1996 850R Rough idle/Fuel Cleaner

wackenhut · Post by **wackenhut** » 22 Jul 2015, 07:29

Hi

I have recently had intermittent rough idle with my volvo upon startup, sometimes even starting and then shutting down. There are no check engine lights.

Has anyone had this issue and would know the cause? It seems to be running fine now.

I decided to put some fuel injector cleaner in the tank (STP Super Concentrated 20oz). I was told that the best one to use however is Chevron...would it hurt to put an additional fuel system cleaner in the tank during the next fillup?

Thank you.

Post by **RussB** » 22 Jul 2015, 08:34

It could be many things, but it's unlikely that fuel system cleaner will do much of anything. Have you thoroughly checked for vacuum leaks? How's the general state of tune with your 850? Miles? Any oil consumption?

wackenhut · Post by **wackenhut** » 22 Jul 2015, 09:21

I have not checked for vacuum leaks. The spark plugs were changed 45,000 miles ago. Right now I have 196,000 miles on the car. The distributor/rotor and starter were all changed recently. I just had an oil change. Other then that, everything seems to be okay, getting about 20 miles to the gallon. I put in 89 octane fuel...maybe I should be using premium?

Aaron

Post by **jgc470** » 22 Jul 2015, 09:29

I believe you should be using 90+ octane in that car, and I agree with RussB check vacuum lines closely, particularly where they curve into intake manifold and turbo unit.

Post by **RussB** » 22 Jul 2015, 10:16

I always ran/run super in my turbo's. 20 mpg is kinda low unless you're doing a lot of stop & go driving. I'm sure you're always running the AC down there!

Post by **erikv11** » 22 Jul 2015, 10:23

I agree on the octane, I use premium (91 around here) in the turbo engines.

45,000 is a lot of miles for spark plugs, even if they are Volvo factory plugs, and these cars are pretty sensitive to ignition components. Pull a couple plugs and inspect them including checking the gap.

Post by **oragex** » 22 Jul 2015, 11:28

Tank or even fuel rail injector cleaners are a great idea.. for making money if you are in the market place. For anything else, I believe they are useless. A part restricted injector can cause poor idling and poor mpg and the only way to clean such injector is an ultrasonic injector bath which runs for about $15/injector on Ebay. However if they cause poor idling it won't go away by itself.

wackenhut · Post by **wackenhut** » 22 Jul 2015, 11:51

Yep, I am running the AC....what should I be averaging mpg with the 1996 850R?

Also, anyone know how much new spark plugs...parts and labor goes for?

Post by **FLXC90** » 22 Jul 2015, 17:59

Spark plugs are a novice level job requiring minimal tools, time, and skills If you are so inclined, they also can give insight to the condition of your car. (PM sent) If your plugs are old, they may not fire efficiently, combined with hot wet Florida air and lower grade fuel, you are robbing the engine of its performance potential. Also, how old is your fuel filter, again, moisture in fuel can cause them to clog which will start by interrupting fuel flow, and will eventually cause your fuel pump to expire. (just like heart conditions!)
Plugs should be about a one hour job in a shop.