Still working to figure out why my 1994 940 Turbo is sputtering on cold start till I rev it and blow black smoke and raw gas fumes out.... once cleared within 30 seconds it will run fine till it sits several hours .

Fuel pressure holds at 30 psi for several hrs so it is not leaking down.

Fuel pressure at idle is 35 psi and 45 psi with regulator vac unhooked.

I watched it during one of its sputtering fits when cold and it showed 35 psi BUT the needle on the gauge was waving back and forth very fast from 30 - 35 psi .... when warm and running good the needle sits right on 35 psi why would it waver so quickly from 30 - 35 when it is acting up?

Also, the gauge I am using has a fuel bleed off line and when I pushed it I thought fuel should shoot 6 foot out but it only went out about a foot and if I had to fill a quart jar it would take over or right at a minute ... I did not time it ....

Am I having fuel volume / pressure problems?

parts changed out with no help curing problem;

MAF
CTS
AIC motor
O2
throttle body cleaned
Plugs
Wires
cap
Rotor

Could someone help shed some light here ... it runs great after the 30 second sputter as I said I have to rev it and clear out what seems a rich condition ...

 

the fuel pressure should be 42-44 PSI (but 45psi is probably within the tolerance of your gauge) *relative to manifold vacuum*. manifold vacuum would bounce around quite a lot if the engine is sputtering. manifold vacuum is typically around -7 or -9 PSI when idling, and close to 0 PSI with the throttle WFO. so your 30-35psi readings are more or less in range. of course, with a turbo, you can have POSITIVE manifold pressure under accelerating conditions (anti-vacuum).

as far as fuel delivery volume goes, its probably constrained by a small orifice in that fuel pressure gauge pressure release thing. if you had fuel delivery problems, those would manifest in 3rd gear at wide open throttle and maximum turbo boost at upper middle RPMs, like accelerating hard up a steep hill, you'd feel the power cut out.

 

What should I do next is the big question. I have found no vacuum leaks doing a visual and smoke test ... only thing left is injectors and ecu ... have read that injector seal can cause a stumble cold and within a minute of running thighten up enough to smooth out. What are your thoughts? It stumbles or sputters every morning for 30 seconds and almost seems to flood out .. once i rev and clear it the car runs great ... power and idle.

 

well, injector seals are yet another form of vacuum leak... if the seals are loose, air leaks around them, so if you did the smoke test in the vicinity of the base of the injectors and it didn't change the stumble, then the seals are probably fine.

 

What about the injectors themselves .. could they exhibit this type of behavior cold and then perform warm with no problem?

What else would cause this behavior cold and change within a minute?

 

if the ECU and ICU don't see the right resistance from the coolant temp sensor, it will run badly. I like to test it by (with the car off) unplug the ECU connector, and use a digital multimeter to ohm the right pins on the inside of the harness plug. start when the engine is hot, measure it, then wait for it to get cold, and measure it again. The CTS has two elements, both go to ground, and one is wired to the ECU fuel injection and the other one to the ICU ignition computer.

read this, it explains it, and gives all the values for the different systems: Engine Sensors


this graph is for lh2.4

 

I ran that ect test after I installed the new sensor and it checked good. I even pulled apart the big connectors behind the strut towers and sprayed cleaner ...

is there a test for injectors .. ohm them out or something?
260,000 miles it might be time for new ones?

 

the test for injectors is to take them out of the car, and hook them up to an injector test stand, which pumps solvent through them at 40psi into buckets, and you visually check the spray patterns of all 4, as well as measuring their flow rate. when they are off, they shouldn't dribble.

you could probably jury-rig an injector test stand from the fuel rail out of a JY car, and a old main fuel pump, and a tank of something a lot less explosive than gasoline but still fairly fluid... you'd need a spark-free 12V power circuit for firing the injectors... they need an amp or two.

 

Well I placed an order to fcp today .. my intank pump is original with almost 300k and the inline has 150k so I ordered both just to cover that ... I did notice this morning I had only 1/8th tank of fuel the car was bogging on heavy excelleration and after I filled it that went away.

Another worth note to the cold start is this. I have a radiator leak and I am thinking over night I could be developing an air pocket in the area of the ect sensor and the ecu is not getting the correct reading of temperature. ... does that sound right? ... I also order a new radiator from fcp