LOST JEEPS :: View topic - Engine starts to "miss" when driving...

Have any codes/ CEL's associated with the behavior?

Check the connection and wiring on the Intake Air Pressure Sensor on the side of the airbox. Seems that a lot of owners have been experiencing unexplained issues related to this little sensor lately. It should have a Mercedes-Benz logo on it.

Something else I've noticed just now ....when I prime the filter with the little plunger (about 10 times) ...the plunger becomes hard to pres down ....at this point, when I press it down, I hear the distinct "pssssst" sound of air coning out somewhere .... what would that be? ....also ... after only 10 seconds, the plunger is soft again, and I again have to pump it about ten times before it gets hard again ....any ideas?

I know in the past, when I pump it till it's hard, and then start the engine, then the plunger becomes soft again ....so your scenario makes sense ....what I don't know, is when you pump it hard, whether it is suppose to loose presure by itself after 10 seconds, without starting anything ...

linewarbr wrote:

Is there another IAT sensor on the airbox? I will have to look now. I thought the Manifold absolute pressure(MAP)/intake air temp(IAT) (all one sensor right?)sensor was on intake manifold. In any case cant hurt to clean either or both of those. My MAP/IAT was caked with soot/oil build up and after cleaning this I resolved the issue where I would occasionally (only 2 times) lose all power/create black smoke (like no boost).

kapalczynski wrote:

linewarbr wrote:

Those are 2 different sensors. I recently confused the heck out of another poster by mentioning it. The Intake Air Pressure (IAP) sensor is on the airbox, on the engine side-top, next to the turbo-to-intercooler boost hose. It is easy to mess up the connection or the wiring when changing the air filter or doing other engine work that could knock it loose. Look for the Mercedes-Benz logo on it.

The Manifold Absolute Pressure (MAP) sensor is on the intake near the top-rear of the engine. That's the one that gets gunked up with oil from the CCV and soot from the EGR.

Have the "stealership" replace the Fuel Filter Housing Assembly...it is probably leaking at the heater solenoid.

Author:	Sonix [ Sat Feb 27, 2010 3:32 pm ]
Post subject:	Engine starts to "miss" when driving...
MAN this engine of mine is not gonna stop with the problems ... I got the car back, with engine piston replaced as some of you will recall ... the car drove fine for 2 days ...now all of a sudden ....when I start the car (cold) ...it will idle perfectly ... when I start to drive it, the engine will start to "miss" ...not actually miss ...more like the fuel is being cut off ... sometimes it will cut...cut ...and bam ...the engine will die ... then after a few tries starting it again, it will start, but then start to "miss" again ... when I pull up into my garage, it will idle perfectly ...but when I step on the pedal, it will miss while revving up ... I will then switch it off, and then it woun't start again ... after I left it for an hour or more, it will startup and idle again like nothing is wrong ....until I try and drive again ... I've checked for air in the fuel, but when bleeding the fuel system, there's NO sign of air in the fuel ... Tomorrow I'll just pull the MAP sensor, to make sure it's clean .....but to me it almost looks like a loose connection at one of the sensors or something? ..I've pulled the connector from the fuel rail, and made sure it is clean ....I then pulled the connector from the high pressure pump, also to make sure it's clean .....then the engine didn't want to start at all! ...a hour after this, I bleeded the fuel system ....no sign of air ...now all of a sudden the engine started again ....until I rev it ...it missed a few times and then the engine just dies ... Any ideas?

Author:	VMKJCRD [ Sat Feb 27, 2010 4:41 pm ]
Post subject:	Re: Engine starts to "miss" when driving...
When was the last time you changed your fuel filter? Could be a dirty fuel filter.

Author:	linewarbr [ Sat Feb 27, 2010 5:44 pm ]
Post subject:	Re: Engine starts to "miss" when driving...
Have any codes/ CEL's associated with the behavior? Check the connection and wiring on the Intake Air Pressure Sensor on the side of the airbox. Seems that a lot of owners have been experiencing unexplained issues related to this little sensor lately. It should have a Mercedes-Benz logo on it.

Author:	kapalczynski [ Sat Feb 27, 2010 6:25 pm ]
Post subject:	Re: Engine starts to "miss" when driving...
linewarbr wrote: Have any codes/ CEL's associated with the behavior? Check the connection and wiring on the Intake Air Pressure Sensor on the side of the airbox. Seems that a lot of owners have been experiencing unexplained issues related to this little sensor lately. It should have a Mercedes-Benz logo on it. Is there another IAT sensor on the airbox? I will have to look now. I thought the Manifold absolute pressure(MAP)/intake air temp(IAT) (all one sensor right?)sensor was on intake manifold. In any case cant hurt to clean either or both of those. My MAP/IAT was caked with soot/oil build up and after cleaning this I resolved the issue where I would occasionally (only 2 times) lose all power/create black smoke (like no boost).

