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Clayso
Clayso, Master Automobile Technician
Category: Chevy
Satisfied Customers: 880
Experience:  ASE Master Certified Automobile Technician. 30 Years Experience.
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When I go to start it inn the morning it kicks and sputters

Customer Question

When I go to start it inn the morning it kicks and sputters like the timing is off or the fuel mixture is wrong then after a few tries and giving a little gas it will go and rev normally and sometimes works fine all day and sometimes it wont go when you give it gas? the throttle body was removed and cleaned (was dirty) the MAF sensor was also cleaned. The transmission was rebuilt and the problem seemed to start shortly after that. I noticed they added maybe a litre too much fluid. Could that be related?
JA: Does the engine stall right after starting? And what about hesitation or jerking during acceleration?
Customer: Once it starts its ok and doesnt stall. There is occasional hesitation but it is an intermittent problem. Some days there are no issues once you get it started other days there is but it is now always hard to start
JA: What is the model/year of your Chevy?
Customer: 2007 LS with 200000 km on it
JA: Are you fixing your vehicle yourself? What have you tried so far?
Customer: Yes myself New plugs and wires and air filter and fuel injector cleaner and removed and cleaned the throttle valve and cleaned the MAF sensor
JA: Anything else you want the mechanic to know before I connect you?
Customer: My friend who is a mechanic says possible fuel pump issue or too much transmission fluid
Submitted: 2 months ago.
Category: Chevy
Expert:  Gary replied 2 months ago.

what make and model and engine size is this ?

Customer: replied 2 months ago.
2007 Chevy Uplander LT 3800
Expert:  Gary replied 2 months ago.

there are no codes set at all ?

did anything you have done so far make it any better or any worse ?

Customer: replied 2 months ago.
Dash shows engine light on traction service required
what i did seems have made the car run and idle a little better when it is running but did not fix the starting problem and there is still intermittent but not always a loos of power. Sometimes when I go to move forward at a green light I hit the gas and it will go slow then it will kick in and go
Expert:  Gary replied 2 months ago.

can you tell me the code numbers set in the computer ?

Customer: replied 2 months ago.
I dont have a code reader but when I brought it to a garage in May they said the codes were:
PO172 Fuel rich
PO326 Knock performance
PO335 Crank sensor
PO336 Crank Sensor performance
PO455 Evap system
Further diagnoses required
Tune up suggested
Battery tests show replace (I replaced the battery since then)
Expert:  Gary replied 2 months ago.

ok the crank sensor codes need to be addressed first

as a bad crank sensor will cause the 172 and the 326 codes

if the wiring to the crank sensor looks good replace the crank sensor then relearn the new crank sensor with a scan tool

that should clear out those codes and stop this engine starting problem which with a bad crank sensor will send a wrong signal to the computer and it will act like the timing is off

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Customer: replied 2 months ago.
Thanks Gary
I will try replacing the crank sensor as you suggested.
Not sure how I will relearn the new crank sensor as I dont have a scan tool
Expert:  Gary replied 2 months ago.

it needs to be relearned if you can not see if the local shop will relearn it for 1/2 labor or so but it has to be relearned when replaced

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Customer: replied 2 months ago.
OK I will have it done and I rate.
I hope you are correct with your recommendation.
It makes sense to me
Thanks so much
Expert:  Gary replied 2 months ago.

anytime

let me know how it goes

you can always get me back for FREE for any follow up any time with this question even after you rate me here at Justanswer

Customer: replied 2 months ago.
Hi Gary,
The crank sensor was replaced.
The engine still starts but will see if there is any improvement in the morning when it is cold because it starts when it is warm but takes extra cranks. Garage said there is no RPM showing on the scanner. Said they show 5 volt and low reference signals,
PO335 and PO336 returned
So now I am at a loss to figure out what is going on. When I drive it at just under 2000 rpm it feels starved for gas the it drops to just above 1500 RPM then it will then increase RPM to past 2000RPM and go fine??
Report said could be problem wiring or ECM??
Expert:  Gary replied 2 months ago.

