Jeep XJ stumbles and stalls (Injector wiring issue)
For quite a while now Jenny’s 1992 Jeep Cherokee has had a stumble or hiccup while driving. We have tried changing a lot of parts to make it go away. New crank sensor, fuel pump, etc.
On her last off-road adventure, the stalling got so bad as to be dangerous. At one point the Jeep would not go into reverse without stalling. It became very noticeable that whenever the engine shifted positions it would stall.
We checked all the wiring connections that could move and they all seemed fine. We were close to ordering a new distributor.
My Jeep had the typical problem where the HVAC only blows out the Defroster. The defroster is the default mode when there is no vacuum supply. So I set about finding my vacuum leak.
It did not take me long to find an obvious break in the plastic vacuum tubing. The trouble was, it was broken on the cabin side of the firewall. It was too far in to reach to make a splice.
After replacing my engine, I had to reconnect the AC lines and replace the freon. The system was originally designed to run R12 but I swapped over to R134 a long time ago. However, I still like to use my old gauge set on the R12 style fittings. I just adapted the yellow hose to fit the R134 cans.
I installed a new dryer and reconnected the hoses using new O rings where the old ones looked bad. I then hooked up my vacuum pump and pulled al the air out. I shut off the pump and closed the valve to see if it would hold. It held vacuum so I assumed no leaks and popped in the first can of freon.
How to delete the troublesome heater control valve on a 90’s XJ
My 1991 Jeep Cherokee had the fragile plastic heater valve. Not only can this valve break and leave you stranded, it is prone to leak at the valve actuator. I have replaced mine a couple of times already so this time I decided to do away with it for good.
The factory manual shows that this valve is open in all positions except closed and full cold on the temperature control switch. In the later years, Jeep deleted this valve.
They say if you don’t use something in a year you should get rid of it. Well, I don’t take that advice on tools. I can’t remember how many years it’s been since I last used this tool but today it was really handy to have.
When I was trying to figure out the trouble with my Porsche tail lights I found that the previous owner had modified the wiring for the left side tail light. Also, the front corner markers have never worked since I have had the car.
Tracing the circuit, I found a dead short in the left side wiring that would blow the fuse. I assume this is the reason why they have jumpered the tail light wires and disabled the front markers.
Using the above tool, I was able to trace the short to somewhere in the front fender area. Without it, I would have just been guessing.
I made a jumper to use the tool to put power to the load side of the fuse and took power straight off the battery. Since there was a dead short I did not want to stress the light switch while searching for the short.
I was able to use the little meter to follow the wire through the car and down into the fender. I then put the car on the lift and removed the belly pan to get access to the wire. Since there was just a short section of wire to inspect I decided to do a visual inspection instead of continuing with the tool.
It took some searching, but I finally found the problem. The wires inside the left side marker were twisted together and the ground was touching the power lead inside the rubber cover.
I hooked them back up correctly and the short went away. I then redid the wiring at the tail lights to put it back as the factory intended. now there is a fuse for the left and a fuse for the right. And another fuse for the tag lights. Germans like fuses I guess.
Review of the Nick In Time Renix Engine Monitor REM
My Off Road Jeep is an 88 two door with the Renix engine controller. It has also been stroked and bored to 4.7 liters.
Based on the engine builder (Titan Engines) recommendation, I installed Ford injectors. However, the engine has always run rich at off-road speeds.
Since the scan tool to read the Renix version was discontinued long ago and the supply has dried up on eBay, I have not had a way to read the codes or do much troubleshooting on my Renix engine.
I was excited to read some time ago that people were working on a way to use an Arduino to read the data stream. However, I never had the patience to learn to build one or even try to translate the instructions from Russian.
But then I found Nick In Time Designs. He has built a nice unit that not only reads the data but interprets it in an easy-to-read format. He has recently sold a few of the handmade units and I was lucky enough to snag one.
I hooked it up in my old Jeep this weekend. I had a little trouble getting the 3D printed adapter to fit on the connector under the hood but it was just a very snug fit. I then set the switch to 4.0 and closed the cover. I then plugged in the supplied Ethernet cable. I found a plug in the firewall and routed the cable inside.
I ended up mounting the module in the hole where the radio used to be with now also has my winch controls. I then plugged in the other end of the cable to the 3D printed display module.
I am amazed at the amount of data that the device reads out. I made a few loops around the trail on my farm. I did have difficulty driving the narrow trails and watching the changing numbers at the same time 😉
I did learn what I suspected, but it wasn’t as bad as I thought. The engine does run rich most of the time and will not stay in closed-loop control mode because of it. It does occasionally go into closed loop and I can watch the O2 reading switch from lean to rich so the O2 sensor is working properly.
My next step will be to swap to some smaller injectors like I did on my Dad’s Wagoneer. Then I can enjoy watching the data stream again.
Update:
I hooked up the monitor to Dad‘s Wagoneer to see what the difference in O2 reading would be. I was a bit surprised to find the yellow trouble light on on the module. Cycling through the data showed me a low TPS reading.
I tested and it appears the sensor is bad. This is likely what causes his off-idle stumble. I will see what happens when the new sensor arrives. Update: the new TPS cleared up the stumble and the odd shifting of the transmission.
Knowing what to pack is always a challenge. Here are seven things I never hit the trail without.
A good tow strap. One with loops on each end and designed to handle the load of your Jeep and whatever else you will be puling. Carry more than one strap if you can. They can be used to extend a winch line, stabilize a tippy Jeep as well as assist to get over a slippery spot or a rock.
Tracking down an intermittent electrical problem in my 1988 Renix Cherokee.
Trouble started a couple of years ago in Harlan when I lost one cylinder. I had five perfectly good running cylinders and one that simply did not fire. After some experimentation, I found that swapping the injector wiring around would move the dead cylinder. Tracing the wiring back under the dash led me to replace the ECU.
I recently swapped the injectors in my Dad’s Wagoneer. I like the results so much I ordered another set of injectors from K Suspension for my Jeep. Both of us have 4.7 stroker motors built by Titan engines.
You can see the previous post for the details on how to pull the fuel rail.
