Check Engine light on, Scanned codes need help!

[W00GYB00GY]

I have a 1996 XJ 4.0 straight 6, and recently it has been running rough, I have to accelerate extremely slow or else my jeep won't go, and if I'm going 55mph or any speed and I try to press a little harder my jeep will kinda stall out, it wont shut off completely but it kinda freezes.

I straight piped my jeep a while back and have had no problems what so ever, and I know the code would come up for it (P0171) but it has never been an issue, and my check engine light never came on because I did the anti-fowler method.

But then I scanned my jeep today and this code came up...

P0172 (M) 1/1 Fuel System Rich A rich air/fuel mixture has been indicated by an abnormally lean correction factor.


Suddenly my jeep has thrown the P0172 for fuel system to rich...

Can anyone help out? I know I'll probably hear it for straight piping, but I have no smog tests and no inspections where I live.

[prerunner1982]

I am not sure about the code but reading the first part I thought Throttle position sensor and to me the code would kind of go along with that.

[W00GYB00GY]

I am not sure about the code but reading the first part I thought Throttle position sensor and to me the code would kind of go along with that.

I was thinking this as well...but I literally replaced the TPS less then 2 weeks ago with a new one.

[saar]

Maybe the new TPS is bad?
I think that O2 sensors can cause that too. you may want to check them.
Saar.

[W00GYB00GY]

So I replaced my TPS, and the first o2 sensor on the downpipe with a new one, and my problem still hasn't changed.

About a week ago I sprayed silicone on my belt to prevent the belt from squealing and I didn't no that was a horrible idea....FML, but I'm not sure if that has thrown the timing off or what but this problem started happening the same day I sprayed the silicone on my belt.

I will be driving and then when I let off the gas my car will almost stall out, If I tap the gas to go faster it wont work, but it isn't my transmission slipping, it feels like its something to do with the acceleration or linkage, or throttle I'm not really to sure.


When it happens, I can put my car in neutral shut it off and restart it, and I can drive it with no problems for like 10-15 seconds then it goes back to the hesitation/stalling problem.

Problem after problem.....any help is greatly appreciated!

[green89]

Hey I just wanted to let you know that I am deployed right now with the b trp 1-180th of the 45th. Be home soon !!!! Im also a very proud owner of my sencond XJ... I have pics let me know what you think. I miss my XJ.. LOL

[W00GYB00GY]

Hey I just wanted to let you know that I am deployed right now with the b trp 1-180th of the 45th. Be home soon !!!! Im also a very proud owner of my sencond XJ... I have pics let me know what you think. I miss my XJ.. LOL

Congrats...can anyone help me out with my problem?

[LizardRunner]

With the TPS working right (you did check it with an meter to make sure the new one is working right? http://xjtalk.com/showthread.php?t=9714) Other things that can cause this sort of problem are the two O2 sensors, If only one is bad you can have problems. The ECM could be bad, just remove the two battery cables and touch them together for a few seconds, this will reset the computer and you can then see if the problem goes away or if it throws the same code again. If it does throw the same code then it's back to the elimination game. The straight pipe thing is not the problem. I have that set up as does Jimbo and everything works just fine. The belt really doesn't have anything to do with the timing, that is a chain drive under a cover on the front of the engine. If you are getting full fuel pressure at the rail, it isn't that sort of trouble either. Tony did a write up on some troubles he had that were similar it should be on the OEM pages, I just don't remember where. If none of this works, Just post it and I'll be happy to search out more answers to what it could be. I'm leaning towards the ECM at this point.

[XJ4IV]

you check your MAP sensor... its the green plug located on your firewall, that is what makes adjustments to your fuel air ratio!

[W00GYB00GY]

you check your MAP sensor... its the green plug located on your firewall, that is what makes adjustments to your fuel air ratio!

I found the map sensor next to my TPS but I'm not sure if I'm trying to look for the same thing...is this right?

[W00GYB00GY]

Here is a video I took of my jeep in action...

http://youtu.be/aleHUQwd0cM

http://www.youtube.com/watch?v=aleHUQwd0cM&feature=youtu.be

When the problem happens in the video, my foot was on the gas pedal the entire time, I wasn't pressing it then letting go, then pressing it....let me know what you guys think...

[big sam]

I have the same problem on mine (1998 XJ 4.0L) Please keep us up to date and I will do the same....

[LizardRunner]

That could also be the crank position sensor (CPS) by your video, when mine went out it started out like that but then it went to where it would just die and rpm's would go to 0. But the code saying rich, I would check or replace the O2 sensor you haven't first, and work down the engine.

[W00GYB00GY]

New fuel filter...problem is still there...nothing changed

http://youtu.be/X77AumVYXCw

I'm going to get a fuel pressure gauge in like 20 mins when I can get a ride and try that to see what that says...

[W00GYB00GY]

Well all the sensors I checked were normal, I then checked the fuel pressure idling in my drive way and it was 45-55psi then I drove around with it hooked up, and when the problem started my fuel pressure drastically dropped to 20-5psi, then I would stall out.

So right away I knew it was the fuel pump, went to the parts store for a fuel pump and strainer and installed it and now we are good to go...I drove it for about 35 mins and the problem never happened. I will test it out later and drive around for longer just to be 100% positive but I'm pretty sure its fixed.

Thanks for all the help on here...you guys are awesome!

[LizardRunner]

glad you found the problem and it's fixed. Pesky fuel pumps.

[W00GYB00GY]

So I'm really on my last fuse with this damn jeep...today the transmission issue started happening again....

My transmission slips when I go into OD, but when I disconnect my TCU, I can shift manually and it works fine.

I've already tried spraying Electronic Cleaner in the adapters near the trans dipstick and it didn't work this time like it did for me the first time.

I've tried a different TCU and it still did the same thing...

It really is one thing after another with this jeep I really love my jeep but these problems are extremely frustrating and make it seem like its almost not worth it...WHAT SHOULD I DO?

Oh and also, my jeep "transmission wise" was driving perfectly fine other then the fuel pump issue, no slipping or anything, I could shift into OD perfectly fine, and then once I put my fuel pump in last night, today is when it started acting up again. I haven't gone mudding or off roading in a week, so that isn't the issue...I just really wish I could put this behind me!!!

[LizardRunner]

I would reset the computer (ECM) at this point, changing out the fuel pump worked for a while but the computer is still trying to configure to the old settings, just pull the battery terminals and hold them together for a few seconds, re-install and go driving to see if that fixes the problem now. anytime you make a change to things that make it go, it seems a good idea to force it to relearn the correct computer settings.