Ok, this is probably two problems but here's the information:

I started noticing after running out of fuel that I get a Check Engine Light. It also stumbles when starting, hot or cold. I tested the fuel pressure, it looks normal when running, but the pressure bleeds down to 0 within a minute or so. I think it may be a bad fuel pump assembly.

I took it to Autozone to have the codes scanned and it returned a P0400 and P0174. These supposedly indicate a problem with EGR flow, and bank 2 running lean. Oh, and I also hear some pinging coming from the left side when I step on the accelerator, so assuming that bank 2 is the driver's side, that may well be an accurate code.

I think that's everything, and if you think I'm a complete doofus for running out of fuel, I had only had the car for about 2 months and the fuel guage does not make it to 'E.' So maybe I'm not a complete doofus.

Any advice?

It's a 1997 Firebird Formula with 140,000 miles, mostly original parts.

 

You indicate the fuel pressure is "normal"... what is it, at WOT/max rpm/max load?

Bank 2 is the passenger side.

 

Well, that's a good question. My gauge has a 12 inch lead which makes it difficult to monitor while driving. I think I should maybe invest in a better fuel pressure gauge setup.

 

Well I haven't got a good fuel pressure set-up yet, but I did record the following conditions from and OBDII scanner.

codes: P0400 EGR malfunction and P0174 Bank II lean.

Freeze Frame Data:

ABSLT TPS: 0%
RPM: 821
Load: 2%
MAF 0.77lb/hm
MAP: 9.7"
Coolant: 214 degrees
LT Fuel Trim1: 25%
ST Fuel Trim1: 3.9%
LT Fuel Trim2: 25%
ST Fuel Trim2: 10.9%
Speed: 0 mph
Fuel Systems 1&2 closed



Now it appears to me that the fuel trims are about pegged. Am I correct? Does anyone have an idea?

 

vacum lines maybe?

 

Yes, in the idle Cell (16) you have maxed the long term fuel corrections out at +25% (160 BLM). What do the long terms look like for Cells 01-15? A small vacuum leak can have a major impact on the long terms at idle, but will disappear as load increases. A shortage of fuel due to pressure might show up as increaing long terms as the it moves to the higher load/rpm cells.

The fact that you have P0174 would indicate its more than a vacuum leak at idle, since that code only sets when the weighted average of the long terms correction cells exceeds 21.8%

0.77#/Min (if that's what your units are???) on the MAF translates to 5.8 grams/sec, and that might indicate the MAF sensor is reading a shade low, but it isn't unheard of for an engine to idle at that air flow rate.

 

Just use duck tape and tape it under the wiper to the windshield and do a couple of WOT runs to see if it drops.

When did you take those readings? I see you are hot and idling, but did you just start it up and let it sit or did you drive around and then take the readings? I believe that your LT's will read lean like that if you don't drive it around so it can average them out.

Looking at your short term the driver's side is looking good only adding 3.9% fuel, but your pass. side is adding more fuel for some reason hence the code telling you that bank is running lean. Check for exhaust leaks, seems logical to me that with a bad enough leak you aren't getting good backpressure to operate your EGR and also getting a fresh air on the O2's causing a false lean and it dumping fuel.

EDIT: I need to type faster

 

I still haven't picked up the hardware to view fuel pressure while driving, but while changing my radiator, I discovered that the screws holding the MAP sensor to the manifold were loose. I removed the MAP sensor and reset the gasket and tightened up the screws. The fuel trims started out at zero since I disconnected the battery, but after a short drive, the fuel trims were showing slightly negative, so maybe I found the problem. Time will tell.

 

I think the previous condition may have fixed the codes, but it is still having intermittent trouble starting. I noticed before when I put the gauge on, that it sunk right to zero ithin a minute of killing the engine. This time, however, it took hours for the pressure to bleed, and it happened to start right up today, so it seems that the time it takes for the pressure to bleed may be another symptom of the problem.

My real question:

I put a fuel gauge on the manifold and went driving. It idled around 42psi and up to 50+ on WOT, but started to sink around 4000 rpm and was around 44psi at about 5000 rpm.

Is this a problem? Shouldn't it remain around 50 or higher through the full rpm range?

 

You put a fuel gauge on the manifold?????

Fuel pressure may not stay constant over the RPM range. You will see lower fuel pressure when engine load is low. Your numbers sound about right to me.

 

The injectors are sized based on the stock fuel pressure of 43.5psi. That's all they need to flow their rated quantity. With a stock fuel system, the "no vacuum line connected" pressure should be 41-47psi. At WOT/max load/rpm the fuel pressure should hold at 41psi or above.

Seems odd you would get over 50psi at any time.... what does your fuel system consist of? Does it include an AFPR?

 

It's a stock fuel system.

1997 Firebird Formula

The gauge may be slightly out of calibration, and it's a little difficult to see the gauge since I can't view it from the proper angle. As long as a drop in pressure at higher rpm's is ok, then I won't worry about it.

I do think the fuel pump check valve has some dirt or something lodged in it. I'm going to run some cleaner through it. I don't think it will work, but it's cheap.

 

The lean condition and EGR code were being caused by a loose MAP sensor as the screws were not even finger tight. This created a vacuum leak as well as prevented an accurate reading of MAP.

The cold start stumble issue I believe was caused by carbon in/on the injectors. I started buying fuel from a different company and also ran a couple bottles of injector cleaner through the fuel system. Now it starts like a champ. I'm wondering if I should look from some SVO injectors; I hear they are more resilient to heat soak/carbon build-up.

I'm glad it was an easy fix. Thanks for the help from this forum.

 

Thanks for posting the solution to the problem.... most people don't take the time to do that. It will help the next person who has a similar problem and takes the time to do a "search".

 

like me ive got a similar issue, except i have a random misfire code and both banks are lean. i'll check my MAP sensor...