Got a code42 from ALDL on 87 Chevy 350

[Bextreme04]

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!

You said earlier that you had properly set the idle. You also said that you set the timing earlier? How did you do any of that if you don't know the idle set procedure for TBI and don't have a timing light. You CANNOT set timing properly without a timing light. You can get somewhat close, but it will not be right. Go buy or rent a timing light from a local parts store. Bonus points if it has a tach function. Double bonus points if it can be dialed back.

The "turn all the way in and then back out 1 turn" is for setting initial idle mixture screws on a carburetor. It has absolutely nothing to do with IAC and mechanical idle setting on a TBI unit. I am getting more and more concerned with the total confusion happening on this thread.

You need to do a full stop and reset on what your thought process is on this truck right now.

First things first, get a timing light.

Find the correct connector for setting timing. Take a picture, point it out or circle it, and post here so that someone can verify that it is indeed the correct connector for you to be unplugging.

Once you have the right tools and know EXACTLY what you are supposed to be doing... then you can fully warm up the truck and set the timing to 0 BTDC using the proper tools and procedure. If you have been setting timing to 12 degrees BTDC by manually turning over the motor to that setting and then putting the rotor on #1 post, you could be WAAAAAYYYY off on the timing.

Once you have set the timing correctly.. it will most likely run MUCH better. Now you can go through the procedure to set the idle and IAC.

Set procedure for idle and IAC involves jumping the A and B wires on the ALDL connector, turning the ignition to ON(not start) for 10 seconds, then turn key off and unplug the IAC valve and remove the jumper wire. Then you can start the engine and adjust idle to 650RPM. If you don't have a tach, timing light with tach function, or ALDL reader, this step will be hard to impossible(you'd be amazed at how hard it is to do this by ear).

The idle set is completely invalid if you have ANY vacuum leaks and/or your timing is not set correctly. DO NOT do it if you haven't solved all of your other issues first.

 

[gmbellew]

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!

here is what the manual says is correct -

 

[Bextreme04]

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!

Just to give you an idea of how absolutely wrong this is. 1/3 of the way between #1 and #8 is roughly 30 degrees of crank rotation, but that still doesn't tell you what the crank location is when the spark plug for #1 FIRES.

If you do what you just said here... you would be setting the engine to around 30 degrees BTDC, which is a lot. I can't imagine you would be able to get it to start or run very well like that.

If you set the timing mark right at 0, and then set the rotor just about centered on the #1 plug location, you might be within +- 5 degrees of 0.... maybe. It will at least be close enough to start and run someone decent just enough to get warmed up until you can get it set correctly with the timing light.

 

[AuroraGirl]

here is what the manual says is correct -

Okay can you show us your VECI label because I have a feeliung your VECI label says something like:

(incase it was not clear by the manual, it says to follow your VECI label. which if your VECI label matches this one, you hopefully understand what that means then?)

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NOTE IDLE AIR SPEED SCREW IS PRESENT AND SEALED AT FACTORY, PROVISIONS FOR ADJUSTMENT DURING TUNE UP IS NOT PROVIDED. DO NOT ATTEMPT ADJUSTMENT

IDLE SPEEDS ARE AUTOMATICALLY CONTROLLED. DO NOT ATEMPT ADJUSTMENTS

See boring blah blah for more.

TIMING (*BTDC) 0° (M in N/AT in P or N)


the actual timing procedure can be read by you and here is a lengthened canadian version of it

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[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.

 

[Hugomartin]

Thank you to everyone sorry for the confusion .

Just to give you an idea of how absolutely wrong this is. 1/3 of the way between #1 and #8 is roughly 30 degrees of crank rotation, but that still doesn't tell you what the crank location is when the spark plug for #1 FIRES.

If you do what you just said here... you would be setting the engine to around 30 degrees BTDC, which is a lot. I can't imagine you would be able to get it to start or run very well like that.

If you set the timing mark right at 0, and then set the rotor just about centered on the #1 plug location, you might be within +- 5 degrees of 0.... maybe. It will at least be close enough to start and run someone decent just enough to get warmed up until you can get it set correctly with the timing light.

