Casper the Cobra - Procharged 96' Cobra

Venompower

Active Member
Joined
Aug 17, 2015
Messages
347
Reaction score
192
Location
Batavia, IL
That’s probably why it had low fuel pressure then. You’ll get leakdown, the key is how quickly it leaks down.
Got busy yesterday running errands with the family and taking the kids to our local pool. I'm going to check the fuel pressure on lunch today, Haynes Manual lists correct pressures as: 30 to 45 psi at idle with vacuum hose attached, 40 to 50 psi at idle with vacuum hose detached, and 30 to 40 psi system hold pressure after 5 minutes.
 

Venompower

Active Member
Joined
Aug 17, 2015
Messages
347
Reaction score
192
Location
Batavia, IL
Ok so the fuel pressure test is complete... at key on engine off the fuel pump priming got the rail to 30 psi, at idle I had 35 psi, and with the vacuum line disconnected I had 45 psi. The 5 min leak down came back solid at 35 psi. The entire time I did the test, the AFR was bouncing around in the 16's to upper 16's. So granted I haven't done any driving or pulls to see what fuel pressure does at load or wot, but it doesn't seem that I have any issues with fueling.

So in my mind the next place to look would be coils/wires/plugs... or MAF. My laptop arrives tomorrow so I will be updating the X4 and then try to get some drives under light partial load to see what the data logs show. Any other ideas as to what could be going on?
 

ttocs

Post Whore
Joined
Oct 9, 2009
Messages
27,659
Reaction score
3,585
Location
Evansville Indiana
just because you have good pressure does not mean that they are firing the correct amount of fuel. Its not hard at all for injectors to get gummed up from dirty/old fuel. Unfortunately the only choices are to remove those and have them cleaned/calibrated or replace them and see if its better after.
 

Venompower

Active Member
Joined
Aug 17, 2015
Messages
347
Reaction score
192
Location
Batavia, IL
just because you have good pressure does not mean that they are firing the correct amount of fuel. Its not hard at all for injectors to get gummed up from dirty/old fuel. Unfortunately the only choices are to remove those and have them cleaned/calibrated or replace them and see if its better after.
Do you think injector duty cycle might shed some light? The lean AFR along with decent fuel pressure had me wondering this as well.

The only hiccup with this theory is my AFR’s were spot on during the cutout.
 

Akurma

Member
Joined
Apr 22, 2020
Messages
177
Reaction score
212
Location
Pennsylvania
I read through the last few pages about the fuel issue. Are you 100% sure your AFR sensor is reading correctly? if so then I think your only two options left after all you have done is to either

A) pull the injectors and have them cleaned/calibrated as ttocs suggested

B) drop the tank, replace the pump and inspect the inside of the tank to see if dirt is floating around inside
 

Venompower

Active Member
Joined
Aug 17, 2015
Messages
347
Reaction score
192
Location
Batavia, IL
I read through the last few pages about the fuel issue. Are you 100% sure your AFR sensor is reading correctly? if so then I think your only two options left after all you have done is to either

A) pull the injectors and have them cleaned/calibrated as ttocs suggested

B) drop the tank, replace the pump and inspect the inside of the tank to see if dirt is floating around inside
I mean the gauge is using a brand new Bosch sensor and had been reading at the expected AFR’s until recently.

So my guess is either fuel pump which is already providing lower end fuel pressures (PTS system lists 35-45 psi) at idle cant keep up under load… or maybe injectors though there are CEL codes for injectors.
 

07GtS197

Well-Known Member
Joined
Mar 16, 2015
Messages
1,721
Reaction score
372
Location
Naples, Fl
Bosch are known to be junk on these cars. I’ve personally had a few go out after a short period of time so I can vouch for that. I’ve read, and take this with a grain of salt, that they are calibrated differently than the stock NTK sensors.
 

