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Deepwater Jeepin · 03-07-2010, 10:16 PM

I don't claim to be a machanic, but im having a problem finding a connection between the flywheel and our misfire issue.

murrman · 03-08-2010, 10:38 AM

The crank position sensor reads the teeth on the flywheel and if the flywheel flexs under a pull from being cracked it will cause the teeth to move out of position just enough to cause a misfire. It could possibly be the crank sensor but usually if it fails it won't even start but it could be that sensor. It is easier to check the flywheel than replace a $74 sensor and that not fix it, but if the flywheel is not cracked then try a sensor. But this is just a idea, I chased a misfire that was very intermittent and I finally replaced the crank sensor and that fixed it but had replaced most of the sensors for the fuel injection one at a time to try to isolate it.

Deepwater Jeepin · 03-08-2010, 12:40 PM

I will have to take a look at it. I just recently replaced my cps, which fixed a studder / stall problem i had. But why only when i try starting it, when it is hot?

JpUseR96 · 03-08-2010, 04:31 PM

Sounds like a starter solonoid problem...yes, I know they are on oppisite sides of each other. If it were a heat sensor problem it would matter cause these bastard's run hot anyway. What are the exact symptoms? No starter movement at all or just slow grinding?

JpUseR96 · 03-08-2010, 04:32 PM

rewrite....heat sensor problem because it WOULDN'T matter, the bastard's run TOO HOT anyway!!!!

Deepwater Jeepin · 03-09-2010, 12:29 AM

Its the exact symptmes as listed in the links at the begining of this thread. The jeep is "heat soaked". But as Mud and others on different sites have reported, new injectors and heat shielding does not seem to cure the problem.

I have actually had it bad enought to where the jeep will shut off, and not start at all. It will turn over fine, but untill i let it sit there a while, it will not fire up, and then i have to work through the misfire. It sucks.

JpUseR96 · 03-09-2010, 07:28 AM

there is an after market relay made by Turbo City that allows the engine's electric fan to kick-on and stay on until the engine temp is down to 180 degrees. You will also have to change to a lower setting t-stat. There are a number of custom T-stat builders onlline. I put on on my 96 4.0 and the engine overheating stayed very controlled. I won't say it still doesn't get hot but it sure helps. It's simple to install.

**muddeprived** · 03-09-2010, 07:44 AM

Quote:

Originally Posted by JpUseR96

there is an after market relay made by Turbo City that allows the engine's electric fan to kick-on and stay on until the engine temp is down to 180 degrees. You will also have to change to a lower setting t-stat. There are a number of custom T-stat builders onlline. I put on on my 96 4.0 and the engine overheating stayed very controlled. I won't say it still doesn't get hot but it sure helps. It's simple to install.

This?

It's a delay timer that I haven't installed yet...cuz I dunno how. Doesn't seem as simple as people say......if you don't know nothin about wiring stuff up like me.

But honestly, I'm really frustrated with this whole ordeal because this is a factory defect that they never put time into fixing properly and I have to spend countless hours and money trying to fix it. I'm on the edge of just tossing out the entire motor for another one.

(sorry it misfired 4 times in just one week......

)

JpUseR96 · 03-09-2010, 03:04 PM

Quote:

Originally Posted by Deepwater Jeepin

Its the exact symptmes as listed in the links at the begining of this thread. The jeep is "heat soaked". But as Mud and others on different sites have reported, new injectors and heat shielding does not seem to cure the problem.

I have actually had it bad enought to where the jeep will shut off, and not start at all. It will turn over fine, but untill i let it sit there a while, it will not fire up, and then i have to work through the misfire. It sucks.

You need to double-up on your electric fans, scavenging extra HP from your no longer running of that damn fan clutch set-up, as well as getting the heat OUT of the engine compartment via custom vents, etc. In addition, if you have he cash there is a solid 4 core radiator out there...all it take's is $$$$$$$. You can only expect these poorly designed 4.o 's to take so much abuse!

**muddeprived** · 03-09-2010, 04:07 PM

I don't think it really matters what radiator or fans you are running because the heat soak issue happens when the vehicle is off and all that heat is trapped under the hood. I was told the heat can cause the gas to boil and the vapors from the gas are what causes the misfire. We need to reduce the amount of heat coming off the headers cuz the fuel line and injectors run right next to it. I have hood vents installed and they let out alot of heat but not enough to keep the fuel from vaporizing. If I drive around and park it with the hood open, it will NOT misfire. It has never misfired when I left the hood open. But who wants to have to pop the hood open every time they park?

JpUseR96 · 03-09-2010, 04:29 PM

Again, the need for dual ELECTRIC low thermostaticaly controlled fans (with the custom low temp t-stat) to push the air OUT; or simply buy the big 4 core radiator and forget about ALL HEATING PROBLEMS. The current 4.0 has a very undersized 2 row radiator...BAD, BAD cost cuts made by Jeep during the design phase. Almost as BAD as the crappy brakes they expect to save our lives!!! The brakes and cooling system are always the first thing cut when the project comes in over its initial build budget!!!

**muddeprived** · 03-09-2010, 05:00 PM

Quote:

Originally Posted by JpUseR96

Again, the need for dual ELECTRIC low thermostaticaly controlled fans (with the custom low temp t-stat) to push the air OUT; or simply buy the big 4 core radiator and forget about ALL HEATING PROBLEMS. The current 4.0 has a very undersized 2 row radiator...BAD, BAD cost cuts made by Jeep during the design phase. Almost as BAD as the crappy brakes they expect to save our lives!!! The brakes and cooling system are always the first thing cut when the project comes in over its initial build budget!!!

What kind of fans do you recommend for the stock 4.0? I have a 01. Are there any bolt on fan upgrades that can be controlled via a switch if needed? I prefer to have a bolt on kit instead of hacking up stuff to make something fit.

JpUseR96 · 03-09-2010, 08:46 PM

Mudd, try going to http:??www.turbocity.com.default.php. If that doesn't get you to the simply relay they make then,email me again and I will scan and forward my iniitial instruction from a couple of years ago and they Turbo City will know hat you are looking for. As stated ealier you will also have to get 180 degree t-stat, and there are allot of custom builders and they don't cost allot. YOU CAN'T EXPECT PERFORMANCE WITHOUT A PRICE!!!! let me know how I can help if this doesn't work. WE ARE ALL IN THIS TOHGTER!!!

**sreppok** · 08-17-2010, 08:03 AM

Quote:

Originally Posted by cubanater

i changed every censor known to man

Stinkin' Catholic priests, meddlin' in our Jeeps!

aka_BountyHunter · 08-17-2010, 12:49 PM

I recently had the mis-firing situation on my '98 4.0L , which produced the "check engine" code PO301 and PO302 as well as a "timing" issue. Turns out that the culprit was the CPS Crankshaft Position Sensor, which controls the timing, and is a bear to get to. A trip to Pep Boys and $80 bucks later, problem solved!
It's pretty easy to check, all you need is an ohmmeter and a Haynes Repair manual.
Good luck.

aka_BountyHunter