Ignition Problem Stalling

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david camarra

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Oct 4, 2016
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Ok guys this is a good one for you. I have a 99 tj with a 4.0 automatic. It started running ruff in the morning. It would surge at the end of the driveway and at a stop light shortly after. When it surges it stalls. Starts right back up. Sometimes it has done it and been hard to start up like the jeep is flooded with gas. Sort of like a stuck choke. (for those of you that remember what a choke is) LOL.
Also every once in a while but getting more than once in a while it will not start cold or stall and will not start. Motor turns over fine just will not fire. Take the coil wire out of the cap and turn the jeep over. Put the coil wire back in to the cap and it fires right up. Found this by checking for spark one day.
I have just had the computer at SLI in IL. and they found nothing wrong with it.
Once everything is warmed up its fine.
The bottom o2 sensor is bad and unhooked. My mechanic is telling me that has nothing to do with it. Opinions?
The jeep has California emissions on it so i'm told. Don't really understand that because its bought in Mass.
It also has a remote starter.
 
yes but that has been on for ever because of a bad filler neck. I have had the codes checked by two shops and it come back with nothing definitive. Seems to look to the control module. But like i said that seems to be fine.
 
When you say the bottom O2 sensor is bad and unhooked, do you mean the O2 sensor that is AFTER the cat or BEFORE the cat?

This could be a slew of things, but usually when it's acting the way you describe it will throw a check engine light, and a code for whatever is going on. If you don't have an OBDII scanner, I suggest buying one.

I would use it to clear any existing codes, go drive it, get it to reproduce the problem, and then scan it again. My bet is if it's behaving this erratically it will throw a code.

I'm just really, really skeptical to try and diagnose anything by just taking pot shots in the dark. It's a good way to waste time and money. Get a list of every single code it's throwing and post the codes up here.

You may have already had them ran, but if you just go to Autozone, they'll scan it for you for free and tell you all the codes. This would really help with a proper diagnoses, at least so we can rule things out.
 
david camarra said:
ok thanks
and its the o2 sensor before the cat
Click to expand...

The O2 sensor before the cat should not be unplugged. That's likely your problem right there.

The O2 sensor after the cat can be unplugged (though it will cause a check engine light) without causing any running issues. The reason for this is that the O2 sensor after the cat has no effect on how the vehicle runs, it's for emissions only.

But back to the point... If your O2 sensor before the cat is unplugged, that needs to be plugged back and have a new O2 sensor put in there. That will probably fix the issue you're having.

Also, do not use Bosch O2 sensors. @Jerry Bransford can tell you that our Jeeps do not like Bosch O2 sensors.
 
Does this problem happen only when the engine is cold? Does the problem go away once the engine has started to warm up? O2 sensor problems typically only show up after the engine starts to warm up. The engine computer doesn't look at the O2 sensors at all when the engine is cold.
 
Hmmm, totally overlooked the part about it being cold. Jerry is right though.

However, I will say that if it was me, I would get a new O2 sensor and plug it back in, just to eliminate that. It should be plugged in, no doubt about it.
 
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To Jerry
I would have to say when it is warming up. When i start it up in the morning it takes off just fine until i get at the end of my driveway which is about a 1/4 mile. Then it surges and stalls. Then when i get the the next stop about 2 miles from my home. Then when it is totally warms it is fine the rest of the day. Unless i let it cool down for a couple of hours.
I will get a O2 sensor put in when my module gets back from SLI.
Which brand should i get and were should i get it. I assume auto zone or one of those places is not a good idea? How about NAPA?
But is there two issues going on here. Lets not forget about the coil problem. As i said it will not start. Then i pull the coil wire from the cap turn the jeep over. Then put the coil wire back in the cap and it starts right up. Coil and wires and cap are new.
Thanks a lot for the help guys.
Dave
 
Get the O2 sensor anywhere you can find an NGK or NTK brand which is what the factory installed. Avoid Bosch O2 sensors which give problems in Jeeps.
 
So if you pull the coil wire out and put it back in, then it starts up? That to me sounds like a bad connection problem. Have someone wiggle the coil wire around while you sit in the car and try to start it. If that works, it's gotta be a faulty connection I would think.
 
nope the wiggle thing does not work. it is almost like when you take the wire off and turn the engine over it is recharging something and then the coil is getting juice again. I am going to try a test light next time to see if there i power to the coil. that will tell me more. It is the strangest thing i have ever seen in a car before. And im 67 so i have seen a lot of problems
 
Kinda making me think the problem could also be caused by a bad crankshaft position sensor. The CPS is what provides the engine's master timing signal and if it's not there, the engine will die. If the timing signal from the CPS is erratic, the engine will run equally erratically. The CPS on your '99 is mounted high up on the driver's side of where the transmission bolts to the engine. It picks up pulses from the flywheel though a gap where the engine & transmission bolt together. If you buy one, make sure to get one for the automatic which mounts differently from the model of CPS made for a manual transmission.
 
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Hey guys
I finally got a garage that has a clue. We have two codes PO 351 AND PO 132. Understand I have had the computer checked out at SLI in IL. and they said it bench tested fine. They did take it apart. Also this jeep has a remote starter and im beginning to wonder if that has something to do with it.
Thanks'
Dave
 
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david camarra said:
Also this jeep has a remote starter and im beginning to wonder if that has something to do with it.
Dave
Click to expand...

That's one of the first things I'd be looking at actually! You very well may have found your issue.

If you trust the shop (sounds like they know their shit), I'd let them figure it out for you.
 
Jerry Bransford said:
Kinda making me think the problem could also be caused by a bad crankshaft position sensor. The CPS is what provides the engine's master timing signal and if it's not there, the engine will die. If the timing signal from the CPS is erratic, the engine will run equally erratically. The CPS on your '99 is mounted high up on the driver's side of where the transmission bolts to the engine. It picks up pulses from the flywheel though a gap where the engine & transmission bolt together. If you buy one, make sure to get one for the automatic which mounts differently from the model of CPS made for a manual transmission.
Click to expand...
I finally got a garage that has a clue. We have two codes PO 351 AND PO 132. Understand I have had the computer checked out at SLI in IL. and they said it bench tested fine. They did take it apart. Also this jeep has a remote starter and im beginning to wonder if that has something to do with it.
Thanks'
Dave
 
Ok so this is the new info on this problem.
It is not the remote starter.
It is not the o2 sensor although it seemed to make it better after i replace it. Is there something that needs to be reset with the new sensor?
It is not the TPS, at the throttle body, i just replaced that.
Now it sits there and drops 200 to 300 rpms when in gear. It idles at 900. It will surge ahead some but not always like it did before.
Im starting to think it might have something to do with the transmission? I had it rebuilt about 3 years ago. Sometimes when i start off it will pop out of gear and go back in. Could there be something or is there a sensor that could be sending the wrong signals to the trany?
Or something else. Garage is at a loss and this is the third garage that it has been to.
 
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