About 20% of the time, when slowing down or coming to a stop mainly, the engine of my '98 S70non-turbo will lag a bit as if it is going to kill.The engine idle sags after a drive on the highway, mostly after letting off the throttle it seems like.To make diagnosis difficult this problem doesn't happen all of the time!After driving to work and home this evening (22 miles each way) the car sat at idle perfectly.

I have sprayed the mass airflow sensor with electronic cleaner, had the plugs checked, no check engine light has come on, and the past couple of tanks of gas I have used premium with gasoline additive. I have also cleaned out the butterfly valve area in the throttle housing. There was a ton of build up residue in there. It seems to need to warm up in order for this to happen. On a warm day recently, 77 degrees, it started acting up right away. This morning though, 30 degrees, it took 2+ miles to warm up to the trouble. Seems worse when warmer.

The car has 160,500 miles on it. I don't believe the fuel filter has been replaced. Plugs and engine air filter are 10k miles old. Any thoughts on what else to try? Thanks in advance!

 

Try cleaning the idle motor.
It is under the cover over the throttle body assembly.
The idle motor is a round cylinder looking thing.

 

Thanks for the reply Tech.I still have the same problem however. I think I was incorrect in saying that itprimarily happened when near idle.That's when it's most painful and irritating for the driver. The engine cutting out happens all over the tachometer I've found.

I removed and cleaned the Idle Air Control (IAC) Valve and the two hoses connected to it. In addition I have put genuine Volvo plugs in the vehicle. The idle and engine seem to be working fine, and I don't get any check engine light(s). This morning on the way in to work, after about 3 miles of driving and around 1500 RPMs it was as if someone was pinching the fuel line intermittently and playing a cruel trick on me! It idles fine and runs fine except when it decides to cut out, but it'll always come back or I can at least save it from stalling by touching the gas peddle.

It is truly as if the fuel line was a rubber hose and someone was pinching it. The car doesn't bog down like it's getting too much fuel, it's cutting out as if it isn't getting any fuel.

I think my next try is the fuel filter. Any other thoughts would be appreciated.

p.s. Unrelated, but I bought an engine oil cap gasket at the dealer for $2 when I got the plugs and checked for recalls. It had been leaking around the cap but isn't any more. I like the quick, easy and cheap fixes for sure!

 

I think you're on the right track with the mass air flow sensor, but I had to replace mine to get rid of those exact symptoms.

 

Thanks for the reply MHPHOTO. On the way home tonight, outside air temp was 67 degrees and after a little warm up it really started to act up. So bad that I took some side roads the rest of the way home. The whole time I was on the highway it was cutting out. It seemed like after I got back onto side streets that it settled down a bit.I found a post on checking the fuel relay so that will be the first check as I can visually inspect it. Here's what I have to check. Any other thoughts are appreciated.

1. fuel relay switch
2. mass airflow sensor
3. fuel filter
4. fuel pump

 

Mine did the same thing a while back and fianally the fuel pump went and I had to call for a tow. Wife said it had been acting like it was going to stall for a while, so I drove it one day and sure enought it cut out on me on the way to work.

 

Actually Shawn, I may be repealing my mass air flow sensor diagnosis. The distinctly odd thing about my situation was that all the problems would stop once I got up to speed. Listen to Jim and Tech. They got beat with the smart stick.

 

[ol][*]Fixed the fuel pump relay per instructions on the following site http://www.matthewsvolvosite.com/cha...pic.php?t=9681[*]Had the fuel filter replaced.[/ol]
Problem has been getting worse it seems so I have it in to a service station. I am sure that it is the fuel pump. It seems to either work great or cut out entirely. There's really no in between, which to me helps rule out any sensors. I'm still not getting any check engine lights either which is another item to help rule out sensors.

 

Just to wrap this thread up, the original problem has been reduced so much that it rarely happens anymore. I purchased a new MAF sensor via FCP Groton and put it in myself. That seemed to reduce the problems a lot. The second mechanic I took the S70 to hooked up some measurement device(s) and was able to verify that the fuel pump was working properly. With that we figured that the MAF was the first place to start. He spoke to some Volvo mechanic peers and they told him that the MAF is a known trouble spot for the Volvo S70. His readings flagged too much air (from the air/fuel mix ratio I assume) so that and everything else makes us try the MAF first. It seemed towork.

Thanks for all of the help.