1996 855R WOT lacking power Topic is solved

[appropriatenoises]

I have an interesting problem for which I am at a loss in explaining. I've searched the forum and haven't found a similar problem.

First some info on the car:
248k km
Recent work includes plugs, cap and rotor, wires and coil. Valves have been cleaned, MAF has been cleaned. No codes to speak of (other than ABS module/TRACS) - the car is not showing CEL, nor has it ever.

First: the problem I had until yesterday (before I replaced the coil and plug wires) was that at WOT the car would buck. I attributed this to "spark plug blow out" (I know thats kind of an innaccurate term, but you know what I mean), and my problem is MOSTLY better: car no longer bucks at WOT in sport mode.

The problem that still remains is a slight lack of power at WOT. I can get into the throttle most of the way (75%) and the car pulls and pulls. But as soon as I mash it, it plateaus in power, or almost has less power than at 75%. Doesn't seem to be RPM specific, though that's hard to tell due to how the turbo spools.

Any suggestions would be helpful, and please let me know if I haven't given enough information.

[rspi]

Check this: https://www.matthewsvolvosite.com/forums ... =1&t=46890

[appropriatenoises]

I don't think that's the problem. I have all the proper vac hoses; redid them about 6 months ago. My rubber turbo/intake hoses are a bit soft and do flex a bit, but nothing at all like that video! Could a seized wastegate actuator be the problem??

[appropriatenoises]

Bump and a comment: Still have this problem. I've now replaced the hose RSPI mentioned. (it quite drastically failed at -20degrees in Alberta this Christmas, couldn't even get the car to go over 2k RPM)

The car feels as though it's stuttering when I accelerate aggressively. but it's a "high frequency" stutter. Anyone else have any insight?

[jblackburn]

Does it stutter at high RPM, high load? What kind of plugs did you replace the old ones with?

[appropriatenoises]

Jblackburn, it stutters at WOT regardless of RPM (within reason, since it's an auto), so I would say anywhere from 3k-redline. Spark plugs were replaced with Bosch Platinums (http://www.ipdusa.com/products/8273/109207-bosch-platinum-spark-plug) and ignition coil was replaced with the MSD unit. (problem exsisted before these items were replaced)

It sure does seem like a spark issue though. Unless it IS air intake/air sensing and I need to have another go at cleaning the MAF and throttle body?

[jblackburn]

Still sounds like spark blowout to me. These cars hate platinum plugs after a few thousand miles, and are very sensitive to the correct gap being set. I thought I knew better too, but my car was quick to prove me wrong.

Get a cheapo set of Bosch Super Copper plugs (a full set will run you around $5-7 here), and try those. Copper plugs are kosher for turbocharged applications; platinum provides the weakest spark. Set the gap to .028".

[matthew1]

Sounds like a collapsing intake hose to me.

[appropriatenoises]

Matthew, is it possible that it could be any of the other intake hoses than the one leaving the top of the intercooler? (That one was replaced a month ago)

If it's plugs, anyone have tips on changing them without stripping? Last time I did, it was the most fretful car repair experience I've had... every one felt like it was going to snap off coming out.

[jblackburn]

It is possible, yes. The hoses get coated with oil and get weak over the years.

Aluminum heads expand/contract thousands of times over the years, and the plugs "fuse" to the head. Always install new plugs with anti-seize lubricant. Remove on a cold engine. They should come back out fairly easily. Torque down til they're just tight enough, no need to go King Kong on it.