My 85' has a problem with the computer automaticaly advancing the timing. If you can keep the car running with checking the timing you can watch the timing mark on the balencer go around and around and so on.
The car dosent run worth a damn so i think this is the problem. What can solve this?

 

You need to open the connector in the Blk/Tan (or is it Tan/Blk) wire that comes out of the large harness near the brake booster.

Then check the base timing; when done shut off and plug in the connector.

 

Yes i know and i have the base good at 6* but with that connector on the engine backfires through the exhaust then the intake and back and forth...put a timming light on it and saw the timming mark go all the way around and around again. Just wondring what could be wrong. Either knock or something?

 

The only way the timing mark can move when that EST connector is open is if the damper has separated.

In that case the outer damper ring will no longer move with the inner ring and the crank shaft, so the timing mark on the outer ring can appear to rotate.

If you tried to time your ignition with a failed damper you may have set it so far off as to cause backfire.

 

He said he had set the base at 6* and then reconected the wire. With the wire connected the timing at idle will jump around like crazy, normal. The computer is constantly changing it.

Triple check your wires and make sure you put them on the dist. starting with #1 and go clockwise. 18436572. Drivers side 1-3-5-7, pass side 2-4-6-8. I know its redundant, but I've done it before 3 times on a truck. Finally had my boss look at it(master mechanic) and boy did I feel stupid. I had the 6 and 5 backwards. I had taken everything off and put it back together 3 times and did it wrong each time. It was like my brain wasnt connected to my hands. Also how are you finding TDC?

 

Its not the wires on backwards because ive checked them and everyone else on my steet has too. I found TDC with bringing #1 piston up and puting a bent pic into the cylinder and when the piston just started to move back down is were i marked the distributor. The mark i made was the same spot as the old one i had when i rebuilt the motor and the engine ran mint before.

The car runs so bad you wouldnt be able to drive it. If you put a timing light on the balencer wile somone else was making the car idle. YOU CAN SEE THE TIMMING MARK GO AROUND IN THE SAME DIRECTION (ADVANCING) AND SO ON. This isnt normal, This is why the car wont run good because the car would backfire through the intake when the timming mark would be auto maticaly be setting after and the car would backfire through the exhaust when the timing mark would be before. And around it goses.
There is somthing that is making the computer think that it needs to constaintly advance the timming so what could it be? If it was getting false knock counts would the computer keep advancng it? Why? Could any of the wires on the distributor be in the wrong place by chance.

I have a pink wire on the BAT terminal(right side ) and a wire for my tach on the other terminal. I put an aftermarket tachometer in and this is were i hooked it up and everything worked great for about a month since i put that in. So now i have an extra white wire with a brown steak on type connector that would plug into the TACH terminal. THe wire in that terminal now is the old tach wire that i used for my aftermarket tach. Which before worked great and the tach on the dash didnt work. But now with nothing connected to the TACH terminal the digital dash tach would work. WTF? I looked at wire diagrams and couldnt see what the wite wire was. I dosent have a tracer on it. But there is two of the same wires (white with a brown connector) one is used for my TACH. But what could the other one be?

 

The problem is there is something cousing automatic advancing constaintly. I cant figure it out and my good friend that is a tech at a chevy dealer cant figure it out either. I've had a number of prople look at this and no one can figure it out. The car fires right up but it wont idle because the car keeps advancing the timming. I have 4 people that have seen the same thing as what im saing with the advancing. I know it sounds wired. Everything was new from the engine build and all the sensors were checked over and all connections too. The ESC, ECM,ignition modual, knock sencor cap/rotor, coil checked to be ok and were new.

 

You need to find TDC on the compression stroke. You could have it 180* out. Pull the #1 spark plug. put your finger in the hole to seal it. Turn the engine over by hand until there is air pressure in the #1 cylinder trying to push your finger out of the hole. Thats when both valves are closed. That will be the up stroke on the compression stroke of #1. Then follow the same procedure you have been doing.

 

It can't be 180*, out, because it wouldn't run. The point he has marked as TDC is probably 6*-8* AFTER TDC, the way he described locating it. Something is FUBAR, maybe the timing light. Normally, I would say that the timing light doesn't lie. But if the timing mark keeps advancing until it works it's way all the way around, it WOULD be 180* out at that time. The engine would have quit running long before that. Without being able to imagine a timing light causing the observation, it goes back to the damper, as suggested above. If I am interpreting what you are describing, correctly, It isn't possible, any other way.

RACE ON!!!

 

Im not sure how to word this but.. if i pull the connector( forgot the name but the one wire you disonect to set the base timming) the timming is set at 6* were it should be and it dosent jump around at all.
When the connector is connected somthing keeps advancing the timing. This is when the timming mark when the timming light is on it you can see the timming mark going around counter clockwise.
Im pretty certain that nothing is installed wrong and the timming is where it sould be. What mechanical device would keep advancing the timming? I've swiched out ignition mod. ecm's and an esc's that i know work and nothing changes.

