Hi folks hello from sunny Scotland, last month bought a 91 3.1 V6 3rd Gen. I drove it home from the seller but was firing on 5 cylinders. Ive spent a month working on the cosmetics and it then came time to work on the engine.
It now wont start, it will fire up for a few seconds then die. Ive changed the fuel pump, fuel filter, all injectors, spark plugs, coil, distributor, distributor cap, distributor rotor arm, checked air lines, checked compression, EGR delete,
Im out of skill and ideas now- and parts. Nobody here has any knowledge and parts are virtually non existent so have to be ordered online and wait days \ weeks for them to come. Ive read about many fixes but cant go blindly ordering parts I dont need.

Please help :-(

 

Does the car key have the resistor on it?
​​​If the car idles for a few seconds, it could be the VATS, the resistor on the key may have gone out, do u have another key to try to start the car with, also, have u checked the SES codes if there is any?

 

Hows the TPS sensor and the IAC valve?
When the car idles for a few seconds, does pressing the gas pedal make it run better or worse or no difference?
Other thing that comes to mind is the MAP sensor, u can try to leave the MAP sensor connector unplugged for a moment and see if it idles any better.

 

Havent a clue where the TPS sensor is let alone how to check it, same with SES codes and IAC - my skills have run out Im a home\ hobby car guy. A friend has asked for the injector wiring diagrams if anyone can point me to those ? Also only have a single ignition key

 

Hi Dave, here is your injector wiring diagram for the 1991 V6. To begin, I will state with complete certainty that VATS is not your problem. VATS will kill the starter and the injector pulse (providing it hasn't been tampered with) so the fact that your starter cranks your engine, and the engine starts briefly, rules out VATS. One thing that CAN cause you symptoms, that I didn't see in your list of replaced parts, is the "ICM" (Ignition Control Module) which is located in the distributor. Note that I'm NOT saying "Buy this, it'll fix your car", what I am saying is that it could be that. Anyway, the top righthand side of the diagram shows your injectors, I hope this helps......

 

Thanks for this - Can anyone tell me how to check the injector location we feel we have possibly mixed the injectors plugs up - its a nightmare.

 

On the third gen fuel injection system, there is no mixing up of the injector plugs possible. The 3.1 MPFI is just that, MPFI and not SEFI (which would be a problem if the plugs were put back in the wrong position). I have to leave my computer for the day, but while I'm gone I want you to do a search for "Batch Fire" and "Sequential" injector setups, so you'll understand why the injector plug placement is not important on your car.

 

The TPS sensor is a short for throttle position sensor, it is located next to the throttle body, on the left side, above that, is the IAC valve, short for idle air control/valve.

U can google for example 1991 Firebird V6 TPS, so u see a pic how it looks like, its a black sensor, both of them.
Sorry that i don't have a pic, but they are on google, and here on the forum, u can check pics how they look like.
U can also try unplugging the connector either the TPS or IAC for a moment, and see if it idles any better/worse.
Same with the wiring diagram for the injectors, google or search bar here ought to help.

As well as checking the SES codes, u can chem em w/o a scan tool, u just need a paperclip or a piece of wire, i found this from youtube, how to check the codes.
If the fan kicks in, don't be alarmed, its normal that the cooling fan starts to spin when the wire is in place, and the ignition is turned on, but don't start the car while u got the wire or paperclip in place.

If it turns out to be the VATS, there are few ways to go around it, and even solutions how to fix it so the VATS still functions like it did before, and some places from ebay even sell new keys that has the correct value on the resistor on a new key, but we can look into that VATS if it turns out to be that.

 

Can anyone post pics or details on how we would check the injector plugs are on the correct injectors - was advised to get a Haynes manual but there are none in UK and prob 2 weeks to ship from the US.

 

Actually, I retract this post, there appears to be a rampant reading comprehension failure in this thread, I'm out......

 

I didn’t see the post in question but thanks for your help anyway.
sheesh imagine living with you wow !

 

Dude, I told you what you needed to do to understand why the injector plug question was irrelevant , and then you disregarded my advice and asked the same question again without bothering to search what I told you too. Then, I specifically stated that if the car starts , runs a sec, and dies, that it absolutely CAN'T be vats, and I got another guy posting "If it turns out to be VATS" crap, , well, yeah, I'm done, too many not paying attention here to waste anymore of my time. I can't flippin SPOON FEED you the answer because it's gonna take some TROUBLESHOOTING on your part vs loading up the ol "parts cannon" , and to do a proper diagnosis your gonna HAVE TO earn it by learning a bit more about how the various systems controlling your engine operate than you appear to know now.

Good day sir.....

 

I can’t disregard advice when I didn’t see it anyhow have a great day we aren’t all mechanical or experts we all have to learn and have a starting point.we all make mistakes - maybe you’ve never made a mistake or were born with fountain of knowledge ?

 

It's not VATS; symptoms don't match. Check fuel pressure, verify you're getting spark. If both of those criteria are being met, it's possible the distributor was installed in the wrong position.

 

I agree that I think your problem lies here in the dizzy. If you remove the cap and rotor there lies the ICM at the bottom. ICM stands for Ignition Control Module. Over here in the states you can have those checked, not sure if the same where you are. I had a similar problem to you and after checking Fuel Pressure and spark it took me awhile to figure out it was the ICM, one of the last things I checked. The ICM is one of those electrical parts prone to fail and you might find a ton of corrosion in between the base and the ICM. If this is your case you may be able to clean it but usually they need replacing. The new ICM should come with grease to smear on the base to help avoid this.

 

No, forget the Haynes manual. This is what you really want.

https://www.ebay.com/itm/40098163267...75.c101224.m-1

I have a 1991 Firebird that has sat since 1998 that I`m trying to get started, Ive moved past the VATS and now suspect an issue with the ECM. I get no check engine light when the key is "ON" nor will my Actron "view" the data from the OBD port. Your crank but not run symptoms sound exactly like mine. Welcome to the life boat, ill post anything I discover.

 

Do you hear pump prime ? Check fuse next to battery for ecm/fuel pump

 

Hi folks thanks for the replies - we have spark, we have fuel, the fuel pump runs and it’s getting through to the fuel rail. Have also replaced ICM same time as dizzy cap, dizzy and rotor arm - we are starting to think either FPS or fuel pump losing pressure - def fueling issue as runs ok if squirting easy start onto throttle body.

 

Hi Dave,

OK, because I feel bad about how our last conversation ended, I'll try again to help you here.

Now, since it runs with starting fluid, you know for sure it's a fuel delivery issue. You say fuel is getting to the fuel rail, how did you establish this? If you haven't yet put a fuel pressure gauge on the test port (schrader valve) at the back of the fuel rail this would be a good time to do that. I'm not sure about the UK, but here in the states autoparts stores have "loaner" tools you can borrow (you leave a deposit which gets refunded when you bring the tool back), hopefully you can get a gauge that way in Scotland? If perchance the fuel pressure gauge gives the proper reading (40 ish pounds when the pump primes upon key on) the next check would be a "Noid" light on the injectors to see if the ECM is sending them the power they need to operate.

One more thought, crazy as it may sound, does the fuel tank have enough fuel in it, and is it nice & clean (not contaminated or very old) ?

 

Hi don’t feel bad it’s Internet forums things can be missed things can be misread - it’s not the crime that should be judged but rather how it’s dealt with afterwards anyhow water under the bridge. We should have access to a pressure gauge ok but that’s really useful about the 40psi on prime - should it remain 40 on crank / run ? We checked it got to the rail by pressing / checking the valve on the fuel rail.