the low reference should be a good ground NOT 5 volts

at the crank sensor there is 3 wires the light green should be 5 volts the yellow/black should be a good ground

Customer: replied 2 months ago.
All he noted was theat he said he had 5 volt and low reference signals but did not state which wires had what
Expert:  Gary replied 2 months ago.

if the codes are cleared and come back then with a new sensor they need to be 100 % sure the wiring to the sensor is good if it is then the only thing left is a bad computer or the reluctor wheel that triggers the senors being bad or the timing chain is outs of time causing a wrong trigger of the crank sensor

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Customer: replied 2 months ago.
Hi Gary,
I will have ask if he cleared the codes. I know they charged me some extra to fix up some wiring..
I guess this more complicated than I thought.
I will contact them in the morning
Thanks again
Expert:  Gary replied 2 months ago.

anytime

let me know

dont forget to rate us here

you can always get me back for FREE for any follow up any time with this question even after you rate me here at Justanswer

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Customer: replied 2 months ago.
Hi Gary
Still same problem
Seems like when ever rpms are at 1500 to 2000 there is terrible hesitation also starting has changed since the new sensor was installed before it would kick and back fire now it turns over fast and constant but must give it gas by depessing the pedel part way down for it to start then it runs and revs fine in park but when driving it still has the hesitation issue around the 2000rpm mark I also removed almost 1 litre of too much transmission fluid So will see if that does anything
Expert:  Clayso replied 2 months ago.

Hi There,
This is Clay, I'm a certified master automobile technician with 30 years of automotive repair and diagnostic experience.

I've been reading up on this problem with your Uplander. I've read and seen the same problem on this model and similar others with the same engines. From your description and codes P0335 & P0336 the problem is crank sensor related, but it's the mating surface between the crank sensor and the engine block where I've seen the same problems. Rust and corrosion builds between the sensor and the block causing an erratic signal from the crank sensor resulting in hard starting, rough idle, misfires and codes P0335 & P0336. Remove the crank sensor and sand the block until it's shinny clean, then reinstall the sensor and preform a crank sensor variation learn. Make sure not to grind down the block with sand paper but make it shine, also make sure to keep all of the debris from entering the crank sensors hole in the block. I've seen other problems with the knock sensor and crank sensor harnesses but not as common as I've seen with the crank sensor's mounting surface.

Let me know how this works out for you. If you have any questions let me know. You can reply back to me through this thread at any time.
Thanks.

Customer: replied 2 months ago.
I will try it, but isn't the bolt that mounts it to the block good enough to provide a proper ground
Can it re learn with out a special tool or do I need to take it back to the garage again $$
Thanks
Expert:  Clayso replied 2 months ago.

Thanks for getting back to me. It's not a ground issue, but the distance from the end of the crank sensor to the to the reluctor wheel on the crankshaft. Any build up between the crank sensor and the block will basically cause the sensor to be to far away from the reluctor wheel. Where the crank sensor is located in the side of the block isn't any fun to get to much less making sure the surface is clean for a proper gap.

Expert:  Clayso replied 2 months ago.

Crankshaft Position System Variation Learn
Important: The Crankshaft Position (CKP) system variation learn procedure is also required when the following service procedures have been
performed, regardless of whether DTC P0315 is set:
* An engine replacement
* A engine control module (ECM) replacement
* A crankshaft balancer replacement
* A crankshaft replacement
* A CKP sensor replacement
* Any engine repairs which disturb the crankshaft to CKP sensor relationship.

Customer: replied 2 months ago.
I agree not easy to get at but I will give it a try
FYI
Everything that has been done to resolve this has made a difference in the starting and driving of the vehicle.
The vehicle will star still start but no kick back just turns over fastt but I must depress the gas pedal a little bit to get it to start and when driving there is a loss of power at around 2000 rpms but fine above that
It is hit and miss with the remote auto starter it is usually a no go
Customer: replied 2 months ago.
I will find out if the garage did a learn after they replaced the crankshaft sensor
Expert:  Clayso replied 2 months ago.

