4-7 firing issue; posting for a member

[scottfab]

Originally Posted by XfireZ51

.... snip....
The DIS should survive firing even a shorted coil because it is "current limited". Obviously the engineers that designed the IM took into account contingencies and malfunctions and safeguarded the IM from them. If all else fails the IM is what provides the "limp home" capability since it is essentially a CO-ECM. That's also what makes it difficult to substitute for without some great expense. Anyway, I bring this up to illustrate the ruggedness of the DIS module. Its probably the last thing to consider when having ignition problems since everything else will fail before the DIS does.
.... snip...

I wouldn't take this to the bank. It'll bounce.
I have a DIS from Mark H that I've examined in detail.
Any current limiting the DIS has still generates significant
heat which takes out the output FET(s) eventually.
If anyone would care to setup an experiment demonstrating
the DIS working into a dead short I'd be very interested.

[Blue Flame Restorations]

He could use a DIS checker if he has access to one.

[XfireZ51]

Originally Posted by scottfab

I wouldn't take this to the bank. It'll bounce.
I have a DIS from Mark H that I've examined in detail.
Any current limiting the DIS has still generates significant
heat which takes out the output FET(s) eventually.
If anyone would care to setup an experiment demonstrating
the DIS working into a dead short I'd be very interested.

Ask Marc H how many DIS' he has had to replace over the last 12+ years.
Also what's the likelihood of a coil going dead short before it goes weak?

[A26B]

Originally Posted by Blue Flame Restorations

He could use a DIS checker if he has access to one.

I could use such a device to check out a couple of DIS modules.

[scottfab]

Originally Posted by XfireZ51

Ask Marc H how many DIS' he has had to replace over the last 12+ years.
Also what's the likelihood of a coil going dead short before it goes weak?

I don't think that many fail but they can be killed.
I've personally never seen a dead short on a coil primary side.
Wires can get pinched though. The failure on the FET will be different
depending on heat vs voltage pop through. If a short is to a 12v supply the
N-channel will open up. Or if an arch from the secondary get into the primary same thing. Biggest failure is heat damage due to poor heat exchange into the plenum. I sure hope his failure is not the DIS.
Other things are cheaper.

[Blue Flame Restorations]

Originally Posted by A26B

I could use such a device to check out a couple of DIS modules.

Jerry, the unit was Tyler's. We used it while getting the 88 EX5023 to run. Give him a shout.

[Jason 91]

First off, I would like to thank LGAFF for posting this up based on our conversation Saturday night. I'm the member who is having the issue and I appreciate the conversation and ideas on this.

I loved driving this car when it ran well, but this issue has been very frustrating. Mainly because I don't have the expertise to figure it out on my own and I've taken the car to local shops relying on their know-how or lack thereof.

This started awhile back when a couple of the injectors were marginal and it was suggested that I replace them which I did. The car actually ran worse after the injector change so the coil packs and spark plugs were changed at my request, but this didn't make a difference. I finally picked up the car from the guy who couldn't pinpoint the real issue.

The car was due for an emissions test and I took it in. It failed, of course, and I should have known it would have.

From here, I took it to a local Chevy dealership north of Denver which prides itself on Corvette sales and service. They quickly diagnosed it as a bad ignition module and said that they double checked everything because these can't be found.

I called Kurt at White Racing who suspected that this wasn't my issue and was thinking it was a bad ECM. So he shipped the ECM and this didn't fix the issue. He sent me the ignition module which didn't solve the issue either. Kurt accepted returns on both of these items, as a note.

When I went to pick up the car, I talked to the technician and service advisor who assured me that they checked everything possible that they could think of twice. At this point, the dealership made it clear to me that I needed to pick up my car and pay for the bill since they had my car now for over one month (due to back and forth trying new parts and locating an ignition module) and there was nothing more they could do for me until I found a good ignition module. In fairness, I'm sure that this is a standard practice given the time they had the car, but it simply added to the frustration.

I called and requested an emissions waiver on the car given what I had spent to try to get it running right and the ignition module availability. I was denied and told that this car is common and there are parts everywhere. It was even asked of me if I had tried AutoZone.

I'm going to try another repair shop here locally and see if I can get someone to work with me through this issue. I’ll pass along your collective thoughts. And if anyone has any ideas on local places to use, please let me know. Like I said above, I just don’t have the expertise and haven't found a consistently good technician since moving to Colorado several years ago.

This has been very frustrating, as I'm sure you can imagine. Thanks for the ideas and support here.

Jason

[XfireZ51]

Jason,

Save ur money and ship it to Chicagoland. The FBI will take care of it.

[Blue Flame Restorations]

Originally Posted by XfireZ51

Jason,

Save ur money and ship it to Chicagoland. The FBI will take care of it.

Best advice you'll get. They can get it fixed.

[scottfab]

I don't know. I think there's got to be a cheaper way to isolate and fix this besides shipping it half way across the country.
If you're willing to systematically go through a set of steps and learn to do somethings yourself, you'll not only learn along the way but you'll pick up a few tools to continue fixing things later.

So you have to ask yourself. Do you want to dive in and get you hands really dirty?
If not start looking at shipping charges or be willing to drive it to the windy city.