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Mar 13, 2009 | 06:17 AM

Epimax

Thread Starter

Burning Brakes

Joined: Dec 2007

Posts: 1,068

Likes: 6

Start/No start

Hello,
I've got a problem with my 93LT1. Yesterday, while leaving a parking lot, the engine just shut off. After a few minutes, it started again but died after about minute or two. (I just sat there and let it idle, for fear it would shut down on me in heavy traffic...)
Anyway, it would start, and then shut off immediately. After a few more tries, you could just tell it wasn't going to fire.
Well, the tow truck arrived, and we couldn't get it on the flatbed due to my recent lowering project, and the fact he didn't have the equip. to handle a lowered car. So, I try to start the car and it fires right up. Let it idle for around 10 minutes, and say WTH and made a run for it.
Got a mile down the road and it shut off again. I wound up pulling it to a safe place and there it sits.

Here's my list of suspects..
Fuel pump
fuel filter
ICM
IAC (It didn't hesitate or stumble, ran fine-then quit)
ECM? Hope not..

The opti/plugs/wires are just a year old...
Ideas???

Thanks!

Mar 13, 2009 | 07:18 AM

pcolt94

Le Mans Master

Joined: Jan 2006

Posts: 5,620

Likes: 206

From: Orlando FL

You could listen to the fuel pump run for 2 seconds as you turn the ignition key to on. This could give you an indication the pump is at least running.

The problem sounds like a bad ICM (if you lucky). Substitution is the only real way to determine if it is bad. Don’t think testing on a heat related problem will tell you anything reliable.

The ECM could definitely could be the problem. They sure do have a reputation on the 93s causing all sorts of weird problems. However before I point to it I always look to see it there are any other symptoms or strange indications. Many times with a bad ECM multiple symptoms will occur like SES light or any other lights coming on.

Its tough to diagnose it on the road. Finding out if you are loosing the injector pulses or spark is easy in the shop. But if it only happens on the road you might have to come up with a plan to at least determine if you are in the spark or fuel area.

Mar 13, 2009 | 08:03 AM

fc_soldier

Melting Slicks

Joined: May 2006

Posts: 3,385

Likes: 4

From: King George VA

I had a 3rd gen that would die while I was crusing down the road. I would start it up right after and it would be a no go. I would wait 5 mins and it would fireup but die 2 mins later. Then I figured out if I hit the gas real hard after I started it, it would run as long as I had the pedal down. After thinking about it and realizing cause and effect I changed the fuel filter. Sure enough it was the filter that was doing it. At WOT I was pushing right thru the clog and allowing gas to get thru. But when cruising or idleing it couldn't get fuel. My .02

Last edited by fc_soldier; Mar 13, 2009 at 08:29 AM.

Mar 14, 2009 | 05:19 PM

Epimax

Thread Starter

Burning Brakes

Joined: Dec 2007

Posts: 1,068

Likes: 6

93LT1.
Opti/plugs/wires all 1 yr old...

Update:

Well, I finally got the vette home and I'm starting to look at it now.
So far, the fuel pressure is within limits: 42psi and holding...I can hear the fuel pump priming with no problem..

I'm going to check for spark next....
I'm also going to pull the codes and see what's going on there.
Any/All suggestions welcome...

Bring'em on!

Last edited by Epimax; Mar 14, 2009 at 05:22 PM.

Mar 15, 2009 | 12:29 AM

jfb

Team Owner

Joined: Mar 2001

Posts: 54,124

Likes: 30

From: Cincinnati, Oh USA

When it won't start, that is the time to do some diagnostics. Engines require spark, fuel, and air to start and run. Use a timing light to check for spark and spark at the right time while cranking. Measure the fuel pressure and see if the pressure will hold. If it bleeds down rapidly, you have leaky injector/s or a defective check valve in the fuel pressure regulator. Get a noid light at a parts store and see if your injectors are being pulsed during cranking. Remove the flexible connector from the air filter and see if it will start. Clogged air filters don't pass much air.

Mar 15, 2009 | 10:31 AM

ragged claws

Pro

Joined: Sep 2003

Posts: 655

Likes: 2

From: Rio Vista ca.

Remove the flexible connector from the air filter and see if it will start. Clogged air filters don't pass much air.[/QUOTE]

Hey David,

The above got me thinking. I think you said that you did a cut-lid/K&N air filter mod recently. Any chance you could have over oiled the K&N and "greased up" the MAF? If so, some MAF cleaner spray would be a simple fix. Of course nothing is that easy.

Kim

Mar 15, 2009 | 10:44 AM

psychodiagnostik

Le Mans Master

Joined: Jan 2005

Posts: 6,115

Likes: 3

It sounds like either the coil or ICM to me. When my opti died, the engine would start and run, but it ran badly.

When my ICM died it did exactly what your car is doing. I think there is a way to diagnose with a multimeter whether it is "switching" or whatever it does, but I think you can only accurately diagnose it when the no-start condition is actually going on. If it's failing intermittently, diagnosing it can be tough.

Mar 15, 2009 | 11:32 AM

Randy93

Melting Slicks

Joined: Feb 2005

Posts: 2,135

Likes: 0

From: Sebastian Florida

St. Jude Donor '06

Failing FP or bad ICM or coil, ECM's are not that unreliable on the 93. Mine is rebuilt, but the previous owner replaced it. 93's are known for is broken wires, I have seen lots of posts where people started thowing parts at the car and it turns out it was a broken wire. Take the FP out of the car and jump the relay while the FP is in a bucket of water or fuel and see how long it will run and then work your way forward till you find the problem.