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Mystery Renix 4.0 Problem...help!

I just got a call and it looks like the CTS bad...of coarse there is no part available until Tuesday so I'll be heading out to Pull and Save.

I'll let everyone know for sure.

Randy

Coolant Temperature Sensor (CTS) -

Located in engine coolant jacket on the driver's side of the block. To test, use a high impedance volt-ohmmeter. Resistance should be less than 1000 ohms with a WARM engine (examples = 212* would be about 185 ohms, 160* would be about 450 ohms, 100* (not warm enough) would be 1,600 ohms).

> What does it do? Adjusts the injector pulse widths (Colder coolant temperatures result in longer injector pulse widths and richer air-fuel mixtures). Compensates for fuel condensation in intake manifold. Controls engine warm-up idle speed. Increases ignition advance when engine is cold. Energizes the EGR valve solenoid to prevent flow of vacuum to the EGR valve.
 
i have a xj manufactured in 91 but has the sticker stating that it meets 92 emission standards and im having the same problem as the rest of these owners. i have long starts, when i rev it theres hesitation then when i put it in gear and go it sputters and bucks and dosent go very well. to go i have to floor it and when the revs pick up above 3000 it finally takes off. i fixed the exhaust leak, replaced the fuel filter, cleaned the throttle body and the small sensor that threads into the intake (dont know what it is but was grimy) and it still didnt fix it. I NEED HELP!!
 
I vote for the O2 sensor
 
Update

It looks like the CTS was acutally missing...There is a plug in the block where it was suppost to be above the driver's side motor mount.

The Jeep has been running fine for almost two years without this CTS "coolant Tempature sensor" but it started acting up when I drove it 18 hours straight from Denver to Spokane, WA.

It has never cleared up and I've been here for almost a month. I would think the CTS is an important part of the how the fuel injection decides how much air/fuel to send to the motor.

I went to pull and save on Sunday and harvested numerous sensors and checked an 87, 88, 89 and 90 XJ they had there and the three that still had engines all had this CTS sensor. I took one from an 88 and will have it installed today.

The only differenece is the elevation from Denver to Spokane but I'm not sure how the CTS could start playing a big roll now except there is simply more oxygen available here in Spokane.

I have it at a shop since I gave up last week and I'm already into them for $230 in troubleshooting.

I asked them to install the CTS and then if it still acts the same install my NEW Mopar fuel pump I've been saving for a rainy day. The current pump is about 5 years old and it gets my vote for the root issue.

The indexing is correct on the distributor and I've swapped every sensor at this point...although the fact that it's been missing the CTS since the motor switch is a little frustrating.

Just how important do you guys think this CTS sensor is?
 
It was probably a newer 91+ block. Is there one in the T-Stat housing they could be using it.

It would make sense that at lower altitudes the MAP and o2 senors could make up the difference but at High altitude they could not.
While your looking make sure the Knock sensor is installed a rebuilt block would have plugs in all the holes.
 
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The new motor was a 1988 Engine out of Jon Jacobs "Mad Cow" from Fort Collins, CO which was an 88 w/ 5-speed.

If anyone was at the 20th Anniversary NAXJA event in Moab you may of seen Jon's white 1988 with the chopped top, black spots and 40" Super Swampers on Dana 60 front and 14-Bolt Rear.

Mine was a 1989 w/ AW4 Auto so the guy in Gilpin, CO forgot to move the CTS over. The Knock Sensor was there and I did notice that something was not plugged in where the O2/Knock-Sensor/CTS wiring junction is but I couldn't find anything to plug into...I thought it was something for the 5-Speed. Now of-coarse the CTS was not even installed or some reason and it makes sense.

The motor was and has been running great in Denver and I haven't thought about that CTS connection for almost two years.

I just don't understand why all the sudden the lack of a CTS could be the cause of my hesitation/stumbling issue.

I would be very surprised if the CTS is the issue; while it makes sense that it is a nessasary EFI gizmo I think in the end it will be the fuel pump.

I'll know tonight...
 
Update...No Dice! Back to the Drawing board.

Well I had the CTS installed in the block and even though it was missing for almost two year has made no difference.

I broke down and replaced my fuel pump last night in my garage with my new $200 Mopar fuel pump...and of coarse no change.

I've had a slight engine vibration for a few months and I think it's getting worse so now I'm thinking that possibly the Flex Plate on the AW4 has cracked and I'm getting some messed up timing because of this.

The harmonic balancer looks ok so after talking with some mechanics this could be the problem.

