• Welcome to the new NAXJA Forum! If your password does not work, please use "Forgot your password?" link on the log-in page. Please feel free to reach out to [email protected] if we can provide any assistance.

Renix issues

T

the_shotty

NAXJA Forum User
Location
Washington
Hey guys, I've never been one to post but I'm not sure where to go from here. I've read pretty much everything I can find gone though posts from 5-90, cruiser, and echomike remix issues and have attempted to address all the issues they have come up with. I have a 90 Cherokee 4.0 auto with an 92 HO block in it with ~230k miles and compression is 128-132. I have done the ground up grades and added a 4ga ground from the manifold to firewall all connectors were cleaned and greased. I did a egr delete, new manifold gaskets new headers for a HO. Replaced all hard vac lines with rubber. I have changed out within the last two years: injectors to 5.0 mustang injectors, IAC, FPR and fuel pump, TPS, MAP, o2 sensor, just did the CPS, new coolant temp sensor which was re located to the thermostat housing for the HO swap. Battery and alternator and starter were replaced this summer. My issue is the motor starts good and runs ok until it warms up then it will randomly die and not start for a while or until I disconnect the battery and re connect it. At that point it starts fine again but revs to 2k for a few seconds then settles back to 500 or so rpms and will run ok for a little while and die again. Then I can disconnect battery and the process starts over.when it's during it is almost like I am running out of gas but fuel pressure is 30/39 with the FPR disconnected and it holds pressure at the rail only dropping to 28psi after ~8hrs. It will crank and I am getting spark when it dies, CPS output is 4.7-5.4 fluctuating during cranking(is it normal to fluctuate?) and has 198 ohm. Coolant temp sensor puts out correct ohm checked against a IR heat gun at the thermostat housing and is within 50ohm of the AIT output. TPS is outing out 4.9 reference and .82 though I seem to have to adjust this often as it seems to drop down to .78. MAP sensor is outing out 5.02 volts. I have tried wiggling the harness and connections at multiple points, my resistance between all grounds seems to be the same. What am I missing what else should I try? My last tank I got 17mpg, it's a weekend use only that I don't put many miles on and was running well all Sumer until October when this started happening.
 
the_shotty said:
MAP sensor is outing out 5.02 volts.
Click to expand...
The map sensor should vary depending on the throttle position. If it is sitting at 5.02v then you most likely either have a bad map or a non existent ground on the sensor.
 
So, on the map sensor, I have 5.04 volts motor off/ ignition on and when I turn the motor on I get 2.04-1.92 when cold and 1.82-1.75 warm .2 resistance sensor ground to battery.
 
I pulled apart and soldered all those grounds in the harness. I have the harnes all pulled apart again right now as I am not getting the 12-14 volts on the orange wire to the O2 sensor and found a brake in the wire at the relay plug and also have no ground at the plug. My TPS ground shows .02 resistance between the battery and ground at the plug.
 
I'll try and sort the o2 sensor out and see if that fixes it. I think I'm going to do an AC system delete while I have everything torn apart so it may take me a little while to get it all sorted out.
 
Ok so tonight I verified the ground wire from the 02 heater relay to the ecu was good and fully pulled out the ecu. Holy cow I forgot how much of a pain that was! It was a little crusty under there and there was a bit of rust on the mounting bolts. I tried cleaning that up, I have already done all the ground upgrades including the under dash one. Anything else I should do/check before I put it back together?
 
And??? Sounds like the O2 sensor was part of it. If not check the spark coil and ICM assembly, and spark quality and the intake air temp sensor ones I can think to add to the list at this point
 
I'm still working through stuff. I pulled the dipstick grounds and cleaned them as well as re greased them even though nothing appeared out of whack and had good resistance between them and negative battery post. I do have a brake in the output wire in the harness for the o2 relay harness but I don't think it is impacting anything. I may try and replace the whole harness as I can't seem to get the wires to come loose. Resistance on the AIT was within 10-20 of what my CTS was which seemed to be normal? It's the way it's always metered though it is one of the only sensors that has not been replaced, just cleaned when I replaced the intake gaskets and did headers. How do you check spark quality? I have one of the inline light bulb spark check tools and the pulse seems consistent and the light seems to light up well, is checking a plug to ground a better test? Coil also has not been replaced, I have taken it out and cleaned and adjusted the connections per cruisers renix tips. I have checked the coil with the aforementioned in line tester when the motor dies and I still get spark. What should I be looking for with the ICM? I have it out right now and cleaned up some of its mounting hardware as it was getting a little crusty but is there some thing in particular to look at? I was going to check resistance of the terminals to see if maybe I had a brake or corrosion but other than that? Thanks for the responses so far. Oh I also got a whole new battery ground wire/terminal at the original had broken and was shortened and re installed on the AC bracket below the battery tray. It has been like that for years but I figured I would finally fix it while I'm in there.
 
