Sorry for the long post but I just thought I'd take a chance and see if anybody would be able to point me out in the right direction as far as diagnosing my 'Vette.

It's a '92 LT1 6 speed.

After getting back from work today, I got in my car, put the key in the ignition and tried starting it but it wouldn't turn over. The battery was clearly strong enough to crank the car so I knew that wasn't the issue. Within a few seconds, there was a really strong smell of fuel outside the car and I could see plumes of smoke coming out the tail pipe, though it was hard to see the exact color of it since it was very windy out and the smoke would just blow away really quickly.

After about 10 minutes of back and forth trying to start the car, it finally turned over and the idle smoothed out and settled down. A quick inspection under the hood revealed no obvious signs as to why the car didn't want to start so I got back in and headed home. I got maybe 3-4 blocks down the street and when I came to a stop at an intersection, the car died on me and never started back up again. Once more, there was a strong smell of fuel whenever I'd try and crank the car.

No need to go into too many boring details but about 1 hour and $100+ dollars later, the tow truck dropped me and the car off at home. After lowering the car, I got in and wouldn't you know it, she started right up again.


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Now, I'm pretty sure this next part is pretty important too, since I'm almost positive it's related to my car not starting today.

About two month's back, the car started to develop a bit of a "stumble" or "stutter" first thing in the morning. It would start up right away but after getting about 2-3 blocks from my home, it would stutter and sputter for about 4-5 seconds and then all was well. Car would run perfectly afterwords.

Over the upcoming weeks, the symptom gradually got worse. She'd still start up right away every morning, but after a few blocks of driving, the stuttering would return but stay on for 10-15 seconds then disappear again never to return until the next morning.

My first guess was that the problem was fuel related since the stuttering would happen just for a few seconds then disappear. It didn't make sense to me that it was ignition related, since (in my opinion anyways) if it was indeed ignition related, the problem would get progressively worse as the ignition components got hotter as the engine came up to operating temperature. I've had a lot of experience with opti-spark failures in the past with previous Fbodie's I've owned and when they start crapping out, it's usually at a specific RPM and when they reach that RPM (whatever it may be) the problem happens all the time at that specific RPM. There was no way around it.

This was something different.....

About two weeks back, I replaced the fuel filter (good thing too since the old one was completely clogged), purchased a set of Bosch III injectors from FIC. and the car already had new plugs, wires and ignition module only a few month's old. My fuel pump comes on when I turn the key to the start position and it's loud and clear so I don't htink the pump is the issues since its clearly coming on.

Could this possibly be my fuel pressure regulator? I pulled the vacume line off it to see if there was any fuel in it (thinking maybe the diaphram had worn out and burst) but there wasn't any fuel in the line. Could there still be another problem with the regulator? Could this possibly be ignition related?

The car's working now, but I won't be taking it out until the problems been solved. This really messes things up for me because my Vette is my only car and my only means of transportation (its a daily driver) so I'm going to have to find some other way to get around now. Any help and/or suggestions would be greatly appreciated.



UPDATE:  , I just checked for codes and there aren't any.  Cars continues to start right up first time around though like I said, I'm not taking the chance to drive it only to be left stranded again.

Thanks to all in advance.


- Phil
LT1*C42009-08-10 19:09:19

I would suggest a fuel pressure check, both during starting, AND when the engine is stumbling.
 A strong, raw fuel smell is something that really needs to be investigated, before all the smoke comes out of the fiberglass... Have you seen any fuel running out anywhere, like under the car, where the filter is?
You said you had bought a set of infectors, but have they been installed? You may have one or more infectors that are leaking, and causing the fuel smell, AND the rough running. The fuel pressure test might verify that, if it doesn't hold pressure after turning the key off, or you never get a steady reading with it running.
You also say you checked for codes...do you have a scanner that gives live data?

The injectors have already been installed yes, and I've checked for fuel leaks around the injectors, regulator and filter and found none.

I don't have a "scanner" per say, but being a '92  (OBD1)  I can display trouble codes by jumping the A+B terminals on the ALDL connector with my trusty paper-clip  

You're right about the fuel pressure test though, I'm going to have to buy a fuel pressure gauge tomorrow after work if I can, and hook it up to the schrader valve on the fuel rail to see if it maintains fuel pressure after the car's been turned off.

Still, if it was the regulator itself that was the problem, wouldn't I be seeing fuel in the regulator vacuum line (caused by a leaky diaphram) ?  The vacuum line is completely dry.  Are there any other visual signs that the regulator might have gone south?


