Missing / Misfire - not the "Usual" ETM ?? Issue - No codes

[C704me]

Hi Everyone,

I'm rather new and have been doing quite a bit of reading over the last year or so (even before I signed up).

Can someone clear up a question I had? Looking to see if anyone has had this particular symptom.

I've been fighting a "Misfire type of symptom" in our 2001 (24,000 mile) C-70. This was our weekend car but my wife now uses it as her daily driver so "there goes our nice low mileage Volvo!)

Symptoms don't seem to fit the ETM symptoms - no check engine light etc , no codes from the OBDII reader either. (But I'm seeing that without the Volvo VADIS / VIDA , I may not see a code that may be there??? - Is that correct?)

My particular symptom is a well defined "miss" or stutter that can be seen on the Tach. I can see the RPM's drop a few hundred RPM (or even less) and it feels like a miss.

It NEVER MISSES at idle.
It starts just fine. The miss can occur at low speed (2-25mph) or on the highway cruising (pretty much at any cruise speed). It could be as little as 1-2 "hiccups" or as much as a constant miss like you are pushing and letting off the gas pedal with your foot on purpose - 10-15-20 times...

It will do it more under load BUT I have determined that if I rev it quite high while it's in park, I can duplicate the "miss / see the fuel pressure drop" while I'm sitting still in the driveway. (However, you almost have to "redline it " to do it);.

It IS intermittent.
It WILL DO IT when the car is COLD or when it's Warmed up etc.
It DOES NOT seem to do it if I "Floor it" / kick into passing gear etc.

If I install a fuel pressure regulator onto the fuel rail, I CAN see a distinct 3-7 psi drop in fuel pressure when the symptom / miss occurs.
I DO see a slight "soot" in the tailpipe BUT MILEAGE DOES NOT seem to be affected at all.

I DON'T have any Codes or Check Engine Light (OBDII scanner). Due to our mileage It does not seem to fit the ETM symptoms (although it is an "old White label" ETM, so that's going to be a reality at some point) - The dealer would not do the upgrade since we have not had any symptoms, no codes or check engine light -- and now we're past the 10 year mark so that's going to be "our problem" when it occurs).

I would Imagine that any sensor, Cam position , crank sensor, MAF, O2 sensor would throw a code and since I see a drop in Fuel pressure, I was leaning toward fuel. Also - the fact that the car is 10 years old and has under 30K, it has not spent a ton of time on the road but it does get driven pretty frequent - just not on long trips.

I removed the plugs and they look brand new. I don't think ignition / coils would "be it" since I see a drop in Fuel Pressure.

I just ordered and received a new fuel filter. I'm wondering if I may be having a fuel pump , fuel regulator / similar issue.

Has anyone had similar symptoms??

Since the Volvo has the ETM Issue / "Electronic gas pedal" and the "whole VADIS thing" I not as familiar with it as my other cars / previous cars. If I could possibly could have a "code hiding somewhere", I could run over to the dealer and pay them to scan it for me - but I figured some on the forum may have had the same issue so I figured I'd post first.

Any input would be a great help. Thanks,

[ronnieleetwist]

Had similar problem with my s80...Check the coil packs on each spark plug for cracks...even tiny cracks will screw you up. If you need to replace them DO IT YOURSELF> I was stranded and had to have a VOLVO dealer do it and they charged me 1300 bucks to replace 6 coil packs. (I can get them for about 60 bucks a piece online if I shop around. They take about 5 minutes each to replace. Auto Mechanics 101 stuff.

[C704me]

Thanks for the reply. I agree, the coils are easy. Just did them on my 540 - can't really get any easier than that.

The only issue I have though is: I'm guessing (like on my BMW and others) that a coil "bad enough" to make the car constantly miss would throw a misfire code. On my Ford F150, when one of the coil banks went bad, a small miss would go pretty much undetected, but as it got worse and would mis 2, 4, 5 times in a row in a short period of time, the ECM would throw a code.

I'm also guessing that my Fuel Pressure would not drop if it was a coil misfire (unless the coil misfire is enough to interrupt the fuel in the corresponding injector - like on some cars). Something to check though.