Erratic idling. Intermittent cutoff while idling.

[windman]

on my previous topic related to p0171 code, it turned out to be unrelated to my erratic idling problem since DTCs won't appear when i only use Gasoline instead of my LPG system. (according to chrysler mechanic)

I am constantly tracking variables with Scangauge, regardles of engine temperature, it idles weird. There is no missfire as far as i observe, also there is no acceleration problem, bucking etc. Fuel consumption is normal. Car drives ok.

When idling problems start to show up, car tries to creep forward when i am waiting at red light then decide no to creep forward, i starts to idle normally.

when moving slowly forward in bumper to bumper traffic, it tried to move forward again like it does while idling. When i put transmission to N, it changes idle speed randomly. This is same for cold engine with open loop mode and warm engine with closed loop.

i went to chrysler dealer to check IAC valve, they checked it for several different idling tests, their advanced terminal sends signals when engine is runnign and expect it to hold the idle at that desired rpm. we tested 1000 1200 1400 etc, it even do not fluctuated. He told me that IAC is ok. thne can died instantly when he was telling me that there is nothign to do since car is ok. It was confusing fr him to see such sitution.

We checked for o2 sensor voltages, and checked for codes nothign appeared.
We checked wires for sensors, TPS, MAP, and IAC motor, he suspected that broken or corroded or oxidized wires can casue such sitution.

I went to my own place, and replaced crank position sensor with mopar branded new one, older wan has a crack on it , i reset computer nothing new on idling problem. only it did not stall on the way office this morning.

it again tried to creep forward even if i do not touch the gas pedal. idle speed was 1200 rpm.

I ordered a TPS sensor even if i has checked its variable voltage output by a voltmeter but i want to be sure that it is ok so i ordered a new one over ebay.

i still suspect that there is a vacuum leak which i cant find and this ****** me off.

summary: car drives well except idling. it creeps forward more than it is used to be before, like i try to open throttle. if i put gears to N, rpm is more than 1100 rpm. it sometimes fluctuate. this condition happens randomly. normal RPM is around 700 rpm. fuel economy is normal, acceleration is normal. no missfires. no vibration. no hesitation, no starting problems, rarely it dies instantly without a warning. no DTCs. (except on LPG fuel i have p0171 code which is lean burn and makes me think it was related to a vacuum leak on BANK1 - weird thing is company who is dealing with LPG sytems told me that all settings and adjustment are in tolerances and systems works exceptionally well! and there is nothign to adjust better)

lugged:

help!

 

[windman]

here is video clip of problem


http://www.youtube.com/my_videos_edit?video_id=E4OxqrOFkEc&video_referrer=watch&ns=1&feature=mhsn

 

[windman]

here is my update. i checked several variables. i have a scan gauge car computer. it can show throttle position sensor - TPS values in percentage.

now... car is not running ignition is on, it shows tps, map values etc.

tps is %16. i tried to change throttle by my hand. it linearly increasing up to %73.
ok i played with sockets around, sockets in PCM etc. it is still %16. i played with wires on sensor nothing happened. i removed PCM sockets it triggered DTCS related to connected sensors. i reset computer by scagauge. then suddenly TPS dropped to %11. %11 is where idling happens normally. i know this from continuous observations on car. when it is idling TPS shows %12 and it is around 700 rpm. (remember i did not do anything to sensor or throttle only PCM socket - socket is free of ozidation or corrosion. it is clean)

when problem is there, TPS shows %16 idle speed is around 1200 rpm gears in N. when approaching to a stop sign TPS shows %12 (rpm is aroudn 900 since car is moving) and suddenly increases to %16 and idling *****.

here is the deal. when it suddenly decrease to %11 i was doing absolutely nothing just looking to scan gauge. i started car and it was idling around 700 rpm.

i turned of engine and started again it was %11 again. rpm was around 700. then i twist the throttle and adjusted speed by my hand where TPS shows %16, it equals to 2400 rpm! this means actual %16 TPS values equals to 2400 rpm way higher than IAC can cause. if it was so there would not need a throttle itself! (these percentages of course belong to my TPS sensor)

here is my conclusion from todays diagonistics.

I think, TPS sensor is going bad. it cant show exact values for idle rpms. when it quikly changes the throttle percentage, even if there is no change, PCM thinks driver is giving gas by pushing pedal, and adjusting mixture by using IAC since there is no actual throttle change to prevent rich conditions and to prevent "low" idle and stall because of lacking o air (which is actually not missing). it reacts by seeing o2 is actually not lower than expected, engine controller want to have more o2 and tell IAC to have mor air to prevent rich condition which makes correct a/f raito to be "lean" on o2 sensors!

this shows itself as lean burn on bank one due to LPG use on idling!

what do you say? there is only proof for that is a new TPS sensor i guess since it is not triggering a code becasue of being under preset range of voltage. it is not toally broken. only idling range problematic.

what do you think?

 

[windman]

Liberty 3.7 idle problem and stalling - YouTube

here is correct video link for erratic idling.

 

[windman]

ok it seems solved. here is update. i parked car and it was totally normal. suddenly it started to act weird and stalled. i checked scangauge for TPS absolute value, its was 16. i grab my little wrench and hit to TPS slowly. it was again 12!. i bought aftermarket TPS over ebay, when received i installed it. there is no problems so far. i will update later.

 

[Strikeking]

My 04 has done this Wierd idling issue a couple times. But has never stalled. Wonder if my TPS is also on its way out?

 

[windman]

update. no problems so far. give it a try. TPS is cheap. i bought standard motor porducts since i was not able to go oem at that moment. remember to reset computer after installation.

 

[TwoBobsKJ]

Thanks for the details on the idling problem. Your post will help others who are having similar problems.

Well done!! :rockit:

Bob

 

[windman]

me again.

I feel there is a problem again. I have a scan gauge. It reads the TPS position by measuring voltage which varies according to the TPS positon. I checked with voltmeter, fully closed idling voltage is 0.63 volts and 12% opening, and full throttle reads 3.80 volts with %77 opening.

isn't full throtlle means %100 opening? what is %77. car hesitates to kickdown when needed and this is probably related to this aftermarket TPS.

can somebody please measure the voltages when engine is not running but when it is fullthrotle? you can use two outer pins of socket. it will directly show a voltage. then i can compare this with oour vehicle.

 

[windman]

here is update. TPS is ok. we checked the software version of TCM and ECU, after we upgrade the software, hesitation at higher RPMs are lowered, low end troque and responsiveness increased. There was a recall for 2004 and 2005 models. for your info.

we did not to TCM quick learn, may be i can go there and do this to see what could be the diffrence after quick adaptaation on higher gears ration.