Mechanics

CAR INTERMITANTLY RUNS ROUGH

2001 Volvo S80

Electrical problem
2001 Volvo S80 6 cyl Two Wheel Drive Automatic 110000 miles

At idle car will intermitantly run rough as if about to stall, but does not stall. No noticable problem at highway speeds. When this happens the dash lights dim. I am told it is the alternator, but I do not understand how the alternator causes the engine issue. To me it seems an electrical problem with the engine is causing the drive belt to the alternator to slow and the lights dim because the near stall.

Solution?
Avatar
Bluemesa
February 25, 2010.




Need to alternator output checked if voltage falls then computer cannot function engine stalls

Docfixit
Feb 25, 2010.
I had the alternator checked and a parts store and the car seems to only idle rough when put in gear and at a stop I replaced two coils so far the cam position sensor all the spark plugs and it seems to only do such a problem when the it heats up so something is getting hot and malfunctioning

Tiny
Childs2415
Oct 7, 2010.
You could be having an issue with the voltage regulator. The Electronic Throttle Module needs 12 volts to operate normally. If it falls below that then you start to have issues. If it falls below 9 volts then the throttle stops responding, so when it starts to act up then you really should try and see what the voltage is coming out the alternator. Also how well do you maintane your vehicle? What kind of oil do you use? If the PCV system gets plugged up then the throttle plate gets dirty and starts to stick causing some idle issues and stalling. What you may want to look into since you are running out of time is if your throttle has the extended 10year/200k mile warranty. You would need to call your local Volvo dealer to verify that it does. If it does have the extended warrany then you should just take it in and have them diagnose your vehicle. They will scan for ETM fault codes and run a test on the throttle to check the potentiameters in the throttle. If it fails then they will replace the throttle under warranty. If they find it is dirty then you will need to pay for diagnosis and decide if you want them to clean the PCV system and throttle body? It is a little expensive because the intake needs to come out to clean the pcv nipple.


http://www.2carpros.com/forum/automotive_pictures/337695_IMG00141_1.jpg



Here is one I cleaned out. The hose is held by the banjo bolt (PCV VALVE) under the intake manifold and that is why the intake needs to come to have access to it. I am using a thin wire to clean out the sludge. Hole diameter is small so it is easy for it to have build up of sludge that it pluggs up.


http://www.2carpros.com/forum/automotive_pictures/337695_IMG00146_1.jpg



Cleaned out the throttle.


http://www.2carpros.com/forum/automotive_pictures/337695_IMG00152_1.jpg



This is a special gage used to check the PCV system. Notice it is in the negative side. That is a clean PCV system. If it is at 0 or on the positive side it is dirty. I did this repair because of fuel trim problems and faulty mass air flow sensor codes and other parameters that were out of spec while diagnosing a check engine light problem. Good luck to you and hope you do get a free throttle out of this because they are very expensive to replace once out of warranty. Keep me posted please.

JIS001
Oct 7, 2010.
Well I recently purchased it and I take pretty good care of my vehicles unsure of the oil b/c I have yet to change it this is my first dohc and first foreign car so its a trip for me

Tiny
Childs2415
Oct 8, 2010.
Well look into the extended warranty. If you do have it, it is good for 10 years regardless of who the owner is.
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JIS001
Oct 8, 2010.

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