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350 TBI keeps retarding itself

Kocher93

Kocher93

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I have a 89 350 tbi and it keeps retarding itself. I thought it was skipping on the chain, but isn't. I'll set it one day and itll be retarded later by a good amount. Any idea on the cause? and no the dist isn't loose.
 
Are you setting the timing to 0 with the bypass wire disconnected? Then turn truck off, connect wire and clear codes. Restart and when warm should be around 16 degrees advanced.
 
Yea, going through all the steps. I Disconnect and set, turn it off and reconnect. I've also left it off the battery overnight. When it starts up and warm its around 16 and over the course of a couple of days itll retard itself about 20 degrees to a -4. I've set this trucks timing probably close to 10 times in the past month.
 
Mark the dizzy and see if its turning its self
 
District gear stripped? So every time you set the timing, you loosen the hold down bolt and turn the distributor and tighten the bolt back up? Can you turn the distributor by hand after the hold down bolt is tightened?
 
Kocher93 said:
Yea, going through all the steps. I Disconnect and set, turn it off and reconnect. I've also left it off the battery overnight. When it starts up and warm its around 16 and over the course of a couple of days itll retard itself about 20 degrees to a -4. I've set this trucks timing probably close to 10 times in the past month.
Click to expand...
30 seconds without battery power is overkill for clearing codes.

This is not possible from the ECM. There is no spark learn in these. Even if you had horrible knock counts or somehow failed knock? Max retard is 8.10 degrees.

So either distributor is loose? Or something is moving, usually if something moves it's not consistent and resetting timing won't help.

That is strange, you sure the distributor is tight and not moving?
 
Yea ive marked it and it hasnt moved and its a brand new dist. Could a new double roller skip?
 
If you really keep advancing the distributor, eventually the wires will be pulled tight. Maybe there is some weird wear or some dirt around the distributor base preventing it from holding tight in the position you need. Maybe you can bend or reinforce the hold down bracket.

You could check the pick up coil and see if it's moving around.
 
Could be your knock sensor too. It's on the side of the block near the starter. Might even be your EST module.
 
Lol oh boy... Talk about your can of worms! Yes a knock sensor can retard the timing. Thats it's job. You shouldn't disconnect it tho. It senses detonation in the motor and can save your motor from destroying itself.
 
y5mgisi said:
Lol oh boy... Talk about your can of worms! Yes a knock sensor can retard the timing. Thats it's job. You shouldn't disconnect it tho. It senses detonation in the motor and can save your motor from destroying itself.
Click to expand...

You'll also get codes if the knock sensor circuit fails to function. It will intentionally cause knocking to listen for it, and if it doesn't it will set a CEL.
 
Knock sensor can only retard 8.10 degrees in this ECM. And I'm pretty sure it can't do it at idle?

Russell is right about the Knock test, it's called a ESC test and adds 11 degrees and looks for knock counts, if it does not find any it adds 22 degrees! :eek1:

I can remove this test, it only causes a little havoc to a stock motor, but man you should here high compression built motors RATTLE when it comes on. Even worse on stock or close to stock motors that have eBay and fancy name off the shelf chips that add extra timing without removing the test. If you have an aftermarket TBI system with no knock sensor? The test still runs! They just turn off the code so you don't know it failed, test still runs... motor still knocks...

:whistle:
 
My guess is you have a cheap timing light that is inaccurate. If you want to drive here to Fremont one evening (or even on a weekend) I have a high dollar digital Mac timing light that I KNOW is accurate to within .1 degree.
 
Are you using a dial timing light or a basic one? I can see the dial light being inaccurate, but there isn't much to go wrong with an old school basic one.

Any chance the distributor gear has a stripped tooth or two on it?
 
You know thinking about it there was some metal shavings on my old dist and it was hard as hell to get out. Think my cam is missin a tooth or two?
 
Kocher93 said:
You know thinking about it there was some metal shavings on my old dist and it was hard as hell to get out. Think my cam is missin a tooth or two?
Click to expand...

Highly doubt it. Like I said, the offer still stands if you want to drive it up here on a weekend (weekends are easiest for me) and I can check it out for you.
 
Thank you for the offer 4x4 but I took it all apart 2 days ago, new dist and cleaned everything and a new hold down. It hasn't done it since? I don't know what was wrong. I'm pretty dam positive that it wasn't spinning because I marked it. Anyway thank you. You go to hollister at all?
 
Glad you got it fixed (whatever it was).

I haven't been to Hollister in a couple years now.
 
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