http://forums.swedespeed.com/zerothread?id=125584

The car is a 98 S70 T5 with 139K on it, I've done everything you can think of, originally for maintenance and then to try to figure out this mis that shows up at about 30 to 40 mph and stays up to 80-90 never realy goes away just gets less noticable with higher speed. But goes away if you slip it in to nuetral. It feels like a bad plug wire.

I'Ve had all the work done by a Volvo Master tech who still works at my local dealer and he's stumped at this point. It's all new; ignition, coil, hub assemblies, axles, rotors, motor mounts, timing belt w/pullies , water pump, even did the evap canaster and chacoal filter to eliminate a code for Vacuum leak.

The last thing we did was a new head and valves. No I don't like throwing money away but we did a compression check and #5 cylinder had almost no compression and #4 was about half what it should have been. So the for sure we thought we found the problem but it has not gotten rid of the mis! When you put your foot in to it sure runs like a bat out of hell now with all the added compression .

The latest idea was the Torque converter because if you slip it in to nuetral it goes away even at speed. Is there a way to test it or any other ideas???

Even have new rims and Mich pilot tires, just put the snows back on today and it is still there. If you have any questions about all the parts they either came IPD or Groton and there were many more than I mentioned, cam sensor, boost control valve and on and on.

Any other ides would be most appreciated.

Modified by gregory914 at 9:37 AM 11-7-2009

Misfire will typically throw a CEl, what codes are you getting?

That's what is so troubling, there are no codes. It's sort of like a shutter more obvious under load but still there when you let off. At idle you can sort of feel the miss in the steering wheel, it goes up and down with the RPMs.

Thanks for input.

Then found out that the connector for the MAF (mass air flow) sensor was corroded and just pulling on it was enough to make it lose connection and kill the engine. Cleaned it off and it stopped stalling over train-tracks (at the least) but still didn't fix it...

Finally it was determined that the Cam Position Sensor was bad. Replaced that and all was good! (Also did replace a few other things along the way: fuel filter, spark plugs, ignition coil, and maybe a few other small bits...)

So, perhaps the "new" Cam Sensor is just bad? Or you have a poor connection somewhere important? Can you tell which cylinder(s) misfire(s)?

And there are no codes?

Thanks!

The only time it goes away is when I put the tranny in neutral, but there still is a sensation of it when parked you can feel it in the steering wheel a little. It's most obvious between 35 and 45 MPH.

Ignition coil getting weak?

Quote, originally posted by gregory914 »

No not that severe and no check engine lights. It's constant, more like the feeling of a bent rim or cv joint going bad, but more repetitiuos then a rim. Those items have been ruled out. The only time it goes away is when I put the tranny in neutral, but there still is a sensation of it when parked you can feel it in the steering wheel a little. It's most obvious between 35 and 45 MPH.

Are you familiar with the term "resonant frequency"? Sounds like something is out of balance...

Parts of the transmission still spin while in neutral, no?

If not the transmission, then maybe it's a belt or pulley or something spinning/moving in/on/attached-to the engine?

Edit: You know, thinking about it a little more, if it's happening most between 35~45 MPH, then it's probably not the engine and most likely something in the drive train at or past the transmission (going away from the engine).

Modified by StarmanDXE at 1:28 PM 11-19-2009

What does a torque converter do when it goes bad. Over my years of driving, any time a transmission would shutter a little, it was toast within about 10 miles or less.

Also talked to my mechanic yesterday about this and he thinks maybe the throttle position sensor, but he's leaning more towards the trans after this cold weather thing stared.

Thank you for the input, I'll post what the next diagnostic adventure shows.