I have a 94' 940 turbo and lately it's been stumbling when it's idling, well I checked everything and ended up changing the flywheel sensor. Well the idle stumbling as pretty much ended but now I have a stumble between 2500-3000 rpm. I just noticed that the fuel gauge is acting up too, it say im on empty when I know I just put 10 gallons in. What your idea on the stumbling???

 

Fuel pressure regulator good?
Does the tach drop to 0 when it happens?
Any codes?

 

Not sure of fuel pressure, and no the tach doesn't drop to zero. I've check numerous times and no codes have shown up.

 

That would be the first place to go now is fuel pressure.

 

Ok I replaced the fuel pressure regulator and it actually got worse. Now if I touch the gas pedal a little to fast it stalls out, and the stumbling and happening all over the lower rpms. What next??

 

Ok I just went out and looked everything over and the fuel pumps are working the fuel filter is new. Could it be the mass air?? I looked at one of the other posts and everyone was talking about disconnecting it and if it did run it was good and if it did it was bad??? Well mine run with it pulled in or not, it runs a little rougher but it runs enough that I can hit the gas and it doesnt die. Any ideas???

 

ANY IDEAS???? ANYONE???

 

It might be the Mass Flow bad.
If you can hit the gas and it rev's better with it inplugged it is bad.

 

It doesn't rev better with it unplugged. I noticed earlier that you cant hear the fuel pumps every time you turn it on and off. I can hear the pumps run when they turn on but the dont hit every time you turn the igntion on & off. Could the relay be going bad? I wouldn't think the pumps are going bad cause it runs fine after you get it started. But it's almost like the pumps lose prime while it's sitting cause its hard to start but after that it'll hit every time.

 

Maybe the relay. But the pump has a check valve built in the pump to hold pressure.

 

But wouldn't some kind of code be thrown if it was the pump or relay?

 

No not at all.
It isn't tied to the ecm.
It is an output signal from the ECM.

 

Isn't like 45psi that the fuel pump is supposed to put out? It's just kind of funny that it would be the pump when it runs great besides starting and 2500 rpm. Below 2500 and above 2500 it runs like a bat outta hell. I don't know I just hate this guessing, I left it with a local mechanic for 6 weeks and he gave up and said he tested the pumps and they were good. But who knows if he did anything or not, cause it wasn't running when my wife dropped it off and it wasn't running when I got it back. So I changed the flywheel sensor and that got it started and here's where im at now.

 

Anymore ideas???

 

You need to try to get a fuel pressure guage connected to the car to monitor the fuel pressure and make 100$ sure your self it isn't fuel pressure when it is running bad.

Did you check for vaccum leaks?

 

Yeah I checked for vacuum leaks everywhere, I'll check the fuel pressure again.

 

If you can get a guage that would be awesome.
Then watch and see if the pressure jumps or anything like that when it runs crappy.

Has any other work been done to it lately?

 

Ok, after 45 minutes to get it to startI checked the fuel pressure. when trying to crank up it's about 44psi while idling its about 38psi and when you hit the gas and hold it about 2500rpm it's about 46 to 48 psi. I didn't see it fluxuate one bit beside whenidling to gaving it gas, when it stumbled at 2000rpm the fuel pressure stayed right where it was.While trying to get it to start it checked about for spark on all 4 and it was fine, checked again forvaccum leaks didn't see any. I did something and I dont know if it helped or not but while messing with the throttle postioning sensor wiring and a friend cranking it started. I dont know if it was just ready to start after cranking for 45 minutes or ifwhat i was doing helped. And yes it was at a shop for 6 weeks and they didn't do a thing. So what do you think now?

 

Sounds like you may have found your problem if it started after you wiggled the wires for the TPS. I would do the wiggle test again and see if it starts right up and gets rid of your stumbling.

 

Only problem is I have to wait unti it gets cold cause it only has a hard time starting when it's cold.