Weird idle then stalls

[Blaiser17]

Ok, I'm finally back. School is out and as you said wright, I am ready t get this thing licked. Replaced the O2 sensor worked to no avail. Car still cranks and sometimes seems as though it will start and then just doesn't. Battery is charged, fuel pressure is good, and I can hear the pump kick on and off. I'm starting to lean towards VATS. I have a bypass coming in soon. Tomorrow I'm going to check out the MAF, TPS...again, ignition control module, and ignition pickup. If none of these things seem to kick the issue, the only thing I think to be left would be ECM and fuel injectors. But I'll keep you updated.

Now we begin....ROUND 2

[Blaiser17]

Well I went out today and checked out the TPS, and MAP. They seem to be working fine. To tell if the MAP is bad you just disconnect and it see if it runs better, right? And the TPS should work the same? Although I did try adjusting the TPS, but nothing different really happened.

As for how it sounds, it still wants to start but just won't. I have an AC Delco fuel pump on the way. The VATS bypass should be here by Wednesday, but I really don't think it's VATS now. The security light never blinks when I try to crank, so I'm thinking it's not VATS.

The smell of gas still remains when I crank long enough. And I remember it used to wreak of gas after driving sometimes.

At this point I'm leaning towards bad fuel pump/ clogged cat.

I will be going out right now to hollow out the cat as a matter of fact. And then I am going to test the injectors, but I'm not quite clear on how that works yet. Can someone fill me in?

Any advice is appreciated! Thanks!

[Morley]

Originally Posted by Blaiser17

As for how it sounds, it still wants to start but just won't. I have an AC Delco fuel pump on the way. The VATS bypass should be here by Wednesday, but I really don't think it's VATS now. The security light never blinks when I try to crank, so I'm thinking it's not VATS.

The smell of gas still remains when I crank long enough. And I remember it used to wreak of gas after driving sometimes.

At this point I'm leaning towards bad fuel pump/ clogged cat.

I will be going out right now to hollow out the cat as a matter of fact. And then I am going to test the injectors, but I'm not quite clear on how that works yet. Can someone fill me in?

Any advice is appreciated! Thanks!

If it cranks over then VATS is a non issue. VATS interrupts the starter.
First start by disconnecting the injectors and put an ohm meter across their terminals. They should read 15-17 ohms and there should be no more than 0.5 ohms difference between any of the injectors.
If they check good I would next look at spark

[Blaiser17]

Thanks Morley! I am going to do that first thing tomorrow when I have light. I was hoping to get to that today, but I'll definitely let you know by tomorrow.

Ok well I accomplished a few things before relatives came over this afternoon. I do have spark, so I guess thats a plus. Also I have 42 psi fuel pressure, which I have checked once again to make certain. I can hear the pump kick on and off loud and clear.

Morley I agree with you about the VATS not being an issue, thats a good point you made. I'm just an idiot haha.

I unplugged the MAP, I adjusted the TPS, and I cleaned the IAC. Sprayed some starting fluid, and the engine almost kicked but didn't. So injectors do seem like the logical thing to check before I jump, and accuse the fuel pump.

Keep in mind, before this all started my fuel filter got clogged and my line blew up lol So fuel seems to be the most likely culprit, now that spark is eliminated.

So tomorrow I'll check the ohms on the injectors, and if that doesn't work I guess it's either fuel pump or ecm.

Thanks once again for the input fellas!

[Morley]

Since you say fuel pressure is 42 psi we are going to assume it is a TPI.

Check the fuel pressure while cranking the engine. If it doesn't drop at all check the inj1 & inj2 fuses on the fuse block. If they are good see about getting a "noid" light (auto parts store). The light goes in place of one of the injectors on the harness. Crank the engine and look for it to be flashing, check each injector connector. If the light doesn't flash, pull the ignition module and have it tested. If it fails the test even once, replace it with an AC delco unit. The module sends an ignition refrence pulse to the ECM to tell it to fire the injectors. If it passes and the noid light didn't light up you'll need a schematic to check the refrence pulse wire for a short to ground or open. If it checks out good it may be time for a new ECM.
If the noid light works, you have proven out the ECM, fuses and harness side of it and the problem is now narrowed to the engine side.
(ohm out the injectors before replaceing them)
Now, if the pressure does drop a lot during cranking you probably have an injector or 2 stuck wide open and flooding the engine. Then its time for 8 new injectors OR the pump is trashed and can't keep up the flow.

If the fuel pressure drops some (not drastically) you could have an injector or more stuck closed, again, time for new injectors.

At this point we can rule out the O2 sensor (has nothing to do with starting).
The only sensors that are going to come into play at this point are the MAP, TPS and CTS.

A bit of bad news...you have Multec injectors. They are crap and the fuel system cleaner has done more harm than good. Those injectors are so bad that the people that run the injector cleaning and flow matching services won't touch them. If you send them in they will send them back and recommend that you throw them away.
A good replacement are the Five-0 motorsport injectors found here
http://www.fiveomotorsport.com/Injec...sTPI.asp#caddy Down near the bottom of the page on the LH side. For the 305 look for
Bosch/Ford
1985-88 Camaro 5.0
1985-88 Firebird 5.0
New - Flow Matched Set
$305.50/8 Set

If you have a 350, at the top of the page one column over from the LH side. Look for
Bosch/Ford
1985-91 Corvette
1985-92 Camaro 5.7
New - Flow Matched Set
$305.50/8 Set

[Blaiser17]

Actually MPFI. I don't know if thats the same.

