I have an 89'IROC with a 5.7 TPI engine. I recently pulled the distributor to check the numbers on the engine block. I thought I had marked on the intake the distributors position but I missed. I bought a timing gun to retime it myself but once it is set the computer interfears and messes me up. When I read my manual it said to disconnect the black and tan wire by the heater box which I did. It also said to ground terminals A and B of the ALDL diagnostic terminal. I think thats the connector under the dash but after that I don't know what its asking me to do. Is it as simple as just jaming some wires in the first two holes of the terminal and grounding them? My other concern is that its been out of time before and it never ran this bad I can't even set it by ear. It seems as though no matter where we put it it pops and backfires. My friend ran his scanner on it and the only other problem is the tps voltage is about .6 which I think is still good.

Thanks

Nick:

 

I think the grounding the ALDL terminal is a load of crap. I believe grounding the A and B terminals would kick it into diagnostic mode now that I think about it. You don't need the computer in diagnostic mode to set the timing! All you have to do is start the car and let it warm up. Turn it off. Disconnect that wire...that's the EST connector... Start the car again and let the idle fall to normal. It might start or idle a little funny, only because it's running base timing now. Loosen the holddown and adjust the timing. Re-tighten the holddown and turn the engine off. Reconnect the EST and re-start the car. Your timing should now be set. Don't even mess with the ALDL or anything else it tells you to do....

I don't know about the TPS voltage, but I assume it's about the same on a V6 as it is on a V8..and I think it needs to be somewhere in the .54-something or other area, but I don't remember the exact #'s. .6 is a little off at idle. Car will probably run better if you re-adjust that. If it's a non-adjustable type, well....you're stuck buying a new one.

And for reference, yes, the ALDL is the connector under the bottom of the dash, near the fuse box. If it says to ground two terminals, all that means is to get a piece of wire, a paper clip..anything conductive...and connect the two terminals together with it. You don't have to run any extra leads or ground anything out anywhere, you just have to wire the two together.

 

When I just disconnect the black and tan wire it jumps 30degrees a moment or so after it is set at 6degrees it does this all by itself which leads me to beleive it is still being messed with by the computer.

 

Do you mean when you RECONNECT the EST wire? See, the timing you set with the EST disconnected is base timing. When you reconnect the wire, the computer takes over. The computer ALWAYS will fiddle with the timing, no matter what.. That's what computers do man. When you reconnect it and check the timing, it's normal for it to jump up to about 30. If it was 30 degrees of BASE timing, it'd destroy your motor...but because it's 30 degrees of electronic advance, it's just fine.

In short, you're good to go man!!

 

It jumps up that high without reconnecting the black and tan wire. It also just doesn't run nice at all it backfires, pops, and has half the power it should.

 

all you do is disconnect the black and tan wire, set the timing then reconnect...you shouldnt be trying to rev it or anything like try to find out that it has half the power, when you have it disconnected there is no advance so it wont have any power.

 

It shouldn't be going that high at all unless the computer is connected.... What does it read initially when you go to time it? And when does it jump up exactly after you time it?? Maybe your distributor holddown clamp sucks and is letting the distributor rotate.....but still, to rotate THAT much? Something fishy sounding to me.

 

My distributor clamp is working fine I can't spin the distributor when it is tightened. As for the backfiring and running rough that happens before and after I recconnect the wire. I only drove it and reved it after the wire was reconnected. What I am getting at is disconnecting the black and tan wire is not bypassing the computer I want to try to ground the diagnostic ports. How do I do it? Which holes are A and B? Even if it doesn't work its worth a shot. Oh yeah it jumps its timing a few seconds after it is set.

 

There is a relay off the positive battery terminal, this is your computers power cable. Unplug it. That will take the computer off line.

 

Won't taking the computer offline shut the car down because it can't control the fuel injectors any more? If not...you can probably unplug the ECM fuse to disable the computer too...might be a little easier. By the way...terminals A and B should be on the upper row, the two farthest to the right. But grounding those together should put the car into diagnostics mode. Not gonna have any effect other than your check engine light will be blinking all sorts of crazy patterns if you get the car started...that's KOER diagnostic mode...the blink patterns symbolize your operating conditions- lean, stoichiometric (I assume this stands for NORMAL! ), or rich.

 

...which will prevent the car from starting.

I didn't see where you were disconnecting the EST *with the engine shut off*...sounds from your description like you may have been doing it w/ the engine running. Don't do that.

With the engine off, disconnect the black/tan wire, hook up your timing light, and start the engine. Shoot the timing light @ the tab, see where you are, adjust as indicated, repeat as necessary. When it's where you want it, shut the engine off, tighten the distributor bolt, then restart and recheck timing *before you reconnect the EST*. If it's still good, shut the engine off and reconnect EST.

 

Thanks guys I finally got it set. I disconnected the est started the car, reset the timing, shut the car off, reconnected the est, and disconnected the battery for five miniutes to clear the codes. Then she fired up and purred like a kitten.

Thanks

 

Don't see what resetting the ECM would have to do with making that process work, but hey..if it works...why bother asking? Don't look a gift horse in the mouth.