LT1*C42009-08-10 19:54:19

The regulator doesn't have to be leaking to be defective. It could simply be stuck/sticky, and either allow too much pressure, or not enough. You could also have some trash in the line, or some other restriction, that can cause a reg. malfunction.
You may want to have a look at the sparkle plugs, too. That may give you an indication of too much fuel. I'mma thinkin you may have a flooding issue, with the smoke you saw, the fuel smell, and the rough running at times. It sounds as if you had this issue before replacing the infectors, so that might run out those, but you could have too much fuel pressure, whcih can overcome the infectors.
A weak spark can also cause these problems, but, as you say, that usually doesn't "fix" itself after driving...
Adams' Apple2009-08-11 19:50:17

My $.02
 
An opti. going out wont do it it at any specific RPM, mileage, rhyme or reason.
That being said; a weak opti. would not burn all the fuel and give the symptoms you stated...ie. strong fuel smell, runs good sometimes, stumbles and stutters, and then returns to operating normal...all that until it dies.
This being an opti. ready to die, or one needed a tune-up inside.
Of course; a vacuum leak can give the same symptoms...though a vacumm leak is not always intermittant (to the point where where it runs fine for days then has problems).

I am NOT stating this is your problem....what I am stating, these are symptoms of a possible failure looming.

When was the last time you put a new cap, rotor, or other parts in the opti.???


What you described is EXACTLY how my opti. died....ran rich, stumbled, no codes,...then ran fine.
Mine would also run good in open loop, until it warmed up, went into closed loop, then would stumble and stutter....it also ran OK on the highway with cruise control ON.
Also; if I feathered the accelerator, nobody would of known ther was a problem.
My dyno-tune guy loves LTx's, no matter what vehicle they are in...I have seen several times him do an "Opti-spark tune-up" vs. a swap and the vehicle returns to normal....seen it with my own eye-balls.
His only criticism obout an opti. unit is; location and accessability.
He stated that if the opti. unit was as acessible as an HEI, the opti. would be as inexpensive as a HEI.

[QUOTE=Adams' Apple]You said you had bought a set of infectors, but have they been installed?[/QUOTE]
Infectors?....man, I hope thats a typo...because if it isnt, it sure is the problem!!...LOL
Hey, we can get Jon @ FIC, and build those BoschIII injectors, especially for our LTx', and call them:
"LT1-4-5, Speed Infectors". 
You should be in advertising if you arent already...LOL  



As stated above; I am NOT presenting this as an accurate diagnosis, just making sure you dont rule out the opti. as a possible culprit.


Good luck...when I get back to my house I think I gots vacuum leaks to find on my automobile.






Jim

[QUOTE=Strats-N-Vettes]His only criticism obout an opti. unit is; location and accessability.
He stated that if the opti. unit was as acessible as an HEI, the opti. would be as inexpensive as a HEI.
[/QUOTE]

Well, there is an option...DigiSpark!!!


And, no..."infectors" is NOT a typo...that's what I call them, for more than one reason...

Infectors

I like that name.............

Ever figure out the problem?



Jim

Unfortunately not.

I went ahead and replaced the coil (the old one was off my LT1 Firebird but was functioning at the time I took it off to put it on my Vette) with a brand new one just so I could be 100% certain it was not the coil.  No luck.  I'll just keep the extra coil as a spare.

Checked the fuel pressure with a gauge and it held steady at about 35psi and retained that pressure for about 30 minutes after shutting off the car so it appears the regulator is  still good as well.

I've been driving the car the past few days and never again has it given me any problems starting.  Nothing.  I just can't figure it out.  There aren't any codes stored and no explanation at all as to why it stopped and refused to start that one day.

The "stumble" is still there though.  A few things I've learned though in the past few days are:


*  Any time the car sits (shut off) for more than 10 minutes, the stumble returns

* If I let the car idle until temps reach about 75-80' on the digital gauge, the stumble never happens

* If I start the car and drive off right away pushing it pretty hard (not smoking the tires off the line hard, but pushing it pretty hard) the stumble never happens



So there you have it.  Never figured out why it stalled and stopped that one time but its never happened since.

My original "stumble" issue still remains.  Car starts perfectly fine first time every time and after about 1 or 2 blocks of driving, I get a part throttle stumble that lasts anywhere from 5-10 seconds then disappears all together never to return (until I shut the car off for more than 10 minutes)

I don't know what else to check.  Everyone keeps telling me it's the optispark but I just can't see an optispark "fixing itself" 10 seconds later after stumbling and then running perfectly afterwards.

I'm lost.
LT1*C42009-08-18 09:31:40

Kinda sounds like it may be an O2 sensor flakin out...
Would be good to be able to get some live data on it when it starts messin up, but that's not always possible....