This Jeep sat for 3 years, I finally got to working on the project.

It is a 2000 Cherokee with a 99 Motor running a eBay stainless header, Instead of the the rail coil it has been swapped out for a Dodge Coil and wires. (look up Jeep 4.0L Viper Coil Swap)

The gas went bad and I dropped the tank and cleaned it out and replaced the fuel pump (with a cheap generic that had good reviews).

I drove it the first time couple of weeks ago to get title & plates transferred and a brake caliber locked up, but it made it home and back and ran ok.

It always needs a little gas peddle to start but will idle fine once running.

Now as soon as it starts to warm up when driving it, anytime you give it a fair amount of gas it starts cutting the ignition in and out around 3000 RPM's - JUST LIKE A REV LIMITER

I was thinking Crank Sensor, but first thing a buddy asked was about injectors (which I was concerned about because of bad gas) and spark plugs (which I thought were for a non-coil motor - but they were the Champion plugs part# on the firewall sticker) - I swapped all the plugs for new NKG's and checked all the injectors, I went ahead and bought new injector seals, so I pulled them all off, found a few cracked casings, replaced all the bad ones with old ones I had in the garage, and checked all the injectors for good spray pattern before reinstalling the rails.

Took it for a test drive and I got the same thing...... as soon as it starts to get warm, anytime I give it any decent gas pedal it hits around 3K rpms and just starts cutting out like it hit a rev limiter.

OBDII had only one code, it was for a BUS Link error, which I think was from when the BUS came up a few months ago on Odometer- but has not since.

OK folks, what is your best guess?????

Crank Sensor?
Use a Dodge Coil and Wires?

Just looking for the next part to try swapping out..... hate being a parts swapper, but sometimes ya just have no choice.

 

Well I went to hookup my Harbor Freight fuel pressure gauge and I did not have the right adapter to connect to the rail. But I did some further testing and found out

1) It does it driving or sitting in neutral.
2) If I shut the Jeep off and restart it - it runs fine for 5-15 minutes.

I still think its the ignition cutting off, now I think maybe the jeep might be going in a LIMP mode.

I do think I have a miss as well, I think cylinder 1 is not firing as I pull the injector wire and hear no difference.

Here is a video I took today.


Thanks for looking, open to suggestion.

This point I am going to try a different coil since I got the one I am using from a buddy used, and try to get an adapter for my fuel pressure gauge to see my fuel pressure.

Thanks, Bryan

 

Get the proper fuel pressure tester and check your fuel pressure when revving the engine. It should hold at 49.2 psi +/- 5 psi.


That el cheapo fuel pump may be bighting you on the ****.


Limp mode is a transmission function, not engine management function.


Consider the Camshaft Position Sensor being defective, but check the fuel pressure first.

 

Well fuel pressure is a solid 50lbs, even when its acting up it just moved from 49-50lbs as it cut in and out.

Also checked all the injectors to make sure they were getting a fire signal with a noid light and all were good (earlier checked the injectors by apply 12 volts to each and check spray)

I did run a bluetooth OBDII and Torque Program on my phone and noticed 2 things, one I could only get a reading for O2 Sensor Voltage Bank 1-1 and Bank 1-2 no Bank 2-1 or Bank 2-2 (but I did not play with it much) as well as Fuel Trim Bank 1-1 and 1-2 showed but no 2-1 or 2-2. (Could be I just was setting thing wrong) - ALL 4 O2 sensors are plugged in (I checked)

But really interesting was that O2 Sensor Voltage dropped to 0 in both O2 sensors showing when it acted up (rev limited), as well as did the fuel trim drop to 0, shut off the car and turn in back on and Voltage came right back, but the trim took a minute or two to come back. - Going to play with this more tomorrow with my Tablet now that is charged and I can have a bigger screen to show all the settings at once.

Still investigating what the above might mean, What next to check Cam Sensor, Coil Pack, O2 Sensors, or PCM.

Since some injectors when the wire is pulled effect idle more than others, I am leaning towards the Coil Pack, might just order one today, then look at the Cam Sensor and its setting, then O2 Sensors, then PCM...... Any words or wisdom or thoughts from the CherokeeForum community ?

Thanks

 

More updates:

It went from hitting a rev limiter at 3000 RPM's, then it quit in the driveway, would not start, I have "NO BUS" intermittently showing and my Gauges are not working at all, unplugged TPS, CPS, CKS and still no gauges, so I pulled the computer and it had like a brown ooze all over where the (3) big plugs plug-in. Have a feeling my computer took a dump.

I was able to hookup my OBDII reader and see that it had the P1694 NO BUS error, so my reader can still read the computer, I hooked up my bluetooth OBDII and Torque on my tablet, with the key forward in the run position I only got OBDII Voltage reading, no reading from the O2 Sensors, or Voltage(CM) which I think is PCM, but I am not sure if any of these would show up unless its running.

Looking at another thread on computer replacements, and found a Mopar PDF on Computers, in theory I am guessing I can use any of the ones listed in this group (I am guessing the letter at the end represents software revisions) so the later the better for the letter....

1. Do you agree brown ooze = probably bad computer
2. Any way to make sure the computer is BAD?
3. I read somewhere that it was commonly a bad solder connection - tempted to try to fix it.
4. Do you feel like any in the group listed in the below image should be compatible with mine

 

I replaced the Computer with one out of a 2001 and it ran again but still same problem with it cutting out at 3000RPM

Changed the upstream O2 Sensors and that did not help.

Then Changed the used coil I got with a new AIRTEC 5C1432 (the one most people were using in the original write-up on stroker motors forum and IT NOW RUNS GREAT !!!!!!

FIXED !!!!!!!

 

Well done
And HOW LOUD IS YOUR EXHAUST?
heheh

 

I bought with a blown motor and can't remember why but the old muffler was completely shot, so I threw a "24in Cherry Bomb" on it that I had laying in the garage a buddy gave me and it currently ends right before the rear axle with a tip pointing down, It also has a eBay stainless header on it with (2) Precats, towards top of the list now that it runs good, plated, and insured is to finish the exhaust all the way back.

To answer your question, its sound great now that it is running right, sounds very similar to my daughters old 2000 Cherokee that Rugged Ridge Header, (2) Precats, Magnaflow Muffler, and pipe out the back. It is throaty and deep at idle and wide open throttle, but fairly quite cruising down the road..... certainly not tin canny!!!!