Got a code42 from ALDL on 87 Chevy 350

[Hugomartin]

On the right plug you see a yellow wire and a pink wire by the ignition coil. I noticed my yellow wire was shorted with electrical tape. My question is was this wire originally fastend to the block ? My truck will sometimes die when I put it in gear but much less so now that I have a new distributor ignition coil feud pump and started. I’ve had to adjust my idle screw clockwise to make it run better at idle. It feels 90% good just not sure what to do with the yellow wire coming off of the plug . Apparently it’s for the EST circuit and the yellow wire is a ground wire? If so where should I mount it

 

[Bextreme04]

You should not be adjusting the idle stop screw to raise idle. The is an IAC adjustment procedure and you are supposed to disconnect the IAC valve and then manually adjust that screw to a achieve a certain engine idle RPM. The TBI should then be controlling the IAC valve to get the correct idle at all times.

I would guess you have either clogged injectors, a massive vacuum leak, or both. I can see what appears to be a massive vacuum leak in the picture you posted. If that hose in such poor condition, I would bet there are more as well.

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[Hugomartin]

Wow thanks for pointing out that vacuum leak. I actually followed correct iac adjust protocol sorry I didn’t state that.

Do you know what I should do with that yellow wire with electrical tape on it? I don’t know where it should be going

Thank you sir

 

[Hugomartin]

I am going to wrap some duct tape on that silly hose!

 

[Bextreme04]

Code 42 is also the code that shows up when you short the ESC to set base timing. Did you do that also? If so, you should just reset the codes and see if it returns. Based on the wiring diagrams, that wire might be the Tach output. Do you have a Tach?

 

[Bextreme04]

I am going to wrap some duct tape on that silly hose!

Tape isn't going to work very well to fix a leak. Either go get the $4 worth of new tubing or just cut the rotted section off and stick the connector back on for now. Then I would go get the correct tubing and replace ALL of the vaccuum hoses, since at least some of them are looking like that. I would almost guarantee that there are more leaks. Vacuum leaks will make the MAP not read right and also have the engine running lean and possibly surging. It will just generally make it run like garbage.

 

[Hugomartin]

Code 42 is also the code that shows up when you short the ESC to set base timing. Did you do that also? If so, you should just reset the codes and see if it returns. Based on the wiring diagrams, that wire might be the Tach output. Do you have a Tach?

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?

 

[Hugomartin]

Code 42 is also the code that shows up when you short the ESC to set base timing. Did you do that also? If so, you should just reset the codes and see if it returns. Based on the wiring diagrams, that wire might be the Tach output. Do you have a Tach?

No sir I did not short the esc. That wire was shorted by the previous owner haven’t a clue why

Thanks

 

[gmbellew]

start with the reference manuals....

 

[Bextreme04]

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 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.

 

[Snoots]

I am going to wrap some duct tape on that silly hose!

DON'T YOU DARE!!!

 

[Bextreme04]

DON'T YOU DARE!!!

 

[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.

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

start with the reference manuals....

thanks I still don’t see what I should do about the yellow wire from my Haynes manual it seems as if is a ground wire

 

[gmbellew]

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

thanks I still don’t see what I should do about the yellow wire from my Haynes manual it seems as if is a ground wire

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

 

[Hugomartin]

Pic from haynes