I have a 1998 V70 T5M with almost 90,000 miles on it.

A few days ago, while waiting at a traffic light, the engine dropped below the idling 900 RPM for no apparent reason, within a second or so it came back to normal. The Check Engine light did not come on, and the car ran fine afterwards.

Earlier today, again while sitting at a traffic light, the engine speed dropped but this time it stalled completely after struggling for a second or two, and the Check Engine light came on. I was able to start the car back up and pull over. After checking the gas cap and under the hood to make sure there was no obvious sign of problem (like something smoking), I started the engine back up again and it appeared to run fine. I drove home and the car did not have any problem the whole way.

Both times the car had been running for some time and the engine was at full operating temp. It was also not raining.

I searched on this board and found many posts regarding the Check Engine light, but none of the cases quite matched what happened to me.

Does anyone have any suggestion on what the problem might be? Also, will I have to take my car in to a dealer just to have the code read, or a good independent Volvo shop would be able to also, for a 1998?

Thank you in advance for your help.

Chie

I have a 98 T5M with 73K miles and recently had a similar problem.
Actually, twice. First case it set off a code that related to the
turbo overboost relay (or similar). That seemed like it was not
really the problem. Second time it stalled at a light and no codes
were set. I have no real fix to offer, but I'll list my symptoms
in case it seems familiar.

I had problems restarting the car both times. Took several tries
and I had to rev the engine high to "clear" it.

In both cases I had gone about a mile and the car was cold but not
very cold (weather was maybe 45 degrees).

Today I noticed that while parked and in neutral I could not rev the
car to 1500 RPM. It would over or under shoot. When I let off the
gas (with the engine between 1800 and 2400 RPM) the tacometer would fall
quickly and often down to 500 RPM where it would stumble and then pull
back to normal idle (if the car had been cold I bet it would have
stalled). This was repeatable. I then cleaned the throttle, disconnected
and reconnected two electrical connectors near the throttle and one
at a relay right above the fan (a vacuum line from it leads to the
throttle area). After this, I could rev the engine to 1500 RPM and
it would hold and when I took my foot off the gas it came back slowly
to idle (never over shooting it down to 500 RPM). Soooo, I'm thinking
something with the idle control mechanisms is at fault. I doubt I
actually fixed anything and I'm waiting to see if the problem returns.

Thanks for sharing the information about your car.

I did more research on this board over the weekend; the more I read the more I think that the MAF on my car was going bad.

Yesterday I reset the codes using the OBD-II scanner I just bought, cleaned the MAF connector as suggested here and on Bay 13, went out to drive around in the neighborhood, and the P0103 code came back. I reset the code again, disconnected the MAF sensor connector and went back out for a short drive, this time the code did not come back. I was too chicken to go for a longer drive though with the MAF disconnected, not knowing if doing so would cause any real problem, and it was raining at the time so I didn't want to get stuck out in the rain. Reading a couple of posts here it seems it is OK to have the MAF disconnected...I am thinking that I should probably go for a longer drive like this to try to single out the MAF.

In the mean time, I have ordered a new MAF sensor from volvoparts.com. I may not get around to work on the replacement until this weekend, but I will definitely post the result here once I am done and if the problem goes away.

Chie
1998 V70 T5M

Went and bought an Actron 9135 OBD-II scanner from AutoZone (in California they are not allowed to read/reset codes for customers), and got 3 codes off of the car:

P0103 MAF or VAF circuit high input

I found many posts here regarding the MAF, and given the mileage of the car and the fact that there is a code, I will order a replacement MAF. Looks to be a relatively easy DIY job.

P0243 Turbo/Sup wastegate solenoid A malfunction

Found a few posts here but didn't find a conclusion of the problem. Any suggestions?

P0171 System too lean (bank 1)

The scanner said this was a pending code, so I assume it is OK to ignore it for now?

Chie
1998 V70 T5M

Received the new MAF from volvoparts.com yesterday. (Great service from volvoparts.com, highly recommended!) Armed with knowledge from this board and the Haynes book, I went to work last night replacing the MAF.

The overall process was pretty straight-forward. The suggestion posted on this board here about heating up the air downpipe was right on (http://www.brickboard.com/AWD/index.htm?id=676407) - until I used a hair dryer on the MAF/pipe joint, all I could do was to rotate the MAF around in the pipe; once I heated it up, the MAF pulled off with ease. I didn't have to heat it up again to pop in the new MAF.

I went out for a couple of 15-minute drives after the new MAF was in, no check engine light and no pending code either - with the old MAF, I would have gotten a check engine light and at least one code. After a one-hour drive this morning, the car is still running great, no stalling at traffic lights during the trip.

Chie
1998 V70 T5M