tbone91firebird

1991 Firebird 3.1 V6 138,xxx miles

Replaced ECU, Fuel Pump, Fuel Filter within past 2 weeks

Replaced Distributor Cap, Plugs, Wires, Air Filter, Vacuum Lines within past year


I took my car to the mechanic about a month ago to get brake work, struts, and the steering column tightened. At this point, the car had been sitting for about 4 months and ran fine before taking it to the garage. When I picked up the car it seemed to be running fine until I got it home and tried starting it an hour later. The car would turn over and run for about 2 seconds and then sputter and stall. If I let the car sit for another hour it would start up and run fine. The next day I decided to take it out to the highway and open it up a little and see if there were any other problems. Low and behold, I pushed the throttle down and got the engine up to about 4k rpms and it would shut down to idle and then back up to 4k again and then back down to idle.

We took the car back to the garage and asked them to look over the work they did on the column to see if anything was wrong with the wiring and they said there was not, however I'm not even sure they took a look at the column at all . After two weeks of swapping out computers, fuel pumps, fuel filters, and ignition modules, they could not fix the issue. I brought the car back to my house, and now it starts fine, but seems to be running rich with very low power and a ton of white smoke coming out of the exhaust and out from under the hood.

If anybody has any ideas on where I should start, it would be greatly appreciated. Don't hesitate to ask me about any other specifics of the car.

Maverick H1L

iTrader: (8)

Check the oil... White smoke means that more than likely you have either a blown head gasket or worse. Black smoke means you should check the MAP sensor... If the head gasket or something is leaking coolant into the cylinders, the oil will look like a milkshake. Remove the spark plugs and check to see if they smell like coolant and check the color of the plugs as well.

tbone91firebird

The last mechanic we had look at the car said the computer was advancing the timing 15 degrees.. Is it possible that this is what is causing the problem?

tbone91firebird

Just checked one of the plugs and it's fouled.. I took a look at the oil level too and it appeared to be over a quart too full.. Does this mean the coolant is leaking into the crankcase and causing the oil to appear too full, or did the assclowns who did the oil change put in too much oil?

I also read it might be a leaky injector, since the exhaust smells like gas, and so did the dipstick..

Maverick H1L

iTrader: (8)

If the plug is fouled black, you either have a leaking injector (or more if more than one plug is fouled), bad MAP sensor, weak spark, or a bad O2 sensor.

The ECM commonly advances the timing 15 degrees... The mark should be on the 10* mark when the set timing connector is disconnected and should be off the scale when the ECM is controlling the timing.

tbone91firebird

Thanks for the input.. I realized that gasoline was definitely the reason for the overfilled oil level. Could my problem possibly have something to do with the Fuel Pressure Regulator among the other things you stated?

Maverick H1L

iTrader: (8)

If the car had been sitting for quite a while before being driven again, it's possible that either the fuel pressure regulator is gummed up and sticking or there is an obstruction in the fuel return lines leading to the gas tank. If you can, remove the pressure regulator. If not, you may want to see if someone can blow the return lines out for you.

:edit: Test the fuel pressure. If there is a problem in the return side of the system, the fuel pressure will be almost 60 PSI. Been there, done that.

tbone91firebird

The car has set in the garage all winter while I was away at college. The FPR is located on the fuel rail correct? I'll pull that out and check it to see what kind of condition it's in. How would I go about cleaning the return fuel lines?

Maverick H1L

iTrader: (8)

The FPR is the thing connected to the throttle body by a vacuum line. Once you get that off (security T10 torx required), you'll need a blow gun with a rubber tip to stick in the brass hole in the middle of where the FPR was and blow the crud out of the return side of the system with 90 PSI air. Take the gas cap off when you do this, and yes, you will hear the gas in the tank bubbling. Hold the air in the line for about 5 seconds and then put everything back together.

tbone91firebird

Alright, I'll do that tomorrow.. Is it possible to clean the FPR or should it just be replaced if it's covered in gunk? I'm going to take the MAP sensor into autozone to have it looked at tomorrow also. I already ordered a set of bosch III injectors, so hopefully all of these repairs will fix the problem.

Thanks again for all your help!

Maverick H1L

iTrader: (8)

Don't clean the rubber part of the FPR... Just make sure the brass part at the bottom is clean and goop-free.

tbone91firebird

Pulled the injectors today.. 5 out of the 6 were at right about 12.4-12.5 ohms. However, there was one that was at 2.3.. Source of my problems? I also pulled the FPR and found it to be completely clean of any debris. One of the fuel lines leading into the rail was spewing fuel until I used vice grips to squeeze the rubber hose further down the line.. I assume this is normal?

Maverick H1L

iTrader: (8)

The low resistance one could be your problem. Since it's more than likely shorted at least partially, it's probably leaning out the one cylinder, which will cause the O2S to read lean and the ECM to command more fuel.

Since you have the FPR apart anyways, I'd blow out the return lines just to be on the safe side.

tbone91firebird

I got my new injectors (Bosch III) installed today.. I also installed a new PCV valve. It still runs like sh*t for some reason.. I'm about ready to run it off a cliff! Any other ideas gentlemen?

Maverick H1L

iTrader: (8)

What's the part number on the injectors?

tbone91firebird

Product Code BOS917

Maverick H1L

iTrader: (8)

Part number off of one of the injectors themselves... Or a link to the page where they were ordered.

tbone91firebird

http://fuelinjectorconnection.com/sh...&productId=186

Maverick H1L

iTrader: (8)

IF those are the injectors I think they are, they're WAY too big for your engine, and that's why it's running like garbage. Unfortunately, the FIC site doesn't list applications. The 94-99 3100 injectors are just a smidge too big for us (same injectors as used on the 3.4), and the 00-whatever year they stopped making the 3100 injectors are even bigger because of a redesign.

tbone91firebird

It says at the top of the page that its made for "Pontiac-Buick-Oldsmobile/Bosch III 3.1 gm v-6..." Is this false advertising?

Also, the car is running identical to the way it ran before I threw the new injectors in.. I'm being told it might be that my piston rings have gone bad?

Another interesting thing I noticed before I put the new injectors in was that the spark plugs on the drivers side of the engine were fouled and soaked in gasoline while the ones on the passenger side appeared to be brand new.. What's up with that?

Maverick H1L

iTrader: (8)

It's not false advertising... The 3100 was used in just about every GM brand. It would help more if they posted a year range.

Could be that one of the fuel injector fuses (FP/INJ1 and INJ2) fuses in the fuse panel is burned out, there is a wiring fault in the harness (check to make sure you don't have a short by removing the harness from all of the injectors and probing a connector with a DMM between both terminals), or there is a problem with the ECM grounding the one side, which is why the injectors aren't firing. Check for power on both sides with the key on at the pink wire on any injector connector.

tbone91firebird

Checked the fuses today and it turned out the injector1 fuse was blown! The bum injector must have shorted out the fuse.. I threw a new fuse in and it stumbled then fired and idled like it did when I first bought it. I let it warm up and took it out on the streets and found out that all the problems I was having were gone. It ran better than it ever has. Thanks for all your help, Maverick.. I feel like I should be handing you my paycheck for this week! You're the man!

Maverick H1L

iTrader: (8)