850R poor acceleration

clawless · Post by **clawless** » 12 Nov 2008, 17:42

Hello,

Sorry for the long post…

I have had an ongoing issue with my 97 850R . It seems that it’s slightly missing under acceleration. No engine codes have been set and it sometimes runs fine but not very often. I have changed just about every sensor, MAF, coolant temp, o2 sensors, TPS, swapped the injectors too. I installed bigger 410cc injectors and get a p0171, lean condition, long term fuel trim (Volvo 2-3-1), when I put the factory injectors back in the code goes away, had both sets cleaned and flow tested and both were fine, that one is still a mystery.

All ignition components have been changed, plugs, wires cap rotor and coil

I have extensively checked for vacuum leaks and found a few small ones that have been fixed, to no avail.

I am down to idle control valve and head gasket…or any other ideas?

The idle valve seems to work however if I start the car and then shut it off after about a minute, the valve still seems to “run”, it buzzes for like 1 to 2 min after the car is off. If I let it warm up it seems to shut off then I turn the engine off but not always. There are no idle issues that I can tell, it sits at about 1k rpm and fluctuates a little. I do notice on an aftermarket boost gauge that I installed, when it idles and pulls about 22in hg it exhibits the issue, when it pulls 19in hg it seems to run better but not always…leading me to the idle valve.

As far as the head gasket, it did semi overheat once, thermostat stuck closed. By semi, it hit the H mark, I turned the heater on full blast, luckily it was in the winter that brought the temp into the very high normal range, it was driven about 15 miles then fixed. I do not recall if the accel issue was present before then. I changed the coolant a few weeks ago and noticed and ever ever so slight milky build up on the reservoir, coolant looked old and a little cloudy. The oil is clean, no water or milkyness there, and is never low and no antifreeze smell / steam from the exhaust. I was thinking a cylinder to cylinder leak.

I have had it to two shops and they say they can’t find anything I was going to have the timing belt changed again and have them do a leak down test for the head gasket issue.

This all evolved from a previous post (https://www.matthewsvolvosite.com/forums ... hp?t=11571) which the engine code was solved by the injectors, the sluggish accel is still an issue

Help?

Post by **MadeInJapan** » 12 Nov 2008, 19:59

Could be the idle air control valve (it should buzz for a few minutes, not be silent when you turn the car off) but I'm also wondering about what plugs you used and what gap as well as what brand ignition wires you used. No to platinum plugs and Bosch wires (bougicord only for the wires).

larryh · Post by **larryh** » 12 Nov 2008, 20:13

you said" I was going to have the timing belt changed again"
did this start after a timing belt change? The timing can be off a tooth and the car will still run OK but be sluggish.

clawless · Post by **clawless** » 12 Nov 2008, 20:59

I have tried several types of plugs, from plain to iridium, which is what is in there now. The wires are relatively new IPD 8mm, however i have tried the original bougicord wires and no change.

thats interesting on the timing belt. To be honest I am not sure when it actually started. How well will it run being one tooth off? The shop that did it is a Volvo only shop and I trust them, still doesn't mean they didn't make a mistake though.

thanks!

Post by **Ozark Lee** » 12 Nov 2008, 21:14

It is easy enough to pull the timing belt cover and check the timing. They will run a tooth off but not well. More than one mechanic - on a Friday - just before Duck/Deer/Pheasant season opens or that Grateful Dead Concert that they have been thinking about all week - will just pull the tensioner pin and ship it. It is easy to get 1 tooth off so I always crank it through a couple of revolutions by hand to let everything settle down and check the timing again against the marks.

...Lee

larryh · Post by **larryh** » 12 Nov 2008, 21:30

My timing was off from my lame belt change (It's really hard to see that crankshaft mark!) when I first purchased my car. It ran fine, so I didn't know it. But after the excellent Volvo shop that works on my R when I'm stumped, or otherwise in over my head fixed it, it was a different car. Definately an R!
They said that they've made the same mistake.

clawless · Post by **clawless** » 17 Nov 2008, 18:53

So over the last few days, I have been watching everything closely. In the morning, most mornings when its cold, it accels like I expect, but not all the time. When the boost gauge settles at 21 to 22 on the vac gauge, it accels like crap, when it settles at 19 its good. So the other night after work I started it and it drew down to 22 but after about 10 sec it "perked up" and seemed to run smoother at idle and was at 19, still holding at 1000 rpm and it acceled fine. On the way home I stopped at the store and when I came back out it started and ran at 22 and was a dog. The following morning it was the same, a dog, then in the afternoon on the way home it was a dog, then it cleared up and was fine after about 15 min. It seems like its not getting enough air but only by a little bit. today it was fine both ways.

one other thing, when it is going to run fine, it starts faster than when it decides to be a dog...

I think i'm gonna try the IAC valve. Its about the only thing that I haven't changed or checked or replaced...