engine timing and code 42 (EST Module)

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10-18-2001, 07:02 PM

formula90

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Location: Webster,Texas,USA

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Car: 1990 Formula

Engine: 5.7 liter

Transmission: 700R4

engine timing and code 42 (EST Module)

well , just finished up changing all my vacuum lines, checked timing(6 degrees of advance) K&N filter charger, PCV valve, and air breather.....well #1, some bonehead before me shoved a small BB into one of the vaccum lines going to the egr valve.. huh, I guess that new egr valve i bought actually works now!! but, I am still getting a code 42 which is the EST electronic spark control.

Now saying that, I have to ask this....
I noticed when i unplug the tan/white wire to time my engine, the mark on the harmonic balancer stays dead on using a timing light. and when i turn the distributer it moves smoothly with retarding or advancing. Now, after I turn off the engine, and reconnect the wire, then restart the engine, then check timing again using the light, the mark kinda jumps around. Am I having issues here? Is the EST causing this? I cant seem to get a good time on this thing. My hesitation problem has really improved probably the bb in the vacuum removed, but, listening carefully as the car sits idleing, I notice everyonce in awhile I hear the engine or exhaust tone change from time to time like it is running alittle rough. So I thought maybe I have to much advance so I retard about a degree and start over. doesnt improve...Should I check the spark control module? Where is it, and can a reputable parts house check this for me on thier bench, or am I going in the wrong direction here? any suggestions......

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[This message has been edited by formula90 (edited October 18, 2001).]

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10-18-2001, 10:38 PM

Vader

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F90,

That is relatively normal. The ECM is using the EST to constantly adjust the ignition timing, "hunting" for the best value at a given RPM that won't produce detonation. The timing affects engine speed and MAP levels, so the marks will tend to wander a bit, bt should be significantly advanced from the base setting.

If you are having EST issues, check the electrical connections between the ECM and EST, the EST to the distributor, and the connection at the detonation sensor. You can temporarily disconnect the detonation (knock) sensor if you suspect that there is feedback from the sensor causing some of the timing problems. Remember that you have no knock protection with the sensor disconnected, so your ears may be the only things preventing damage from detonation. Try not to drive the car that way.

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Later,
Vader
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