Wildcat7878

A little backstory; this is my '01 Firebird Formula. It's a manual and when I bought it (just under four years ago) it had had a remanufactured engine installed 25,000 miles ago. Recently, it started drawing the battery down while parked. I did a draw test and it was pulling ~1.5 amps with nothing on and actually melted the solder out of the + terminal overnight.

Being in the military it sat for about a month before I got the time to tear it apart. The alternator was the problem; near as I can tell the diode went bed and the battery was discharging back through the alternator. Either way the new alternator fixed it but now there's a new problem; it barely runs.

After I put it back together I started it and let it go through idle relearn then took it for a drive. Almost immediately as I pulled off in first it was bogging out, had no power, shaking violently. It picked back up then down the road it started again, and the SES light started flashing, which I'm sure is probably the multiple misfire code being thrown. I checked the simple stuff like connectors and the O2 sensor wiring in case I'd broken a wire messing around under the car and I sprayed the MAF of with contact cleaner.

After spraying the MAF it ran great for about a half mile but as soon as I turned around the idle dropped and it started throwing the flashing SES again. Here's the weird thing; I had to drive it to work today, and it would run fine for 10-15 seconds after startup and then start dying, but if I just cycled the ignition off and on again quickly, it would run fine for another 10-15 seconds. This is how I got to work. Drive 10-15 seconds, bog out, clutch, cycle ignition, let off clutch, lather, rinse, repeat.

My first suspicion was fuel pump, but I don't understand why its capable of running normally for 15 seconds before dying, but running fine again just because I cycle the ignition. I'm not a great troubleshooter so any help you wise individuals could give would be appreciated.

smitty2919

1)Put a scanner on it and pull codes. This may tell you your problem pretty easy.
2)Data log the car and see what it is doing if the code is not so obvious.
3)Verify fuel pressure with a mechanical gauge off the fuel rail if you think it's fuel related.

Then report back.


If you don't have a scanner, get one or get a laptop and buy TTS Datamaster for logging. If you don't have a FP gauge then pick one up at Harbor Freight or Autozone. They are not expensive and always handy to have for diagnosing issues so you don't go throwing parts at your car.

Wildcat7878

Ok, I didn't see your reply until last night, too late to go pick up a gauge. I'll run into town soon and grab one. As for my codes, I pulled these:

P0174-Fuel Trim System Lean
P0332-Knock Sensor Circuit Malfunction (Bank 2)
P0113-Intake Air Temperature Sensor Circuit High Voltage
P0300-Random Misfire

smitty2919

P0171 is a lean bank 1 code (or drivers side)
P0174 is lean bank 2 code (or passenger side)

"lean code" is there is too much air in the system and thus the computer will keep dumping fuel into the motor to compensate. There is a limit to how much fuel the computer will add, so when the added fuel is maxed out and a stable air/fuel ratio mixture is STILL not met, a code will be triggered. THIS IS ASSUMING THE O2 SENSORS ARE WORKING PROPERLY.

I would suggest picking up a scanner to live data log the car and pay attention to the Long Term and Short Term Fuel Trims on each bank.

A lean condition can be caused by a vacuum leak somewhere, clogged fuel filter (would most likely get BOTH banks lean), failing fuel pump (would most likely get BOTH bank lean), or intake gasket leak etc.

P0113 could be a failing/faulty air intake temp sensor. It sends a 0-5V signal and when the voltage seen by the PCM is above 5V it will trip this code. It is a thermistor (resistor based off temperature). The voltage put out by the IAT sensor is dependent on temp. Low temps = High signal voltage.

The P0332 and P0300 could be byproducts of the other 2 codes.

Check all vacuum hoses, check voltage at IAT sensor as well as STFT and LTFT's. via a scanner along with verifying fuel pressure at idle and certain RPM's to make sure fuel pump is keeping up (if you can even raise the RPM's and not have the car die on you).

This will suck if you can't keep the car running long enough to perform any of these checks.

Wildcat7878

Ok; I went and picked a fuel rail gauge and a scanner; I'll let you know what I find. The IAT defaults to like -40 degrees doesn't it? So if it's giving high voltage then isn't it just not working at all?

Wildcat7878

Ok, ran the scanner and took fuel pressure.

Fuel pressure was steady a steady 60psi at idle and fluctuated from 57-60 at RPMs

IAT was reading between 89° and 101°; ambient temperature was ~61°.

SHRTFT1: -39.1%
LONGFT1: -10.9%
SHRTFT2: 50.8%
LONGFT2 25.0%

I could check IAT voltage or look for vacuum leaks yet; its too dark and we've got no lights outside. I'll check after work tomorrow.

smitty2919

At what point were these fuel trims taken? Was the car warmed up and in closed loop?

It looks like your bank 1 is taking away fuel (running rich) and your bank 2 is giving a lot of fuel (running lean). Get the car warm and see if you can hold a steady 2000rpm and wait for the fuel trims to level out and see what they are.

Wildcat7878

This was taken at idle after a test drive. The car was warm. We'd just driven it and let it sit idling until it started run poorly.

smitty2919

Well according to your fuel pressure readings, it seems to rule out fuel pump or fuel filter issues and most likely no injector issues either.

Next would be log and see what your O2 sensors are doing. The data logger should be able to show you a live graph of the O2 sensor voltages as the car is running.

Knowledge is powahh!