timing advance adjustments

[george_tlc]

Well, the manual says IDL-E2 2.3k ohms or less when at 0.50mm feeler gauge (which is the 'closed' resistance requirement). I agree that with the drawing of the TPS shows that IDL-E2 is a switch and I was expecting zero ohms when closed - 16 ohms seemed wrong. But, if you believe the manual it appears that it is still within spec.

My cables are not tight at the throttle closed position.

Can someone measure IDL-E2 resistance on their 80? Just pop off the connector and poke in an ohm meter.

Anyhow, need to convince one of my local 80 owner friends to visit for some comparo measurements...

george.

 

[landtank]

Well I just ran out and checked mine and it reads about 14 ohms. I've got to read the manual fully as it is depicted as a switch which is what I'd expect.

Hello Dan? got one laying around the shop? We need a ohm check accross pins 1 and 2.


Ok read the manual. That 2.3ohm or less figure is with vacuum applied to the throttle opener and the throttle valve closed against it. So in that respect it isn't really closed all the way as I just checked.

 

[cruiserdan]

I am out at the moment. I have one coming in tomorrow morning and I can check it then.

 

[Scamper]

[quote author=george_tlc link=board=2;threadid=14390;start=msg138447#msg138447 date=1081890837]
Well, had a few minutes to measure stuff today.

With a meter across the pins of the TPS I measured the following:

Throttle closed (engine off)
VTA-VCC 3180 ohms
E2-IDL 16 ohms

Throttle wide open (engine off)
VTA-VCC 850 ohms
E2-IDL open circuit

Opening the throttle just a fraction beyond closed would cause E2-IDL to go open circuit.

These measurements appear reasonable for the TPS when compared to EG-158 of the manual. I guess the next step is to perform the steps with the feeler gauge to ensure the TPS is correctly adjusted. Appears I need one of those small vacuum pump gadgets to perform the tests & adjustments though...

george.
[/quote]

It's amazing to me how anally retentive we all are... I just did the same thing after reading this thread (I have the vaccume thingy). I noticed that there was a bit 'o stickyness in the throttle cable and that the resistance measurements were being affected, so I pulled the TPS and measured the resistance off the truck, and sure enough it was making contact when fully closed. The TPS functioned as advertized in the FSM.

I suspect that if you can't jump your diagnostic port into timing mode, you should jiggle the throttle cable manually--even trying to "push" it down to close it. I'd try that before replacing the TPS. Obviously, the cable needs to be addressed at some point, but a slight stickyness won't be noticed under normal driving conditions which is why I think I didn't notice mine.

Tom

 

[CodyRx7]

Ok, found this thread, and I am having the same problem. A couple days ago I bumped the timing up a few degrees.

I went through the instructions, and shorted the E1, TE1 pins to get the vehicle into service mode and as described, the timing went down to 3 degrees BTDC while shorted.

I tried to readjust today, and I am NOT able to get the vehicle to go into service mode when shorting the pins and restarting the car.

Whats the fix for this?

 

[CJF]

Did you read the last paragraph of the last post (not counting yours) in this thread?

 

[CodyRx7]

Yes, tried the jiggling/pushing down method...

Landtank in another thread said that since I already adjusted the timing in service mode to 10 degrees, that is where it will return to when I jump it...

The 97 doesn't have the blinking Check Engine light when you access service mode, so I have no way to confirm I'm actually IN service mode...(that I know of)

 

[landtank]

service mode eliminates the timing advance control of the computer so you can base line the distributor. In the old days this was done by removing the vacuum line from the distributor. This is for a mechanical adjustment of the distributor and if you move the timing in service mode (move the distributor) it will remain where you left it when you re-enter service mode.

In service mode the timing should be almost rock solid while under computer control it will bounce around.

 

[SUMOTOY]

service mode eliminates the timing advance control of the computer so you can base line the distributor. In the old days this was done by removing the vacuum line from the distributor. This is for a mechanical adjustment of the distributor and if you move the timing in service mode (move the distributor) it will remain where you left it when you re-enter service mode.

In service mode the timing should be almost rock solid while under computer control it will bounce around.

Agree. And I see this all the time in my shop, incorrect idle caused by: linkage bind, mechanical bind, electrical switch open (wiring at EGR, etc), or bad WOT switch.

From the FSM, the idle spec is at the WOT switch and has to do with the pins between between IDL and E2 (the two lower pins on the WOT *switch* with the ailgnment tab to the right). This overrides the low end of the potentiometer circuit, and is required for baseline timing set mode.
At 50mm or less measured at the closed throttle stop = continuity E2>IDL
At 70+>mm measured at the closed throttle stop = no continuity E2>IDL

Forget the VTA spec, as this appears to do with decel.

IOW, if you have continuity at E2>IDL at 50mm or less, you should have active baseline for timing. If you have no continuity at 50mm or less, then you have to either correct the mechanical problem causing stop at 50+mm, or adjust the WOT switch to reflect idle spec, or fix the wiring. I'd also suspect it might clear up your primary problem as well. Trace the wires back thru the harness.

HTH

Scott Justusson
QSHIPQ Performance Tuning
Chicago
94 FZJ80 Supercharged