2001 Grand CherokeeWorking on vehicle.Throwing a few codesRun smooth at stsrt up. Abo

Run smooth for a minute and then it gets rough. It is the same weather engine us warm or cold. Jeep sat for about a year too. I've been working on it the last week or so trying to get it road worthy. Been cleaning contacts and grounds too.

Sent from my SM-G900P using Jeepz.com mobile app
 

It cold be
A leak in the intake or vac lines.
A bad water temp sending unit.
A bad upstream O2
Sensor.

When the engine is first started it is in open loop and runs off of a lookup table for air fuel mix.
Once many items are met it enters closed loop and runs off of many sensors to get the air fuel ratio correct.


JPNinPA
Using Jeepz.com app
 
Add to it bad injector or low fuel pressure.

Bad battery or bad power and ground connections.


What codes are showing?


Oh and is it only rough when idling or when accelerating?
If only at idle you need to clean the TB and IAC





Regards,
JPNinPA

Sent using TapTalk
 
JPNinPA said:
Add to it bad injector or low fuel pressure.

Bad battery or bad power and ground connections.


What codes are showing?


Oh and is it only rough when idling or when accelerating?
If only at idle you need to clean the TB and IAC





Regards,
JPNinPA

Sent using TapTalk
Click to expand...


New Battery installed. Sorry for my initial messages being scrambled. Was using app at work. Like I said car seems to run fine in "start up loop mode". But after a minute of start up (cold or warm) it runs rough. I looked at the iac, hard to tell if it was bad . Cleaned it up with some carb cleaner. exercised the connection on the tps. Replaced Bank ! sensor 2 with a Bosch. I'm a BMW guy so Bosch has been good to me. :) . After replacing o2 sensor I still got P0136. Oddly enough I have been getting some transmission codes too.
Transmission codes
P0743
P0753
P1765
Also getting P1495 (leak detection) and P0051. Funny thing is the car had no codes when it was layed up. I was thinking the mice might have chewed on some wires but things look ok. Not sure of what is causing the bad idle after a minute. Can hear the valves tapping when it happens(dieseling?) and some little backfires too. Chasing these codes down is a bit of a witch hunt. I keep on plugging away at it though. Thanks in advance.

dlm ny country
 

Ok with jeeps only use OEM sensors. Bosch gets mixed results mostly bad from what I read. NTK is the correct mfg for O2 sensors.

P0136 is either a bad DOWNSTREAM O2 bank 1 sensor 2, shorted wiring to it or an exhaust leak pre O2 sensor.

The P0051 is bank 2 sensor 1 O2 bad heater. This will cause intermittent readings and rough running. Remember NTK


The P1495 can be a leaky gas cap be sure it is on tight. Other than this check all your vac lines to the evap can and solenoid and leak detect pump. Perhaps sitting dried out some vac lines.

I'm not sure on the transmission items but check the color and trans fluid level..



I'll just put out there that bad power and ground connections can cause a number of faulty codes.


Regards,
JPNinPA

Sent using TapTalk
 
Last edited:
Thanks JPA. Good to know NTK is oem sensor for Jeep. For the record the miss is bad enough where I am NOT driving the Jeep. Too much bucking and loss of power. My code reader (Actron ?) doesn't give me live diagnostics. I think I need that so I can read my o2 sensor volt levels before and after the cat as the Jeep is running. Any good phone apps for OBD 2 live data you would recommend?
Thanks
dlm ny country

2001 Grand Cherokee Laredo 4.0
1987 YJ Wrangler.....sold !!!
1974 BMW 2002
1991 BMW 318is
 
You didn't note any misfire codes. Are there any?

To check you could unplug the offending O2 sensor and see if the bucking persists. You will throw another code but good validation. Remember to tie up the wiring so it doesn't get burnt.


JPNinPA
Using Jeepz.com app
 
Got a chance to disconnect some 02 sensors today. First one was the one I replaced code P0136. No change. I then pulled the precat sensor P0031. No change. I then finally pulled the P0051 sensor. No change. Gave the Jeep a run up and down my road....same stumble, dieseling, valve noise, poor acceleration. Tried pumping the pedal a bit to see if it would help getting more gas if I have a fuel pressure situation. No change. Exercised temp sensor switch. No change. Back to square one. :(

dlm
2001 Grand Cherokee Laredo 4.0
1987 YJ Wrangler.....sold !!!
1974 BMW 2002
1991 BMW 318is
 

After fresh start, Idle is around 800. After stumble kicks in, it usually is around 650- 750 rpm's. Will shoot video next time I run sequence of start-up to rough idle. Thanks for your helpful insight.

dlm
2001 Grand Cherokee Laredo 4.0
1987 YJ Wrangler.....sold !!!
1974 BMW 2002
1991 BMW 318is
 
Pumping the gas will not help determine a fuel pressure issue. Pressure is expected to be constant 49 psi +/-1psi


And how did you exercise the temp sensor switch?

JPNinPA
Using Jeepz.com app
 
Last edited:
Just thought of this. What temp is the engine when the sputtering starts?

Also when testing bu unplugging O2s. Unplug all before starting the vehicle to rule out O2s overall. Then you could try one or another. If you do one at a time and have two bas ones you will think it's not the O2s or have a hard time finding it. And you had codes for two O2's


Regards,
JPNinPA

Sent using TapTalk
 

https://www.youtube.com/watch?v=vLStQbS5NiU&feature=youtu.be


Exercised temp sensor by resetting the connector a few times. Will try disconnecting all o2 sensors and see if that changes. Been focused on getting Jeep to run right and not paying too much to the transmission codes that have been thrown. Last night after test driving the transmission would not down shift at all. Shut the car off and transmission was fine after that even though I didn't check for transmission codes at that point. Here is a video of engine running with some revs and it cutting out. Not sure if it will help but it's out there. Engine stumble happens at any temp too. Warm/cold..

dlm ny country
 
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