I did follow the procedure you gave me though which was soooooo helpful I might add!

I checked pressure while cranking, stayed at 42 psi never went down even a little. So after this I checked the inj1 and inj2 fuses, they were both in tact. Then I went and got a noid light and checked the harnesses going to the injectors. They all made the noid light up.

So this told me ignition is all good, right?

Then I ohmed out the injectors, and this is where the problem lies I believe.
2 injectors came to 16. 3 injectors came to 13.5. And 1 injector came to 10.
I am assuming this is a huge problem haha.

So I pulled out the throttle body and intake and I'm cleaning those, while they are off.

I'm going to order a new set of injectors. And I have an AC Delco fuel pump coming in already from summit. Do you agree this could be the problem? I'm going to check out the injectors on that site you gave me Morley. Thanks!

You have no idea how helpful you have been I really appreciate it.

Let me know if you can think of anything else, I'll keep you updated with what happens. Also, is there anything else you can think of I should replace while I have this all torn apart.

I also must add, I've torn apart several engines, but never this one in the 3 years I've owned it. And it was cake to work on, I love it.

[Morley]

Originally Posted by Blaiser17

Actually MPFI. I don't know if thats the same.

Close enough for our troubleshooting

I did follow the procedure you gave me though which was soooooo helpful I might add!

I checked pressure while cranking, stayed at 42 psi never went down even a little. So after this I checked the inj1 and inj2 fuses, they were both in tact. Then I went and got a noid light and checked the harnesses going to the injectors. They all made the noid light up.

So this told me ignition is all good, right?

Kind of, this tells us that the ECM is getting the refrence pulse from the ignition and that the wiring harness is good.

Then I ohmed out the injectors, and this is where the problem lies I believe.
2 injectors came to 16. 3 injectors came to 13.5. And 1 injector came to 10.
I am assuming this is a huge problem haha.

There's the problem! You have 2 good injectors, 3 on their way out and one that is complete trash. That one at 10 ohms is probably shorted enough that it prevents the other 5 from firing when you crank it over.

I'm going to order a new set of injectors. And I have an AC Delco fuel pump coming in already from summit. Do you agree this could be the problem? I'm going to check out the injectors on that site you gave me Morley. Thanks!

Well, since you already paid for the pump and are going to be waiting for the injectors to get to you and winter is over...may as well replace the pump.
I would hold off on replacing anything else (unless you KNOW it is broken) until you get the new injectors in.

[Blaiser17]

Sounds like a plan Morley!
I'll get the stuff in, and let you know how it goes this weekend!
Thanks!

[Blaiser17]

Before I purchase these injectors do you recommend 15, 17, 19, 21, or 24 lbs./hr?
They are all equal price, just curious what would work best for my car.
Also, what is the stock pushing?
Again, this is for my '91 3.1L v6 189 MPFI Camaro

[Blaiser17]

Ok nevermind I was able to finally find some information on it. For my car 15#'s is stock, but I guess 17# would work without needing a computer mod too because of it being high impedance. I'd rather not risk it so I'm going with 15#, plus this is just my daily driver not my race car.

[Morley]

Originally Posted by Blaiser17

Ok nevermind I was able to finally find some information on it. For my car 15#'s is stock, but I guess 17# would work without needing a computer mod too because of it being high impedance. I'd rather not risk it so I'm going with 15#, plus this is just my daily driver not my race car.

Yes, go back with stock fuel flow injectors. Since your car is MAP based you'd need a custom chip burned for anyhting over stock flow. MAF based systems are a bit more forgiving and can stand a couple pound increase without reprograming.

[Blaiser17]

Well I managed to get the fuel tank out to replace the fuel pump, and man was that a biznitch. Did it without having to do anything to the shocks, but I had to cut off the exhaust and blowtorch every other possible bolt all while trying not to blow myself up. So it was an interesting experience needless to say. The tank looks like brand new though, so the combination of having a new fuel pump, new filter, and new injectors, I hope clears up the situation. I plan on finishing up the project tomorrow, and I'll let you know how it goes.

[Morley]

Cutting the exhaust is a real bummer. When I did my pump (back in 1994) I took the entire cat back out and put in an after market one.

[Blaiser17]

Hell yeah! Camaro is resurrected! It was the injectors! Thanks so much Morley!

Yeah I had to cut off the exhaust before the cat cause the cat was plugged anyway. Suck part about it was everything after the cat is only 8 months old haha. But it was the cheapo exhaust I put on when the car was running shitty. Now that it runs again, I'll treat my baby well and get a nicer exhaust.

Kinda funny that before all this the car went to 3 shops, because I had too much going on with school, and none of them could figure it out. I have had it back now for 2 weeks and with your help it started like a charm.

HELLZ YEAH!

[Morley]

Congratulations. Feels good to fix it yourself, huh?