

BRBauer2 07-01-2019 01:59 AM

My random stalling issues were solved by replacing the ignition coil.

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RepBolt 07-03-2019 12:00 AM

This is all wonderful feedback that I'll need to look into once I have some time with my ZJ.

HighLonesome 07-03-2019 12:52 PM

I did this on all my ZJs when I bought them..
disconnect the battery.
remove the TB, remove all sensors (anything non-metal) from TB

get a gallon of carb cleaner and soak the TB overnight
scrub the entire TB clean, make sure you get all the tiny passages, use a single strand of copper wire for the smallest ones
clean the IAC plunger, do not disturb it's position

inspect/replace the small hose for the MAP
reinstall everything and inspect all the hoses/fittings/tees/unions that connect to the TB
start up, let her idle to operating temp

RepBolt 07-05-2019 12:05 PM

Quote:

Originally Posted by BRBauer2 (Post 40664245)
My random stalling issues were solved by replacing the ignition coil.

Sent from my ONEPLUS A6013 using Tapatalk

What ignition coil do you recommend? I'm thinking the NGK 48812 {#U1086} NGK HEI, but I plan to run CHAMPION 9203 Iridium spark plugs, and wondering if they'll work well together.

HighLonesome 07-05-2019 03:02 PM

I bet they run great together. I'm running iridium plugs in my 5.2 and 5.9, both running great. Not sure why the coil says HEI, I think it's just a standard replacement.

paulsheer2 07-05-2019 03:57 PM

1. idle air control servo
2. clean out IAC hole with carb cleaner and toothbrush until there is no black in there at all
3. install extra ground from engine to battery and body
4. engine temp sensor wires (rewire from ecu)
5. switch to MSD ignition and MSD coil
6. install extra bung for aftermarket AFR test dial

RepBolt 07-05-2019 09:10 PM

Quote:

Originally Posted by HighLonesome (Post 40669151)
I bet they run great together. I'm running iridium plugs in my 5.2 and 5.9, both running great. Not sure why the coil says HEI, I think it's just a standard replacement.

This is the ignition coil I was referring to. The description says "HEI", but it's under "Standard Replacement" in RockAuto.

BRBauer2 07-05-2019 10:06 PM

Quote:

Originally Posted by RepBolt (Post 40668963)
What ignition coil do you recommend? I'm thinking the NGK 48812 {#U1086} NGK HEI, but I plan to run CHAMPION 9203 Iridium spark plugs, and wondering if they'll work well together.

Standard Motor Products UF97T Ignition Coil https://smile.amazon.com/dp/B004BTQ7..._sabiDbHE62ZKX

I went with that one. Installed almost 2 months ago and no issues yet.

4.0 engine

Sent from my ONEPLUS A6013 using Tapatalk

RepBolt 07-08-2019 12:10 AM

Does anyone know if the Champion Iridium 9203 {#RC12WLPB4} Spark Plugs from RockAuto come pre-gapped to .040?


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