'94 940 turbo-idles well-can't hold steady RPM's

Zdadgeezer · Post by **Zdadgeezer** » 08 Jul 2012, 18:48

I tested the car today and it appears to be running much, much better above idle. It still stutters here and there but overall it seems much more stable. Also I must be insane because the fuel pump that I thought was not working --is( next to fuel filter)I hope it is not an intermittent thing I hate those, but if it fails and my RPMs go all over the place then I guess I found one problem at least.. Still trying to find the info on proper fuel pressure readings at the rail and schrader fitting between tank and pump. I disconnected the vacuum hose to the regulator and nothing changed performance wise. Going to see if I can find an inexpensive fuel pressure test gauge.

SOOooo, I got into the code reading a bit more and since I still have the 231 and it is possibly related to this stutter I wanted to try and pinpoint the cause. Checked Ignition (none stored) 1-1-1 and Fuel codes (one stored 2-3-1)
DTM 2 Throttle Position Sensor test with throttle body at full load it continued to flash so I need to get the adjustments article all other tests appeared normal.
TBC

Post by **jimmy57** » 08 Jul 2012, 21:25

The full throttle position on B230 turbos is not used so no acknowledgement of that one.

Zdadgeezer · Post by **Zdadgeezer** » 08 Jul 2012, 21:46

jimmy57 wrote:The full throttle position on B230 turbos is not used so no acknowledgement of that one.

You really know how to shatter ones ego.

TBC

Zdadgeezer · Post by **Zdadgeezer** » 09 Jul 2012, 21:04

Well I discovered that my hearing sucks and I need an in tank fuel pump I believe.
Picked up a relatively inexpensive tester $39.99 @ Pep Boys(cheapest they had) and after a bit of cursing at the rail fitting finally got it on. Just a hair of a degree angle either way and it would have been much easier but it is possible( because of the adaptor needed. It comes with gauge but made it much more difficult).
Read 43-44 psi at rail ignition on and after starting dropped to 40 psi at idle I didn't bother to raise RPM's because I believe it should be at least 50 psi at idle if I read correctly on some other thread and probably would have dropped with the greater demand for fuel..Besides I didn't have anyone to do it while I held the gauge and really didn't feel lucky trying to raise the throttle at same time.
I guess I should have pulled the regulator vacuum hose while it was running but again I didn't feel lucky and I am not sure what that would have shown.
Reading on fuel line before pre-pump was 14 psi with car idling and less than 10 psi with the car ignition on but not running.
If anyone could confirm the values I would appreciate it and in the meantime I will price out in-tank pumps.
TBC
Thanks

Zdadgeezer · Post by **Zdadgeezer** » 10 Jul 2012, 22:07

While searching for in-tank replacement pumps I looked at a Walbro model and in the specs it said working pressure is 12 psi if this is correct it would seem that my pumps are operating. I will have to see if I can get a reading off the rail at a higher RPM than idle. Any input on what it should read is appreciated.

TBC

Thanks

lummert · Post by **lummert** » 10 Jul 2012, 23:28

I don't think engine RPM will have any effect on fuel pressure. the fuel pressure regulator controls fuel pressure. The fuel pressure at rail with vacuum hose connected to FPR should be about 37 psi. With the hose disconnected from FPR and plugged the pressure should be about 43.5 psi.

Zdadgeezer · Post by **Zdadgeezer** » 11 Jul 2012, 15:33

That means I need to look elsewhere.
Thanks
( A couple of hours and some driving later)
I believe the nature of the problem has changed. The car starts and idles well it never really had a problem there. Initially for the first 5 to ten minutes of running it has the roughness or difficulty maintaining steady RPM. After it is nice and warm it is steady as a rock. I still have the 231 code however and that just irks me to no end.It passes all the diagnostic tests and I can clear the code but it comes back on the next start up. Would disconnecting the battery negative to clear it all and start over be worthwhile in anyones opinion? Or do you think it may cause more than it cures?
I did find a minor exhaust leak at the turbo input. It doesn't appear to be affecting anything but I seek more experienced opinions.

To summarize I believe changing the fuel filter resolved my major complaint on the bogging and inability to maintain RPM above idle regardless of how long the engine ran. No effect on 231 code. I found that the fuel pressure on this car is anywhere from 10 to 14 psi from the in-tank pump to the main and 44/43.5 psi KOEO at the rail. it holds 41 psi at idle.

Now I still have a code 231 but the car really doesn't run poorly after it warms up.

Anyone? Bueller!! Bueller?

Thanks

Zdadgeezer · Post by **Zdadgeezer** » 12 Nov 2012, 19:13

Just an update -- Car is still running OK although it is still a bit unsteady running at speeds above idle. Having a similar situation on my Z and wondering if it could be a faulty TPS.

My jury rigged fuel line repair finally started leaking last week. Kudos to FCP EURO parts I ordered Friday evening and arrived this morning.
Will update as things evolve.

'94 940 turbo-idles well-can't hold steady RPM's

Re: '94 940 turbo-idles well-can't hold steady RPM's