I was wondering if someone could help me figgure out how to properly troubleshoot the EST. Maybe even help me understand what other components the EST works with and why it could cause problems. My 89 IROC-Z L98 has an idle problem, and while doing some troubleshooting (which inc checking the timing) I found it runs perfect with the EST connector by the blower motor disconnected, and runs bad when its connected. From what I've read this can be a bad connection, a bad distributor, bad ECM, bad Knock Sensor. Anyone know how to test these components out without replacing them? I've read you use a resistor to dummy out the Knock Sensor and prove that one out. And help is appreciated ...

 

are you throwing a certain code? if so, you can just go to autozone and have them print out a troubleshooting flow chart

 

I'm getting a code 42 (bad EST) after I unplug the EST connector, but I think thats supposed to happen after I unplug it. If I plug it back together and clear the codes in the ECM, I dont get any codes unless I unplug the EST connector again (this is with both the paperclip method and WinALDL). With the EST connected my timing is all over the place. I know the ECM will advance/retard timing with it connected, but I think something is wrong because it idles really bad, RPM's all over the place, and stalls with the EST connected. If I disconnect the EST it runs perfect at the correct RPM very smooth.

 

yah you will get 42 just from disconnecting est. when it idles crazy can you hear it miss from the exhaust? how does it drive other than idle? i had a simular problem, which turned out to be a bad fuel pump. if it drives like ****, its probly your pump.

 

I've checked the pressure at the rail, all tests were within spec and solid. I have not tested the injectors so thats still a possibility. Vacuum is good, TPS and IAC have been replaced. But I'm pretty sure it has something to do with the EST, I'm thinking if the module is out of whack its telling the ECM to advance/retard the timing too much or something. When the EST is disconnected the car runs perfectly.

 

Temporarily replace the detonation sensor with a resistor. In the event the KS is picking up random knock events or is failing, the timing will be all over the place.

 

CrazyHawaiian,

Hope this helps

From the book "How to Tune and Modify Chevrolet Fuel Injection"

 

Or this one:

 

Hey thanks so much you guys, this is exactly what I was looking for. YOU GUYS ROCK!! I'm gonna do the KS thing first, then follow those charts. So excited now, can't wait to get this thing running good. Thank you again!!

 

Forget the charts, they can still be confusing.

You will need to drop your ECM so you can test the ESC wire at the ECM, you will need a digital voltmeter, you will need some long wires to test it and it is much easier to teat a KS that is not in the block.
Just hook up a jumper wire between your Knock sensor and the wire it plugs into (I stuck a aligator clamp wire between the KS and its plug in). Run your digital volt meter in 20Kohms. You should get a reading with Key On Engine Off when 1 voltmeter lead is hooked to your jumper wire and the other is hooked to 1 of your wires that go to the ESC module. Test the length of the KS wire this way, then test the length of the wire that sends KS counts to the computer this way. Try tapping on the block or KS to see if signal change is being sent on both wires (I used a spare KS so it was easier to tap and so I didnt have to take mine out, then I put a new one in).

I wasted 2 weeks with the charts and came up with this simplfied version. Everything checked out on mine and I still could not believe it. Turns out I over cammed my new motor and the only thing wrong with my KS was that I used sealant on the threads when I put it in the block (putting sealant on the KS makes it harder to pick up the knocks)
https://www.thirdgen.org/techbb2/sho...hreadid=311511
Good luck Brah

 

Thanks for the tips. I used my DVM to run tests and the results indicated both the Ignition Module and the KS were bad. So I replaced them both and nothing changed. Still runs great when the EST bypass is disconnected, runs horrible when its connected. Next I'm going to replace the ECM. If that dosnt do it, then ESC module. Car throws no codes, all sensors appear to be within spec on the scantool, I'm stumped.

 

Well, replaced the ECM with a new one (but still the same memcal) and its still jacked. Runs great with EST bypass disconnected, stalls out when its connected.

 

Checked the pickup coil and reluctor?

 

After reading into it more last night I think you are right Vader, its something to do with the pickup coil or other parts inside the distributor. I'm gonna head off to the parts store to price this stuff out. Might just go for a whole new distributor. Thanks for the help guys!!

 

have you been to autozone or oriellys to have you ICM tested?

 

ICM is Ignition Module right? When I did some testing I got 5 volts and dwell was at 90 so we replaced the Ignition Module with a new one, was very carefull to distribute the silicone paste evently and completely. Unfortunately it didnt solve the problem.

I priced out the pickup coil and reluctor, each under $20. New distributors are between $100 to $160 for the OE replacements and apparently $280+ for performance brands. Ouch.

 

Hi I'm new here this is my first post and I'm having the same problem on one of my cars Firebird v6 and wanted to see if you fixed yours yet and what caused it. I replaced the knock sensor and the pick up coil so far. I'm not running at all with it hooked up it shuts off right away. I also get code 42 when I check the codes. This is the only problem I'm having with this car and barely have the time to work on it.
I have to this fixed asap my township is on my back about my cars and I got hauled into court once and am trying to avoid another trip there.

Dav1962