Pops out the exhaust

[Justin Fleming]

Guys, I just had a 1988 tbi delivered from cali to Michigan. I knew there were likely some issues so I am looking for a little help.

When the truck showed up the dist. was loose. So I set the timing at 0 with the wire unplugged. The truck sits and idles just perfect no missing at all. I did double check the plug wire order, there is new plug wires new plugs new cap and rotor. When I free rev the truck it pops out the exhaust. The truck is not license and I have not received the title as of yet so I have not taken it down the road.

Any ideas??

 

[76k5blazerr]

Your timing is not right

 

[Justin Fleming]

It is set at zero and when I plug in the connectors, shut truck off, dis battery, reconnect and start the truck it is running at about 18-20 degrees

what part is not right or can your expand to give me a hand.

I have been doing some reading and I wonder if it has something to do with the air pump?

 

[76k5blazerr]

What are you using to check the timing, it should be set between 8 and 12 degrees before TDC if your going by the timing tab and harmonic balancer. It sounds to me like your timing needs to be advanced.

 

[Justin Fleming]

What are you using to check the timing, it should be set between 8 and 12 degrees before TDC if your going by the timing tab and harmonic balancer. It sounds to me like your timing needs to be advanced.

The sticker on the core support says zero tdc in (P) park or (N) neutral.

I was going by the timing tab, and wire unplugged like the stick states.... Is that not the case?

 

[4xcrazy]

That is how you time it. Sounds like excess fuel, heck I can even get the '05 Avy to pop out of the exhaust when going downhill and lower the gear at a certain rpm to road speed range.

Does your truck have cats on the exhaust at all?

 

[Justin Fleming]

That is how you time it. Sounds like excess fuel, heck I can even get the '05 Avy to pop out of the exhaust when going downhill and lower the gear at a certain rpm to road speed range.

Does your truck have cats on the exhaust at all?

yes there is a cat, its the y-pipe to cat, then muffler and splits to duals, you think I can get away with 4 degrees base with wire unplugged

 

[4xcrazy]

It's not going to hurt anything, I hve seen some earlier years I believe that said to set at 4 and I've read about some guys on here doing it. Shouldn't hurt, if it's not right the computer will retard the timing as needed anyways.

Not sure though, since it's all typed out stuff what you are considering "popping"

you're gonna get some muffled exhaust back firing through the exhaust when you snap the throttle on and off from a higher rev. Obviously there is a point though where it is too much. Difficult to determine what you have without hearing it.

 

[4X4HIGH]

An exhaust leak will make the exhaust "pop" when on decelleration.

 

[rdn2blazer]

Your timing is not right

this. And don't pull out so far, at least she can't get pregnant that way doin it back there

 

[Justin Fleming]

the pop noise is excessively loud, like the neighbors two down hit the floor....

 

[diesel4me]

Maybe a sticking or leaky exhaust valve?....fuel being ignited in the catalitic converter ?...could be a dozen different causes,or a combination of some..

 

[Stomis]

First off you are setting the timing correctly. Limp wire disconnected, you shoot the timing to 0-4* depending on the year, plug the wire back in and the computer will advance the base timing to what you would think it should be. So dont screw with the timing, youve got it right!


The computer controls the timing so you need to make sure that the parameters controlling it are correctly inputting wtf is going on. In other words make sure your MAP, TPS, etc are functioning properly. In fact even if you are running too rich and getting a fuel pop from air hitting hot fuel in the exhaust you should still check sensors etc.

A better description of what is going on when it takes place will help. Just winging the gas in park and getting a loud pop sounds like an exhaust leak and a rich condition. My camaro used to do it and yes it was loud as all hell.