I had a bad ICM-coil assy that was causing my problems for weeks till I lost the ability to start the engine. Swapping out the entire assy with a used one solved the problem (3 years ago on a DD). Never found a test to confirm the bad part. I think it was an overheating part in the ICM buried under the epoxy as I found a hot-melted spot on the ICM epoxy.

AIT should be running about 40 to 100 F cooler than the CTS, as one is sensing moving ambient out door air passing through a warm intake manifold. The other is sensing a constant coolant liquid temperature. If Ambient outside air is 32 F and the Intake is 140 F at say 2000 rpm, then the IAT should read about 100 F for fast moving air. Best to pull the IAT and compare ambient air temp versus the data table resistance spec as one of several tests. Hot air hair dryer might useful with a know working temp tester...for another test. Heat the sensor in boiling tap water, dry it quickly and test for about 190 F (it will cool quickly) might work too for the high end reading.

Spark quality is sound and color, want a loud snappy blue spark IIRC. A spark plug is useful. Also might be useful to use a wide gap plug to see if the voltage is high enough for a wider gap than new spec gaps. The ICM does control spark timing as well as the ECU, and if it is bad, even with a spark it will not run, or will die due to poor spark timing....

If the O2 sensor is not getting 14 volts to the heater, it will cause the warm engine to run badly at times as it gets hot and cold from operating, Cold at idle, hot at cruising. The heater in the O2 sensor is to keep it in closed loop when idling. The engine is not hot enough at idle to keep the O2 sensor at operating temp at idle. Switching back at forth confuses the ECU...
 
Ecomike said:
I had a bad ICM-coil assy that was causing my problems for weeks till I lost the ability to start the engine. Swapping out the entire assy with a used one solved the problem (3 years ago on a DD). Never found a test to confirm the bad part. I think it was an overheating part in the ICM buried under the epoxy as I found a hot-melted spot on the ICM epoxy.

AIT should be running about 40 to 100 F cooler than the CTS, as one is sensing moving ambient out door air passing through a warm intake manifold. The other is sensing a constant coolant liquid temperature. If Ambient outside air is 32 F and the Intake is 140 F at say 2000 rpm, then the IAT should read about 100 F for fast moving air. Best to pull the IAT and compare ambient air temp versus the data table resistance spec as one of several tests. Hot air hair dryer might useful with a know working temp tester...for another test. Heat the sensor in boiling tap water, dry it quickly and test for about 190 F (it will cool quickly) might work too for the high end reading.

Spark quality is sound and color, want a loud snappy blue spark IIRC. A spark plug is useful. Also might be useful to use a wide gap plug to see if the voltage is high enough for a wider gap than new spec gaps. The ICM does control spark timing as well as the ECU, and if it is bad, even with a spark it will not run, or will die due to poor spark timing....

If the O2 sensor is not getting 14 volts to the heater, it will cause the warm engine to run badly at times as it gets hot and cold from operating, Cold at idle, hot at cruising. The heater in the O2 sensor is to keep it in closed loop when idling. The engine is not hot enough at idle to keep the O2 sensor at operating temp at idle. Switching back at forth confuses the ECU...
Click to expand...

Tip 4 in my link below would be worth doing.

www.cruiser54.com
 
Nice website cruiser. First time I have seen it. Just bookmarked it :)
 
cruiser54;246278267 Check out what I added last night. A helpful lings page.[/QUOTE said:
About the blower ground? Ill probably do that cause my blower seems to eat a lot of amps
Click to expand...
 
You must log in or register to reply here.

Similar threads

Z
1990 renix electrical issues
Replies
3
Views
76
cruiser54
C
J
2001 4.0L issues
Replies
15
Views
251
Saudade
Saudade
S
Issues flushing dirty coolant
2
Replies
29
Views
4K
fenns7
F
O
2000 XJ Failed Colorado Emissions high CO
2
Replies
27
Views
2K
Ken M
K
A
Renix TPS nightmare
Replies
19
Views
3K
Saudade
Saudade
Back
Top