Author:	kapalczynski [ Sat Feb 27, 2010 6:29 pm ]
Post subject:	Re: Engine starts to "miss" when driving...
Thats rough man, I hope you get it figured out. Is it black smoke like too rich when dieing or clear? It definately sounds fuel/air related...but could also be timing. Besides the fuel filter, I would make sure the o'ring on the MAP sensor is in good condition (i'm sure u will when u clean it anyway) so it is reading correct manifold pressure. Do you have any way of reading fuel pressure or boost pressure? If so check that those are normal and that your intake system is holding pressure, though at low rpms that shouldn't be a factor too much. The fact it was only out of the shop 2 days and started malfunctioning leads me to believe something may have happened while appart/during assembly. Hopefully something simple. Good luck.

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Author:	racertracer [ Sat Feb 27, 2010 6:33 pm ]
Post subject:	Re: Engine starts to "miss" when driving...
I second the fuel filter being the culprit.

Author:	ATXKJ [ Sat Feb 27, 2010 6:39 pm ]
Post subject:	Re: Engine starts to "miss" when driving...
Fuel filter first - quick easy check. your root problem on the piston was an injector wasn't it? were the other injectors replaced?

Author:	Sonix [ Sun Feb 28, 2010 4:04 am ]
Post subject:	Re: Engine starts to "miss" when driving...
I already replaced the fuel and air filter yesterday ...didn't solve the problem ...bleeded the fuel system and everything ....stil same problem ... The no1 injector is till pushing more fuel by the overflow, than the other injectors, so I guess I'll have to look at that as well some time.. I doubt that that could be the problem though, else the engine would have done this right from the start ... Will have a look at my sensors today ...

Author:	Sonix [ Sun Feb 28, 2010 8:00 am ]
Post subject:	Re: Engine starts to "miss" when driving...
ok ...I've cvleaned the MAP sensor .... wasn't dirty anyway ... The following is happening constantly now ... the jeep will strugle to start a bit (sounds like no fuel is supplied ...starter just turns)....then, when it starts, I hold my foot stable on the accelerator, to try and let it rev constantly at 2500rpm ....but here is what it sounds like ....remember ...all of this happens while I hold my foot still on the accelerator ....no revving from my side ...in the end, the engine dies by itself ...here is the soundfile of what the engine does: http://www.haroldf.co.za/jeep_engine.mp2

Author:	Sonix [ Sun Feb 28, 2010 10:50 am ]
Post subject:	Re: Engine starts to "miss" when driving...
Something else I've noticed just now ....when I prime the filter with the little plunger (about 10 times) ...the plunger becomes hard to pres down ....at this point, when I press it down, I hear the distinct "pssssst" sound of air coning out somewhere .... what would that be? ....also ... after only 10 seconds, the plunger is soft again, and I again have to pump it about ten times before it gets hard again ....any ideas?

Author:	kapalczynski [ Mon Mar 01, 2010 1:20 am ]
Post subject:	Re: Engine starts to "miss" when driving...
Sonix wrote: Something else I've noticed just now ....when I prime the filter with the little plunger (about 10 times) ...the plunger becomes hard to pres down ....at this point, when I press it down, I hear the distinct "pssssst" sound of air coning out somewhere .... what would that be? ....also ... after only 10 seconds, the plunger is soft again, and I again have to pump it about ten times before it gets hard again ....any ideas? Not sure if this helps, but I just checked and mine is currently easy to pump (afraid to try it more than once since it is starting fine and running fine currently and i don't to flood it (if thats even possible?).

Author:	Sonix [ Mon Mar 01, 2010 2:22 am ]
Post subject:	Re: Engine starts to "miss" when driving...
I know in the past, when I pump it till it's hard, and then start the engine, then the plunger becomes soft again ....so your scenario makes sense ....what I don't know, is when you pump it hard, whether it is suppose to loose presure by itself after 10 seconds, without starting anything ...

Author:	kapalczynski [ Mon Mar 01, 2010 4:07 pm ]
Post subject:	Re: Engine starts to "miss" when driving...
Sonix wrote: I know in the past, when I pump it till it's hard, and then start the engine, then the plunger becomes soft again ....so your scenario makes sense ....what I don't know, is when you pump it hard, whether it is suppose to loose presure by itself after 10 seconds, without starting anything ... Yeah, i would think that sounds like a leak, but I am not a Mopar tech and don't really know. I have heard of people having issues with their CRD's dieing like this and they put in a Mopar lift pump to "resolve" the issue. Really it just band-aids the issue if you still have a leak somewhere i would think. It may be easier than to find a leak, but I would still try to get it back to stock with no leaks if this is indeed the problem.