Everything I've seen you do in this post seams to have made a difference. The CKP's information sent to the ECM is critical to the vehicles performance and operation, it's gotta be 100% or the PCM will think there is a timing issue and or misfires. Remote starts don't work when there are codes set, anytime the ECM sees there is a problem the remote start is disabled, same as if the vehicle was very low on fuel. You can try cleaning the surface and see if it operated any better, then after all repairs have been made then the CKP system variation learn procedure should be preformed.

Customer: replied 2 months ago.
Ok Thank you
Will clean it and have it re learned
Expert:  Clayso replied 2 months ago.

You're welcome. I have to go fix an old Ford, I'll be back in an hour or so.

Thanks

Expert:  Clayso replied 2 months ago.

Hi There,

Just wondering if you found any build up around the CKP's hole and if you did is there any change in how it starts this morning?

I read back through this complete conversation and if cleaning up the block and the CKP doesn't change anything I can walk you through verifying the integrity of the harness from the ECM to the CKP. Personally I use a #194 marker light bulb and the car battery to verify any circuit in question. A couple of comments you made "Garage said there is no RPM showing on the scanner" and "I know they charged me some extra to fix up some wiring". Would lead me to believe there could still be a problem in the harness. Most all techs use an ohmmeter to check continuity (I can show continuity with a simple pencil scribble on paper). With a bulb and a battery you can load test a circuit and assure its integrity 100%. To load test a circuit is easier to do than explain. Basically bend the prongs out on a #194 marker bulb and plug it into 2 of the CKP's terminals and load this part of the circuit from the ECM connector with the vehicles battery. The connectors have to be disconnected from their components of course and the battery disconnected from the vehicle.

From the ECM to the CKP there is one connector that joins the #1 Knock Sensor (KS1) and the CKP sensor into a jumper harness. I read a couple of problems within the jumper harness and the connector. I don't know what the garage meant by fixing up some wiring or if they did in fact solve any wiring issues. Verifying this circuit is a must before trying to preform a crank sensor variation learn procedure.

I can offer a premium service for an additional 5 dollars and continue this conversation through regular email and or the phone, which ever works best. I have diagrams and connector views specific to this vehicle. Regular email is so much easier for sending technical information, diagrams and images. It's also straightforward for you to send me any images if needed. Please accept my offer for 2007 Uplander CKP so I can better assist you.

Let me know if cleaning up the CKP made any difference and if you're interested in my offer to make this problem easier to deal with.

Let me know.
Thanks

Customer: replied 2 months ago.
Hi Clay
No build up found and starts like it turns over fast but wont start until I give it a 1/3 push of the gas pedal Then it seems to run fine except there is a stall spot at around 2000 rpms it hesitates then if I floor it it will go
Expert:  Clayso replied 2 months ago.

The hard start, fast spin and fall out at 2000 rpms leads us right back to no rpm signal and the CKP, wiring and or the ECM remain on the top of the list of potential problems.

Following the wiring harness from the CKP & KS1 sensors should lead you to connector C104. C140 connects the CKP and KS1 jumper harness to the engine harness. C140 has 6 cavities and should be located at the right lower front side of the engine near the oil pan (the right side being the back). Let me know if there is any evidence of wiring or harness repair. The circuit from the CKP has to be near perfect for a stable signal to the ECM.

You can also try disconnecting the negative battery cable then the positive and holding the cables together for several minutes to clear any Diagnostic Trouble Code (DTC)s. Then reconnect the battery, positive first then negative and operate the vehicle to see what all codes return.

Let me know how this works out for you.
Thanks

Customer: replied 2 months ago.
Thanks Clay
Will try it
Expert:  Clayso replied 2 months ago.

You're welcome. I'd really like to know for certain there are zero problems in the harness from the ECM to the CKP & KS sensors. I hate the thought of throwing a part at a problem and hoping for a positive result.

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