91 s-10 timing problems

[91TBIguy]

Hey all,
This is my first post here, but i have been reading alott on here and it seems that alot of you guys know what your talking about. So i though mybe you guys could help me. I bought a 91 s-10 4.3 TBI automatic about 4 months ago. Its been parked for about that amount of time. I had to pull the intake manifold and replace it and new gaskets, and water neck because it had a coolent leak. Then distributer kit, plugs, wires, new optima battery, exast system, floor pans ,tires, new shocks all around and new radiator.

Now i have reconnected the battery and got the distributer pointing to #1 cycliner, and rotated balancer to 0 degrees TDC. I was told to disconnect the electonic spark wire, then start and time motor to 0 degrees, then shut it off and reconnect wire then timing will be set. When i do that and check timing its about 15 degrees advanced and eratic, when i unplug wire it is constant timing and at 0 degrees. What do i do? it starts ok and after about 5 seconds runs fine. but that may have somthing to do with the hose that has no home...(read below)

also when i tore the motor down for intake swap, then put it all back together everything went where it should have but now theres a little black box that has a cap that says filter with a plastic hose running off it stopping infront of my throttle body, but the odd thing is thers no place for it to go? what do I do? I cant find a 4.3 to compare it with... Im stumped...
Thanks for the help guys,
john

[camohog1]

Do you have a haynes or chiltons manuel? that may be the best place to get started. Keep us updated on the job.

[91TBIguy]

i have the haynes manual, and its telling me nothing. I had to get online to findout about the electronic spark wire thing to disconnect. My manual is worthless.
I guess ill jsut leave it unhooked! hope it dont blow up...
thanks,
john

[bigd7315]

the timing jumps around when cold when the computer senses the mixture is too lean which in reality it is rich because a valve is not sealing all the way closed very common problem get u a bottle of rubbing alcohol and run it through her after let me know if she's better or changing the alcohol won't hurt the truck just burn the carbon from around the valves

[sector95]

Now i have reconnected the battery and got the distributer pointing to #1 cycliner, and rotated balancer to 0 degrees TDC. I was told to disconnect the electonic spark wire, then start and time motor to 0 degrees, then shut it off and reconnect wire then timing will be set. When i do that and check timing its about 15 degrees advanced and eratic, when i unplug wire it is constant timing and at 0 degrees. What do i do? it starts ok and after about 5 seconds runs fine. but that may have somthing to do with the hose that has no home...(read below)


Does your truck have an underhood emissions label? If it does, then it will give you the correct initial timing for your engine and the correct configuration (in Park, A/C off, etc). There is no "one size fits" all spec for these engines. It might be zero deg/TDC but then it might not be. In any event it's important to get the initial setting right for the computer baseline; the old garbage in garbage out kinda thing. If the decal is missing, you might go down to your local Chevy dealer with VIN in hand and see if they can look up the spec. I had a '91 S10 also and I can't remember what the initial timing was on my engine.... my Chilton's says to refer to the underhood label.


also when i tore the motor down for intake swap, then put it all back together everything went where it should have but now theres a little black box that has a cap that says filter with a plastic hose running off it stopping infront of my throttle body, but the odd thing is thers no place for it to go? what do I do? I cant find a 4.3 to compare it with... Im stumped...
Thanks for the help guys,
john[/quote]

Sorry I can't help you with the filter.... My Chilton's doesn't have an overall shot of the engine emissions gear. The only things plugged into the TB are the vac lines for the PCV, Charcoal canister, EGR vacuum source and the snorkel preheat vacuum motor..... Maybe check with the local Chevy dealer... it should have a part number on it and they can look it up and at least tell you what it is.....


Good luck,

mike

[91TBIguy]

Originally Posted by bigd7315

the timing jumps around when cold when the computer senses the mixture is too lean which in reality it is rich because a valve is not sealing all the way closed very common problem get u a bottle of rubbing alcohol and run it through her after let me know if she's better or changing the alcohol won't hurt the truck just burn the carbon from around the valves

Sorry I am not going to put rubbing alcohol in my motor! thanks anyway.

[91TBIguy]

Originally Posted by sector95

Now i have reconnected the battery and got the distributer pointing to #1 cycliner, and rotated balancer to 0 degrees TDC. I was told to disconnect the electonic spark wire, then start and time motor to 0 degrees, then shut it off and reconnect wire then timing will be set. When i do that and check timing its about 15 degrees advanced and eratic, when i unplug wire it is constant timing and at 0 degrees. What do i do? it starts ok and after about 5 seconds runs fine. but that may have somthing to do with the hose that has no home...(read below)


Does your truck have an underhood emissions label? If it does, then it will give you the correct initial timing for your engine and the correct configuration (in Park, A/C off, etc). There is no "one size fits" all spec for these engines. It might be zero deg/TDC but then it might not be. In any event it's important to get the initial setting right for the computer baseline; the old garbage in garbage out kinda thing. If the decal is missing, you might go down to your local Chevy dealer with VIN in hand and see if they can look up the spec. I had a '91 S10 also and I can't remember what the initial timing was on my engine.... my Chilton's says to refer to the underhood label.


also when i tore the motor down for intake swap, then put it all back together everything went where it should have but now theres a little black box that has a cap that says filter with a plastic hose running off it stopping infront of my throttle body, but the odd thing is thers no place for it to go? what do I do? I cant find a 4.3 to compare it with... Im stumped...
Thanks for the help guys,
john

Sorry I can't help you with the filter.... My Chilton's doesn't have an overall shot of the engine emissions gear. The only things plugged into the TB are the vac lines for the PCV, Charcoal canister, EGR vacuum source and the snorkel preheat vacuum motor..... Maybe check with the local Chevy dealer... it should have a part number on it and they can look it up and at least tell you what it is.....


