Ok, I was trying to check and set the timing on my 1990 automatic and I am kinda lost. I havent really ever done timing on a car before but I have been reading the Helms manual. Now I am stuck and kinda discouraged from learning how to work on my car. First I checked the timing and it looked to be at 5* about the 0 mark. Not knowing much about timing I thought it had to be set at zero. So I moved the mark to 0 and thought I was done. (Yes, the ECM wire was unplugged). Plugged the ECM back in and the car idled like crap. Looked at the label again and saw that the timing had to be set at 6* DR. Looked at the Helms manual and it said to set the timing to 6* BTC. So now I am stuck. I think DR means drive but what is BTC? Where is the timing mark supposed to be? 6* above the zero or below? Basically what I am asking is can someone provide me with explicit instructions on setting the timing correctly or directing me to a place on the internet where I can read the instuctions. Right now I set the car back to the way it was before I started, 5* above the zero with the car in park and the ECM unluged. Thanx!

 

Disconect the est wire(tan) connector by the brake booster.
BTC is " before top center
Adjust dist. till line on balancer lines up with the 6btc on the timing tab
:cheers:

 

ok, so with the car in drive, ecm unpluged, where should the timing mark be? At point 1 or point 2?
This is an image of the timing tab as viewed from the drivers side.



[Modified by C490Vette, 7:08 PM 3/21/2004]

 

Mark #1 on your drawing. Keep the car in park while setting your timing.

 

Are you sure about having it in park? The helms manual reads..."With engine running at idle speed, check timing by aiming light on timing mark on engine. Timing is 6* BTC in "Drive" for automatic transmission and 6* BTC in "Neutral" for manual transmission." I have an auto so...?

 

In drive, with the parking brake applied and wheels blocked

 

In DRIVE. This is what the sticker says.

Keeping it in PARK would have the initial idle speed higher and that will result in an inaccurate timing setting at the end of it all.

 

Thanks for the illustration. I was having trouble reading mine due to rust and corrosion. :thumbs:

 

Well,

I set my car at 900 RPM in neutral. This gives me about 650 RPM in DRIVE. The timing shouldn't change until you hit 2000 RPM anyway. That's when the advance kicks in. I'm not exactly sure if it's 2000 RPM or not but I seriously doubt if that 250 RPM difference between NEUTRAL and DRIVE would change the timing at all. IMO, keep it in PARK when you do your timing readings.

Also, get the type of timing light that has the dial on the back. You just turn the dial to the timing you want then line up the mark on the harmonic dampener to the easily-seen "zero" mark on the timing gauge and you're done. No need to "guess" if you want a setting between the two numbers marked on the gauge.

It's sort of like the difference between the precise measurements of the earlier C4's dash digital display and the ambiguous "hand" resting somewhere between two numbers on an analog display, like the later C4's. Give me the digits anytime.

BIG JIM

 

:iagree:

I wouldn't be too concerned about setting timing in Drive, unless someone is there to step on the brake.

 

OK here is the deal. Adjust your timing in park if you wish. The timing you are doing is initial timing. Unfortunately since the outer ring of the balancer is mounted to the hub with a strip of rubber, the outer ring may slip slightly after time. Adjust it by the book but then give it a tweak if need be. I fill my car with the gas I run. Then take it out in the street punch it, and advance it slightly until the car runs best. Remember the computer will adjust this for temp, fuel, load etc on the fly. You will hear pinging if it too far advanced, and it may be a dog if not enough. You will also have to adjust the IAC, and Idle screw if you mess with timing.

Good luck

 

The 0* tab actually has a much deeper cut on it.

 

Ok, so when I readjusted it for the last time last night before making this post, I set it back to about where I found it to begin with which is right around 6* in park (I found it on about 5* in park but I figured as long as I am setting it back to where I found it, might as well just set it to 6* since it is close to 5*). Now the car seems to run real good, the engine feels tight and in tune, it doesnt shake as much. I havent driven it much so it might have been in closed loop? or warm up mode, whatever it is called. It did seems to get alittle ruff towards the end of my test drive yesterday, kinda felt like it was missing a cylinder but it may just be normal. So does it sound like I did this right? Can the timing be set wrong, yet yield a better feel and cause damage to the engine. I don't know, kinda :confused: Thanx.

 

C490: Suggest you drive the car for a few days at the 6 degrees BTDCtiming. Then try the timing at 8 degrees BTDC. If she knocks and pings, go back to a 6 degee timing. My 89 runs like a rabbit at the 8 degree setting and does not knock or ping with 93 octane fuel. Hope this is helpful. SAM