'95 850 T5 MISFIRE PROBS

norfolkpauly · Post by **norfolkpauly** » 09 Dec 2010, 07:42

Hi Everyone

I just registered and have to say what a great forum!

I recently bought my first volvo, had been spotting a tiny amount of oil which i decided to have sorted at my localgarage. Turned out to be the rocker cover gasket, which they replaced.

On collecting my car, it almost immediately developed a hesitant and intermittent misfire. The guy at the garage was none the wiser, a couple of times it wouldn't even start, and he suggested my starter motor sounded rough. The next day, he replaced that and said it seemed to be running fine, the misfire had "gone". It was fine for about an hour, after which the misfire came back worse than ever, undriveable. The next thing he replaced was the distributor cap, that sorted it out for about 2 hours this time!

Yesterday i renewed the plugs and leads, and again the problem was solved for a bit. It seems to be much worse when the engine is warm, i'm not mechanically minded i'm afraid but a friend of mine who is, suggests the problem is more than likely electrical, something breaking down, a coil for instance?

Any advice on likely scenarios would be greatly appreciated, it's a lovely car and i've hardly been able to drive it!!

Thanks, Paul.

Post by **jblackburn** » 09 Dec 2010, 08:12

Welcome to the forum!

You may have either a bad cam/crankshaft sensor, or the ignition coil itself could be causing problems. When it gets dark, open the hood with the car running and look for any blue arcing from the ignition coil, and listen for zapping noises. If that checks out OK, read over this thread for a quick, simple check of your sensor wires.

https://www.matthewsvolvosite.com/forums ... 08#p161508

norfolkpauly · Post by **norfolkpauly** » 09 Dec 2010, 08:55

Thankyou, i will investigate further....

norfolkpauly · Post by **norfolkpauly** » 13 Dec 2010, 01:21

Well, all my ht leads are neatly tucked away from sensor leads etc, so there's no issue there....

My mechanic friend has sourced a cam sensor and a coil (both £15 from ebay), and we're waiting for them to arrive, but for the last couple of days the car has run really sweet, not missing once! (2 days ago it ran awful, juddering and stalling every time i stopped at lights etc).

I understand these bits are fairly binary ie they either work or they don't, have i got this right i wonder?

Any input would be gratefully appreciated.

Post by **jblackburn** » 13 Dec 2010, 05:18

Not always - the sensors can work intermittently at times, especially if they are old.

norfolkpauly · Post by **norfolkpauly** » 14 Dec 2010, 08:43

Well, i'm waiting on a coil and a camshaft sensor.... if that doesn't solve it, i'm going to try the crankshaft sensor. Fingers crossed! By reading through the advice on here, i would say that if my problem persists it ought to be the airflow sensor next?

Thanks for your help Mr Blackburn by the way.

Post by **jblackburn** » 14 Dec 2010, 08:50

No problem - hopefully you can get this issue resolved fairly easily.

Nice price on those parts - they'd be about $300 or so new. If you suspect the mass airflow sensor, if it acts up after replacing it with your new parts, unplug the sensor altogether before you order another - if it runs fine then, you've found it. In my experience, though, I got a bucking sensation with an old Buick at partial throttle; my Volvo's just sputtered in the middle of the highway and died and refused to restart and stay running. I never got any misfire codes; just a messed up fuel/air ratio I think.

Post by **boosted5cyl** » 14 Dec 2010, 11:12

What plugs did you put in and what are they gapped to? Pull them out a read them. Have you noticed it running overly rich at all?

Post by **Red-Arrow** » 14 Dec 2010, 13:35

Clean the AMM or MAF in the intake side. Also clean the idle control valve and throttle plate. Gap the plugs and check them from inconsistent impedance readings. What ever problem you have sound like it related to heat making something change.

norfolkpauly · Post by **norfolkpauly** » 15 Dec 2010, 06:32

Red-Arrow wrote:Clean the AMM or MAF in the intake side. Also clean the idle control valve and throttle plate. Gap the plugs and check them from inconsistent impedance readings. What ever problem you have sound like it related to heat making something change.

Errr.... excuse my ignorance, what's the AMM?