1996 850 R Strange cutout with all newish ignition parts Topic is solved

Post by **Clemens** » 18 Feb 2020, 04:55

So this time, it is my 96 R that is giving me headaches.

Thing is, when flooring it, above 4000 rpm something feels like cutting out, kinda like misfiring. And at idle when warm, it cuts out a bit as well.

If someone described the problem, I would suggest replacing the ignition components. But rhey are all newish.

All ignition components that I can think of are new or newish (maximum 4 yrs old and 20.000, maybe 25.000 miles on thwm).
all parts are blue box Volvo or OEM.

new in 2016 parts: spark plugs, distributor (cap and rotor), wires
new in 2017-18: cam sensor, crank sensor, throttle position sensor
Fall 2019: TME catback exhaust
new as if today: all 6 wires (Bourgicord) and Bosch coil.
Car has good vacum and runs solid.
I think all vacum lines are max. 4 yrs old and TCV and wastegate diaphragms is new. boost is areound 15 psi on the stock gauge.

The problem I have appeared last fall. I thought new wires and a coil are the last things to replace (I swapped wires eith my 94T5 2 yrs ago).

could the new exhaust I installed last fall lead to fuel cutoff situations? if so, this woulfn't explain the sporadic misfiring at idle.

what else could it be? bad ground comnections, dirty rotor (although just 4 yrs old), knock sensor, MAF?

And of course, I have no CEL on.

Any help would be appreciated.

Thanks

Post by **wizechatmgr** » 18 Feb 2020, 06:43

Happen to check fuel rail pressure when this occurs?

Post by **abscate** » 18 Feb 2020, 08:23

If someone described the problem, I would suggest replacing the ignition components. But rhey are all newish.

I think I would try a new set of plugs - I had one go bad one week after install.

Post by **misha** » 18 Feb 2020, 08:59

Can you find someone who can perform live data while driving?
Are there any pending codes present?

Cel will light ON when permanent fault is stored after a few driving cycles...but there can be pending codes stored without turning ON cel.....yet.

Post by **Clemens** » 18 Feb 2020, 09:04

For live codes I will need VOL FCR, right?

What I found out meanwhile: the cap had some kinda metall flakes on the conductive elements. Seems to run better now. Wonder where that comes from?

I'll swap plugs with my 94 T5 if the problem persists. Thanks for the idea.

Post by **Clemens** » 18 Feb 2020, 09:32

No, still there.
Next step: switching sparkplugs

Post by **misha** » 18 Feb 2020, 09:42

Vol-Fcr is for M4.4.
Does your R have m4.3 or m4.4 ecu?
Are spark plugs Volvo plugs?

Post by **Clemens** » 18 Feb 2020, 10:24

It has the M4.3 ECU and Volvo plugs. They are either 4 or 2 years old. I will pull them tomorrow and see if they are in good condition and gapped correctly. Then I will swap them with the ones out of my 94. The 94 runs quite smooth right now. If the problem trnasfers, I know it is the plugs.

Post by **Clemens** » 18 Feb 2020, 12:11

Now I switched the plugs.
The ones out the 94T5 were a little on the darkish side, maybe carbon buildup. The ones out of the teoublesome 96 were whitish. Photo attached. One of them was a tad brownish around the shaft, maybe oil that got down the upper part of the plug when refilling oil?

Let's see how it runs tomorrow, because the cutouts at idle only happen when it is warm and in D (not in N).

Post by **misha** » 18 Feb 2020, 16:11

Thats not from oil....i guess it is from the heat.
Whiteish look is ok....good combustion sign.
'94 T5 could run a bit rich or driven on short distances and that's why they are darker.