[Jessy James]

I have a 89 firebird with a 305 with TPI. I've had it for about a month and have had no problems. This morning I went to start it up, it started ran for about 20 seconds and stalled. Turned the key, started right up ran for about 15 seconds and stalled again. Turned the key again, started right up sounded like it was going to stall so I stepped on the gas and it didn't help. Started the last time, reved it up a few times, waited about a minute put it in gear and I was on the road. I was wondering if it might be my mass air flow sensor? Anyone know how to check them or have any ideas of what it could be?

 

[Siggy_Freud]

Indeed it could be. However with that sort of setup there are a number of things it could be. Is it throwing any codes? It also possible that it could be fuel pump/fuel pump relay related, computer or main power relay related etc. Whats your oil pressure at? A sudden drop in oil pressure will kill the fuel feed to the engine. Does your fuel pressure drop when it shuts off? Even with the engine shutoff your fuel rails should hold pressure for awhile. It would be wise to invest in a few tools to help diagnose this. One is an engine scanner for the GM OBD1, and the second would be a fuel pressure tester. With the scanner you can get the readings of the various sensors and from there I can help you further.

Generally in my experience MAF usually go bad and stay that way. Its a very delicate sensor. While its running tap on it a few time with your fingers and see if it causes anything to happen with the engine.

-Dylan.

 

[Jessy James]

Looks like I got some work to do. It just happened for the first time this morning so I haven't had a chance to check for codes. Fuel pump is new (according to the seller) so I'll try all the less expesive fixes first. Would a scanner be of more use then just getting the codes by using a paper clip in the diagnostic port? By the way, thanks for the quick reply and help!

 

[RCastle]

To check your codes if you dont want top spend the coin on a scanner you can make a jumper wire approx 4" long,strip approx. 1/2" off of each end.There is adiagram in a few books as to where to insert this at.The port is under your dash,below the steering wheel.I have to go eat as so the wife dosen't throttle me.Ill get the pic of the datalink up after dinner if you need it.

 

[Jessy James]

Hmm interesting, no codes I just get the one two blinks.

 

[RCastle]

A 11 code means all is ok as far as the ecm is concerned

 

[Siggy_Freud]

A scanner does way more than read codes. While it does read the code and give you what the code means, it also gives you up to the second operating information. It will tell you engine temp, how many grams of air are moving through the MAF, knock sensor count, Injector pulse width, Manifold air temp, if you are in open or closed loop mode, if you are running rich/lean, Oxygen sensor cross count information, etc.

I would not have gotten my TPI running without the use of one. If you plan on modifying or upgrading this system, you'd be miles ahead to have one. For now, you might be able to borrow one.

Also, a fuel pressure tester is going to be really handy in determining that its not a fuel related problem.

How long are you waiting for the codes. It will blink "one, two" three times to signify that its beginning, then it will blink all the codes, and then blink "one, two" three times again to tell you its complete.

 

[Jessy James]

I let it keep blinking one two blinks about ten times. About how much does a scanner run? Strange there were no codes after stalling three times. Hope it's not the computer.

 

[RCastle]

Have you ruled out vacum leaks?There are a few lines under the upper intake plenum.Fuel regulator could be a possible problem.Just throwing some ideas out.Like Siggy mentioned,may try borrowing a scanner or find out if someone can run test it.It is alot of money to buy a scanner if you don't need it all the time.

 

[Jessy James]

Haven't checked for vacuum leaks yet. I'm wondering if it isn't something like that (non electrical). That would explain no trouble codes right?

 

[Restore60s]

Mass Air Flow

Here is a quick way to test the Bosch GM mass air flow sensors. I learned this years ago from one of the GM engineers. Take a screw driver and use the plastic handle on it and tap the Mass Air flow sensor. If it stalls it's bad. The sensor plate screen wires are what usually goes bad in them so if any are loose the "tap" test will find them. That's why back a few years ago the diagnostic time for mass air flow sensor replacement was changed to 2/10ths of an hour. :thumbup:

 

[Jessy James]

I'll give it a try, shouldn't I get a trouble code though?

 

[RCastle]

That is why I thought possible vac problem.The MAF sensor has a fine filament element that runs thru it,when started the filament heats up,as air rushes over it,the filament vibrates sending a reading to the ecm on what the demand for sparkadvance,fuel to the injectors etc. should be.You would most likely get a code if the MAF sensor was shorting,but you can tap it.An aEGR or an IAC solenoid would cause a code to set.What is the coolant level?There is a nipple in the throttle body for coolant to go thru to warm the charge coming in,if you are in one of the cold climates this may also pose a problem,as you stated that after a while you got it on the road.

 

[Jessy James]

Coolant level is fine, I did the tap test and it did not stall. I'll check the vacuum lines tomorrow got some things to do. Thanks everyone for you help.

 

[RCastle]

Good luck man.Yell at us if you get it figured out.

 

[Lonestar]

May sound stupid but did you check your fuel level? I've seen it happen more than once.

 

[camaroman7d]

When your car stalled/died. Did you turn the key back to the off position or just start the car again? Computer controlled cars will "wig" out from time to time. I have seen the exact same thing in several cars; 1991 Camaro RS, 2000 GMC Truck, 2004 Pontiac Grand Prix. Once the key was turned to the off position and the car was started again the problem never happened again. You didn't mention if this problem has continued or if it was a one time deal?

Royce

 

[Jessy James]

Plenty of fuel, I never let it go under 1/4 tank. One time deal, I think I did not turn the key back to the off position. I'm not sure if I did the last time when it started and kept running. I was taking off to work and kinda freaking out about what was going on. I'll let you guys know if I find anything or if it happens again.

 

[camaroman7d]

Jessy I wouldn't worry about it unless it happened again or more often. If it is just a once in a long while type of thing. This will also explain why you had no codes. If you have a tach, did you notice if it was jumping around? If so those are the exact same signs I have seen in the past.

Royce

 

[Stickman]

"May sound stupid but did you check your fuel level? I've seen it happen more than once."

This cracked me up, because I once put 2 (count 'em, TWO) fuel pumps in a 85 Suburban because the stupid thing was out of gas. Guage read 5/8 of a tank, but it was bone dry. And yes, I replaced it twice because I was too stupid to realize there wasn't a single drop of gas in the tank when I put the first one in and thought I'd gotten a bad pump from the parts store. I was looking at the guage reading 5/8 of a tank and ignoring anything that tried to tell me differently.

The moral of the story? Check the GAS level, not the gas guage, when there is any uncertainty.