Hesitation and stalling

[SilverXJ]

Well, the new CPS was well wasted money. So, the MAP, CPS, TPS, IAC, IAT, CKP and CTS all check out good. That is all the sensors besides the O2 sensors and any stupid emissions related sensors. The O2 sensors appear to be operating fine by watching the OBDII data and comparing it with what the wideband is showing. I also removed the Apexi from the system and that had no effect. Fuel pressure is good and nothing blocking air flow. Gas in the tank is good as that was one of my first efforts to fix it, top off the 1/4 tank two week old midgrade with premium. No change. Fuel pump relay was swapped out. Battery was swapped out with a known good one. Didn't check the coil rail as I don't know how to and it revs fine after the hesitation. Besides I doubt that all the coils in the rail would go out at the same time and this condition appears to be on all cylinders. Engine compression is good at 180 psi. Plug gaps are good at .035", and the plugs look good. Can't find any vacuum leaks. The fuel injectors should be fine as they are new with the engine and were cleaned and flow tested.

So.. maybe recheck for vacuum leaks, but it idles just fine.. all day long too.. its only when you blip the throttle or accelerating from a stop

Maybe clogged cat? Its only two years old, but had been through several cam breakins and god only know how much zinc has been through it.

[SilverXJ]

Did the vacuum check and temp check for a clogged cat and they didn't indicate a clogged cat. No vacuum leaks found either

I did notice that it I held the RPM around 1000-1080 the engine shows lean, like 15.3:1, I watched it on the wideband and also watch the feed from the PCM O2 sensors show lean.. and the PCM did nothing to try to correct it.

I'm beginning to think that my draining the battery several times may have made the PCM throw a fit. Everything else checks out. I'm going to contact the people that did the upgrade on it and see if the could do a reflash then flash their changes again.

[Flash]

Did the vacuum check and temp check for a clogged cat and they didn't indicate a clogged cat. No vacuum leaks found either

I did notice that it I held the RPM around 1000-1080 the engine shows lean, like 15.3:1, I watched it on the wideband and also watch the feed from the PCM O2 sensors show lean.. and the PCM did nothing to try to correct it.

I'm beginning to think that my draining the battery several times may have made the PCM throw a fit. Everything else checks out. I'm going to contact the people that did the upgrade on it and see if the could do a reflash then flash their changes again.

I cant member the term right now but it make the ECM start over. as if it was a fresh ECM......any ways, with the key OFF remove the neg Bat. cable and hold it on the pos for 20 sec. then re-start and drive it, of 10 minutes,letting it stall when it wants. just keep starting it and driving it, until it has re-learned its self...

I thing the ECM learned a few bad thing when the bat was hanging on to the last fuw volts.

May do nothing for you but worth a try before you go about sending the ECM out to be re-flash

if that don't work, unplug both your 02 sensors(ecm will go into a dealt fuel trim) and let the mil light come on. If it fixes your problem, you know you have a shorted o2 sensor or wire.
I know, I know it, should have set a mil if it was shorted, and your wide band is agreeing with it........try it any ways.


Flash

[SilverXJ]

I did the master reset several times and same thing. I have also done a master reset before this whole mess started and it never did this. Last time was when I went with the larger injectors. It had a hiccup on the first start but never did one of these stall/hesitation things. Also, if it was trying to relearn its program in that 1000-1080 RPM range where it is running 15.3:1 I would see the fuel trim moving, which it didn't. It just sat there around 15.3:1, which made the engine feel weird and sound weird.

[Flash]

I still think you need to un-plug the o2s and see how it run in dealt .

Other then that, it time to get the Volt meter out and un-plug the ecm. Start checking reading like tps at the ecm connector to see if a wire has gone bad.

Flash

[Flash]

OK just went back and read thru you hole post again.

and this is way out there................but my be it will trigger a though in the right direction

Why did you change you crank Trust bearing in the first place?

Any ways is it passable that the crank thrust bearing has shifted causing the CPS to miss read?(meaning the install of this new bearing caused this movement )..........

Did you replace the Flex plate?(auto) or inadvertently put it on backwards.

do you have a scan tool? Does it show the Cam and Crank are, "In sink"?

Not insulting you intelligence, just standing up a few more straws too grasp

one last though, when it stumbles, is it a complete eng shut down, then come back up, or a miss........or does it fill like there all firing, just fire weak or poorly


flash

[SilverXJ]

OK just went back and read thru you hole post again.

and this is way out there................but my be it will trigger a though in the right direction

Why did you change you crank Trust bearing in the first place?

