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Discussion Starter #1
Hi!

My car idles at around 500mm Hg. According to the "follow me" this equates to the lowest vacuum control setting in the fuel map.

The problem is when I rev the car up a little and completely release the gas pedal (like driving around off-idle in a parking lot), the car runs down around 550-600mmHg. This is off the scale of the fuel map and the car runs really lean here causing it to jerk a little and hesitate.

How do I add fuel here?
 

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TRACK CAR
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When you are decelerating independent of what cell you are in you should be running totally lean. So if you are having problems with a hesitation it probably isnt that.
 

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StokerSix said:
Hi!

My car idles at around 500mm Hg. According to the "follow me" this equates to the lowest vacuum control setting in the fuel map.

The problem is when I rev the car up a little and completely release the gas pedal (like driving around off-idle in a parking lot), the car runs down around 550-600mmHg. This is off the scale of the fuel map and the car runs really lean here causing it to jerk a little and hesitate.

How do I add fuel here?
When you completely release the gas pedal in the Supra you experience "fuel cut off" where the injectors are stopped for a period of time. So, there will always be a super lean spot there, nothing you can tune out with the MAP ECU.

Thanks

JH
 

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Discussion Starter #4
Thanks.

It didn't do this with the VPC setup.

I don't run that lean except when I let off abruptly and then try to give it a little gas. If I don't let off abruptly, then everything is fine once the gas pedal is fully released. The vacuum only seems to dip that low when I let off real quick.

The injectors shouldn't fully close when this happens, that wouldn't make much sense.

I hope there is something that can be done. The car jerks around too much.

:(
 

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Discussion Starter #5
What about the TPS enrichment settings at low rpm? Will that setting add fuel upon a rapid change in TPS when decelerating? Or is that just for accelerating? Thx
 

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8secsupra said:
When you completely release the gas pedal in the Supra you experience "fuel cut off" where the injectors are stopped for a period of time. So, there will always be a super lean spot there, nothing you can tune out with the MAP ECU.
When I let off at higher speeds above 40 mph it gets super lean but when I let off at lower speeds like 20-25 mph it gets really rich to 10.xx afr. Does this mean something is wrong?

Thanks
Chris L.
 

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StokerSix said:
Thanks.

It didn't do this with the VPC setup.

I don't run that lean except when I let off abruptly and then try to give it a little gas. If I don't let off abruptly, then everything is fine once the gas pedal is fully released. The vacuum only seems to dip that low when I let off real quick.

The injectors shouldn't fully close when this happens, that wouldn't make much sense.

I hope there is something that can be done. The car jerks around too much.

:(
StokerSix, i had similar problems to this. Read below & see if it's similar or not.

Here's what i experienced:
When i was cruising, trying to maintain a particular speed, let's say 75-80mph, i would let off & press the gas ever so slightly. when i did this, the A/F would jump to 17/18:1 (while pressing the gas) and the car would stutter. annoying.

How did i fix it?
The vaccum was going pretty high (can't remember exact numbers), but somewhere along the line, my TPS voltage settings got screwed up. i re-adjusted those and i know longer have the problem.

Why did this happen?
I'm guessing the TPS voltage setting was not providing enough resolution for the minor blip of the throttle i used to maintain constant speed. Throttle would open, more air would come in, but the map-ecu wasn't reading any throttle; more air, no fuel, leaner settings.
 

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Discussion Starter #8
thx Chuck.

That is exactly what is happening. When I let off and then apply a slight pedal pressure the car stays lean and bucks. Yep, it's annoying!

So are you talking about the TPS voltage settings in the ECU configuration menu?

There is a TPS idle and another one. Which one did you re-set (if either)?
 

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i don't have the program in front of me, but there's a min & max voltage, right?

my min was 500-something; max was 2750. i raised it to 4000 and the problem has mostly disappeared. obviously, i need to get the *right* min & max in there, but you could try raising your max and see if that eliminates your problem.

i used to experience the problem all the time; since i changed the max voltage a few days ago, i've only experienced it 2-3x. i haven't been able to discern a pattern yet, but i'm guessing if i just get the correct TPS values in there, most of it will go away.

if not, i plan to:
1. play w/ TPS enrichment. mine is already pretty rich (6-8s across the board) compared to others, but i could try bumping them up a notch or 2.

2. disconnect TPS input & play w/ map enrichment to see if i can make it run smoother than TPS enrichment.
 

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Discussion Starter #10
Yeah, I can't recall the exact nomenclature of those settings either. I thought there was a TPS idle and two boxes with settings. Not sure.

