93 850 Idle Surge and Stalling

Mulvane · Post by **Mulvane** » 19 Jun 2007, 21:44

My 93 850 GLT(trim level..Not sure about how to know this) just out of the blue started acting up. I'm not totally sure of the miles. When I bought it 5 months ago, it said 168K, and had receipts from prior month around that. I add about 2K a month as I drive 100miles a day (almost all interstate) to and from work. I live in Southern Illinois near St. Louis and my car is built for the US. I have checked the fuel filter for blockage and do not think it is a fuel problem as I can get the car up to speed (60+) and can keep it going in spurts. In idle the rpm's will surge between 400 and 1000. I have just got done replace the Throttle Position Sensor as this seemed to be the problem. While driving the car, or in park, if I keep the gas down, it seems like it eventually starves itself for fuel. Listening to the car in idle reveals a hissing sound right after it surges. Any advice for what it could be greatly appreciated.

Alwick · Post by **Alwick** » 20 Jun 2007, 06:28

I had a similar problem on my V70 recently. It ran fine when I applied the throttle, but at idle the rpm's jumped around exactly like you described, and it felt like it would stall if I didn't give it gas.
Turned out to be a split vacum hose. Cost about $200 parts and labor as the hose in question was deep inside the engine.
Hope this helps.

Post by **Ozark Lee** » 20 Jun 2007, 07:13

Is your Check Engine Light on? Have you checked port A-2 for codes?

Start by pulling the codes, not all of them set a CEL, and post them back.

Instructions for code checking are here:

http://volvospeed.com/CheckEngine.php

...Lee

Mulvane · Post by **Mulvane** » 20 Jun 2007, 07:18

I finally figured out how to get the codes from my car. What I got was a 5-1-2. Makes sense as it SEEMS like a fuel problem but pump and filter all seem fine. Like mentioned before, thought this could be the TPS which I already replaced which oddly did make it run better than it did but still not drivable..

Post by **Ozark Lee** » 20 Jun 2007, 07:28

The 5-1-2 code is an O2 sensor limit code. The car is grumpy about either fuel pressure or the MAF sensor.

Start with the easy stuff and, at idle, unplug the MAF (AMM) sensor. If the idle smoothes out that is the culprit.

9 time out of 10 you can simply clean the sensor with MAF cleaner from the auto parts store. Just spray it on and let it dry, don't scrub or even touch the sensor.

If that doesn't work you will need to check the fuel pressure at the end of the fuel rail.

...Lee

Mulvane · Post by **Mulvane** » 20 Jun 2007, 07:31

I already did this during initial trouble shooting. After I pulled the MAF sensor on while running in idle it ran for a few seconds and died. It sounded like for a minute it tried to smooth out. Buddy came over and we did the same thing with me on the gas after he pulled. Revved fine but died still.

CarVolvo · Post by **CarVolvo** » 20 Jun 2007, 08:29

heavily suspect the vac lines. I would replace all of them since the rubber elbows get all mushy and spring leaks.

I would also look at the vac tree which is located near the idle control motor. Also check the idle control motor and ensure that there is no leaks in that line (1 inch hose) and the unit is working properly.

Since the 93 does not have a EGR .. there is a control module/ computer which controls that...but that would be on the end of your check list.

GLT is the trim level for that year.. but it depends on how the car was optioned up.

Mulvane · Post by **Mulvane** » 20 Jun 2007, 08:42

I posted this in the original but I will elaborate a little more. When the car sits in idle, it will erratically go between 400 and 1000 with a spike every minute or so to 1500 and then back down to almost stall. Right after a peak, I hear a quick hissing sound. Its on the right side of the engine and seems to be somewhere below the air filter. I can't quite find it but its the only strange noise it makes.

BTW, thanks for all the help. I'm used to fixing things on my older trucks. Got the Volvo mostly for the wife but I use it for work since the gas mileage is so much better than a 93 F-150 manual with a straight 6.

CarVolvo · Post by **CarVolvo** » 20 Jun 2007, 08:44

you have a reservoir for your cruise control vac reservoir there under the battery tray and a brake hose line boost runs under the air box/ air filter holder.

These all feed off the vac lines. Maybe some have come off or you have a break in the cruise control unit itself. Have you hit a curb or anything on the drivers side lately? Hows your cruise control working or do you have one?

Also check the lines for your galsoline fumes emission control system just in case which is under the fender in front of the wheel to see if there is a break in that while your there.

I would suggest you remove the air filter box and inspect further.. easy fix if you can find it!

Mulvane · Post by **Mulvane** » 25 Jun 2007, 07:27

I've manged to figure out a few more things about the problem.

1. fuel pressure is good. I get a good 45psi with key in pos 2 with engine off, and still with engine on. Under pressure, it dips to about 38 but stabilizes again fairly quickly.
2. Fuel filter is clean. Easy blow through.
3. Throttle Position Sensor is brand new. Replaced it myself as a possible solution to this problem.
4. Searched for vacuum leak with a can of engine cleaner. Sprayed it in and watched for any vacuum or pressure leaks. None found.
5. Car will accelerate to 80+ on interstate. Once I reach these speeds, it will begin a stall and reduce down to about 65, but suddenly. Its like its over-compensating with fuel every few seconds.
6. At lower speeds (below 35-40), the car will starve itself to a near halt until I either shift to neutral, power down, and turn it back over with foot on gas.

I had a garage look at it, and they said they pulled a DTC code for a knock sensor. This morning I filled up with 93 to see if that would help with any knock that might be present with no benefit. Could this surge/stalling be caused by a bad knock sensor or should I investigate something else? Research seems to indicate the knock sensor could cause this, but almost always, something else is causing the knock and the sensor is acting right.