I told you guys this was a totally weird issue. I had the AW4 overhauled with a new flexplate and ring gear in 2002 several years before the new engine was installed. The crank may have weakened the flexplate since it moves a lot being so old and worn out.

When I put the new tight engine in the stress of the fixed crank probably caused the flex plate to crack.

This all theory right now but I'll keep you posted as I'll pull the flex plate cover to see if I can notice any visual issues with it.

I'm going to replace the fuel pressure regulator tonight since I have a spare from pull and save.

I hadn't thought that there could be an issue with the AW4 flex plate and that could be messing up the timing and causing the hessitation.

This has got to be one of worst problems I've ever experienced with any of my four XJs...Very frustrating but I'll eventually get this figured out.
 
I fixed my hesitation and low idle problem by advancing the dist. one tooth. I had installed it incorrectly by lining the rotor up slightly before #1 TDC. I read somewhere that the trailing edge of the rotor should be lined up with #1. I tried it and it works, drives and idles much better with no hesitation(when warm).

But..... now.... I have a slight miss/stumble on cold mornings untill the engine temp gets to around 150, then it goes away. On warm days it is O.K. I'm working through this problem now.

Not trying to hijack I just thought you may wan't to check yours.
 
in response to what i was told before i replaced the o2 sensor, cts, and treated the engine with seafoam (fuel additive) with no results. Still sputtering bucking and backfiring with 3 ideas left, injectors, champion plugs, or tps. still lost and troubled. also is there any tranny sensors? i have auto tranny not sure which one though. still need help







91 green cherokee laredo. stock with custom convex rear leafs(hahaha) and factory chrysler 8 1/4 rear
 
Randy, if the harness convolutes are in need of replacement, I'd get going on that and check all the wires closely while you're in there.
And I'd hate to think anything happened with the motor, but have you checked base compression? Solid power and ground readings at the PCM connector pins?
 
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Hey guys,

I was having similar problems with my 90 XJ and I changed out (with junkyard parts) the TPS, IAS, Fuel Pump resistor, MAP sensor, ignition coil, and finally I pulled a REnix computer from the same XJ as mine. Changing the TPS and the IAS did not seem to help the problem, neither did replacing the ignition coi...or the MAP sensor. It was when I switched out the Renix that it began to run much better.

Oh I also didn't mention that I put in Champion spark plugs.....which made a huge difference!

No bucking or stalling.

The place where I got the Renix has a number of Jeeps with the REnix still in them, let me know if someone needs a late 80's early 90's REnix.

Thanks,

LTK
 
champion plugs no good didnt work absolutley no difference none at all
going to get the sensor on intake manifold tps and junkyard computer
still lost and need help
 
iheartmyjeep,

Sorry to hear you are still having problems. Is your XJ a manual or automatic. As i mentioned before there are a number of renix computers at a local pick and pull here and I could get one for you if you would like. They are relatively inexpensive and as I mentioned it really helped mine, but I have been a little leary to take off the map sensor and coil I put on to see if that was the problem. You might also want to look at your battery, while I was searching for a solution to my problem I ran across a few people that had changed their battery and the stalling and bucking problem went away. It was stated that the alternator does not kick in until after 1200 rpm and if a battery is not up to par it will cause the bad idle you speak of.. hope this helps..

LTK
 
thanks friends for the xj help but i no longer need assistance for i totaled the green xj but i will say i took out a chain link fence dropped off a 5ft embankment bouced the front axle off a huge boulder then hit a tree i started it shifed it into full time for the last time and drove it out thank you jeep vehicles





R.I.P 91/92 green xj
 
My 91 was doing the same thing after replaceing the 02 it ran good for about a week.
I don't know why but one day when it was acting up real bad and I grabbed the plug at the distributor and it died.
After getting it to start again I did it again and it died.
I pulled the plug apart and hit it with some PB Blaster (it's all I had with me at the time).
Put it back together and problem gone.
When I got back home I cleaned the plug with contact cleaner that was about 8mo. ago still running great.

Good luck and 73's KG4BET
 
im back in the club cause i found a 90 xj for 400$ with blown head gasket so im fixin this weekend and i could be cool with the rest of you guys post if you need 92 aj parts!!!
 
Sounds like a bad egr or an ambient air temp sensor. Thats just my .02
The reason im thinking the ambient air temp sensor is that you said it gets a little better in the cold weather, The sensor tells the ecu to adjust the timing accordingly to the air temp to prevent pinging. maybe its sending a bad signal and the computer's retarding the timing. Well maybe this will help ya.

Alex

Henderson Nevada
 
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