Got a code42 from ALDL on 87 Chevy 350

[Hugomartin]

Sorry better pic I’m assuming I need to ground the yellow wire to the block or body?

 

[Hugomartin]

the yellow wire would be the tach wire. it won't go anywhere unless you have a tach hooked up.

Thanks man

 

[Hugomartin]

That is all wrong. The computer controls the timing. You have to disconnect the wire(NOT the one you have been asking about, but the tan/blk wire coming from the distributor that is labeled as "set timing connector" on the first screenshot that GMbellew posted) and then set the timing. Then you reconnect that lead and carry on. The knock sensor is used by the ECU to pull timing out of the ignition system, so if there is an issue there it will not be running right at all.

I did have a good ol time getting the timing right I used to have it back fire when I accelerated.

DON'T YOU DARE!!!

im gonna put a lil zip tie on it too

 

[gmbellew]

Thanks man

no worries. hit up the reference library section of this site and get the manuals for your year. they will be better than Haynes. then invest in a Bluetooth aldl reader and the aldldroid app and you will be unstoppable!

 

[Bextreme04]

Yes I did that with the Black and Tan wire connector.

That's what set the 42 code then. You need to reset the computer after you do that to clear the code.

As GMbellew said, you wont do anything with the "shorted" wire you keep referencing. Is it actually shorted to something, or just folded over on itself and taped up to prevent it from shorting to something?

I set it on 13 degrees before top dead center compression stroke when I put in the new distributor . No I don’t have a tach wich shows rpms I wish I did, I guess that’s what you’re referring to. It has set this code before after I replaced nearly everything. I also get a knock sensor code also but I don’t think that’s a big deal?

That is WAAAAAAAY too advanced. Factory spec is 0 degrees and the computer advances it from there. I think you can be +- a few degrees without it throwing a code, but it still won't be happy. I've seen some people say they have tried setting initial at 4 or more BTDC and it seems to run best at 0.

I would bet that almost all of your issues are stemming from massive vacuum leaks. They are causing poor idle, massive lean condition, and just general poor running. You have then had to set your IAC and timing way outside the correct spec in order to try and get the truck to run right. You need to go down to the parts store and buy some correct size vacuum line and fix all of those vacuum issues. DON'T use tape or zip-ties or other garbage, just fix it right the first time. Then, set your timing back to 0 after unhooking timing connector. Then re-run the idle set procedure(it will probably be WAY off with correct timing and no vacuum leaks).

Once you have done all of that, reset the ECM by unhooking the battery for a few minutes, then go take a nice long drive to see if it will throw any new codes.

 

[Hugomartin]

Thanks I replaced a rotted vaccum from the vacuum reservoir . And I noticed a broken vaccum line under the pump relay so I used what I had to fix it was a very skinny plastic hose. When I started the truck up and put it in reverse then drive a few times it rumbled and stumbled then died setting a code 42 again. I also cleaned the iac with some throttle body cleaner. I guess my next step is to put it on 0degreesbtdc I reckon then adjust dist cap and idle screw? Thanks

 

[Hugomartin]

with my index finger I’m pointing to that skinny hose that was broke . I then added a sleeve over it and connected it to the t fitting

 

[Hugomartin]

When turning the crankshaft to achieve 0degrees btdc I must have the Black and Tan wire disconnected . Once I’m on 0degreesbtdc I reconnect the Black and Tan wire then reconnect the battery correct?

 

[Bextreme04]

The code 42 means that the ESC line is disconnected or shorted. Did you ever find the connector on the brown wire? Is it connected or disconnected? WHile that code is being set, you should be able to set the timing to 0 BTDC and then set the idle usign the correct procedure. Then you need to troubleshoot why you are getting that code.

 

[Bextreme04]

When turning the crankshaft to achieve 0degrees btdc I must have the Black and Tan wire disconnected . Once I’m on 0degreesbtdc I reconnect the Black and Tan wire then reconnect the battery correct?

