Topic: Jeep "Hickups"

[lqdtrance]

My 94 YJ 2.5 "Hickups" while driving. It cuts out (the tac drops out) for a brief second. It used to do this only on occasion. But today I drove it on the freeway a few towns over and on the way back it started doing it 10 fold. Now it barely will sit and idle and when I drive it is quite embarrassing because it looks to the outside eye like I do not know how to drive standard 
Has anyone experienced this before? I have already replaced my map sensor because of some codes. I do have a couple of codes still there that to me do not make sense. I have a code 33 which is for the a/c clutch relay. I do not have an a/c system so I am unsure why I have this code. I also have a code 12 which comes up as the "battery power to the pcm was disconnected". I am thinking this might be the problem but wanted to run it by you guys before I waste time and effort.

[Jeffy]

You are correct about 33.  That's normal and will always be there if you don't have AC.  12 is what I'd look into.  This could mean anything from the battery being disconnected to an open circuit someplace else.

[jcsanders79]

What about O2 sensors?  My Jeep bucks like that when they go bad.  Usually at low speeds though.  When my Jeep started acting like that at speed it was a crank position sensor.  

[lqdtrance]

My battery has not been disconnected in quite some time. For the life of me I cannot find any info on the location of the pcm. Would you happen to know the location? I would like to see what is going on with the voltage at its location. Maybe it just needs to replaced?

[sharpxmen]

the PCM is located on the firewall inside the engine compartment between the fender and the master clutch cylinder - it is a black plastic box. Check if the screw in the center of the connector is tighten properly and the connector is seated properly
but first i would check these
Fuse 1 (30A) and circuit A14 which is 16 gauge wire and is red/white color (this is going to pin 3 on the PCM connector and is the one powering the PCM). it also feeds power to the Automatic Shut Down Relay (check this one as well) - this relay powers the O2 sensor, injectors and the ignition coil and the wire color on this is Dark Green with an orange stripe.

you can find detailed info on these in the service manuals more specifically this file 95YJ_8W.pdf

EDIT: like jcsanders79 said, could be a sensor also - he had a problem with a crank sensor, i had sort of hiccups on mine when the tps went bad, but mine did throw the appropriate code. if you got this code "battery power to the pcm was disconnected" i would check circuit A14 starting from the fuse and battery to make sure there are no interruptions - the error codes are quite accurate and if you have this one my money is on something related to that (sounds like it too based on what you describe).

[lqdtrance]

sharpxmen, thanks for the detailed info! I'm heading out the door now to check these. Thanks again!

[jwalls4x4]

When my wifes xj did this it was a crank position sensor.  It was doing crazy stuff and had me 

[lqdtrance]

I found it but it is a pain to get to. I also have no clue when it comes to vehicle electronics. I checked fuse 1 and it is ok. I cannot find circuit A14 in my Haynes repair manual  .
To make sure I am looking at the right thing. There is a connector that has a screw in the center where a ton of wires go into in that exact same area you mentioned (between fender and master cylinder, mounted on firewall). But there is also a box directly below that that also has some wires going into it. Which am I supposed to be looking at? I assume it is the one below? thanks again.

[dtoliver]

a similar thing happened to me on my 95 yj. I replaced the tps sensor and all is well and a cheap and easy fix!

[sharpxmen]

I found it but it is a pain to get to. I also have no clue when it comes to vehicle electronics. I checked fuse 1 and it is ok. I cannot find circuit A14 in my Haynes repair manual  .
To make sure I am looking at the right thing. There is a connector that has a screw in the center where a ton of wires go into in that exact same area you mentioned (between fender and master cylinder, mounted on firewall). But there is also a box directly below that that also has some wires going into it. Which am I supposed to be looking at? I assume it is the one below? thanks again.

I recommend you do all this with the ground of the battery disconnected
you are supposed to check Fuse 1 on the fusebox (actually the distribution box) by the battery - this fuse will not be blown or you engine won't start - there is also another fusebox with smaller fuses, that is not the one - fuse 1 is 30 amp i believe and the one beside it is 50. Check if there are any signs of interruptions on the fuse terminals and if it fits snug in there. there is a power feed between the battery and this box, check that as well. You can check the continuity of the circuit between the + of the battery to pin 3 on the PCM connector (with the connector taken out and using a multimeter) and try to move the fuse and wires and see if you get interruptions.  the connector is the one with a screw in the center - to get to it remove the washer fluid tank (it is a philips screw located on the closest side to the firewall towards the center of the engine bay). once you did that i think it is an 8mm socket for that screw. You can also remove the distribution box and check the connections from under. The Haynes manual is useless (the one for the Jeep at least). Download the service manuals from this site (type in service manual in search) and then look at the pdf file i mentioned. I can look and give you the specific pages if you want but i'm not sure if i can do that today.

You can also try and replace sensors, but usually a bad sensor will give you the appropriate code.

[lqdtrance]

Yeah, I checked the cable going from the battery to the dist. box. I'll take a closer look at the pcm connector tomorrow. What is it directly below the pcm connector? is that the computer?
Thanks for the tip on the manuals. You don't need to go as far as specific pages, I should hopefully be able to locate them on my own. I'll keep it in mind though just in case. Your a wealth of knowledge man. Thanks again!

[sharpxmen]

i hope you'll find the problem. the pcm is the computer - i'm not sure what's under, i'll have a look and let you know in the next couple of days. I'm also thinking that this might occur while you're driving due to vibrations, so you could eventually start the motor and move the wires a bit, tap on the distribution box and try to see if you can replicate the issue - if you can you could be close to find the problem.

[outrunthemoon]

i have a similar problem. Sometimes when I start up my Jeep it stalls out on me. Just sitting there. It has always taken a little while to start but now sometimes it takes 2/3 tries for it to start. But it only does that on the initial start for the day then its fine the rest. It also bucks a little when in 1st gear or reverse and the RPMs drop significantly regardless of how much gas I give it and it has little power until I can get it high enough to shift into second. but that takes some time. Like it feels as if I shifted into a higher gear when the RPMs weren't high enough.

[sharpxmen]

the pcm connector is the long narrow connector (60 way connector in the image below)

[lqdtrance]

the pcm connector is the long narrow connector (60 way connector in the image below)

Ok. that is the box on the bottom that I was talking about. The image above the pcm is what I was originally looking at, which also has a center screw. The one above appears to go to the interior fuse box. Thanks for the clarification. I figured I was looking at the wrong one once I saw that it went to the interior fuse box.
On another note. I cannot get it to replicate at the moment. I test drove it and nothing happened. It seems that the longer I drive it the more it starts to act up. I did notice the negative connection on my battery was loose enough for me to move. I tightened that down. Maybe that was the problem, I doubt it though.