Blacktop problem

[Akis308]

I've recently put an bt 20V on my AE92.
Everything are perfect except one thing....
Here is the problem.
Imagine that you are moving with steady throttle and then put on the right pedal very very gently... the engines is stalling.
I think it runs very rich at the moment.
If you put some more, the engine accelerate normally.
It doesn't matter if you are with 2000, 3000, 4000, 7000 rpm.
Its the same feeling, with a lot of backfire too...
The Ox sensor is from the AE92 (4AFE) (4 wires).
No speed sensor is connected....
I've put a fuel regulator and I drove the fuel pressure at 4 Bar, instead of 2,6 stock and the problem was partial solved, but still the engine is stalling, but not that much as without it.
Setting the pressure lower than 2,5 is causing more lag....
I'm a bit of confused and disappointed, so any help or opinion would be great...

[Michel H]

I have ae92 + BT too. My lambda is dead so idle is bit higher, +/- 1400rpm. If I give a little bit throttle then you can feel it's just running way too rich, sometimes the less throttle, the more "free" the engine runs. So in your situation, MAYBE the higher fuelpressure is making things worse ? How does it run at full throttle ?

Have you checked your ignition/timing ? I've set mine @ 10 deg. with diagnostic thingy connected. (this was still with functioning lambda though)
10deg. is VERY safe, but you'll lose bit power. 20v's are very sensitive with timing.

Also check your vacuum lines between your MAP sensor and your fuelpressure regulator.

Speed sensor shouldn't be a problem. I'm running without lambda and without speed sensor (purple/white cable) and no problems other then it just runs filthy rich

[dikolotour]

Akis,

I suppose that this one would be helpfull unless you have already read it.

http://www.club4ag.com/faq%20and%20tech_...%2020V.htm

I didn't read it but i saw it has a hole paragraph speaking of engine management e.t.c.

I hope this helps

[Akis308]

I've all ready read this Dionisi, but nothing for me....
Michel H.
My idle is at 750 rpm steady (cold 1200 rpm).
At full throttle the engine rev perfectly.
The crazy thing is when I take off the regulator the problem gets worst.
Vacuum lines are Ok.
Timing at 10 deg.

[domi]

Had a similar issue. Running higher fuel pressure isn't helping, tested and failed.
The fact that it chokes on partial throttle but not on full such is what makes me think of this, but check your MAP sensor and your TPS sensor. Could be both.
For both of them the FSM has guides to do resistance checks. For the TPS, you'll need an extra hand for someone to open the throttle or hold the multimeter leads on, but it's easy. For the MAP, you'll need a vacuum gun. I borrowed one from the local parts store and did the checks. If you can get one with a very low pressure resolution it'd be best, i almost had to guess what it's at. =<
Also check that valve/tube thing that's probably between the throttle body and the MAP, it might be clogged or in other ways inoperate. If you want the easy way out - disconnect the TPS and see if that changes anything. Still not able to determine if TPS disco'd throws the ECU in safe mode, but it should change it from a bog to a slight hesitation. Disconnecting the MAP is probably a very poor idea, at that point you should be able to work with the resistance check. If you have the chance it might be better that you don't check it on the sensor, but on the ECU side of the harness instead as that would account for bad soldering/generic wiring issue.
Are you sure the vacuums are routed well [not trying to rub it in, but i thought mine were and took me months to find what was wrong with them]. I had a similar issue, although mine was immense bogdown with the throttle open too wide [including backfires out of the throttle bodies]. Ended up being PCV valve not getting vacuum, weird as hell, still makes no sense. My ECU is still recovering, but it's been making a LOT of progress over the last few days, including today being the first day it's gone without needing to disconnect the TPS so the car doesn't choke itself on startup [cheers to that, may it last long!].
I hope it helped or at least gave a hint. I'm guessing you've checked your ECU for error codes, ya? If your CEL isn't connected, i can offer a solution.
Good luck and good night!

[Akis308]

From what you said I'll keep only the staff about the TPS.
Everything else is double checked.
I'll check the TPS, first on the throttles and then on the ECU.
Thanks Domi!

[domi]

Any time, man, thank jamie for it, i haven't been checking this forum lately - he directed me to the thread. =)
If you're certain the MAP isn't it - try unplugging your TPS and revving up [preferrably after warming the engine up] and see if it does the same trick as usual. I just spent 3 days driving the car with TPS disconnected to have the ECU remap itself and not bog on startup, running on MAP feedback alone, 2000rpm idle, no fuel cut when off the throttle and from what i could tell - no VVT. It was nightmare. Glad to have my engine running with the TPS connected again, missed engine braking =) [without the fuel-cut it was more of engine-coast, often actually going faster than if it were in neutral].
If you disconnect the TPS and it runs better [disregard small hesitations, as it wouldn't have that neat injection-precognition function] on semi-throttle, then hope it's a wiring issue.
I've also seen talks about TPS calibration of sorts, if i happen over it, i'll post it here.

[EDIT]
Just remembered something else: You're running stock ECU, right?
It kinda sounds as a fuel-map issue. If you're running standalone - try another basemap. If not - try no TPS and drive around a bit same as i did. It does miracles.
[/EDIT]

[Akis308]

I'm running on stock ECU, yes.
I've unplugged the TPS and the engine run perfect....
And had the power of my 4AFE....
So I believe there is the problem.
I've talk with the yard where I've took the engine and told me to calibrate the
TPS.
I have the service manual, but I haven't notice something about it.
I also try to check the TPS and I notice that as I was turning it the resistance is going 0 for a moment and then rises again.
That shouldn't be normal, right?

If understand correct, you are advising me to disconnect the TPS and drive it for 2-3 days?
It could fix the problem?

[domi]

If you see the resistance go to 0 halfway opening the throttle - that is your problem. Get another TPS and try using that. 0Ohms should be fully closed. Just replace the TPS and that should solve it!

Cheers!

[Akis308]

Οk.....
I've check again the TPS and notice that it is not going 0, but, just changes the scale on the meter.
I've then tried every possible position on the TPS, but only turned worst.
But.....
When I put my hand on the plenum hole, It works absolutely fine.
Same thing, when i press the fuel return line....
Is it possible, the whole problem caused from the Ox sensor?
As I said on my first post it is from a 4AFE.