1998 Volvo V70 shutting off after start up

mctruth · Post by **mctruth** » 20 Mar 2010, 05:26

I'm new to this forum, and also new to Volvos, I bought a 1998 V70 GLT in December. Despite it's flaws i like the car a lot and just want to get it running right so I can enjoy it.

I've been trying to get to the bottom of a engine shut off issue I've had since I got it. Whenever it's been about 2 hours or more since I last drove the car it starts no problem everytime, but as soon as it starts the rpms jump over 1000 and than plummets down right away and the car shuts off. I have to keep my foot on the gas to keep the rpms up until the engine warms up or it will keep shutting off. It usually takes anywhere from 2-5 minutes for the engine to be ready. The engine code is reading PO171 which is related to one of three things, bad or dirty MAF sensor, vacuum leak, or a dirty fuel filter. I've already replaced both the MAF sensor and the fuel filter and the problem and the engine code are still there. I also had two different mechanics check for vacuum leaks and couldn't find any.

Since i've covered all three areas related to this code I don't know where to turn. I'm also experiencing insufficient power, I got beat by an old mini van that I was trying to pass the other day

A friend of mine also mentioned the knock sensor as a possible culprit. I really want to put money into the car (tint windows for the fam, put performance exhaust on, get cpu flashed for increased HP) but I can't put money into luxury items when the car aint running right. I'm on the verge of selling it or trading it in but I really would like to just fix the problem. THanks in advance for your time and help!

Safe Travels,
Matthew

mctruth · Post by **mctruth** » 20 Mar 2010, 22:10

I guess I should add that the car has 110,000 miles...Any help would be much appreciated...

Post by **Ozark Lee** » 21 Mar 2010, 02:24

The next time it acts up check the fuel pressure at the schrader valve on the end of the fuel rail. What you describe sounds very much like a bad fuel pump relay. They get very intermittent before they die altogether and they don't post a code.

...Lee

Post by **jblackburn** » 21 Mar 2010, 22:39

What Lee said, but I actually wonder about the pressure itself while the car is running. If you can test the fuel pressure, you should see upwards of 38 psi while the car is running, 43 with the key in position II and the engine not running. You replaced the fuel filter, but there is a chance the pump itself could just be weak.

The MAF can cause idle and power issues, etc...but usually they are evident all the time, not just when the engine is cold. Did you replace it with a genuine OEM sensor or aftermarket one? What happens if you unplug it entirely and start the car? Have they looked into the idle control valve?

The knock sensor would more than likely throw a code if it was retarding you timing that much to the point where you didn't have any power left. Or it was one of those 80's Turbo Mopar minivans

mctruth · Post by **mctruth** » 22 Mar 2010, 22:28

Thanks for your help guys. I used a genuine Volvo MAF sensor. I'll try unpluging the MAF sensor and start it up like you said. I'll also look into the idle control valve. But it seems both of you think the most likely cause is a fuel pump that is on it's way out. I didn't think of that sense I don't have a problem other than when than engine's cold. I thought the fuel pump going bad would give me starting issues and the car would cut off at anytime not just when it's cold. That's not the case though?

Where is the Idle control valve located and how hard is it to replace?

Appreciate your help,
Matthew

Post by **jblackburn** » 22 Mar 2010, 22:37

Does it stumble at all when you get your foot into it?

My thinking was it uses more fuel when cold. But I was tired at the time and it could be a lot of other things

Idle control valve:
http://www.volvoforumsrepairs.org.uk/800Repairs/iac.htm

I recommend taking it out and spraying cleaner through it like this guy does rather than trying to clean it in the car. On the other hand, if the flap inside is ridiculously loose, you probably need to get a new one.

Try a zip-tie on the plug of the MAF connector. Sometimes this will help it make a better connection.

I wish we had a straight answer for you, but sometimes you have to start eliminating things before getting down the the real problem.