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1988 Firebird Formula TPI 5.0 automatic. Car sat for 19 years.
I noticed that when I shut the car off the fuel pump will run intermittently for a few seconds, this happens for a few minutes after I have parked. I read that this is probably a faulty Oil Pressure Sending unit. I am also having trouble with the car stalling when putting into gear or if I come to a complete stop and wait a few moments the engine will idle, then all of a sudden it just quits like it's starving for fuel. Wondering if at lower RPMs, it may be turning off the fuel pump. I will test the fuel pressure but currently the car is up on stands waiting for some other parts. I ordered an Oil pressure sending unit today.
Some history this is my first project car. Bought from a tow yard for $500! Interior was well preserved as it was stored in a shed for 17 of the 19 years it did not run. I've replaced the fuel tank, sending unit, fuel filter and pump. Tank was a crusty mess. I actually tracked down the former owner and she got rid of it when the fuel pump went and she had a 1 month old. Car was impractical. Diagnosed that there was no power at the fuel pump relay. The green wire that sends a prime signal did not have any insulation at the connector. Replaced the connector and found that the fuse was not getting any power. Had a bad wire at the junction of the battery cable. The positive wire from the alternator was bad and I already replaced the Alternator too. Ugh
The throttle body was frozen and I tried for a couple of days to get it to free up. I ended up taking a throttle body off a I believe 1986 IROC Camaro. (Had rear brake light in the top of the glass.) I cleaned it up it was full of carbon. I knew nothing about IAC or the TPS at the time. (Newbie) I cleaned it up best I could leaving the IAC connected. The car started up! But it idled at 1200 rpm. I also replace the MAF sensor as the car would start but die immediately. After reading on here about fast idle. I replaced the IAC, old one was actually bent and full of carbon. I also set the TPS at .54 volts. I took off the throttle body again and cleaned out the ports for the IAC this time. Lots of build up. After changing the IAC car idles much better at lower rpms. I am also going to be testing for a blown head gasket as there was a discussion on here about that causing stalling. (I hope it's not!) Air bubbles in coolant lines when I turn off the car after it is warmed up. Might be radiator cap. Picking one up today along with exhaust gas tester.
BTW, the $500 car is now up to about $5,500. Nothing was really expensive just a lot of new maintenance parts that needed replacing. I have a lot of RockAuto magnets! Tires were the biggest expense $600 and $300 for windshield. (I also bought some salvage parts for vanity sake. Taillights ($100) that were in better shape than mine, T-Top bag and extra set of T-tops ($100), rear straight spoiler ($60), (Retrofitting Gen 4 Trans Am spoiler at some point. It was also $60), complete set of factory rims that were in better shape than my 3 ($200). My car was missing one rear wheel when I purchased it.)
Last edited by DigitalDan3; May 18, 2026 at 09:37 AM.
Reason: Grammar
The oil pressure sending unit could only cause stalling if it were shorting power to ground, or if the FP relay is not operating properly. 99% of the time the pressure switch doesn't do anything except act as a redundant backup for the relay.
If there are any doubts, you can test this by manually jumping power to the fuel pump for your test drive. If there is still stumbling with the FP constantly running, you would need to look elsewhere.
Thanks Vader!, I didn't think to jump power to it. Makes a lot of sense. I was also going to hook up the fuel pressure gauge and monitor what happens when I put it in drive.
did you do anything with the fuel injectors? all of mine were shot after sitting for 15-20 years. others have stated on here the fuel lines can corrode up too from sitting which also causes issues... I'd suggest to rig up a volt meter at the relay and see if the voltage drops or dies leading up to the stall if you think the pump is losing power. also the pump will shut off when it loses pulses from the distributor. I'd also check fuel pressure, the regulators are known to deteriorate, the rubber diaphragm tends to go bad.
but before you throw more parts at it, here's the service book for '88, run through the diagnostic trees and prove out stuff to eliminate it as being a source of the issue. gonna save you $$$ it sure did me.
