Help please I give up TPS problem.

[metsuki]

For two years, i have Still the same issue.
Hesitations at partial throttle in any gears
I am searching for a solution since then
I replaced many parts

O2 sensors
Plugs
Coils
Decat pipes
Cambelt
filters



Last day I found a fellow primer with a TPS issue sounding like what I endure for so long.
I disconnected my TPS and beside the CEL light coming on, I can tell that the car seems to ride perfectly. I reconnected it and the problem came back directly. It seems consistent with what I endure for so long I ordered a new TPS with confidence it will solve my issue at last

I changed my TPS today (5,02v VCC, 0,48v idle 4,45v wot), I clean my throttle body and check the idle at the same time (little too low eacv disconnected as the engine won't idle )

And for God sakes the issue is still there

I now that the car runs open loop when the TPS is unplug, so what else can cause my problem

I am sorry but here I feel upset and hopeless

Please help me

[goldnsx]

Year/mileage? Could you describe more under which conditions it hesitates? Below or above 4k rpm?

Did you check the fuel delivery?

Short test: did you disconnect the o2 sensors and see if it's any better? Two plugs on the cylinder head.

[metsuki]

1993
145000 kms
Manual
Hésitation at very little throttle but i think all the way up
I already bypass the fuel regulator with no effect at all, but did not go forward checking fuel delivery precisely
Both O2 sensors are New ans did not change nothing

the only thing i cannot understand is why TPS unplug everything Come back to normal. Can a bad fuel pump work fine acter unpluging thé TPS?
Actually i already went far beyond what i thought i could troubleshoot

[goldnsx]

I'd bypass the fuel pump resistor and see if it makes a difference. Done in 1 minute.

[metsuki]

You can ses Just above, i already done that without result

[goldnsx]

Did you also clean the injectors and replaced their o-rings, esp. the lower one?

Did you also check for 'wrong' air?

[Pride]

As you've already replaced almost everything except ECU why not remove the fuel tank and replace the old and weak fuel pump.

[metsuki]

exactly because i already replaced so much thing for nothing (and in fact sometimes for worst).
i know the pump will have to be change at one point, but i do not think it is the culprit because bypassing the resistor did not change anything and i do not see why tps unplug the car would run good with a bad fuel pump
but an easy way would be too check fuel pressure and i am planning to do so

[Pride]

My 92 has developed similar symptoms when away in Spa last weekend (strangely enough when giving it some beans on the 3 parade laps) and the consensus of opinion around a lunch table general chat was to replace the fuel pump as apparently they are known to get weak over time and in your case 25 years now.

[goldnsx]

Not sure if it's a weak fuel pump. Could be but I'd monitor the fuel pressure before taking out the fuel tank. Fuel pressure gauge and small camera while accelerating.

FPR ever changed?