 

idle or not i think it will always advance timing... i and doing this right now too... but i think my problem is that i have a vaccuum leak causing it.... and i definitly have an exhaust leak.... could that be it? sucking in mopre oxygen and confusing hte o2 sensor?
tj

 

Ya....but my computer advance the timming and never stops doing it untill the est connector is unpluged.
This is what is cousing the car to backfire through the exhaust and then the intake.
The computer advances the timming for whichever knock counts its getting through the knock sensor. Wich say bad gas-pings co the computer advances the timming.

 

are you saying its alwasy adjsuting back and forth or you think its always adjusitng, ut in the + direction? if it went from 2-4-6-10-20 ect. it couldnt get to 180 or all the way back, it wold die out....

tj

i would think it woudl benormal for it to always adjust back and forth.. thats what its supposed to do.... thats why i think i have a vaccuum leak that is causeing the erattic idle... you arent getting any lifter tick, like your lifters arent adjsuted right are you?

i actually adjsuted my lifters with it 180 out and hten swapped the distributor 180 .... i dont think this should matter though cause at tdc on the exhaust/intake stroke they are both closed or nearly anyway.. but i guess this could be it too...

 

No the timming mark with the computer connected the timing mark goes counter clockwise and keeps on going around and around thats why you have to try to get it to stay running. It dosent advance it alittle it advance's it so much that the mark makes its way around and a round again. Like a circle.
With my engine running right after the engine build everything was working correctly. The computer will advance it but with a perfectly running car you shouldnt be able to see the timming mark move back and forth. But in my case it dosent move back and forth it will mover all the way around.
SO im wondering what wound couse this?

 

i really dont see how it could do this.... it couldn't go 180 * around and still run.... take your eectronic advance off and spin your distributor 360* and see if it runs... the engine physically cannot run that far out.... a matter of fact to go all the way back to around 6 * advance it wouldh on the exhaust/intake stroke.. since the cam only turns half when the crank turns once....

aside from this how could you ever physically see that it is going all the way around? you cant realy point the light at anywhere besides about 20 degrees either side of 0 ... ??

 

If i have someone in the car making it stay alive and i have the timming light on the banencer you can see the timming mark go around and yes you cant see it but then it wiil come up the other side. going in the same direction all the time. This is with the ect connector on which i know you set the base timming with that conector off but i did this to see what the computer was doing.
I set the base timming (with the connector off) and its at 6* and it doesent move. But your not suposed to run the car with the ect connector off. The placement of the distributor is in the same spot as when i rebuilt the motor and the car ran supper up untill the computer or somthing automaticaly advances the timing.
Like i said before the car would bayily run with the advancing i think this explains the backfiring throung the intake/exhaust. WHen your watching the balencer with the timming light when the mark is around were its suposed to be the car would idle fine and the further the engine advances thats when it would backfire through thr exhaust and the timming would work its way around to THE OTHER SIDE and puff through the intake and then it keeps on going like that.

I dont know anyother ways of explaining this. Many people have witnessed this. mY friend thats a car machanic dosent know why its doing this.
The reson for this post was to see what would couse the computer to advance the timming like this. Everyting is new and checks out good. The timming was gone over many times. But that shouldnt even matter because the distributer was never pulled.
Is there anyother sensor on an 85' that would make the computer think it needs to advance the timming?
Is there anything in/on the distributor that would make the computer think it needs to advance the timming? other than the ignition modual?

 

All fixed there was a problem with the ecm.

 

I'm glad it's fixed. I wrote a lenghty post, yesterday, but I had a crash before it made it to the forum computer. In part, I mentioned that the ESC RETARDS the timing when it sees knock counts. The other thing I said was, that what you were observing, couldn't be happening, if fact, because the engine wouldn't continue to run through the timing advancing through a 360* cycle. Was it a bad connection, or did you just replace the whole ECM?

RACE ON!!!

 

Thanks,
I replaced the whole ecm. It may have been a connection but i believe it was intarnal. The car was actin funny before and throing random codes everytime i drew the codes up after disconnecting the bat.
The ecm was on order...but i was tring to dee if it could have been anything else.

I have some tuning to do because after taking everything apart to find the potential problem.

When under throttle and then if you were to give more gas the engine choke's out/ stumbles. TPS? i tested it out and i was getting the right voltage.

Anyway's thanks again for the help guy's

 

It sounds like you've verified that the TPI voltage is set properly. NOW, observe the voltage as you advance the throttle. if the voltage increases steadily and smoothly from idle to WOT, you can rule it out as part of the problem.

RACE ON!!!