ciffer
1/2 ton status
I am trying to check/set the timing on my 88 suburban. The emissions sticker mentioned that I need to disconnect something to get an accurate reading but I was not able to figure out what needed to be disconnected.
CK5
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timing a TBI 350
- Thread starter ciffer
- Start date
Over by the steering column under teh hood, there is a weatherpack connector with just one wire in it, that is sorta left out of the harness loom. Light brown with black trace. Disconnect it with teh engine running, and if it stumbles, but keeps running, you found the right wire. Its the electronic timing advance wire, that must be disconnected to set base timing.
ciffer
1/2 ton status
cool, i'll take a look when i get home.
I like to set TBI engines a few degrees advanced myself, like 3 or 4 degrees. I find it helps with power a bit, as the TBI timing tables are pretty conservative.
Yeah, I always bump the base timing as well.
Martin
Martin
79rustyk10
3/4 ton status
I am not trying to start a giant debate, but I have tried advancing the timing on TBI engines before with no noticable difference. Nowadays I just go to 0 deg.
I didn't say I've noticed a vast difference, I just said I always bump it.
Martin
Martin
Technically speaking, if the knock sensor loop is working correctly, it shouldn't make any difference at all. The ECM should be advancing the timing until it receives word from the knock sensor loop that there is pinging going on, and back the timing off.
That said, I don't think the knock sensor stuff always works like it should, so advancing the timing does seem to help with some engines
That said, I don't think the knock sensor stuff always works like it should, so advancing the timing does seem to help with some engines
ciffer
1/2 ton status
the engine in my 88 has knock sensors?
lectric80
3/4 ton status
Most likely a single knock sensor in an 88. The dual sensors didn't start until later.
ciffer
1/2 ton status
wow, chevy started pretty early with the knock sensors. does it just pull timing?
lectric80
3/4 ton status
It allows the computer to back the advance off if the engine starts pinging, at least in the rare cases it works right. I know my 88 Astro with the 4.3 liked having a base timing of about 3*, which woke it up a bit. It wasn't a huge difference, well no more than the difference between the old engine with 200k on it and a new engine, but it did wake up a bit off the line. And there was a single knock sensor mounted at the rear of the engine on the block itself. The newer 94 Astro has dual sensors, but the 92 I took the engine from had a single sensor.
Maybe i should bump mine. But remember, smog checks check timing (ive failed for retarding one to keep it from pinging), so make sure to set to zero for smog.
lectric80
3/4 ton status
I am so glad I live in an area that doesn't smog!
xCaliK5x
1/2 ton status
IIRC the knock sensor talks to the spark module on the right of the throttle which then tells the module in the dizzy to adjust the timing.
I would think, in theory, that if you bump base 4*, it just changes the range on available timing the dizzy can use. Mine is still set to 0* for smog reasons, I will change that when I get it to the shop.
This info may not be entirely accurate as I'm still learning these trucks.
I would think, in theory, that if you bump base 4*, it just changes the range on available timing the dizzy can use. Mine is still set to 0* for smog reasons, I will change that when I get it to the shop.
This info may not be entirely accurate as I'm still learning these trucks.
IIRC the knock sensor talks to the spark module on the right of the throttle which then tells the module in the dizzy to adjust the timing.
I would think, in theory, that if you bump base 4*, it just changes the range on available timing the dizzy can use. Mine is still set to 0* for smog reasons, I will change that when I get it to the shop.
This info may not be entirely accurate as I'm still learning these trucks.
THat is my guess too, hopefully someone can verify. My 94 350TBI would ping bad on 87 octane under load and lower rpms. Retarding the timing about 3˚ helped.
You can be off by no more than 4* before a smog tech is SUPPOSED to fail you on that.
ciffer
1/2 ton status
Glad I have no smog checks here, at least no until 2012 at which time my state switches to california standards. I am thinking that anything I do before that time will be exempt on the basis that not being exempt would constitute an ex-post-facto law.
You will not be exempt to anything. You will be required to have everything installed as the vehicle came from the factory. Emissions is a FEDERAL thing but with California having MORE than the FEDERAL requirement.
My 83 305 has a knock sensor and ESC box in the dash. I had no clue that 83s had any electronics but they do.
On the timing issue. I was a buddies BBQ joint and there was this really old guy, a life long mechanic who suggested putting a few degrees timing on my 383. So I did. It did make a difference I could feel. Even thought seat of the pants is not a good stick to use, it was noticable to me.
On the timing issue. I was a buddies BBQ joint and there was this really old guy, a life long mechanic who suggested putting a few degrees timing on my 383. So I did. It did make a difference I could feel. Even thought seat of the pants is not a good stick to use, it was noticable to me.
