TPS readings

[b4black]

I found out secondaries on my GN weren't opening. This time it was the little spring on the end of the shaft. Hooked it back up and found my missing boost.

I checked the TPS readings:
Cold (highest step on fast idle cam) - 1.48
1 step down - 1.24
2 steps down - 1.12
3 steps down - no change

Fully open - 4.72
Point when secondaries start to open - 4.24

It takes 90% throttle movement to get the secondaries open. They're either fully closed or fully open. Not much in between.


Does anybody know at what point TPS WOT enrichment begins? (anybody know what this means? )

 

[Freddie's Buick]

Rich,

Since the ECM/TPS at WOT defaults to mechanical operation,
my guess would be somewhere between 3-5 volts.

The spec's I have for the '82 GN VIN3 is 1.30v at the high step.

Note: When I cut out the plug on my '83 turbo carb I noticed that the factory TPS adjustment was not funtional.

At no time did the screw make any contact with the TPS and OEM reading was 1.45v at the high step. But the specs I got for the '83 turbo carb is .77v at the high step. Why the discrepancy?

 

[b4black]

This is actually an '83 carb which I put on my '82. And at the moment it's on my '83 while I'm trying to diagnosis a knock problem.

I have two '83 carbs. Both have never had the plugs removed. And both have the exact same build code 3332 HDP. The car runs the same way with either. I drives great, just knocks more than it should.


Where did you get those settings from? I haven't been able to find any. I just tried setting the TPS at 0.77. This brings the WOT down to 3.96. No noticable changes in driving or knocking. I don't have a good idea what effect changing the TPS has.

 

[Pick]

The instructions that came with my replacement TPS also list .77 as the idle setting for the '83.

I don't have it put back together to test it yet though.

 

[Freddie's Buick]

Originally posted by b4black
I have two '83 carbs. Both have never had the plugs removed. And both have the exact same build code 3332 HDP.

My '83 has build code 2512 HDP. Prior to removing the plug, the setting was at the high step 1.45v. Once I removed the plug I noticed that the adjustment was not funtional from the factory. The screw did not touch the top of the metal handle that sits on the TPS.

Where did you get those settings from? I haven't been able to find any. I just tried setting the TPS at 0.77......

I recently purchased a new TPS from 'The Auto Zone', ( great place), the specs chart cover way up to 1987 on all Rochester carbs.

This brings the WOT down to 3.96. I don't have a good idea what effect changing the TPS has.

As of yet I too am not quite clear on what exactly an off spec reading on the TPS would result in. It seems more then likely that it's for mixture control after the engine's sufficiently warmed up to operating condition.

We know that when the engine is cold at start-up the carb defaults to mechanical operation. (At this point the TPS serves no function). Also, at WOT the carb defaults to mechanical operation. So in between 'open loop' and WOT the TPS serves a purpose.

Hope this helps.... I now know that knocking is real bad for the turbo cars.

One tool I highly recommend for sensor diagnostics is the one I joked about one time. Its made by Actron and it test virtually all ther sensors on these cars. CP9087.....it aint cheap, ball-park $30.00-40....But man I tell you it checks the TPS, MAPS, Coolant and many other sensors very accuratly. The turbo cars really need checking at the MAPS and it's vacuume line.

 

[Ttype83]

This is what I noticed and the TPS adjustment.

@ operating temp TPS set to 1.2v car runs rich at idle
@ 1.12v car doesn't run as rich.

So I figure that the TPS helps to control fuel setting by telling the CC where the throttle is just like the SFI

When I took it into the buick shop they set the TPS to .67v
and said that this was the only setting that they could get
my car to adjust right at.

B4Black (Rich) with your knock problem...is it the 83?
You were having a lot of the same problems as me at higher rpm's
Change your valve guide seals, I blow all mine out.

 

[b4black]

One thing I have noticed at the 0.78 TPS setting is that converter clutch is engaging/disengaging much more often.

My car bucked once going down the highway today, then a little later the knock alert was going off and the trans started slipping in OD. I think the TCC is overheating the trans or the convertor letting go.

I'm putting it back to ~1.4 and see if the TCC quits going on and off. I hope I can make it home with all the trans intact.

 

[Ttype83]

Rich you will make it home I drove my like that for the last year(first..flare bang, second early, third flare, forth early and bang) TC would lock and unlock, then it would only lock underload.

You can unplug the TCC at the trans and run it as a nonlock-up. If it flares once going into 3rd you need a rebuild.
Sounds like you are have the same problems as me.

 

[b4black]

I made it home, but the trans is unhappy. I'll have to diagnosis it further this weekend.

I hooked up the scan tool When cruising down the highway, the TCC is disengaged. If I apply a light throttle it engages, but then again disengages. I think the 0.78 is too low for proper lock-up.

 

[b4black]

Originally posted by b4black
Does anybody know at what point TPS WOT enrichment begins?

OK, I was just looking a Poston's catalog. They have a device (made by Casper's I belive) that tricks the ECM into believeing that the TPS is open further than it is to provide eariler WOT enrichment. It claims that the factory setting is at 4.66 mV for the SFI cars. The devices provides WOT enrichment at 3.5 mV.

If WOT enrichemtn begins at 4.66 (presuming our cars use the same setting), this means the TPS setting at fast idle needs to be at above 1.42. This is a problem. The range of the TPS is not wide enough to achieve both the high setting and the low setting at the same time.


It looks like you'll have to choose low or high. Low may give better drivability, high will give better WOT (less detonation). I know which I'm choosing.

 

[Freddie's Buick]

Makes sense Rich,

That is why the '83 turbo carb's OEM preset seems to be around 1.45v at the high step, (the reading I got were there is no contact).

Also, that is why the suggested setting from a new TPS manufacturer is .77v at the high step. Obvious trade-off don't you think?

 

[Ttype83]

Originally posted by Freddie's Buick
Also, that is why the suggested setting from a new TPS manufacturer is .77v at the high step. Obvious trade-off don't you think?

When you say high step are you talking about the choke settings?

Then if 1.45v is high step....minus .25 ....1.2v for curb idle right

 

[Freddie's Buick]

You're right on the money!