Fuel Pressure Regulator,stumble

[Tim Hensley]

Car runs good BLM 125-130 all the time.but at idle it will stumble here and there,fuel pressure gauge will drop  or jiggle 1to 1 1/2 lb
could it be reg or pump

[1KWIKSIX]

Hey Tim,  what brand of FP regulator do you have installed?  A large group of members running the Accufab unit seem to be having some suspicious problems with these.  Kirbans' billet aluminum adj FP regulator looks to be the recommended cure.


Can you tell us what brand of fuel pump is installed?  How old & how many miles?


dave

[Steve Wood]

I don't see any reason at this time to suspect the regulator, and very little to suspect the pump at this point.

What does the voltage to when it stumbles?  Don't rely on the scantool voltage.  Connect your meter to the fuel pump test connector under the hood and see what happens when the stumble occurs.

Also watch your scan tool readings for maf, o2, and iacs  to see if there is a fall out on one or all associated with the stumble.

[Tim Hensley]

Fuel pump test connector ? Fuse block on alt?
Working on laptop I hate Windows . The old Dell field agin
Looking for something different so I can look at those happiness so quick I really don't see any thing on Scanner
It is accufab hot wired  all five year old 4000 miles old
Thanks

[Steve Wood]

the fuel pump test connector is the single gray wire that comes out of the wiring harness at the front of the driver's side valve cover.  the Tach test connector is the other one that comes out there but it has two wires going to the connector and they are white...

If you like, connect the meter at the back of the car where the fuel pump connects to the hot wire

[Tim Hensley]

I know that wire
That's what it dose

[Steve Wood]

apply 12 volts to it and the pump will run...


Or, when the car is running, it will have 12 volts on it from the factory fp relay

[Tim Hensley]

start up volt 14.2
water temp 160-165
volts drop to 13.8 ,steady at stumble
AF 6-7-steady
IAC 40-46 it will jump up 1 or2 at stumble
O2s 12.9-13.1 steady this seems rich at idle
my INT and BLM steady 125-128 at idle
My cruse BLM 125-130
forgot fresh  engine 200 miles

[Steve Wood]

what are the factory O2's?

and what does the fuel pressure read when you pull the vacuum hose off the regulator, and does it still stumble when idling with the hose off?

[Steve Wood]

and...try setting the iac..sounds like it is way high...should be closer to 10-20 on a warmed up engine...in park and no ac

[earlbrown]

forgot fresh  engine 200 miles

Has the oil been changed (and inspected) yet?

[Tim Hensley]

740
43
Yes  no Change 

[Tim Hensley]

Yes on the oil inspection
First at 15 min tinny tiny bits of trash
Second oil change 30 min no trash at all
3ed at 35 miles spotless
Tomorrow 200 miles will see
Got 250 on it as of today
Runs good temps BLM all look good just has a funny stumble her and there
Grab the wires no shock Autolights 25p got NGK

[Steve Wood]

I don't believe it is the regulator or the pump....sounds like something electrical.  If you wiggle each injector harness connector, does it cut out while wiggling?

When you are adjusting the iac, take it all the way down to zero and see if it acts up then

does it do it at higher rpm?

[Scoobum]

Been watching this thread...and I think Steve's right. Sounds like Dans car...traced it back to a broken IAC wire just where it went into the weatherpack connector.