A few days ago, I noticed a type of pinging(best way I can describe it) when I romp on the throttle. Only while in gear driving. No power loss. I'm going to adjust my timing tomorrow, hopefully. In my Chilton book it talks about the EST(huh?) and grounding terminals A and B. But When I had some engine trouble codes, I was told NOT to run my engine with A and B jumped, or it could fry my ECM. What's the deal here? Anyone got a set of instructions that is a little more clear and tells me what the darned abriviations mean?!?!?! Thanks guys

 

If all you plan to do is adjust the ignition timing, here's the procedure.

First start and warm up the engine until it reaches normal operating temperature.

Now shut down the engine and look for a single wire, usually tan with a black stripe, that is near the engine side of the power brake booster (at least that's where it is on my Vette).

That wire has a weatherpak connector (black plastic) and it's your EST Electronic Spark Timing wire.

Diconnect that wire at the connector and restart the engine. Now attach your timing light and set your timing to wherever you want it.

Disconecting it prevents the ECM from adding ignition timing during the period that you're making the adjustment.

Shut down the engine and reconnect the EST wire.

You now must disconnect one of the battery leads for at least 30 seconds. When the car's computer (ECM) detected that the engine was running with the EST wire disconnected it set a SES code. Disconnecting the battery or pulling the ECM fuse will clear the code.

Now you will have to start the car and drive it a while so that the ECM can learn the Intergrator and BLM values that were loss when the battery was disconnected.

The car may run slightly worse for a short while until the new values are learned and stored in the ECM's memory.

Hope this helps.

Jake

 

Excellent. Thank you much! I'll give it a try this afternoon.

 

Put some better gas in it- you're timing may be fine- just a bad batch of fuel.

Next question of course is: why isn't ECM compensating for this and still allowing "pinging"- in theory it should retard the timing automatically- car will run like crap, but not ping. Is this a TBI or carb'd engine? Maybe this batch of gas was so poor that engine can't compensate enough for it.

I am assuming here that everything was running A-Ok before you filled up last time?

 

I dont know if this is related or not, but I recognized the A and B terminal talk. I was reading another topic about these terminals. At least I think its the same terminals you are talking about. This is it(its under "Tech/Gen Engine"):

Topic Name: "One more time How do I check to see if I am in open/closed loop with a paper clip?"
https://www.thirdgen.org/messageforu...ML/002222.html

I hope this helps

[This message has been edited by Godti (edited October 25, 2000).]

 

It's an '85 z28 TPI 305... I used the timing light, unpluged the one tan wire with black stripe.... and the timing was right on at 6D BTC. Which is where both my books say it should be. The pinging is worse when the engine is cold, and it seems to fluctuate. Which would rule out timing and rule in bad gas. I'll get some 92oct today at a good station, and run a tank or two through it and see if it gets any better. Thanks

 

Here's a swing- has the mark on your balancer moved?

Follow this procedure for finding TDC of your #1 cylinder: https://www.thirdgen.org/messageforu...ML/001869.html Then, when you find TDC, check out the timing indicator. It should line up with the mark on your balancer. As a triple-check, you could also remove the distributor cap to see if the rotor is pointing towards the #1 cylinder's terminal.


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