1995 850 GLT "hiccuping" and weird revving

[erg2k]

Hi, all,
I'm new to the site but have used it many times when looking for answers.

2 days ago I was on the highway when I noticed that the coolant temperature gauge wasn't registering. Ever since the weather got cold it's been registering lower than normal on the highway and then returning to a normal level at lower speeds. A few minutes later, it was back to a normal level, which I thought was weird since I've gotten used to low levels when it's cold. I then noticed a slight jerk or hiccup, and the temperature gauge went back to zero. This continued the rest of my trip, including off the highway.

When I turned off the ignition, the engine revved to about 2500 rpm and then cut out. I tried restarting the car and it wouldn't in park. It took me a few tries in neutral to get it started again, at which point it went down to about 500 rpm before catching itself and going back to a little under 1000 rpm. On that trip, as I was sitting at a stop light, it suddenly revved up to around 1500 rpm without my touching the accelerator and stayed there for a few seconds before going back to normal. This revving continued at random intervals most of the way home, with the temperature gauge going up and down each time. By the time I got back, everything was back to normal.

I started looking online and thought it might be the MAF sensor that was causing the problem, but didn't have time to check for fault codes. I also noticed that no one mentioned the revving problem, so I wasn't positive about the MAF sensor.

Today the same thing happened again, although the temperature gauge didn't go all the way down this time. The revving got to be bad enough that I didn't need to use the accelerator the last half mile home but instead simply used the brakes whenever I needed to stop.

I checked for fault codes on port A2 (fuel system) and got the following codes:
1-2-3: coolant temp sensor signal absent or faulty
2-3-1: long term fuel mixture too rich in part-load stage
2-3-2: long term fuel mixture too weak at idle
4-3-6: rear HO2S compensation

I assume the first code explains why my coolant temperature gauge has been acting up. The last one is due to a leak in the gasket between my exhaust manifold and the cat pipe, although this has been there for a while so I'm guessing it doesn't have too much to do with my current problem.

If it helps, my car is a 1995 850 GLT with a 20-valve engine, which would make it the LH3.2-Jetronic fuel injection system.

[volvo850black]

I had the exact same issue. First try cleaning your Idle Air Control Valve. It is located under the plastic cover over the throttlebody. it is the metal cylander. Unplug it take off the hoses and spray it out with throttle cleaner. Sometimes this does not work and you will have to replace it. Also clean you MAF sensor use only MAF cleaner I ruined one with the wrong cleaner. If neither fixes the issue try replacing plug wires use only Bougicord Volvo OEM (aftermarket is crap). Hope this helps
Matt

[Pauloil]

you need new temp sensor soon, and reset adaptives by removing neg batt cable when you put it in. it is 19mm, do thermostat at the same time.

http://www.ipdusa.com/prodtype.asp?CAT_ ... crumbs=998

[Bigken15]

Hello, I have a simuilar issue at 3500 RPM in driveway and under load.
I have looked at all vacum lines with no issuses found.
The only Code I have had is 1 2 1 Mass Air Flow which is new along with the tube that connects the Air box to the Throtle Body. I have cleared codes codes and then with one rev the CEL is on and the Code is 1 2 1.
Battery volatage when car is idleing is 13.5V
I do not want to just replace random parts. In the last 6 months cap rotor plugs and wires car ran great untill about two weeks ago.

[erikv11]

Is the MAF from Volvo or Bosch brand? Those are the only two sources that will work.

If it isn't a Volvo/Bosch MAF, then try unplugging it and see if that fixes the problem. You will set a code for no MAF, you will just have to clear it.

[Bigken15]

I removed the connector and the car ran fine on a short test drive. The CEL code was 1 2 1 again.
The MAF is neither Bosch or Volvo, The car has 180K and am looking to replace in the spring and wnet with at $50 part instead of the $180 part.

Thank you

[erikv11]

OK so the problem is the aftermarket MAF. I would take it back, tell them it doesn't work, maybe they will give you your money back.

Also, maybe you can still solve the problem cheaply by getting a Bosch MAF from the junkyard, pretty much all of them at the yard are in working condition. Just insist it is Bosch.

[taxi]

Hi, I would like to add (I am not perfectly sure) that code 121 could mean that there is a leak some where.
This is based on me remembering the meaning of the code; the air measured by maf does not add up to readings from O2-sensor. If I am right or wrong, either way it is worth looking into.
Good luck!