Venompower

Active Member
Joined
Aug 17, 2015
Messages
347
Reaction score
192
Location
Batavia, IL
Bosch are known to be junk on these cars. I’ve personally had a few go out after a short period of time so I can vouch for that. I’ve read, and take this with a grain of salt, that they are calibrated differently than the stock NTK sensors.
I have brand new NTK 02 sensors, the Bosch is the wideband 02 for the AEM wideband 02 gauge and was widely recommended both by AEM and the forums.
 

Venompower

Active Member
Joined
Aug 17, 2015
Messages
347
Reaction score
192
Location
Batavia, IL
Ok, so one other thing to throw out. When I got the car the traction control light was on, as the front passenger sensor was not clipped correctly and was worn through. I have a replacement sensor, but the current one is seized and I haven't gotten around to replacing it. In the meantime I just unplugged the damaged sensor.

Could this be related to traction control, my understanding is that it can pull timing and fuel? It might explain why I have no CEL or codes.
 

ttocs

Post Whore
Joined
Oct 9, 2009
Messages
27,659
Reaction score
3,585
Location
Evansville Indiana
so the light is no longer on? I know getting the sensor out of my 94 was a pia and I thought it was seized as well but it just needed some penetrating oil and a good twist.
 

Venompower

Active Member
Joined
Aug 17, 2015
Messages
347
Reaction score
192
Location
Batavia, IL
so the light is no longer on? I know getting the sensor out of my 94 was a pia and I thought it was seized as well but it just needed some penetrating oil and a good twist.
ABS light is still on, I just decided to remove the damaged section, and then haven't put the new one in. The only reason I wondered is the relation to traction control, as this feels like the injectors are getting a signal to cut... it feels in the pedal like traction control kicking in where throttle position is being over ridden. It could again be something simple as fuel pump can't keep up at WOT even though it's putting out normal pressure at idle. It doesn't feel like a single cylinder misfire.
 

joe65

Well-Known Member
Joined
Feb 4, 2020
Messages
1,189
Reaction score
1,075
dang man, i've lost track now what all you have going on. AFR now?
 

Venompower

Active Member
Joined
Aug 17, 2015
Messages
347
Reaction score
192
Location
Batavia, IL
dang man, i've lost track now what all you have going on. AFR now?
This and some suspension are the last things… AFR had been in the 13-14’s on cold start and 14’s at idle going to 11’s with load. While measuring my fuel pressure it was idling in the 16-upper 16 range.
 

Venompower

Active Member
Joined
Aug 17, 2015
Messages
347
Reaction score
192
Location
Batavia, IL
So here are the first two data logs. The first is a quick 3 minute idle, and the second is a rev alternating from 1,500 to 3,000 rpm holding each rpm for 15 seconds. I plan on doing the driving and wot logs tomorrow.

Anything stand out, I probably could have let it idle a little longer to get coolant temp higher... but the idle didn't feel right and I figured maybe these logs would show something glaringly obvious.

Edit: Doesn't seem to let me attach the files?
 

Venompower

Active Member
Joined
Aug 17, 2015
Messages
347
Reaction score
192
Location
Batavia, IL
Does it show it pulling timing or anything?
Things that stand out:

Battery Voltage was 7.94... guessing this is measuring PCM battery voltage, because it measured 12.6v at battery and at both fuse boxes. Ground issue?

Fuel Pump duty cycle measured average 1.63

Bank 1 LTFT was 192.41
Bank 2 LTFT was 255.96

MAF counts averaged 21.56

Spark averaged 63.75

This configuration doesn't show timing, may have to make a new one tonight.
 

ttocs

Post Whore
Joined
Oct 9, 2009
Messages
27,659
Reaction score
3,585
Location
Evansville Indiana
7.94 volts would cause a lot of problems. Yea start simple and check your ground/power. I know my holley efi HAS to be wired directly to the battery. I had it connected under the hood at a large fusebox with the battery in the back but they said it had to have its own wire to the battery. I was having issues with starting at that time and it seemed to fix it along with another fix.
 

Latest posts

Forum statistics

Threads
74,871
Messages
1,452,371
Members
13,557
Latest member
afield00

Members online

No members online now.
Top