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Rough idle and misfires

Tiny
PETRIEPETE
  • MEMBER
  • 2002 SATURN VUE
  • 3.0L
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 92,000 MILES
Rough idle and random misfires when accelerating slowly from low rpm while driving. Misfire while driving causes check engine light to flash and the car "bucks" pretty severely. The flashing light and bucking sometimes stops by backing off on the throttle, otherwise turning vehicle off and restarting will stop it. Then it is back to just the rough idle. Can avoid the flashing and bucking by accelerating quickly and keeping the rpm's high (2000 or higher). Check engine light stays solid until the code is cleared. Codes are usually P300 through 305, sometimes multiple, sometimes just one. Have replaced plugs, wires, coil packs, mapi sensor and intake manifold upper and lower gaskets.
Also, have random issues with turn signals and cooling fan. At times the turn signals stop working, no lights inside or out. The cooling fan also runs high speed at times when it should not. Like right after startup when it is cold outside. Turning vehicle off and restarting resolves both issues. I have checked and cleaned all ground connections I could find.
I am thinking these issues are unrelated but am running out of ideas. Any suggestions?
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Sunday, November 12th, 2017 AT 9:14 AM

10 Replies

Tiny
SATURNTECH9
  • MECHANIC
  • 30,869 POSTS
What are the exact code numbers not code descriptions you have? Also, on that engine there is a blow off valve on the driver side of the intake manifold it is plastic. I have seen those get stuck open and cause issues with vacuum leaks.
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Sunday, November 12th, 2017 AT 9:26 AM
Tiny
PETRIEPETE
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Thanks for the reply. P300 is random misfires. P301 through 306 are misfires specific to each cylinder. I will look for and mess around with the blow off valve. This engine has high and low rpm solenoids to control the valves which are located on the same side off the engine. Are you familiar with these? Can they cause this type of issue? I have also heard it is possible that one of the cam gears may have slipped a tooth or two on the timing belt or a cam position sensor could be bad. Do either of those sound plausible? If I brought it to a shop, could they diagnose to this level or would they just start replacing parts until the issue disappeared?
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Sunday, November 12th, 2017 AT 9:48 AM
Tiny
SATURNTECH9
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I do not remember variable valve timing on those engines. A bad cam position sensor should set a code. Also, if it jumped time it would run bad all the time.
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Sunday, November 12th, 2017 AT 9:07 PM
Tiny
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So could the valve timing solenoids be the problem? How about the ECM?
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Tuesday, November 14th, 2017 AT 8:32 AM
Tiny
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Again there is not any variable valve timing on that engine. Also, when the ECM on that vehicle fails it usually does not start and you cannot talk to the ECM with a scan tool. So did you check that blow off valve yet?
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Tuesday, November 14th, 2017 AT 2:39 PM
Tiny
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Have not checked the blow off valve yet. This engine does have the variable valve timing. The 2002 and 2003 six cylinder engines have it.
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Tuesday, November 14th, 2017 AT 2:53 PM
Tiny
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When they switched to the Honda v6 engine in 2004 then they had variable valve timing. That is the same engine they use in the Saturn L series and the Cadillac Catera cars and they do not have variable valve timing they have cam sensors yes, but variable valve timing no. Does it always run bad all through the rpm range or just at idle etc?
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Tuesday, November 14th, 2017 AT 3:34 PM
Tiny
PETRIEPETE
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  • 5 POSTS
It only runs bad at low rpm (less than 2000). If I am driving at fifty five mph and need to accelerate, I have to fool it and quickly "pump" the accelerator to get the rpm's up, then no problem. If I do not pump it then it starts bucking and the CEL starts flashing. If I accelerate quickly from a stop I have no problems. If I accelerate slowly, when it gets to the point when the rpm's drop to 1.5 - 1.7k and I am still accelerating slowly then it will buck.
I do not know if they call it variable valve timing but there are two valve control solenoids on this engine. According to the manual, one is for low rpm and the other for high rpm.
By the way -Thank you for your time and effort on this issue (it is starting to make me crazy)!
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Tuesday, November 14th, 2017 AT 4:44 PM
Tiny
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I think your talking about the cam position sensors. Have checked the camshaft timing yet? Also have you checked for vacuum leaks?
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Tuesday, November 14th, 2017 AT 9:48 PM
Tiny
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I would also be checking that blow off valve.
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Tuesday, November 14th, 2017 AT 9:49 PM

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