Author:	linewarbr [ Mon Mar 01, 2010 5:15 pm ]
Post subject:	Re: Engine starts to "miss" when driving...
kapalczynski wrote: linewarbr wrote: Have any codes/ CEL's associated with the behavior? Check the connection and wiring on the Intake Air Pressure Sensor on the side of the airbox. Seems that a lot of owners have been experiencing unexplained issues related to this little sensor lately. It should have a Mercedes-Benz logo on it. Is there another IAT sensor on the airbox? I will have to look now. I thought the Manifold absolute pressure(MAP)/intake air temp(IAT) (all one sensor right?)sensor was on intake manifold. In any case cant hurt to clean either or both of those. My MAP/IAT was caked with soot/oil build up and after cleaning this I resolved the issue where I would occasionally (only 2 times) lose all power/create black smoke (like no boost). Those are 2 different sensors. I recently confused the heck out of another poster by mentioning it. The Intake Air Pressure (IAP) sensor is on the airbox, on the engine side-top, next to the turbo-to-intercooler boost hose. It is easy to mess up the connection or the wiring when changing the air filter or doing other engine work that could knock it loose. Look for the Mercedes-Benz logo on it. The Manifold Absolute Pressure (MAP) sensor is on the intake near the top-rear of the engine. That's the one that gets gunked up with oil from the CCV and soot from the EGR.

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Author:	kapalczynski [ Mon Mar 01, 2010 8:48 pm ]
Post subject:	Re: Engine starts to "miss" when driving...
linewarbr wrote: kapalczynski wrote: linewarbr wrote: Have any codes/ CEL's associated with the behavior? Check the connection and wiring on the Intake Air Pressure Sensor on the side of the airbox. Seems that a lot of owners have been experiencing unexplained issues related to this little sensor lately. It should have a Mercedes-Benz logo on it. Is there another IAT sensor on the airbox? I will have to look now. I thought the Manifold absolute pressure(MAP)/intake air temp(IAT) (all one sensor right?)sensor was on intake manifold. In any case cant hurt to clean either or both of those. My MAP/IAT was caked with soot/oil build up and after cleaning this I resolved the issue where I would occasionally (only 2 times) lose all power/create black smoke (like no boost). Those are 2 different sensors. I recently confused the heck out of another poster by mentioning it. The Intake Air Pressure (IAP) sensor is on the airbox, on the engine side-top, next to the turbo-to-intercooler boost hose. It is easy to mess up the connection or the wiring when changing the air filter or doing other engine work that could knock it loose. Look for the Mercedes-Benz logo on it. The Manifold Absolute Pressure (MAP) sensor is on the intake near the top-rear of the engine. That's the one that gets gunked up with oil from the CCV and soot from the EGR. Thx for straightening that out...i went out and looked at the air temp one now. I always thought the Map sensor was a combined air temp/map for some reason...not sure if i was misinformed, or if my brain just made that up. lol

Author:	kapalczynski [ Mon Mar 01, 2010 8:50 pm ]
Post subject:	Re: Engine starts to "miss" when driving...
Sonix wrote: I know in the past, when I pump it till it's hard, and then start the engine, then the plunger becomes soft again ....so your scenario makes sense ....what I don't know, is when you pump it hard, whether it is suppose to loose presure by itself after 10 seconds, without starting anything ... Saw this on this site: From http://www.topix.com/forum/autos/jeep-liberty/T9SFPBGK58K8613UJ Quote: Have the "stealership" replace the Fuel Filter Housing Assembly...it is probably leaking at the heater solenoid. Perhaps this a area that has alot of issues and would be worth checking out?

Author:	BVCRD [ Tue Mar 02, 2010 9:33 am ]
Post subject:	Re: Engine starts to "miss" when driving...
Sonix wrote: Something else I've noticed just now ....when I prime the filter with the little plunger (about 10 times) ...the plunger becomes hard to pres down ....at this point, when I press it down, I hear the distinct "pssssst" sound of air coning out somewhere .... what would that be? ....also ... after only 10 seconds, the plunger is soft again, and I again have to pump it about ten times before it gets hard again ....any ideas? When using the primer, you don't want to forceably push in on the plunger. I never go more than 3 plunges until I bleed air. This thing is cheaply built and it will start to leak. That is the mistake that many on here have made and started having leaks in the electrical connection. The sound you hear is most likely fuel being forced past the plunger seal. Not air.