I am experiencing an issue with setting the timing on my Corvette. After following the instructions for setting the base timing, which includes warming up the engine, shutting it off, disconnecting the EST wire, starting it up again, setting the base timing to 6 degrees TDC, shutting it off, reconnecting the EST wire, and disconnecting the battery for 30 seconds to clear the codes.

When I attempt to start the engine after setting the base timing, it backfires and won't start. To get the car running again, I have to twist the distributor until it runs reasonably well. However, this is not ideal. When I take the car out on the road, it misfires under load and has very little power, indicating that there is a problem somewhere.

Has anybody had an issue like this?

This all started from a no-spark issue where I replaced the following:
Distributor cap (Pin between the coil and rotor had disintegrated)
Coil
Rotor Button
(Still no Spark)
Pick up coil
(Running but, like crap)
Spark Plugs and new leads (Found a bad spark plug) and,
The ignition control module in the HEI Distributor

 

This is sounding like you have a pickup coil issue.
I had the same symptoms when I replaced my pickup coil with one that is supposed to work, but ran terribly after EST connected.
Posted here and found a few members with the same issue with the brand of pickup coil.
Standard Ignition LX-320 Pickup coil
Replaced with AC Delco D1945X and now runs normal.
What brand pickup did you install ?

 

It backfires? Through the intake? Make sure all the plug wires are hooked up correctly. 18436572.

What was wrong with the "bad spark plug" you found?

Are you able to do a compression test on this engine?

 

Take a look at your Balancer see if it is flush with the hub or if there is any rubber hanging out, your outer ring may have turned a bit throwing the timing line way out. It's a hunch since you said it ran you timed and now its Popping

 

Im with 86...My money is on that pick up coil... lol

 

To verify your timing marks:

Remove #1 spark plug

Insert a long screwdriver in that hole

Have someone slowly turn the engine over by hand while you feel for the top of the piston with the screwdriver

When piston is at TDC verify timing mark is at 0.

 

Hi All,

Thank you all for your help and suggestions.

Well, I just got my car back from the mechanics, and it's still not fixed. The trouble is, I live in regional Queensland and finding a mechanic who can work on a 35-year-old Corvette is a little bit difficult. All the shops around town can't even run a scan tool because of the age of the vehicle.

They tell me that they tried everything they could even getting on here trying to find solutions for what's wrong with the vehicle. Its now down to the pick-up coil or the ECM.

Things that they did:

Fixed several vacuum leaks and replaced all the gaskets for the intake manifold (No longer hunting at idle)

Checked the Harmonic Balancer and proved to be ok

Eliminated the knock sensor spark control being an issue

So now it runs nice and smoothly with the EST cable disconnected and the timing set at 6° before top dead centre. As soon as this is connected it advances the timing too far.

Unfortunately, in Australia, you can't go to your local parts store to get what you need. Everything has to be online. There are some parts suppliers in Australia, but they can be very limited, and I have to get what I need from the USA.

@Agent 86. To answer your question. It was the Standard Motor Products so probably the LX-320. I have been trying to find an AC Delco pickup coil but with no luck or way too expensive.

I want to eliminate the ECM but I don't know how to go about it.

 

I would suggest first checking the Memcal chip in the ECM to see if it's stock or aftermarket. There's a small aluminum plate on the ECM held in place by 2 screws. Just remove those screws, take off the plate and the Memcal chip is right there. If it's stock, there will be a 4 letter code printed on the chip. Something like APYP (that's the code for an 89 6 speed manual. ) That's also referred to as a "broadcast code".

The ECM is located underneath the glove box. You should be able to drop it down in the footwell area.

 

If you have the LX-320 coil, 99.999% sure it's not going to work even if your ECM is good. Enough people have experienced that coil (including me) that there's something inherently wrong with that part.

Can you get stuff from Rock Auto? If so, order a D1945X.

 

I apologise for the hijack.....
is there a place to lookup those 4 char values? My C4 is running rough and the ECM is aftermarket. My memcal has ACtU on it. I wanna verify what those letters should tie back to?
Sorry. It is a T. And using your link i have the corect chip. Thanks.

 

What year is your C4? Below is a listing up to 1995, but there's no ACBU in it. By "aftermarket", I assume you mean factory replacement aftermarket?

https://www.corvettesalvage.com/c3-c...des-1980-1995/

 

Thank you C4industries. That is a good piece of info to know about. The thing is the car was running fine up until I lost the spark when the small button under the distributor cap disintegrated and I have had no end of trouble since.

 

Thank you ULTM8Z. I have been trying to get the ACDelco version but being in Australia. I am pulling up zeros.

 

Check out WVE 4P1209 on Ebay or other Vendors, looks identical to AC Delco D1945X
https://www.ebay.ca/itm/185669134700...mis&media=COPY

 

Corvette Central sells pickups, I doubt they sell ones that don’t work with our cars.
Probably any other brand than Standard Ignition LX-320 would work. 😆

 

Thank you for the heads up Agent 86.

 

Do you still have the old pickup coil ?
Should read about 800 ohms.
My old pickup coil tested good when cold, and no continuity when hot.

 

Yes, I still have the old pick-up coil, which is cooked. Reads 0 on the ohm meter. With having no spark after the pin between the coil and rotor had disintegrated, I traced it to the pick-up coil. The Corvette fired up after that and I went on a tangent thinking I had stuffed up the timing. Everything in the distributor has now been replaced. For what that cost, I would have been better off buying a new dizzy.

Anyway, I have put this to bed for a while as I am going in next week for a major operation and will be out of action for a while. So, she will be up in the shed on the battery tender until I can get to it again.

Thanks again for everyone’s help on here. I will report back once I have the new coil installed.

 

When you twist the distributor to make it run, are you retarding it or advancing it?

Are you sure you did the base timing on cylinder 1?

 

Apologies for the late reply. Yes advancing it from what I can gather. And on cylinder 1. I have been through the loop so many times with this.

On another note, I finally found a NOS ACDelco pickup coil. Being in Australia this isn't easy, to say the least.

https://www.ebay.com/itm/356441855120