I don't wanna join a Cheby forum just to ask one question.Hopefully I won't get flamed too bad,here.

I'm trying to help a friend time his tahoe after he did some top end work. He pulled his intake manifold so,he had to pull the dizzy,too.

1993 Tahoe
TBI 350
Auto

The symptoms: While underway,the truck seems to run fine.It's when we decellerate to a stop,or low idle,the truck wants to die.Or,does die.

Also,when we first start the thing up,it lopes at a very low idle for just 10 seconds or so,then something advances the timing and the engine revs to a steady idle. At this point,if you drop it into gear,it wants to die.

If you can keep it running,and get going,it runs good.Until you come to a stop.Then it wants to die again.

A brand new reman dizzy didn't do a thing to fix the problem. It acts the same with the original dizzy as it does with the new dizzy. Besides,the truck ran fine before he pulled the intake manifold off to simply replace the intake gaskets because of water leaks. Thats what he told me,anyway.
I wasn't around for that part of the job.

We're not timing it right,or,not installing the dizzy right.I think,anyway.

So,I put #1 TDC. I simply dropped the dizzy in so it engages the oil pump shaft and,the rotor is lined up with #1 post on the cap.

I disconneceted the tan wire,black stripe on the firewall to inhibit timing advance.(per chilton's)

I start the engine and let it idle down,warm up a bit,then I set the timing a 0 degrees BTDC.

Shut it down,tighten the dizzy clamp,reconnect the tan wire,start it up and it runs like crap.Unless your driving down the road.

Anybody wanna save me from joining a Cheby forum?

 

take it to the dealer, they will hook it to their reader, and move the distributor to the correct place.............you are probably one tooth off, even though it looks correct
how do I know?
had the same issue with a blazer with a leaky manifold, fixed the leak, put it back together and it ran just like you described
cost about $35 and only took about a half hour
good thing about it was the leak repair was a lot cheaper than the dealers price of $450
btw, there were two other Blazers in the dealers shop to get the leak fixed, fairly common problem

 

One tooth off,huh? Ok..I'm going to re do the dizzy drop. I'll favor one tooth clockwise and see if that helps.

He can't afford to go to the shop.He couldn't afford the reman dizzy either,but he really cant afford to not make it to work. You know,struggling like everybody else.

 

Seems to me that your timing proceedure is spot on. I think I would look elsewhere. Are you sure the plug wires are on right? Have you checked for vacuum leaks? Is the SES light on? If so have you checked for trouble codes? Are all the sensor plugs around the throttle body and manifold pluged on? Are any ground wires at the manifold properly connected?

 

Ditto. Check all your vacuum lines. Those engines are stupid-simple. (I used to own one.) There are only 4 vaccum line connections in the entire engine bay. Manifold/TBI to brake booster; Manifold to EGR; TBI to EVAP canister; TBI to PCV.

At that age, most if not all of the rubber boots on the plastic factory vacuum lines are shot. Probably also the plastic vacuum lines.

Additionally, the intake gaskets on the 350's, with the newer manifold style, are NOTORIOUSLY easy to screw up when laying the manifold back down on the lifter valley. You may have to re-do the gasket job.

Note that if the battery connections weren't pulled (and thus giving the ECM a reboot), the engine MAY be trying to run on old engine data, that included compensation for a leaking intake (assuming small vacuum leak), which is now no longer present.

-blaine

 

Thanks for the help,guys. I just got back from over there. I pulled the air cleaner assembly off,climbed up on the passenger wheel to access the dizzy and I find a Vac hose laying there Not connected. It was one that fits on a nipple directly on the back side of the Throttle body. I believe it was the manifold to egr.

Arg...That's the problem with coming in late in the game,I guess. Hard to know whats been done and not been done. It runs Great now. Especially with the new reman'd dist..

Thanks again.

 

Glad to hear it was simple.

> So, I put #1 TDC.

Is the Chevy#1 on the driver's side?

 

Yes. The numbering goes ACROSS the engine, not DOWN. So you have the "odds" on the driver's side, and the "evens" on the passenger's side. Firing order is 1-8-4-3-6-5-7-2. (can you tell how many times I did plug wires? )

-blaine

 

the deceleration issue makes it sound like you need to concentrate on the EGR...mebbe the vac line going to it.

As for the timing issue, sounds like you got it going in the right direction with the rest of the advice.