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2001 4.0 Intake Backfire

2001hero

NAXJA Forum User
Ok after searching to no avail i will post my problem. Sorry if this isnt the correct thread. Moving my be in order! SO here is my problem

2001 Jeep Cherokee 4.0
AW4 Trans

So i was accelerating up an onramp on to the freeway like normal. Not on it hard or anything just getting up to speed. Once i merged, got off it a bit it backfired thrugh the intake. I pulled over to check if anything was disconnected or loose. nothing

Drove it home very slowly and it would buck, stumble ever so often.


Any ideas?



As for background info on the jeep. 4 months ago i did exhaust and intake. 5 Weeks ago i did an airaid TB spacer. 4Weeks ago i did 4.88 Gears from the 3.55 gears. 3 Weeks ago i did full tune up and oil change (champion truck plugs) 2 weeks ago i did a Jet stage II chip and water pump and 180 degree T stat. I only run premium (required by Jet chip but did befor the chip anyways)

Only thing i can think of that has been different for the condition is that i filled up at a king soopers and the issue started in after aprox 80 miles on that tank.


I removed the Jet Chip and drove. Problem is still there. Not as bad, but still there. Now feels more like the jeep is trying to drive over itself (bog)

Idle is fine. Got down to half tank and filled back up at usual gas station. Problem Still there.

Checked plugs. All in great condition.

noticed oil pressure gauge reads at 80 at all times now. Possible connection? have a new one on order should be in tomorrow.


Any ideas hints or suggestions are welcome!

Thanks sorry for the long thread

Jess
 
What is your fuel pressure?

Why the 180 thermostat?

What is the static battery voltage? With engine running?
 
not yet. was going to do that this weekend. Just seems wierd to me because its so intermittant. Even tried powerbraking it and couldnt repeat the problem. But hopefully its an easy fix like fuel pump or something!

Thanks
 
Voltage at battery termanials is 14.05 while running. when off slowly creeps down to 12.7 and stands.

180 TStat because Jet recommends it. had one in my other cherokee (2000) ran about 10 degrees cooler. IMO

Havent checked the pressure yet will hopefully tomorrow. Ideas on Specs?
 
Bucking and stumbling are often caused by a failing O2 sensor. The sensor is slow to respond and the ECU/PCM will cycle between Open Loop and Closed Loop because of the strange O2 sensor readings. Open loop runs rich. The Chip probably richens the mixture also.

You removed the chip, but did you re-boot the ECU/PCM ?

O2 sensors are recommended to be replaced every 100,000 miles for best perfromance and emissions. Yes, they will often work well enough that you can keep the originals longer than 100,000 miles.

Testing the O2 sensors and monitoring their functions with a scan tool would be a good idea.


Info from a JEEP Technician -

This very simple procedure will Erase the “Adaptive Memory” stored inside the PCM and allow a new “Adaptive Memory” to be developed.

After performing this procedure the PCM will re-learn and store into Adaptive Memory your engines performance characteristics.

Please perform these steps exactly as they are written, in the order they are written. This will cause the adaptive memory in the PCM to be erased and cause the PCM to go into Fast Learn Mode adaptive mode.

Disconnect the POSITIVE battery Terminal and touch it to ground ( not the battery negative terminal ) for 30 seconds. The engine block or the A/C compressor pump will work as a ground. (This is to discharge the PCM capacitors, which maintain the Adaptive Memory.

Reconnect the Battery Cable
Turn Ignition Switch to the “On” position but DO NOT start the engine
Turn Headlight “On”
Turn Headlights “Off”
Turn Ignition Key “Off”


The PCM Adaptive memory has now been flashed, or erased from the PCM.

When you start the engine it will be running off a set of pre-programmed tables that come with the PCM from the factory.

When you get the engine up to operating temperature the PCM will start to collect data for the “Adaptive Memory”.

The PCM will collect data for Adaptive Memory for the first 50 Warm-up Cycles.
 
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