Hi everyone, I am in some desperate need of help I bought my 91 bird about 2 years ago, and drove it happily for about a year, when one day I was driving down a highway coming into town and the motor stalled, I was luckly able to coast into the gas station, which was pretty ironic because I thought it was just out of gas, "fuel gauge doesn't work"

Anyways I fueled it up, and went to start it and she popped right off and away I went, within a month it did the same thing, but this time I was left stranded, BUT this time I knew I had a full tank of gas, so that was out of the question...

The car eventually started and stayed running long enough for me to make it home, where the car has now been sitting for around a year. Sadly the problem had gradually grew worse until it's at the point where the car will fire up, sound good, and 5 seconds later it will shut it's self off.

Here is a list of parts that I have installed in the car trying to fix it.

"New fuel pump"
"New fuel filter"
"New spark plugs"
"New rotor/dist cap"
"New plug wires"
"New o2 sensor"
"New MAP sensor"
"New ICM"
"New TPS"
"All new vaccum hoses"
"Drilled a hole in the excaust just before the caddy"
"Took the intake completely off and cleaned carbon build up"
"Cleaned injector tips"
"Took apart the EGR and tried running the car without that on "no difference"
"New air filter"

I'm sure there is more that I have done or tried I will update soon. When I remember lol.

 

Actually having installed all of these new parts the car does seem to run smoother for that 5 seconds it does run

 

Ohm your injectors and check if the fuel pressure regulator's diaphragm is not ruptured. I had to replace my injectors and rebuild the FPR. Good luck.

 

As antares57 said, check your FPR. A quick check is to pull the vacuum line on top of it and smell for gas (or see gas in the line). If you do, then it is leaking past the diaphragm. Use a fuel pressure tester on the schrader valve to confirm your pressure is dropping quickly after the fuel pump shuts off.

The vacuum line is at the right front under the intake manifold. (if looking at the engine from the front, it will be on your left)

 

And don't spend a ton of money on stuff until you know what the actual problem is!

 

Thanks for the reply guys! I actually installed these parts based off of what I have read on this forum, you guys and the local parts store must be in cahoots, haha just kidden.

This would make sense because I hear the fuelpump turn on then it shuts off I go to start it and it runs for about 5-10 seconds and the car shuts off. By the way what does ohm mean exactly? Also, I borrowed a old code scanner and the only code that shows is "low voltage throttle position sensor" or something like that?

 

ohm is the measure of electrical resistance. It can indicate the electrical condition of a wire. In this case the little coil inside the injector. If it's not correct the injector is bad. If it's correct the injector MAY be ok. But the resistance check is an easy first step.

 

What is the tool called that can perform this task?

 

You need a Digital Volt Ohmmeter, or DVOM. Fry's and Best Buy are two places where you can find one, or any electronics supply store. They range in price from cheap to pricey, based on features and quality. For automotive testing, the one thing that is critical in whatever DVOM you buy is 10 Megaohms per volt input impedance. That may sound like alot of mumbo jumbo, but it is a measure of the tester's accuracy when measuring voltage and it is critical when measuring sensor signals in your car's EFI system. Fluke is the most common brand of good quality DVOMs.

The code 22 "TPS signal voltage low" is the likely culprit of your start, run, stall issue. You will wish now that you had an actual scan tool that can read ECM data. That way you can see what the ECM is actually seeing for TPS voltage. You can do the testing using your new DVOM. It will just take longer, be more complicated and less certain.

The TPS "throttle position sensor" is mounted on the throttle body opposite the throttle linkage. It has three wires connected to it. It receives 5 volts and ground from the ECM and sends back a signal between .5 volts and 4.5 volts, depending on throttle position. This way the ECM knows where the throttle is. It's vital for idle, fuel, and timing control.

At this point, you really need to invest in a good service manual so that you have wiring diagrams. A good service manual will also have trouble trees for each of the ECM trouble codes. The trouble tree walks you through the testing to verify the cause of the fault. In the case of low voltage, the fault is either an open 5 volt reference circuit, an open or shorted signal circuit, or a faulty sensor. In a car this age, all three are equally possible.

You could try just replacing the TPS to start with. It may save you some time. One absolute necessity is that you use quality parts. Cheap parts are only future problems in a box, if they even work in the first place. Part brands that you can generally trust are AC Delco, Standard Motor Products, Delphi.

Good luck.

