1990 corvette runs rough

[vetteboy86]

I did this once on my old firebird. Got the timing all screwed up after putting an HEI on and replacing the old points. What I did to get it "close". Providing you have the plug wires back correctly. Number 1 plug, trace that back to the distributor and mark which terminal it goes too. Remove # 1 spark plug. Turn the motor over by hand, by placing a ratchet and appropriate socket on the crank pully nut. Put your finger of the #1 plug hole, while a buddy turns the motor. You will feel pressure building up on your finger, keep turning the motor until the moment that the pressure goes away. Now adjust the distributor so it is point at the terminal you just marked that goes to #1. Put everything back. Put the timing light on and see where it is at.

 

[vette 53]

thank you,, will try that also,,,

 

[doggiedave]

Just my .02, did you disconnect the tan wire that goes to the spark control before setting the timing? it is located near the brake booster and has a connector. a must do to properly set timing otherwise at idle the timing will be advanced.

 

[chevylu]

1990

Perhaps these pictures from my 1990 will help you:

How my distributor cap is numbered (oriented from driver's side)

Picture of wires on cap (oriented from passenger side)

Picture of rotor mount pointing to pencil mark on intake prior to pulling distributor. When you re-insert distributor, the rotor mount must point to exactly the same place. You may have to turn the drive slot in the bottom in order to get it to fall into place correctly.

The EST connector must be disconnected to time engine. Below windshield wiper motor near brake booster.

From 1990 Factory Service Manual

 

[vette 53]

okay from what I can see there is no data coming from the ccm,,, I understand that controls the security and the the injectors correct?

does any one know what the cost would be?
please help,, hopefully fixes the car,,, would love to be able to drive it soon...

 

[vette 53]

okay put in new dist,,complete,and runs great,,seems the dist, when it was rebuild was not done right and it has been causeing all the problems, but now I can just enjoy driving my vette,, thanks guys for your support,,,

so this is what I did
new ecm
new injectors
new plugs
new wires
and new dist, complete

results runs like it should,,,hurray,,,,

 

[Hib Halverson]

When you tried to set the timing did you first read the service manual to understand how to do it?

If not, you need to disconnect the EST timing connector in the wiring harness before you try and set the timing. If you don't do that, when you put the timing light on the index, what you see won't make a lot of sense.

Now, if the dist is a tooth, off you need to address that first. Rotate the engine by hand such that you set TDC #1 at 10 deg adv. Drop the dist. in such that the rotor will be even with #1 in the dist cap once it seats on the intake manifold. If the dist. won't drop all the way down, bump the starter a bit until the oil pump drive indexes and the dist. seats.

Fire the engine and set the timing per the FSM. Reconnect the timing connection then clear codes.

 

[KANE]

I had the intake off of my car apart for a couple months and when it came to the distributor I could not remember what position it was in (now I take notes and pics before and during long projects). It turned out it was 180 deg off. It may seem like a big deal but it isn't. Take your time. Remove the distributor cap (probably screws onto the dist body). Mark on the distributor where the rotor is pointing with a marker for reference. Note where the distributor is positioned (it is going to be about where it is now when you are done). Loosen the clamp enough that you can slide it off of the distributor shaft. Lift the distributor out of the engine (it only has to life out about 2 inches, I can't remember if the two electrical connectors have to be disconnected to get enough travel to lift the distributor). You will notice the rotor turns slightly as you lift the distributor. Turn the rotor 1/2 turn (this is the 180 degrees). Now lower it back into the engine. Assuming the distributor went back in properly the mark you made for reference should be 180 degrees from where the rotor is now. Tighten the clamp. Install the cap again. Use your timing light to set the static timing.

I make three marks when I remove the distributor. I use little colored stickers to mark the position of the rotor and distributor relative to each other and where they were relative to the block.

• First sticker goes on the wiper motor.
• Second goes on the distributor.
• Third goes on the rotor.

When all three stickers are in line with each other- it's pretty close to being set. Then, I drag out the timing light.

 

[vette 53]

I make three marks when I remove the distributor. I use little colored stickers to mark the position of the rotor and distributor relative to each other and where they were relative to the block.

• First sticker goes on the wiper motor.
• Second goes on the distributor.
• Third goes on the rotor.

When all three stickers are in line with each other- it's pretty close to being set. Then, I drag out the timing light.

as in my last post,,, all is well,, the problem ws the guy who rebuild my dist. didnt do it right, I bought a new one, and all is well,,, thanks for the imput though,,,,

 

[G Winter]

persistence pays off. enjoy.


Glenn