uncertain problems on M20 engine

[chriseunos]

Hi, im currently driving an E30 with a M20B25 engine. I have some questions to ask, feel free to give some input.1) During High revs, be it at the rev limit or almost reaching the rev limit, my car suddenly hesitates and doesnt want to rev. My question for other E30 driver is, during rev cut, does the engine still revs or the whole car "died off". During the hesitation, i tried pressing the accelerator, sometimes will have a loud misfire from the exhaust and my friends said that they saw ball of flames :stupid: 2) Im using a M40 meter cluster, which is not suitable for the M20 engine. The temp gauge and the tachometer flickers irratically. Does this meter have any effects on the engine? I've check the SI board in the meter and it works fine with no corrosion to the SI battery and the meter board. Will this cause the hesitation during high revs?3) I did adjusted the TPS and the hesitation still occurs. Sometimes, not even high rpm, the car just hesitates. 4) Another suspect is the 02 sensor. My car doesnt have the CAT and the previous owner for some reason extend the 02 wires and now my o2 sensor is at the middle of the car. It is plugged after the exhaust bullets.Sorry for the long post, just wanna give as much information as possibleChris

 

[cempaka]

I'd guess fuel delivery is the issue. Rev limiter would just keep you from going higher, it won't kill off your engine. Youd just be bouncing off of it but your engine wouldnt be hesitating.

Ask your mech to attach a pressure meter to the fuel line, mount it so you can read it through your windscreen, then take it for a drive. It should be reading 3.0 bar. If when the hesitation happens you see your fuel pressure drop, you know it'll be something with your fuel system. Could be dirt/rust from the tank clogging the line, bad fuel pressure regulator, bad pump, etc.

Is yours a conversion (sounds like it)? Are you running M40 or M20 pump? Has your pump been noisy lately?

 

[chriseunos]

the pump im using is an M20 pump, i did the M20 conversion twice before. This is my 2nd time. The first engine blew due to a broken crankshaft.

Another question, m20 fuel lines and M40 fuel lines, any difference?

 

[cempaka]

Which tank are you using, and how have you set it up? Swapped in an m20 tank or using m40 tank with siphon to external pump? I ask because if you have a rusty/dirty tank it would give symptoms as you describe, with debris clogging your prefilter and pump and hampering fuel delivery, especially under hard acceleration.

Also when your engine is hesitating, is it that your engine cannot rev any higher but can maintain current power, or your engine basically loses all power (revs drop)?

 

[chriseunos]

i did swapped the whole fuel tank. regarding the hesitating, it hesitates for 1 or 2 sec, then the car will go again..its like when ur're revving, u lift off your foot. Its kinda a sudden surge. Btw, my current exhaust system is customised. From the extractor, i maintained the twin piping, after the mid bullets, i customised a single 2.5" piping to a 2" remus exhaust. My friend said that due to the massive amount of backpressure, it backfires? Opinions?

Chris

 

[cempaka]

Where did you source the tank, and did you inspect the interior before install? Kedai potong tanks are usually filled with dirt and rust because they're stored improperly, if so then the particles could be causing your problem.

As for the backfire, since youre seeing flames its probably from running too rich. The flame is unburnt air/fuel mix detonating in your exhaust system instead of the cylinder.

 

[chriseunos]

the tank i got it from a running car, i've check the fuel filter before. Its clean.

Im really confused now. God...sucks that i cannot rev the car. Maybe i'll check the Plugs and see if its running rich. Thx for the input man. Guessed others are too busy to chip in.

Chris