You can't set timing that way. You need to unplug the timing set connector. Start the truck. Use a timing light and set the timing to 0 BTDC. Turn off truck, plug timing set connector back in, disconnect battery ground for a minute and then reconnect. Now start the truck and see if the code 42 is gone or resets.

 

[Hugomartin]

That's what set the 42 code then. You need to reset the computer after you do that to clear the code.

As GMbellew said, you wont do anything with the "shorted" wire you keep referencing. Is it actually shorted to something, or just folded over on itself and taped up to prevent it from shorting to something?

That is WAAAAAAAY too advanced. Factory spec is 0 degrees and the computer advances it from there. I think you can be +- a few degrees without it throwing a code, but it still won't be happy. I've seen some people say they have tried setting initial at 4 or more BTDC and it seems to run best at 0.

I would bet that almost all of your issues are stemming from massive vacuum leaks. They are causing poor idle, massive lean condition, and just general poor running. You have then had to set your IAC and timing way outside the correct spec in order to try and get the truck to run right. You need to go down to the parts store and buy some correct size vacuum line and fix all of those vacuum issues. DON'T use tape or zip-ties or other garbage, just fix it right the first time. Then, set your timing back to 0 after unhooking timing connector. Then re-run the idle set procedure(it will probably be WAY off with correct timing and no vacuum leaks).

Once you have done all of that, reset the ECM by unhooking the battery for a few minutes, then go take a nice long drive to see if it will throw any new codes.

What would be the way to set my idle screw to spec, I think I read to tighten the screw all the way then back out a full turn?

 

[Hugomartin]

You can't set timing that way. You need to unplug the timing set connector. Start the truck. Use a timing light and set the timing to 0 BTDC. Turn off truck, plug timing set connector back in, disconnect battery ground for a minute and then reconnect. Now start the truck and see if the code 42 is gone or resets.

Thanks man but sorry I am confused. I don’t have a timing light. I was under the impression that turning that crankshaft till it hits zero degrees on compression was step one. Then step two would be to adjust the distributor cap 1/3 past number 1 cylinder

 

[gmbellew]

Thanks man but sorry I am confused. I don’t have a timing light. I was under the impression that turning that crankshaft till it hits zero degrees on compression was step one. Then step two would be to adjust the distributor cap 1/3 past number 1 cylinder

you will have a hard time setting the timing without a timing light. you may also want to start the truck and let it warm up, then unplug the EST wire, then loosen distributor and set timing to 0 by turning distributor and watching the timing marks with your timing light, then tighten distributor and turn off truck, then plug in EST wire, then disconnect negative battery cable for a few minutes to clear codes, reconnect negative battery cable. finally start it up and see what you have. if you still have a code 42, you need to follow the diagnostics I posted earlier.

 

[AuroraGirl]

You need to follow the procedure because the old school ignition systems was being intertwined with electronics as you can so obviously see from how bex is giving you procedures and such and you see wires all over. The systems are all fundamentally tied to the assumption the shorting block is used how he explained to set the timing to the proper setting, and that it cannot control for variables if thats not true(properly)

 

[Hugomartin]

you will have a hard time setting the timing without a timing light. you may also want to start the truck and let it warm up, then unplug the EST wire, then loosen distributor and set timing to 0 by turning distributor and watching the timing marks with your timing light, then tighten distributor and turn off truck, then plug in EST wire, then disconnect negative battery cable for a few minutes to clear codes, reconnect negative battery cable. finally start it up and see what you have. if you still have a code 42, you need to follow the diagnostics I posted earlier.

Disconnect battery ,Unplug my est then I thought I had to turn the crankshaft by hand to get the rotor pointing roughly in the 7 o’clock position or 1/3 between the #1 firing order and #8 firing order on the compression stroke . Put back on distributor cap and wires then Plug in est , reconnect battery. Start the truck Then adjust distributor cap by feel or intuition. What part of my method is wrong? Thank you everyone!