 

FireBired, if the OEM factory injectors are still in the engine, just replace them. Don't even worry about measuring the resistance, just install new/reman injectors. And not with re-manufactured Multec's (they can't be re-manned).

The OEM Multec injectors fail by having the coils short out. With the ECM not being able to drive them once this occurs, which is also very intermittent. Very much heat dependent.

I'm rather tired of making these posts as it is a well known failure mode. I've been there while 400 miles into a road trip with them failing. No fun at 70 MPH to have the engine just shut off, then a second or two later come back to life.

Funny thing is, I still have those OEM injectors and not once has the injector resistance been in the red zone. But on the engine at temperature, they were failing.

RBob.

 

I may have solved it! I installed a new coolant temp sensor and she popped right off and stayed running long enough for me to discover that the new TPS i installed was faulty, it is running really rich and has a high idle. You were right Ace doc, i should have bought the high quality TPS instead of going for the cheap one. Lesson learned. I'll post the results when I get the new one installed! Thanks to everyone for the help!

 

Absolutely correct. If not now, you will eventually have issues with the factory injectors, especially in the 3.1 due to the injectors being mounted under the plenum. The solution is Bosch III replacements. I see that Fast now sells the Bosch IIIs under their brand. Southbay is also an excellent source for injectors.

If you didn't get the point already from mine and other replies, please do test and verify failures before you replace parts. You will save yourself and those who try to help you alot of grief this way. Probably half of the sensor faults that I see on this vintage of engine are due to circuit or connection faults rather than the sensor itself.

Injectors are an exception to this as they are so severely affected by heat and because aside from electrical testing, we can't really see them operate. While we can perform cold and hot resistance tests on the coils, we have no way of verifying spray pattern and consistency. I have caught sticky injector pintles using my labscope, but I prefer to have them tested on a flow bench by an injector service shop. In the case of the Multecs, this wouldn't be a good investment since the Multecs are faulty in their very construction. The wise money is in replacing them with an improved design.

 

ok ok ok, I lied it isn't fixed, she just likes to run abnormally long on occasion because she likes to play with my heart. I will install new injectors asap and get back to you guys, thanks for continuing the reply's.

 

Southbay injectors worked well for me. Great price and they are a sponsor here and will give you a discount.

 

results are in, NEW INJECTORS WIN! I replaced all 6 and project fire chicken is back in action. Thanks to everyone who has helped, I don't want to go as far to say that I'm glad this happened to me but if it hadn't I wouldn't have learned anything about the car. So here's to everyone at TGO

 

Awesome! Thanks for letting us know how things worked out.

 

had the same problem with my 91 3.1L. I got a used set from the junkyard from a Ford V6 I could not identify because it was not in a vehicle. Runs like new. Thanks guys!
New injectors all read 16 ohm

 

What brand injectors did you install, OP? New,reman?

 

I know this thread is a few years old but I recently bought a 91 firebird with the 3.1 I’m having a start stall issue. The issue is persistent. It will start up immediately then just stall. I’ve replaced plugs,wires, ICM, cap, button and coil.
ive also replaced the injectors with southbay. The fuel pump. Fuel filter. Replaced EGR valve and gasket. Replaced TPS and IAC. And replaced Temp coolant sensor. I’m at a loss. It has good fuel pressure. Good spark and starts up everytime just stalls immediately. What the heck am I missing?

 

Check out response #4 above. Even if you have good fuel pressure - check the fuel pressure regulator or rebuild it as necessary.

 

I’ve had the same start, run, die issue on my 91 Camaro with 3.1 V6 and went ahead and changed some parts (TPS sensor, regulator diaphragm, fuel pump) and bought some injectors from Southbay. Finally got time to work on it yesterday and got the old injectors pulled out but when comparing them old to the “new” they look completely different. Not concerned about the body shape but the top of the injector on the Southbay units has two grooves. With the injector seated fully in the fuel rail, the groove closest to the injector tip would be the one that the C clip would fit in, however, that groove doesn’t go 360° around the injector therefore, once the injector is seated, you can’t rotate the C clip around to lock it in.
Also, the injector tip area and its O ring are completely different then what I took out so I’m afraid these may not be correct. Obviously, Southbay is closed over the weekend and I’m gonna call Monday but curious what brand the original injector is…the pic below shows the two side by side. RH side is original, LH is the Southbay injector. Thanks!

 

did the injector replacement get the issue sorted then? the car started again?

 

Yeah, this fixed my issue and the injectors worked fine, despite the minor differences.