I think I was having some success this weekend just adding fuel from 1krpm to 2.5krpm. Although it helped it has added fuel where I don't need it and I'm getting a "system too rich bank 1" MIL.

I'll start using the map I used befor I added the fuel and try the TPS settings.

Thanks.
 

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any luck?
 

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Discussion Starter #12 (Edited)
Thinking about driving it to work tomorrow. We'll see.

Which of the two parameters did you adjust...the TPS max?

Seems like you'd want to adjust the min value?

The manual has a value of min=400, max=4095. My min is at ~290.
 

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well, i did some re-wiring this weekend and my car was all screwed up again... hesitation at part throttle as described above... so much for my new & improved TPS settings.

i disconnected the TPS wire, and set up the MAP enrichment table. the car seems to be running fine now (after approximately 50 miles of hard driving) so i'm guessing my problem has been a bad TPS all along.


this might be another path to choose if you want to eliminate variables.
 

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What settings did you put into the enrichment table. Why would disconnecting the TPS wire help? "Please excuse my ignorance"
 

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Discussion Starter #16 (Edited)
My car is running perfectly now. Strangely enough, I hardly did anything.

I went to button everything up and put the ECU floor cover back on. When I did this I fired up the car to make sure it was OK before I put the carpet back over it. It ran really rich at idle. Somewhere around 10.5:1 AFR.

So, I'm thinking that I pulled something loose like the vacuum hose from the MAP ECU. I took everything back apart, checked everything out, re-fit the vacuum hose (it was fine though) and verified no loose wires or other problems.

Fired the car up and same thing. Car was running real rich. After a couple minutes in seemed to lean out a little learning it's way upwards toward stoich.

I asked myself what I changed then it dawned on me that I reset the ECU to clear a "system too rich" code. I didn't use my PDA to clear it because I was to lazy to take my PDA cable off my computer and the one for the FJO wasn't easily removed. I cleared it by disconnecting the neg battery terminal. First time I reset it this way in a long time.

I cleared the ECU once more and removed 7% from the lowest three vacuum settings. BAM! The idle AFR came up almost to a perfect stoich value. I then leaned out all vacuum settings to 0psi. Car was fine.

The TPS enrichment settings MTR recommended fixed the hesitation between shifts. Now here is where the mystery comes in. The problem I described in my first post on this thread is GONE. I had planned on making some adjustments to the TPS idle setting (not the max setting) but when I looked, low and behold it was different then before I cleared the ECU. Before I reset the ECU it was at 29x (I think 293). Now the setting is at 520. My idle max changed to some lower value. I changed it to 4000.

Car runs great. I can totally let off while driving in a parking lot at around 1400 rpm, ease back on and the transition it very smooth. No jerking or leaning out. The FJO doesn't read nearly as lean. Maybe a little over 15.0:1 AFR. Used to read 20.0:1.

I do have one lean spot on boost at 4k rpm. I'm think I just need to add 3% or so in the map enrichment area. This is where my car starts to build boost quickly so i hoping that'll fix it.


Edit: To summarize, I think I had the car set way too rich, and the ECU was trying compensate in strange ways. It had learned it's way back up around stoich, but was still suffering from the overly rich settings. You may want to rest the ECU and try to get a good indication where the tune is at before the ECU learns it's closed loop operation.
 

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Discussion Starter #17 (Edited)
carendt242 said:
well, i did some re-wiring this weekend and my car was all screwed up again... hesitation at part throttle as described above... so much for my new & improved TPS settings.

i disconnected the TPS wire, and set up the MAP enrichment table. the car seems to be running fine now (after approximately 50 miles of hard driving) so i'm guessing my problem has been a bad TPS all along.


this might be another path to choose if you want to eliminate variables.
My car has a new TPS on it. A friend needed mine when my car was being modded all to hell :) So he got me a new one because mine was low mileage and he liked the way his car was running.

The TPS is simply a rheostat, and they are not high failure items. I think his just needed calibrating becaused it tested fine.

Reference My TPS calibration tips

The calibration is very tideous for the TPS. No way the TPS numbers in the MAP ECU configuration should be the same for any two cars. Also, my TPS and MAP enrichment are all zero'd and the car is running great (except for one small lean spot I need to fix).

Edit: And if you notice on the above link I posted, page 3 says that at idle the TPS volatge VTA1 should be .7v. I think that is the value we're trying to adjust with the TPS min value?
 
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