Truck Keeps Dying =(

[relyt120]

Hey all,

 

I picked up a 2nd truck the other day and this one is a manual.

In fact it is the first manual I have ever owned, though I do know how to drive stick.

Well I got all the signals working and got a temp tag for it so it is street legal and I have been trying to drive it some to find the kinks.

 

My issue is that when driving it if I am not giving it gas it will die, it does matter if I am coasting around a corner or at a stop light or the like it just dies and then it doesn't want to start for about a minute. :hmm:

It has a really long crank time too so I am surprised it hasn't killed the battery with the multiple cranks I am having to do for a short trip around the block.

The truck idles pretty good but due to the huge hole in the muffler it is really loud making it a bit tough to listen for much while it is running.

 

So my question is: has anyone else had the issue where it dies if not given constant gas, and if so what causes it?

The truck is an 89 4.0L manual(4+O) not sure which tranny though.

 

Thanks in advance for your help!

[ComancheKid45]

Sounds like a failing Crank Sensor.

[ftpiercecracker1]

I would say the TPS is out of adjustment.

[87MJTIM]

Your trans is probably an AX15 unless the PO changed it.

 

If it stalls when you try to give it gas, I would suggest replacing the fuel filter. It sounds like it isn't getting enough gas.

 

Then check all the fuel lines for blockage.

 

Also, check out Cruiser54's info.

[relyt120]

Thank you all for such prompt responses! I will check into each of those issues in turn. Would any of these (crank sensor, or tps) cause the extended start time? I'm assuming the answer is yes.

As for the fuel filter I assumed that it had been changed recently cause I found an old one in the bed when i picked the truck up, I find that I have made too many assumptions with this one and will check it and replace if need be.

Once again thanks!

[cruiser54]

Here's the first thing to do:

 

Courtesy of TJWalker:

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The Idle Air Control (IAC) is mounted on the back of the throttle body. (front for 87-90) The valve controls the idle speed of the engine by controlling the amount of air flowing through the air control passage. It consists of a stepper motor that moves a pintle shaped plunger in and out of the air control passage. When the valve plunger is moved in, the air control passage flows more air which raises the idle speed. When the valve plunger is moved out, the air control passage flows less air which lowers the idle speed. Over time and miles, the IAC can get carboned up which can have an adverse affect on idle quality. Cleaning the IAC may restore proper function and is an easy procedure to perform and good preventive maintenance so it is never a bad idea.

CLEANING THE JEEP 4.0 IDLE AIR CONTROL

Remove the air filter cover, associated hoses and the rubber boot that goes from the air filter cover to the throttle body. Remove the IAC with a torx driver (2 bolts; one can be kind of hard to get to)

“Gently” wiggle out the IAC from the throttle body. Gasket on the IAC can be re-used if it is not damaged

Clean the IAC with a spray can of throttle body cleaner; inexpensive and available at any place that sells auto parts. Throttle body cleaner is recommended rather than carburetor cleaner as it is less harsh, safe for throttle body coatings and is best for this task. Use cleaner, a rag and a toothbrush and or Q-Tips. Be gentle; don’t twist or pull on the pintle that protrudes from the IAC as it is fragile and you could damage it.

Thoroughly spray clean and flush where the IAC seats in the throttle body with the same spray cleaner

It is also a good idea to clean the entire throttle body itself, the butterfly valve inside of the throttle body and all associated linkage as long as you have things disassembled

[cruiser54]

Renix Ground Refreshing

The Renix era XJs and MJs were built with an under-engineered grounding system for the engine/transmission electronics. One problem in particular involves the multiple ground connection at the engine dipstick tube stud. A poor ground here can cause a multitude of driveabililty issues, wasted time, and wasted money replacing unnecessary components.

The components grounding at the dipstick tube stud are:

Distributor Sync Sensor, TCU main ground, TCU “Shift Point Logic”, Ignition control Module, Injectors, ECU main ground which other engine sensors ground through, Oxygen sensor, Knock Sensor, Cruise Control, and Transmission Sync signal. All extremely important stuff.

The factory was aware of the issues with this ground point and addressed it by suggesting the following:

Remove the nut holding the wire terminals to the stud. Verify that the stud is indeed tightened securely into the block. Scrape any and all paint from the stud’s mounting surface where the wires will attach. Must be clean, shiny and free of any oil, grease, or paint.

Inspect the wire terminals. Check to see that none of the terminals are crimped over wire insulation instead of bare wire. Be sure the crimps are tight. It wouldn’t hurt to re-crimp them just as a matter of course. Sand and polish the wire terminals until clean and shiny on both sides. Reinstall all the wires to the stud and tighten the nut down securely.

While you’re in that general area, locate the battery negative cable which is fastened to the engine block just forward of the dipstick stud. Remove the bolt, scrape the block to bare metal, clean and polish the cable terminal, and reattach securely.

Another area where the grounding system on Renix era Jeeps was lacking is the engine to chassis ground. There is a braided cable from the back of the cylinder head that also attaches to the driver’s side of the firewall. This cable is undersized for it’s intended use and subject to corrosion and poor connections at each end.

First off, remove the cable end from the firewall using a 15mm wrench or socket. Scrape the paint off down to bare metal and clean the wire terminal. Reattach securely.

Remove the other end of the cable from the rear of the head using a 3’4” socket. Clean all the oil, paint and crud from the stud. Clean the wire terminal of the cable and reattach securely.

A suggestion regarding the braided cable:

I prefer to add a #4 Gauge cable from the firewall to a bolt on the rear of the intake manifold, either to a heat shield bolt or fuel rail bolt. A cable about 18” long with a 3/8” lug on each end works great and you can get one at any parts store already made up. Napa has them as part number 781116.

A further improvement to the grounding system can be made using a #4 cable, about 10” long with 3/8” terminals at each end. Attach one end of this cable to the negative battery bolt and the other end under the closest 10mm headed bolt on the radiator support just forward of the battery. Napa part number 781115.

For those of us with Comanches, it’s very important to remove the driver’s side taillamp assembly to access the ground for the fuel pump. Remove the screw holding the black ground wire. Scrape the paint from the body and corrosion from the wire terminal. Reattach securely.

 

If you want to upgrade your grounds and battery cables in general, contact Jon at www.kelleyswip.com. He makes an incredible cable upgrade for a very reasonable price.

 

Revised 12-04-2012

You're nuts if you don't do this:

[relyt120]

I tested the cps and it was reading just a tad low so I cleaned it with a toothbrush attached to a ratchet extension and some carb cleaner and it reads adequately now and I took it around the block a few times and the issue seems to be gone. Crank time is till.a bit higher than I'd like it but I will worry about that after I take care of the leaking injector I found. Thank you all for your help.

[cruiser54]

Renix has a longer than normal crank time. I am not sure I understand your post. Did you clean the throttle body and adjust the TPS?

[relyt120]

I cleaned the crankshaft position sensor, I accidentally typed tps I have edited my post to reflect this error.

[Minuit]

Now that you've fixed your problem...

 

:needpics:

[relyt120]

http://comancheclub.com/topic/36528-codename-bumblebee/