I pulled the distrib cap off and it looks like the rotor is pointing directly at the #1 on the distributor cap. The rotor is also pointing slightly toward the passenger side( should it be pointing towards driver side?)

Ok, I then disconnected the est wire (black with tan stripe) , then I put a 2 degree retard on the cap , (no timing light used) then started the truck, seemed to idle good , put it in gear sounded ok , I shut truck off , reconnected est wire, disconnected battery for 8 minutes , reconnected battery, started truck n test drove it, seemed to have better power , only slight bogging when put in gear with brake depressed it didn’t die on me but rpms do dip (no tach)


I am pretty positive that I can find the perfect marriage setting between the idle screw setting and the dist cap setting just by making small estimated adjustments on either one

I do feel I might be wrong with the rotor pointing slightly towards passenger side?

Thank you everyone

 

[Hugomartin]

Slightly pointed at passenger

 

[Hugomartin]

Okay can you show us your VECI label because I have a feeliung your VECI label says something like:

(incase it was not clear by the manual, it says to follow your VECI label. which if your VECI label matches this one, you hopefully understand what that means then?)

You must be registered for see images attach

NOTE IDLE AIR SPEED SCREW IS PRESENT AND SEALED AT FACTORY, PROVISIONS FOR ADJUSTMENT DURING TUNE UP IS NOT PROVIDED. DO NOT ATTEMPT ADJUSTMENT

IDLE SPEEDS ARE AUTOMATICALLY CONTROLLED. DO NOT ATEMPT ADJUSTMENTS

See boring blah blah for more.

TIMING (*BTDC) 0° (M in N/AT in P or N)


the actual timing procedure can be read by you and here is a lengthened canadian version of it

You must be registered for see images attach

How can I get my idle screw back to (stock setting).

Thanks

 

[gmbellew]

GET A TIMING LIGHT AND SET THE TIMING CORRECTLY!!

sorry for the yelling. but you are going to be chasing your tail until you set the timing right. don't touch anything else until you set the timing to 0 BTDC on a warmed up engine with the EST unplugged.

you will need a tachometer to set the base idle and will need to either force the IAC closed or remove it and block off the opening IF you even need to adjust the base idle. the base idle is covered by a knock out plate foe a reason - you shouldn't have to mess with it.

 

[AuroraGirl]

How can I get my idle screw back to (stock setting).

Thanks

he told you dude.. @Bextreme04 Laid out how to do so... you cannot turn it mechanically the right amount to a preset, every engine is different and the engine computer only is able to manage the idle under strict parameters, which your truck doesnt meet and you can only meet it with the procedure he outlined.

 

[Hugomartin]

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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When I adjust my idle screw I hear the idle change. Without having to fool with the IAC procedure. Why would I need to go through the IAC procedure if I can simply adjust my idle with the torx bit. Thank you for helping

 

[AuroraGirl]

When I adjust my idle screw I hear the idle change. Without having to fool with the IAC procedure. Why would I need to go through the IAC procedure if I can simply adjust my idle with the torx bit. Thank you for helping

because the ECM assumes your idle is set very SPECIFICALLY to a preset amount that means 650 or so without any IAC. it means when its operating its adding or taking away with that as a base setting. too low you could stall and your truck is freaking out not bebing able to idle proper, and too high your truck thinks theres a vacuum leak or irationality with the tps etc etc.

the systems were like that for ford too. You need to put that back to factory and then fix the actual problem and not confuse the hell out of your ecm you do that enough and you will have other issues that will be seemingly impossible or exhausting to figure out.

 

[Goldie Driver]

DON'T YOU DARE!!!

WRONG !

I haz de proofs from teh Intewrwebz !!

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[AuroraGirl]

WRONG !

I haz de proofs from teh Intewrwebz !!

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[Snoots]

WRONG !

I haz de proofs from teh Intewrwebz !!

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Wiff beeer in hannd I syt dutifullly correctted.