Good luck,

mike[/quote]

Thanks mike, Most of the 4.3 TBI motors do time at 0 degrees TDC. I do not have an emmisions sticker under hood, but mine never did. my emmisions sticker is listed on my fan shroud but timing says automatic 0 degrees (N) what does N mean?

as for the electronic spark advance thing, how do i get it to stay timed at 0 degrees when its connected?
Thanks,
john

[sector95]

Thanks mike, Most of the 4.3 TBI motors do time at 0 degrees TDC. I do not have an emmisions sticker under hood, but mine never did. my emmisions sticker is listed on my fan shroud but timing says automatic 0 degrees (N) what does N mean?

as for the electronic spark advance thing, how do i get it to stay timed at 0 degrees when its connected?
Thanks,
john[/quote]

Okay... the sticker(?) on the fan shroud is the "emissions" sticker. It should have info like spark plug type and gap; initial timing and parameters (tranny in neutral, A/C off, ESC wire disconnected, etc) and base idle rpm (again with parameters).

"N" means neutral...as in tranny in neutral.

The short answer is you can't; once you reconnect the ESC wire, the engine management computer takes over and controls the timing based on inputs from coolant temp, knock sensor(s), outside air temp, RPM, throttle position and probably a couple more things. You really want to have the computer working for you since so much of the performance of the engine is tied to having the computer controlling the various systems (fuel mix, timing, etc).

When the wire is reconnected, you say the timing becomes erratic; does the engine idle okay? ...Does it run okay? I mean if the truck runs good with the wire reconnected, then the computer is doing it's thing, constantly tweaking the timing...and if the engine is cold....well it's gonna run under a different "program" until it reaches normal ops temp.

mike

[91TBIguy]

OK, the motor starts quickly like it always did but now it takes about 5 seconds of running a little rough no badly just not 100% then like i said about 4-5 seconds later its fine idles good, but i havent driven it so im unsure of the power it may or may not have. It was very powerful before ill see to day if it still is.

So if what i am hearing is correct then i need to just plug the compter in and let it go? even though tis running warm or cold at idle at 15-17 degrees advance? I have never seen a motor time the far in advance.

So ill go plug the computer in and take it for a drive, and see what happends.

john,

[sector95]

So if what i am hearing is correct then i need to just plug the compter in and let it go? even though tis running warm or cold at idle at 15-17 degrees advance? I have never seen a motor time the far in advance.

So ill go plug the computer in and take it for a drive, and see what happends.

john,[/quote]

John,

I would say quit worrying about the timing....the engine management computer will make all the adjustments; both increasing and retarding the timing. Definitly put her back together and take a test drive. Providing the computer is functioning correctly and has all the required inputs from the various sensors (coolant, knock, throttle position, O2 sensor etc), then everything should be fine.

Let us know how it goes........

mike

[91TBIguy]

well guys got her running and drove it down my driveway, and then it wouldnt stay at idle, then died and then started one more time and now nothing, cranks, but wont start at all! also blowed smoke like its running to rich...

So thanks for the helps guys but im not going to bang my head aginst the wall anymore. Im taking it to the chevy dealer and let them screw with it. Im about 100% sure its computer troubles... Damn computers never had a place in any car if you ask me. But ill say one thing this is my last computer controled car. its all 1970 and down for me...
thanks guys,
john

[91TBIguy]

well i checked my timing and leting the computer do it thing screwed the timing nows it almost 30 degrees out and wont come back. Any idea how to reset ECU? disconnecting battery dosent work...
thanks,
john

[cyclonetwister]

Originally Posted by 91TBIguy

well i checked my timing and leting the computer do it thing screwed the timing nows it almost 30 degrees out and wont come back. Any idea how to reset ECU? disconnecting battery dosent work...
thanks,
john

Uh, gentlemen, that's why the wire is disconnected to time the engine....

It bypasses the ECM control of the distributor...once the timing is set to 0-dc the engine is shut off and the wire re-connected...the ECM takes control from there...

A engine will surge, even sometimes stalling when first started and even when warm...this is called SEARCHING....the control modules and sensors have not had time to set the proper codes in the ECM...the vehicle must be driven on the open road to properly set these codes within specs...

as for that connection....if it's to the intake manifold, it could be vacuum related..vac leaks will cause a bad idle as well...

[91TBIguy]

Well i thought i wasnt getting spark because of a weak coil, replaced it and still nothing.

Ill have to go down to advanced auto parts and see if i can rent a code reader and check my ECM for errors. Then hopefully i can correct the errors and reset ecm and i should be ok.

I know i dont have vacume leaks because when i got the truck it ran great, and since i have had it i have replaced all cracked or old vacume lines, only bad ones were for cruise control.

Hopefully i shouldnt have to time it again, and i know that it needs to be driven to re-set some sensors but it has to start to be driven...

anyway im gonna do some more reading about my electronics system, john

[cyclonetwister]

Originally Posted by 91TBIguy

well guys got her running and drove it down my driveway, and then it wouldnt stay at idle, then died and then started one more time and now nothing, cranks, but wont start at all! also blowed smoke like its running to rich...

john

This is typical if you just replaced the intake manifold. You've gotten antifreeze in the cylinders. It'll blow black smoke and stink like burning gunk until it's all out of there...you should have even gotten a huge black blast of crap from the tailpipe on the ground where you started her...I just did mine Sunday..same thing..it runs rough and will pop all kind of codes...EGR, O2 sensor, and most likely the O2 sensor will set a "too lean" code..this is the moisture burning out of the system.. Run it till warm, change your oil because that antifreeze went there as well.