I have a 87. Recently, my car will die while I am driving. I try to check the ignition timing after I disconnect the EST connector. The timing line on pulley will line up with timing mark at 6BTDC (6 degree Before, not After). The only problem is once a while (let's say 5~10 seconds) The timing line will rapidly jump around (i.e. from 6BTDC~0BTDC and 0BTDC~6BTDC). The most of time will stay at 6BTDC. I don't think this is normal. Anyone has same experience? What should I do to find out the problem? Thanks

 

Does the engine RPM's change. This will cause the timing mark to move. Is the distributor bolt tight enough?

 

The rpm will stay at either 600 or 700rpm with no change. the distributor clamp is very tight.

 

How many miles...timing chain and/or balancer can be worn...

 

Maybe the balancer is slipping. I've heard they go back sometimes and silp around. That's my only other guess if the rpm's are steady. Any slight change in rpm's will cause the timing mark to move.
Hopefully someone else chimes in. Now you have me interested...

 

my 87 has only 86k miles. I don't know about the timing chain or balancer has ever been replace. I just bought from my very good friend. Is it could be idle air valve sensor, or Mass air flow sensor, or ECM, or manifold pressure sensor?

 

Your timing should bounce around a little at idle because the computer is trying to retard or advance your spark to keep the engine at a certain RPM.

Rev your engine up to about 1,500 RPM's and then check your timing. If your timing is still bouncing then there could be a problem. Your MAP sensor is the first place I'd look.


[Modified by SuprJames, 6:16 PM 4/3/2003]

 

top -
First, you probably ought to go over to the right Forum for your car - we C3 guys don't even recognize the existence of an ECM....

Some comments on suggestions given to you on the preceding posts:
Once you have your ECM wire disconnected (the correct way to check the timing), there are no engine inputs that will cause the timing to change: The '89 has no centrifugal advance - it's fully controlled by the ECM. Variations in rpm will not affect timing with the ECM wire pulled. Also, other engine sensors have no input to spark advance once the ECM connector has been pulled. If you have ignition scatter with the ECM disconnected, you have a mechanical wear problem, most likely a sloppy timing chain. A balancer will not walk back and forth as you describe - once the balancer slips, it shows steady timing, just way off the scale.

To test the T-chain for slop and wear, just pull your distributor cap off. Rotate the engine so that the line on the harmonic balancer lines up somewhee on the timing tab. Now, rotate the engine in one direction until the rotor starts to move. Make note of what line the balancer line aligns to. Now, rotate the engine in the opposite direct very slowly until the rotor starts to move again. Make note of how many degrees you rotated the crank before the rotor started to move. I'll bet you that the number of degrees is equal to the amount of timing scatter you are seeing. If it is, your problem is the timing chain. Not uncommon for the t-chain to have quite a bit of slop at under 100K miles.

 

Let me tell you a little bit more about this car.
1. I just finish my intake manifold job. I put the new gaskets in intake and valve cover.
2. the car won't start since I mess with spark plug wire firing order
3. the car start ok after I put spark plug wire firing order correct.
4. adjust timing to 6BTDC. the car runs fine.
5. the car die during driving because the distributor not tighten enough.
6. the car run good after tighten the distributor
7 a few days later, the car won't even start
8 I found out TPS throttle postion sensor is bad(voltage stay high=5V). I put a new one. the car start right up and run good and no " engine service soon" light anymore.
9. the car run shaking when I try to rapid accelerate.
10. I found one of spark plug wire has a cut on outer insulater. This cause some arcing to ground.
11. I put the new spark plug wire. The car won't shaking anymore when I ramp up the rpm.
12. I try to recheck timing with new spark wire. at this time I found the timing will jump around once a while(every 5~10 seconds)
13. This morning the car die three times when I cursing the car the stop sign (when I am not pushing accelerator).
14. when I try to start the car. the car will start again if I pushing accelerator to start with.
15 the car won't die if I push a little bit on accelerator while I cursing the car.

Could anyone tell me why the timing will jump around? Why the car will die when I not tap the accelertor? Are these two problems related/

Thank you very much.

 

when I check my timing, I disconnect EST connector. So I don't think the computer has any effect on timing. By the way my idle air connector is kind of chiping.

 

you probably right. I will go ahead to check my timing chain. I forget to tell you that my car also has a metalic/bearing ringing/pinging from one of pulley. I never has this problem before. This might has to do with the timing jumping. This sound will go away if I ramp up the rpm. Let me tell you what is my other question:
1. I disconnect EST connector
2. set timing to 6BTDC as standard
3. turn off engine reconnect EST connector
4. start the engine again. now check the timing with EST connector connected.
5. The timing line show even more advance(I would say about 12~13BTDC) than 6BTDC and stay there. of course once every 5~10 seconds timing line jump around.
Why the timing won't stay at 6BTDC after I reconnect the EST connector?
Thanks

 

I'd check the timing chain first.

 

[quote]13. This morning the car die three times when I cursing the car the stop sign (when I am not pushing accelerator).
14. when I try to start the car. the car will start again if I pushing accelerator to start with.
15 the car won't die if I push a little bit on accelerator while I cursing the car.
quote]

I have your problem figured out. You are cursing your car. Mine doesn't act right when I curse it either. :lol: :lol: :lol:

Brett :thumbs:


[Modified by Brettmc, 2:21 PM 4/3/2003]

 

Hi guys. I means during my driving when I take my foot off gas as the car slowing down, the engine will die instead idling. Most of this happened when I slowly approaching to stop sign.

Thanks