Fuel Pressure Regulator Question 94
Thread Starter
Instructor
Joined: Apr 2005
Posts: 195
Likes: 1
From: Columbus OH
Fuel Pressure Regulator Question 94
I have a 94 MT. I'm having the high idle surge in closed loop but I'm still working through that.
I replaced my FPR because the pressure before starting was 41psi, then would drop to mid thirties at idle as normal when started. However, it would stay there under normal driving until I got on the throttle hard, then it would go back up to about 40psi. I thought when above idle, the pressure should go back up to normal (FSM says 41-47psi). My new FPR does the same thing except all the pressures are 2-3 psi lower (it won't go up to 40PSI but will go up at hard throttle).
The new FPR is a NAPA Echlin brand.
Could there be another cause for the low fuel pressure? I think the pump is OK because the pressure will increase at throttle. BTW the filter is new (I still smell like gas to prove it
).
Any chance this is related to my surging idle/stumbling issue?
Thanks
I replaced my FPR because the pressure before starting was 41psi, then would drop to mid thirties at idle as normal when started. However, it would stay there under normal driving until I got on the throttle hard, then it would go back up to about 40psi. I thought when above idle, the pressure should go back up to normal (FSM says 41-47psi). My new FPR does the same thing except all the pressures are 2-3 psi lower (it won't go up to 40PSI but will go up at hard throttle).
The new FPR is a NAPA Echlin brand.
Could there be another cause for the low fuel pressure? I think the pump is OK because the pressure will increase at throttle. BTW the filter is new (I still smell like gas to prove it
).Any chance this is related to my surging idle/stumbling issue?
Thanks
Instructor
Joined: Feb 2007
Posts: 197
Likes: 0
From: Carriere Mississippi
I have a 94 MT. I'm having the high idle surge in closed loop but I'm still working through that.
I replaced my FPR because the pressure before starting was 41psi, then would drop to mid thirties at idle as normal when started. However, it would stay there under normal driving until I got on the throttle hard, then it would go back up to about 40psi. I thought when above idle, the pressure should go back up to normal (FSM says 41-47psi). My new FPR does the same thing except all the pressures are 2-3 psi lower (it won't go up to 40PSI but will go up at hard throttle).
The new FPR is a NAPA Echlin brand.
Could there be another cause for the low fuel pressure? I think the pump is OK because the pressure will increase at throttle. BTW the filter is new (I still smell like gas to prove it ).
Any chance this is related to my surging idle/stumbling issue?
Thanks
I replaced my FPR because the pressure before starting was 41psi, then would drop to mid thirties at idle as normal when started. However, it would stay there under normal driving until I got on the throttle hard, then it would go back up to about 40psi. I thought when above idle, the pressure should go back up to normal (FSM says 41-47psi). My new FPR does the same thing except all the pressures are 2-3 psi lower (it won't go up to 40PSI but will go up at hard throttle).
The new FPR is a NAPA Echlin brand.
Could there be another cause for the low fuel pressure? I think the pump is OK because the pressure will increase at throttle. BTW the filter is new (I still smell like gas to prove it
).Any chance this is related to my surging idle/stumbling issue?
Thanks
Pro
Joined: Nov 2006
Posts: 638
Likes: 0
From: Plano TX
Could be a simple vacuum leak too. On my 85, I had a few bad old vacuum hoses and a dead EGR. Fixed those and reset my minimum idle and things were great again.
Though mine is an L98, they all could have a vacuum leak some where, right? It's worth a shot checking for one.
Though mine is an L98, they all could have a vacuum leak some where, right? It's worth a shot checking for one.
Thread Starter
Instructor
Joined: Apr 2005
Posts: 195
Likes: 1
From: Columbus OH
I did and it checked out fine. I'm slowly going through all the steps. Can't find any vacuum leaks. I replaced one O2 sensor that had a broken pin. Injectors ohmed fine. Trying to solve this issue is what got me on the fuel pressure. Going for Map sensor, and then ICM and coil next.
I'm stumped by the fuel pressure issue. Even with a new filter and FPR it is out of spec, in fact worse.
