1993 Volvo 940 Turbo, Bosch Ignition System.

This all started coming home on a long road trip. We made it 2 miles away from our exit ramp and then we lost power. We stopped and turned the car off. I did a quick check under the hood and saw nothing popped off or leaking/smoking. we started back up and tried to take off again and the car starting bucking. too much throttle and it would "mis-fire" . Use barely any throttle at all we got to a gas station. I turned the car off and unplugged MAF, started back up and same conditions. No codes were thrown, timing is spot on, plugs are a good color and not we/black. I checked the fuel relay under the radio and for safe measure i resoldered it when i got the car home. Still having the same problem. I thought maybe the cat was plugged somehow to I pulled the bolt out from right in front of it with no difference at all. Last tune up was 2 months ago with plugs,wires,cap,rotor, and oil change. What should I be testing for next?

Thanks!

 

Well,

tune up done
no leaks
fuel relay ok
died after a long trip...

Battery/Alternator test
look for white smoke
look for yoohoo milk on oil cap
pull spark plugs to see if they are wet or oily
check Air Idle control valve
jump fuel pump relay to test pump.

clean maf sensor....let dry and disconnect battery terminal first
lets rule these out and you can go from there....

check out the link below for your diagram

VOLVO 940 1993 - wiring diagrams

 

Have you pulled the OBD codes? There is a little black box on the rear of the left front fender. You need to pull the cap off to reveal an LED and a wire. Plug the wire into port #2 on it and press and hold the button for like 3-4 sec. The LED should flash codes.

Google Volvo OBD 1 codes and you should come up with (probably better) instructions on how to do this plus the meaning of the codes.

 

What I've done today so far

No OBD codes
I've cleaned The MAF Before, will do again
IAC has been cleaned a few times and yesterday
Plugs are dry after trying to rev the car
No Smoke out the Back

 

There is no oil in the coolant.
There is no coolant in the oil.
Battery was a low from cranking it.
No smoke out the back.
Pumps come on i can hear them cycling
Now when you touch the throttle is dies immediately.

 

Going to test the Crank Positioning sensor as soon as I get my multimeter working ...

 

I tested the TPS by unplugging it as per another thread and it still acted up. idles fine for awhile. but as soon as the throttle is touch it dies. going to locate a fuel pressure gauge and do some real testing when i can.

 

pressure regulator

 

Well, I've checked that and from my understanding if it isn't leaking on the vacuum side it's probably ok. If I'm wrong say so.

 

Crank sensor is good at 160. I couldn't test at the fuel rail for pressure, the gauge i bought doesn't fit. for some reason it's pointed toward the head... ANYWAY, i tested under the car and it was at 17-18 psi.

 

According to my Haynes manual, the pressure on an LH2.4 system should be 32-38 psi. Now my manual is for a normally aspirated B230. The turbo may be even higher.

Either way, your pressure is low. This may explain your symptoms. I would check out the whole system. Make sure your in-tank pump is working properly first, then your main pump. If the in-tank pump isn't working, it causes strain on the main pump causing it to fail prematurely.

 

according to everything I've seen, fuel pressure on the LH2.2 and 2.4 are 44 +/- 2 PSI above manifold vacuum, which would likely be about 32-38psi at idle with the throttle closed.

turbos are the same, the difference being that manifold 'vacuum' is positive instead of negative when they are under boost.

 

Just to clarify,

Fuel pressure should be just about double BEFORE the second pump?

 

the tank pump doesn't generate significant pressure, it just delivers fuel to the main pump.

the main pump generates all the fuel pressure. the fuel pressure regulator (at the front end of the fuel rail on the intake manifold) maintains constant pressure by allowing extra fuel to go back the return line to the tank.

 

going to track down an adapter for the fuel rail so i can measure pressure there.

 

the fuel pressure adapters fit at the input end of the fuel rail where the main fuel line connects, they are a threaded T fitting. you'll find those in a professional fuel pressure gauge kit that has european adapters.

 

an update on the progress..

I can drive the car .. ish.. As long as I don't get the needle into the boost zone it is fine. The second I try to put the engine under positive pressure is when it craps out. When i let my foot off the accelerator I hear the weird hiss from the turbo side of the engine from the cab of the car.'
Could this be a stuck Blow off valve
Or my main guess is a clogged cat.

as always thanks for all the help!

 

check all the big air tubes from the MAF -> turbo -> intercooler -> throttle body.

also check all your vacuum lines. anything cracked or loose, positive boost pressure will cause it to leak and mess things up good.

my 92 740T, the rubber hose that goes from the MAF to the turbo was soft from oil rot at the bottom, and the turbo would suck it in, causing all kinda power loss til I backed off. messing with the hose clamp would fix it for awhile, but finally I got a new hose and its fixed 100%. dealer-only part, as far as I know.

 

are the hubs Sturmey Archer? Sachs/Torpedo? Shimano ?