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Renix stalling when warm

67TEMP

NAXJA Forum User
My 87 4.0/aw4 is stalling when it gets up to operating temperature. The stall happens when I shift into gear or if I start moving it before it's fully warmed it will run for a while and I lift off the throttle it will die (once wram). When it stalls it will crank but not fire untill it sits for about 10 minutes. The weird part is if the fuel pump is unpluged it will fire after a few seconds of cranking but will sometimes stall again when the pump is plugged back in. Seems almost like it is flooding.

I've tried swaping the tps, iac, and fuel regulator from another jeep but it's still doing it.

Where should I start looking?
 
I would look at relays and the resistor block first. They won't cost you anything but your time. I still have my resistor but I have heard that they can be bypassed. As for the relays there are several all clusterec together on the passenger side inner fender well. They are interchangeable. One is the fuel pump and one is the latch relay while another is the A/C relay. There may be others depending upon your options. All are the same and they just plug in so swap them around and see if it helps.
Blue
 
I had the same problem and I don't have an exact solution. First I cleaned all electrical connectors with CRC cleaner and used light CRC grease on everything. Swapped TPS and it ran better. Dialed that in and still stalling. So I changed sparkplugs to standard champion plugs puled the cap and rotor and put all new wires and such back in. Runnning better but still stalling out hardly. Check your o2 sensor on your header manifold. Mine is cracked and I think that might be throwing my Jeep off loop with itself. Since I don't have an exact awnser im just trying to help a fellow Renix engine guy out. Search for Renix Files in search and maybe there are a few tips there. Next I'm changing CPS Idle stepper motor and o2 sensors. See how it goes from there.
 
Fuel presure is at 35. Pretty sure it's nothing to do with the ignition since it will refire when I disconnect the fuel pump and starve the motor.

I'll check the renix files thread to see if that helps with ideas.
 
Bad temperature sensors (engine and air) can easily cause your engine to run rich after it's warmed up. I'd check the wiring to the sensors first, then check the resistance, using an digital volt/ohmmeter, to insure correct values when cold, and at operating temp.
Engine "cold", both temp sensors should read ~3400 ohms when the engine is at 70*f. They should both read ~450ohms when the temps are at 160*; both sensors change resistance inversely proportional to temperature. They range from ~25,000 ohms at 0*f to 185 ohms at 212*f.
 
67TEMP said:
Fuel presure is at 35. Pretty sure it's nothing to do with the ignition since it will refire when I disconnect the fuel pump and starve the motor.

I'll check the renix files thread to see if that helps with ideas.

I got the perfect fix for ya and I am sure it will fix your problem as it fix mine.

Ignition Switch located on top of the steering column. Not that hard to get too and only 10 bucks for a new one at auto zone. Mine was melted somewhat and if i let the engine get too warm I wouldnt be able to start it for a while. But it would fire up everytime cold. I was going the route you went checking pressure adjusting TPS. never fixed it. Real easy to get too. Remove the lowest dash piece its like 6-8 cross tip screws. and then you will see it on top of the steering column. You can do it from there but it is a PIA in that position. I took off the too 15mm nuts and let the steering column drop down for easier access to the switch.

This is what it looks like

http://www.autozone.com/R,APP370669/...ductDetail.htm

Inspect it before you go crazy with sensors and what not.
 
I work on this truck with the owner.

When we say it won't start we mean that it won't run. It cranks over just fine but doesn't start. If you disconnect the fuel pump, it will crank for a bit then catch and run for a few seconds weather you plug the fuel pump back in or not. The ballast resistor should be a good place to start.
 
Not likely the ballast resistor, since its only failure mode is to open up and not let the fuel pump run. In fact, you don't need the ballast resistor at all. It's there to slow the pump down to reduce noise.
You can try holding the gas pedal to the floor when your cranking the engine. Doing so puts the ECM in "flood mode", which turns off the injectors while cranking. Of course, do so will not fix your problem, just another way to confirm it's too rich during warm start up.
Again, a common cause for running rich when warm, is a bad temp sensor; it's the modern day version of the choke, telling the ECM to richen the mixture when cold, and to lean the mixture when warm.
 
crawfishstu said:
I work on this truck with the owner.

When we say it won't start we mean that it won't run. It cranks over just fine but doesn't start. If you disconnect the fuel pump, it will crank for a bit then catch and run for a few seconds weather you plug the fuel pump back in or not. The ballast resistor should be a good place to start.

My vehicle would crank all day and then maybe start (then die again) most of the time it would just crank. then i would leave it alone for awhile and it would just crank right up and i could drive it all around till i shut it off again. i Didnt ever mess with the fuel pump so i can't say wether unhooking it or what not would help you start wuicker i am just informing you of an easy check that could be your problem.
 
its just an ignition switch. not the part the key goes into. it is under the dash on top of the steering column it has a big wiring harness going into it that sometimes just gets to hot and fries. You dont have to take the column apart or nothing to get to it just have to drop it down a bit. Hmmm i just looked at the link I will try posting it again

This is the thread i was looking at when i found some good info and I also posted the link here and it works fine... now the link is dead WTF just worked 10 minutes ago for autozone. well let me look around some more

Page 2

http://www.naxja.org/forum/showthread.php?t=939364&page=2&highlight=ignition+switch
 
Stryker is that the $300 part that fixed your hot no start problem, or the $35 part?
 
With the coolant temp sensor disconnect, Renix assumes 176 degrees and will keep the mixture appropriate to that temp. So, just as a suggestion I would disconnect the CTS when its hot and see what that does since it sounds like you might be flooding.

It on the lower side of the block-you get at it from underneath. Don't confuse it with the knock sensor which is also in that area.
 
90Blue_XJ said:
Stryker is that the $300 part that fixed your hot no start problem, or the $35 part?


Not sure what you mean. I know i talked about it on cherokeeforum.com but dont remember saying what it cost. The ignition switch was a 10 doller one frome autozone i guess they dont carry them any more so there 20 bucks at advance. but yeah it fixed my hot no start problem.
 
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