3TC EFI can idle but can't rev up..

[CHB]

i've converted my 3TC to EFI. the system can idle but once i touch on the throttle, the engine seems to bog down and dies.. check with FPR and ignition and everything looking good..
once it bog down and dies, its very hard for me to start it up again. often i got back fire on the intake after few cranking. what would have cause the problem?

[WDE_BDY]

What sort of computer etc are you running? My initial thoughts would be a vacuum leak between the manifold and the airflow meter if you are running a factory 3T injection setup, mate had exactly the same problem on his 2T-GEU when it had a split in the pipe to the AFM.

Callum

[CHB]

i'm using Bosch L-Jetronic ECU which can be found in Datsun 280Z fairlady and running a 450cc/min low ohm injector. it will be a turbo charge 3TC but for the moment i just rebuilt the whole engine, so right now there is no intercooler piping and i left the turbo as a dummy(of course with motor oil hose attached).

[Norbie]

This behaviour usually occurs when the ECU is getting an incorrect signal or no signal from the AFM. The engine will typically idle OK but as soon as you open the throttle the mixture goes so lean the engine dies immediately.

[CHB]

This behaviour usually occurs when the ECU is getting an incorrect signal or no signal from the AFM. The engine will typically idle OK but as soon as you open the throttle the mixture goes so lean the engine dies immediately.

ok.. i guess i need to reduce the spring tension in the AFM..
how about the back fire? what would cause it? it happened after few times cranking..

[WeekendWarrior]

the backfire back out through the intake usually means timing is out. so just check your timing and it mite help the situation. check your throttle position sensor(T.P.S.) it can play havoc with that sorta stuff. your tps could be causing al sorts of dramas. it sounds like its getting a gut full of air and not enough fuel or the other way round. either one can cause this.

[CHB]

yes.. sort out the back fire.. my ignition was was too low (10 ATDC).. now started correctly but the problems still there.
i've tried to loosen the spring tension in AFM, the motor won't wan to rev up even. so i do it another way round.
tighten the AFM spring, it can rev up to about 2000RPM with vacuum 0.5 before the engine almost die off. once i realease the throttle, everything idle back to normal. checked with the AFM voltage output, signal at idle is 1.53V. this voltage does increase proportionally with the flap angle. when it reach almost 4V, the engine start to lag and choking. so i release the throttle again.
spring tension is tighten to the maximum possible but the problem still there..
any one can share something?

[Norbie]

Just a guess here, but you're using EFI from a 280Z, which has a 6-cylinder engine right? And your 3T-C is a 4-cylinder engine. Methinks the engine computer isn't supplying enough fuel because it's only getting two thirds of the ignition pulses it's expecting. Maybe you should try adapting an EFI system from a 4 cylinder engine...

[CHB]

hmm... if not mistake, 280Z is using 295cc/min injectors and fire all 6 injectors twice in complete crank rotation. i've tried to compromise it with a 450cc/min injectors in my 3TC but still fail to get a smooth a/f ratio. this is my first time dealing with AFM type fuel injection. help please..

[WeekendWarrior]

mate ive been told u can use camira injection on four cylinders as a universal thing not shore how true it is though.
there is a nice fella in warhope his name is danny and he is used to applynig efi to carby cars. he is really helpful and he can supply new universal microtech kits with computer lume and everything you relly need. just tell him what u have and what you want to do and he will order it for you. the system he talked to me about was a stand alone fuel management setup controlled and tunable by laptop. he also has some second hand mechanical adjustment efi computers there aswell.

best of luck.

[CHB]

well.. i've been considered to switch over programmable ECU but microtech seems too big for my pocket.. but Megasquirt II seems working quiet well with injections and ignition control.. any one try it before?