94 850 turbo erratic idle surge

kurt robinson · Post by **kurt robinson** » 01 Nov 2007, 09:26

Problem: Car will intermittently and with no warning surge up to about 4K RPM and sometimes come back to normal idle or hang at 4K rpm until I shut it off. If I have to shut it off, the car will only crank, and then it floods itself out. Then if I let it sit for about 15 minutes it will crank up and run rough, really rough. If I let it sit overnight then it will run fine until it throws its fit, and then it starts all over again. The car is not producing any error codes. CEL is not on but is functional b/c it did come on when I was disconnecting the idle control sensor/motor while it was running. I then cleared code by replacing brain box. The car runs fine, when it runs, plenty of power, no smoke

Post by **tailor** » 01 Nov 2007, 11:36

1)You might have to replace the the plugs as they can get soaked.
2)Perhaps you have PCV blockage.
3)Have a look at your throttle cable sounds like it may be getting stuck.
4)Did you replace the gasket on the throttle body !

Ok! send the twenty bucks as a donation to Matthew

Let us know what works!

Tailor

kurt robinson · Post by **kurt robinson** » 02 Nov 2007, 05:51

well, replaced the cap, plugs, wires, and still the same thing.

I've been thinking the PCV is clogged up...I did the vacuum test over the oil dipstick, and revved it, no vacuum....EVER! Would this cause the surge problem? I don't understand the theory behind an idle surge and crankcase pressure.

Anyways I'm off to Viking Imports to pick up the oil separator and some hoses, anyone got an exact list of what parts to purchase to complete the job?

Jeez i am dredding pulling that intake off.

Kurt

Post by **tailor** » 02 Nov 2007, 11:18

Look at Fcp Groton they have a kit for replacement.You will have to know your engine number as to which parts are required as the parts change according to the engine number. Go here http://www.fcpgroton.com.
There are good posts about the pcv on this forum.
Btw I did read in another post that if your injector seals are no good you might experience this surge problem.
You might as well replace them if you are going to do the Pcv.
Before you rush off and buy parts get a 2nd opinion about the Pcv.

Tailor

Mij and Lee what you think!!

Post by **MadeInJapan** » 02 Nov 2007, 16:39

I suppose the PCV could cause this but that hasn't been my experience so far.... It certainly can't hurt to replace the PCV (probably needs it anyway). Please report back if that took care of it or not. It that's not it, I'm inclined to think that the pick-up lines in the oil sump are getting stopped up and drawing the oil up to the top of the engine (recirculating) intermittently. If you're getting the PcV taken car of at a mechanic, then have that checked out at the same time. If not, then just wait until the PCV is done and then see how things go. It does certainly sound like something is "clogged and then unclogged" for it to surge and then be normal again.

kurt robinson · Post by **kurt robinson** » 02 Nov 2007, 19:07

alright guys here's the deal...I am inclined to believe the original stalling and erratic temp gauge problem has somehow morphed into the surge problem and this is why; The car only surges when the temp gauge jumps around erratically and never heats up. This morning I drove the car to school b/c it was relatively cool out, the car usually does fine when it's cooler weather. I drove it about 5 minutes, the temp gauge never left 0. Car ran fine. On the way back home, the gauge started moving around; up and down, same old erratic behavior. Then the car surged to about 2K rpm and then calmed down once the temp gauge returned to 0 and ran fine as long as the temp gauge didn't move.

From another post I read the temp gauge woes stem from the cooling temperature control sensor located near the thermostat. I haven't had a chance to replace it yet but I am going to attack that sunday.

Here is my theory: The stalling problem morphed into the surge problem through the ECU 'relearning' that it is better to keep the car running vs. a stall, and instead of dying the car now surges. Both problems happen at relatively the same intervals; randomly. I am probably running away with this idea and am probably reaching, but I will try anything before I spend the whole weekend removing the intake

So I am going to first replace the Electronic Cooling temp. sensor first. I will report back next week and let you folks know how it goes.

Thanks for all the replies...........it is very much appreciated.

Post by **MadeInJapan** » 02 Nov 2007, 19:21

When you replace the temp. sensor also go ahead and replace the thermostat as well (it's cheap and relatively easy, especially if you already have the temp senor out). You probably need to replace it anyway. Somehow on your first post I didn't catch anything about erratic temp. display when your surging is happening. I'm in agreement with you that this probably the reason for your woes. Good luck!

kurt robinson · Post by **kurt robinson** » 03 Nov 2007, 08:23

I'm really glad someone agrees w/ me. I will change the thermostat w/ the sensor. Do you guys recommend OEM or do you think aftermarket aka auto zone/advance auto would be okay for the thermostat?

Post by **MadeInJapan** » 03 Nov 2007, 14:59

If you can hold off buy from fcpgroton.com it has the rubber gasket with it. I know it's made by Mahler or someone else (European) and not American. I really don't know what AutoZone et al. has on their shelf.

kurt robinson · Post by **kurt robinson** » 03 Nov 2007, 18:38

thanks for the heads up on fcpgroton.com they are really a great source! Seems like they are really in the know on volvos and the people who own them.