Crank's flange wasn't as smooth as it should have been, which wore the thrust bearing.. the machine shop missed this. I had to clean up the crank surface and install a new bearing. Crank end play was .015" after I replaced the bearing it ended up at .004"

Any ways is it passable that the crank thrust bearing has shifted causing the CPS to miss read?(meaning the install of this new bearing caused this movement )..........

Even if I ran without the thrust bearing I don't think there would be enough movement for the CPS to mis read.

Did you replace the Flex plate?(auto) or inadvertently put it on backwards.

Yes, I replaced the flex plate prior and it ran fine with the new plate. No, it is impossible to put it on backwards.

do you have a scan tool? Does it show the Cam and Crank are, "In sink"?

My scan tool doesn't have the function to see the crank and cam sensor signals. Even if it did I think only the dealer DRB has the option to see if they are in sync. I have had the cam sensor/oil pump drive out and back in at least 12 times and never had this problem.

Not insulting you intelligence, just standing up a few more straws too grasp

I understand... all help is appreciated... expect the idiot at Autozone... god that guy was a moron.

one last though, when it stumbles, is it a complete eng shut down, then come back up, or a miss........or does it fill like there all firing, just fire weak or poorly

This is how it goes. In neutral I tap the accelerator off idle just long enough to bring the RPMs up a bit. It hesitates, like someone pulled the spark, then the RPMs rise, then rpms drop low, sometimes so low the engine dies. Now, if it doesn't stall the engine will do that lean thing for a few seconds then bring it back to the 14.7:1 or so where it wants it.

If I am driving I push the pedal sort of fast and it hesitates for about half a second and goes.. like it has to think first.

Today I drove it 50 miles just to satisfy the theory that the computer hasn't learned... well, it still does it. So that sinks the learning issue... too bad that would have been a nice easy fix.. just drive the damn thing.

[SilverXJ]

Below are two AFR graphs from my log. The first one is how it originally was behaving, the second is how it is behaving now. The vertical dashed line is where i stopped the accelerator pedal. Take a look at how lean the rich the AFR goes on the bad one. Don't pay attention to anything that happens say two seconds after the initial spikes. You can also see the hesitation in the RPM scale.

Orginal:


Now

[Flash]

well I'm out of suggestions

Speaking, in carb terms, it's like the ECM forgot to activate the decelerator pump squinter.

[SilverXJ]

Speaking, in carb terms, it's like the ECM forgot to activate the decelerator pump squinter.

Exactly.

[dwg86]

For what its worth, I was reading on the alldata trouble shooting chart. For hesitation and stalling one of the things they said might be the problem is the coil rail. Although I don't think that would cause your fuel to be what it is doing....would it?

[SilverXJ]

One would think that if the coil rail isn't firing 100% that it would make the AFR go rich as there would be unburnt fuel, not lean. Unless... it is firing weak at all other times until that moment when I push the pedal then it is actually firing 100% .

Does alldata say how to check that stupid thing?

[Flash]

One would think that if the coil rail isn't firing 100% that it would make the AFR go rich as there would be unburnt fuel, not lean. Unless... it is firing weak at all other times until that moment when I push the pedal then it is actually firing 100% .

Does alldata say how to check that stupid thing?

You got to remember that a o2 sensor read 02 or AKA air, not fuel!

In other word, if you loose one cylinder due to spark, the "o2 sensor would read lean. Why? because it has no idea that raw fuel just past by. But the air, that should have been consumed with fuel, the sensor will read or show lean.

The coil could be the problem (remember were grasping at straws here).........the spark plug has the hardiest time fireing the fuel when it lean(like when you bop the throttle)..................................

Just for kicks, get a spray bottle of water and spray the coil pack. it it cause a cylinder to drop out you have found you problem.
If its just a weak coil, this won't help find it, of course.

Flash

[SilverXJ]

http://jeep.blackonyx.net/stroker/vids/rev1.mov

Watch it from around 0:32 and you can see what it is doing.

I tried to disconnect the O2 sensors today with no effect... it didn't even throw an engine light, which I though was odd. Same thing with the downstream O2 sims. I also tried moving the cam sensor. A little movement clockwise made it not run at all, anti-clockwise it appears that there is more room for error as I had to turn it pretty far to get a negative result. I turned it in small increments then tried to duplicate the problem. However, it was still there no matter what.

Coil rail maybe?

At least I got around to replacing the ZJ's steering pump... year old Advance Auto pump and it was starting to fail.. got a used one.. hopefully that will hold up. Its quieter now.

[Jeep4xb4u]

I cant find anything in my all data about procedures for checking your coil rail. It does mention that the "Primary Resistance" should read out 0.71-0.88 ohms @ 21-27 deg C. Looks like the only thing that can be serviced that is linked directly to the rail itself is the "ASD" relay. There is test procedures for this.