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Chevy Uplander 3.9 2008 hesitate when acelerating
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hockey4ever
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Feb 12, 2015, 1:49 PM
Post #1 of 12
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Chevy Uplander 3.9 2008 hesitate when acelerating
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In the morning, when i go to pick up my news paper at local convenience store, the van is running rough and hesitate when accelerating.
When i take the van 1 hous later, it will run smoothly and there will be no hesitation and i will be good for the rest of the day.
If i skip the trip to convenience store and the first thing in the morning i do a long trip, let's say 2 hours trip, the van will run rough all the way during those 2 hours.
When the van is running rough it will stay in this state until it's turned off, wait and restarted again.
When the van is running soothly, it will stay in this state until next morning.
While driving, it never happened that the smooth running engine became running rough and the opposite is also true. It never hapenned while driving that the rough running engine became smooth.
I suspect that at engine start up, a parameter is stored and kept in memory until the car is turned off, wait and restarted again.
DTC code P0336 and P1174
Any idea? Leaving in a cold climate in Montreal Quebec aera. Thanks
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Discretesignals
Ultimate Carjunky
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Feb 12, 2015, 2:46 PM
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Re: Chevy Uplander 3.9 2008 hesitate when acelerating
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P0336 is a crank sensor performance code. It means the engine computer is detecting an abnormal signal on the crank sensor circuit. You'll need to connect a lab scope to the crank sensor signal circuit and monitor the signal during your drive-ability issue. Crank sensor signal issues can cause stalling, misfiring, hesitation, etc.
P1174 has to do with the computer detecting an air/fuel imbalance in bank 1. Has there been any o2 sensors changed recently? Crank sensor performance issue could possibly cause this code to appear.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
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hockey4ever
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Feb 13, 2015, 6:59 AM
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Re: Chevy Uplander 3.9 2008 hesitate when acelerating
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no o2 sensor were replaced recently. I don't have a lab scope to monitor the crank sensor. I think i'll bring it to the shop!!!
Could it be the opposite? P0336 being caused by P1174?
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Discretesignals
Ultimate Carjunky
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Feb 13, 2015, 5:17 PM
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Re: Chevy Uplander 3.9 2008 hesitate when acelerating
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Probably not. An air fuel imbalance shouldn't cause a crank sensor performance issue. That could be caused by a wacky crank sensor signal causing misfires or there is another problem besides what ever is causing crank sensor performance code to show up. I would tackle the crank sensor code first and then see if the fuel imbalance trouble code reappears after clearing it from the engine computer's memory.
When the crank shaft sensor signal isn't correct according to how the engine computer should see it, the engine computer will default to using the cam sensor to keep the engine going in a limp state. The code doesn't mean the crank sensor has a circuit issue, it is just a signal issue. Crank sensor could be outputting a wacky signal or something could be generating EMI on the crank sensor circuit. That is why I stated a lab scope would be the best tool to determine what is going on with the signal. A volt meter can't show you the true signal because it averages the voltage. The signal is a 0-5 volt square wave that changes in frequency in relation to crankshaft speed.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
(This post was edited by Discretesignals on Feb 13, 2015, 5:39 PM)
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hockey4ever
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Feb 16, 2015, 7:09 AM
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Re: Chevy Uplander 3.9 2008 hesitate when acelerating
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This week end, i plugged in my osb2 scanner and i monitored the rpm sensor while the engine was running rough. I was not able to get any signal.
I was getting signal from other gauge like coolant temp, mass sensor but not from RPM.
Am i right to assume the rpm gauge in my obd2 scanner is getting the signal from crank sensor?
RPM gauge in instrument panel cluster (dashboard) was showing correct RPM. Is it related to crank sensor?
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Discretesignals
Ultimate Carjunky
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Feb 16, 2015, 5:03 PM
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Re: Chevy Uplander 3.9 2008 hesitate when acelerating
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You really need to monitor that signal to see why it isn't showing up on your scan tool. If the crank signal isn't getting to the PCM, it may be calculating rpm based off the cam sensor signal to operate the rpm gauge.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
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hockey4ever
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Feb 17, 2015, 12:18 PM
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Re: Chevy Uplander 3.9 2008 hesitate when acelerating
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Do you know where is the crank sensor located? In one pdf manual that i downloaded it says it is located in the back of the engine close to the bottom. In another manual it say is is up front.
Yesterday i put the van on the ramp and i crawled under the engine and i wasn't able to see anything. There was a cross member blocking almost everything.
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Hammer Time
Ultimate Carjunky
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Feb 17, 2015, 2:20 PM
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Re: Chevy Uplander 3.9 2008 hesitate when acelerating
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It's in the side of the block on the back side. #7 in the picture.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
(This post was edited by Hammer Time on Feb 17, 2015, 2:21 PM)
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hockey4ever
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Apr 3, 2015, 3:07 PM
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Re: Chevy Uplander 3.9 2008 hesitate when acelerating
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Crank sensor just got replaced. Now it always hesitate when accelerating and it always run rough at idle. Intermittent problem became constant.
CKP variation relearn procedure was not done because I don't have a scan tool for this. Should I bring it to the shop? Can I do it without the scan tool?
Do you think it's the cause of my problem or it is something else? Thanks for your help
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Discretesignals
Ultimate Carjunky
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Apr 3, 2015, 3:21 PM
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Re: Chevy Uplander 3.9 2008 hesitate when acelerating
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Is that crank code still showing up? Did they test the circuit and monitored the signal to see what exactly was going on or did they just guess and slapped a sensor in it?
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
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hockey4ever
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Apr 5, 2015, 3:19 PM
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Re: Chevy Uplander 3.9 2008 hesitate when acelerating
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In reality, I asked my mechanic to replace the ckp sensor. He did what I ask him to do. He just do basic mechanic.
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Hammer Time
Ultimate Carjunky
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Apr 5, 2015, 4:08 PM
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Re: Chevy Uplander 3.9 2008 hesitate when acelerating
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He's not really a mechanic at all then. He just changes parts. You need someone that can actually diagnose a problem.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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