Sudden Crank, No Start After Hitting a Bump

[fatcatbestcat]

Hey, it's my dumb ass again.

So my '91 940 Turbo is still my daily. Haven't had any hiccups since I replaced the timing belt in October, which I re-tensioned some 1000 miles ago.

This morning I hope in the car to get to work, it starts up normally. I back down my driveway (which is on a hill), and I hit the sidewalk. There's a bit of a bump, which is normal. The car stalls out and won't start again.

It has battery voltage, and cranks kind of disturbingly fast, almost like it doesn't have compression. I pull the oil cap off to check if the cam is spinning, and sure enough it is. It sort of coughs when I give it throttle when cranking, so I put my foot to the floor and it fires and cold revs to 5,000 rpm. I let go of the gas and it slowly returns back to its normal cold idle.

I drive it to work and the idle returns to normal when it warms up. I did notice it was perhaps a little sluggish in the midrange, but that could have just been me subconsciously driving it carefully. I'll see if this issue happens again this evening when I leave work.

My first thought is this is some kind of throttle position problem? My old D24 245 had a similar issue when the throttle cable adjuster broke - I had to put my foot to the floor to get it started.

Is there a way I can test the TPS to see if that might be an issue, or is this just an LH "glitch" that people have encountered before?

 

[bobxyz]

You can test that the TPS idle switch is seen correctly by the ECU, and that the IAC valve clicks - see Diag Test Modes 2 & 3 here:

Engine and OBD Diagnostic Codes<

Volvo Engine and OBD Diagnostic Codes<

www.volvoclub.org.uk

I'd inspect the TPS connector, and the IAC connector, to make sure they're OK and fully seated.

 

[fatcatbestcat]

You can test that the TPS idle switch is seen correctly by the ECU, and that the IAC valve clicks - see Diag Test Modes 2 & 3 here:

Engine and OBD Diagnostic Codes<

Volvo Engine and OBD Diagnostic Codes<

www.volvoclub.org.uk

I'd inspect the TPS connector, and the IAC connector, to make sure they're OK and fully seated.

Thanks, I'll check my connections and try and some diagnostics when I get home. Whatever the issue is/was, it didn't seem to store any codes.

 

[dl242gt]

This seems like more of a flooded engine and weak spark. Take a look at your plugs. Maybe they need a regap if they aren't too worn.

 

[fatcatbestcat]

This seems like more of a flooded engine and weak spark. Take a look at your plugs. Maybe they need a regap if they aren't too worn.

I'll take a look at my plugs on the weekend. I didn't notice any abnormal wear on them last time I changed them in late May, and they were gapped to spec at the time but that was also before I put a chip tune in it.

I suppose the update since my no-start the other day is that the car is running fine. Nothing really out of the ordinary, and I've had no issues getting it started in near-freezing temperatures.