Hesitation and stalling

[SilverXJ]

My Jeep was down for repair for about two weeks. I replaced the thrust bearing and cleaned up the crank thrust surface. Since it was drained of oil I removed the cam sensor to prime the engine before starting it. I got it buttoned up last night and now it doesn't run as it use to. When I blip the throttle or first accelerate it hesitates. Also, when I blip the throttle after it hesitates it then comes back past idle and stalls or nearly stalls. I checked the TPS, MAP, and the IAC. I also swapped out the IAC and MAP with spares I had on hand. No luck. I checked the plug gap thinking I may have knocked one and that is good. I checked all the grounds. I rechecked the cam sensor 5 times. I tried rotating it a few degrees in either direction and that just made it run worse. It also feels rough at 1000 RPM and sounds like it is having several slight misfires at 1000 RPM as well. No CELs and it will do it in drive , park, neutral, etc. I tried resetting the PCM and that didn't help. Also, engine temp sensor and air temp sensor both check out good. Also, fuel pressure is good.

Any ideas?

[toybuggy_yj1ton]

Hey there, new to the site.
I read your post and have the same issue, everything checks out as far as sensor voltage and such, fuel pressure is good and everything. the only way i can get it to idle for any length of time is by unplugging the map sensor. In addition, I give it a little throttle and it acts like the rev limiter is kicking in at 1500 rpm unless I give it a lot of gas. Also runs extremely rich.

Have you had any luck?
Justin

[dwg86]

This is one reason I haven't installed my stroker yet. So many people seem to be having troubles like this. Have you tried removing the piggyback computer? Maybe try taking it to the Jeep dealer for a scan.

[toybuggy_yj1ton]

I dont have a piggy back computer in mine. In addition to the stroker, I also did an engine swap as well the engine was a 2.5l so I may have some underlying issue there as well. Either way, I checked all the sensor voltages and they all checked out. My only concern is the computer is from a 92 xj, while the harness I used is from a 95 xj which doesn't have a ballast resistor circuit. I'm not sure whether this will effect the fuel mixture and or the way it runs. It does throw a 76 code which is the ballast relay circuit code. So I re pinned the computer plug with the circuit and it didnt change the way it ran, that just cleared the code.

[SilverXJ]

Way to hijack a thread.

No I haven't tried messing with the piggy back, but it isn't actually doing any corrections at the moment. See, it ran fine before I dropped the oil pan to change the thrust bearing, but now it is misbehaving. I don't think this is stroker related per se. It never did this before even on every iteration of the titan engines.

I'm pulling the oil pan to see if I screwed something up, like something that could cause extra resistance, as I did check the rod bearings while I was in there. Maybe I didn't seat a bearing half correctly. But it starts both hot and cold fine.

The MAP checks out, the TPS checks out, air and coolant temp sensors check out, I swapped the IAC out with a used one I had on hand and no change (I could understand it doing something with the stalling but not with the hesitation). The only sensors that I would question are the O2 sensors and the CPS, but I don't know how to check those. I could look at the O2 sensors voltage output on my notebook with scantool. And from what I understand a CPS on the way out it either will stall out at random or not start at all. No vacuum leaks. Fuel pressure is good.

[dwg86]

I just don't understand???? Dropping the oil pan shouldn't have caused this, and it was running good before. I'm stumped.

[SilverXJ]

you think you are stumped? The only thing I can think of that the low battery did something.. and perhaps resetting the PCM when the battery was still quite low had and effect... but it should have cleared up by now.

[jsawduste]

Perhaps a dumb question but have you checked that you did not accidently cross ignition wires ?

[SilverXJ]

Perhaps a dumb question but have you checked that you did not accidently cross ignition wires ?

Perhaps a dumb question, but I don't know how I would even be able to do that? Are you talking about coil wires or spark plug wires?

[SilverXJ]

I dont have a piggy back computer in mine. In addition to the stroker, I also did an engine swap as well the engine was a 2.5l so I may have some underlying issue there as well. Either way, I checked all the sensor voltages and they all checked out. My only concern is the computer is from a 92 xj, while the harness I used is from a 95 xj which doesn't have a ballast resistor circuit. I'm not sure whether this will effect the fuel mixture and or the way it runs. It does throw a 76 code which is the ballast relay circuit code. So I re pinned the computer plug with the circuit and it didnt change the way it ran, that just cleared the code.

I think we have two different issues. Did you index your distributor correctly? The ballast resistor has no consequence on fuel. I think its just there to quiet the pump down and slow it down, but it is a common mod to remove it. How is your fuel pressure?

[SilverXJ]

Dropped the pan and it was almost a complete waste of time aside from the fact that it made me feel bette rthat it wasn't a problem there.

Anyhow.. I tried to test the CPS... all the tests I have seen say test the middle and either the left or right pin. Well, all the info shows the pin numbering differently. The resistance should be 0. So, I set my meter to 20M, which is the only setting it would read anything. Testing pins 1 and 2 yielded 17.18 Ohms and 2 and 3 yielded 12.88. Not exactly 0. So I don't know if I even tested it correctly. I was going to test the coil rail, but it fires at all instances other than my little issue. Just shows I have been working on Jag V12s too long, as they have two coils and one can fail and show weird symptoms.

Any ideas?

[Muad'Dib]

You said you removed the cam sensor when you primed the engine again. Did you try removing it completely again and see if something got messed up there? Sound like this is the only thing you did that could cause the problems your having.

[toybuggy_yj1ton]

Sorry for the Hijack if you are reffering to me. I have never posted on any forum before. I didn't know it worked that way.

At any rate, it sounds like the only thing you changed that would have effected yours would be the distributor, as in, when you pulled it out and primed it could it be off a tooth? If so then it's possible I may have installed mine incorrectly as well?

[SilverXJ]

At any rate, it sounds like the only thing you changed that would have effected yours would be the distributor, as in, when you pulled it out and primed it could it be off a tooth? If so then it's possible I may have installed mine incorrectly as well?

Try this http://www.angelfire.com/my/fan/dist_index.html, yours definitely sounds like a cam indexing issue. And make sure its on the compression stroke.

[SilverXJ]

You said you removed the cam sensor when you primed the engine again. Did you try removing it completely again and see if something got messed up there? Sound like this is the only thing you did that could cause the problems your having.

I checked it like 5 times already. I can't get it any better. I swapped the sensor part out and that didn't have any effect. Besides, I've done that many times before and never had a problem... not saying that one time it won't be off but as I said I went back through that 5 times.