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1991 Pontiac Firebird - Third Generation

Third-Gen TPI Cars Are Cheap! Our $1,500 '91 Formula Proves It, But First We'll Show You How to Overcome

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'It's the TPS, dude! This is our third F-body project car in the past 5 or 6 years, and we hear that tip from the local help nearly every time there is an undiagnosed problem. In reality, the TPS hasn't failed on any of our cars. It's the computer, dude! The ECM has barfed at least once on every one of our TPI cars, and when you go down the diagnosis flowchart, what's usually at the end is a little dialog bubble smugly stating "Faulty ECM." Bummer. That's a $100 headache.

But the car has potential, and in the following months were going to build this sucker to try and redeem ourselves for that red Formula we ruined a few years back, and to make it simpler than the black '91 Camaro we did with a blown 383. We'll also keep this one smog legal. Sound easy? Not in California. We've found from past experience that these cars have to be nitrous-oriented if you want to go fast and not spend a fortune in the name of compliance.

So treat this as an introduction to another third gen that we are going to make fast. Look for day-to-day stuff and little details at and look in the magazine for the big fun. If we can do it, there's no excuse for you.

Day One:The Trouble BeginsThe car is a 150,000-mile '91 Firebird Formula that Freiburger picked up for $1,500. It has the original Tuned Port 5.7L that uses a speed-density EFI system rather than the mass airflow sensor used on pre-'90 cars. A quick check of the Service Parts Identification label located on the inside of the console door below the hatch on the driver side revealed the four RPO (Regular Production Order) codes we were interested in: B2L, MD8, GU5, and G80. The B2L indicates this car has the 5.7L (350) V-8 instead of the 5.0 (305). The MD8 is the 4L60 overdrive automatic. The GU5 means the car has the 3.23:1 ratio in the 10-bolt, and the G80 is the code for limited-slip. Other cool RPOs to look for: G92=performance axle, GU6=3.42:1 differential, N10=dual exhaust, and F41=heavy-duty suspension package.

It's actually a lot of car for the price. The only problem was that it barely ran.

Day Two: Budget Code ScanningWe've found that with each TPI car we bring home, we're destined to spend $1,000 on stuff just to get it running right. We saw bad credit looming when the Firebird would hunt in Neutral and stall completely in gear. So we started the diagnosis. The first thing to do on these cars is to check for engine codes. The best way is to use a scanner like the Actron CP9145 Super AutoScanner. It relays the ECM signals in real time and can read and store codes. Jeff Smith had one lying around, but this is Car Craft so we decided to use the field-service technique by jamming a piece of wire between the two upper right terminals on the ALDL (Assembly Line Data Link) under the dash. The engine light flashed the number 12 three times then gave us a code 32 which indicated a faulty EGR solenoid (according to the factory service manual we had left over from the '91 Camaro days). It made sense to us, so we pulled the plenum off the engine to get to the EGR after using a test light to probe the connector harness for power. The EGR was clogged with carbon and stuck open so we replaced it.

Day Three: Tune-up TimeWith the EGR problem solved, we moved to the basic tune-up with plugs, fuel filter, distributor cap, and rotor. The No. 5 and 7 plugs were actually easier to reach from underneath the car. We changed them on the lift, where we also changed the fuel filter (it's on the floorpan under the driver-side rear seat) and a broken transmission mount. We also installed new U-joints and a rear transmission seal. Done

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