Over Lean/Rich Symptoms

[Wilson13B]

My car have this kind of problem recently,when accelerate until 4K RPM the car will stumble/Hesitate "act just like a rev limiter" sometime back off the accelerator and push it again it ill go fine.....and when the hesitation happens if i keep on accelerating sometime knocking will happen.......

I've checked the fuel pressure and everything seem fine,could it be spark plug or could it running too rich or too lean,i really can't figure this out,thanks for any help =)

 

[fazid88]

i have the same problem before..my mechanic says its not knocking...its misfiring...when u accelerate under load like u say till 4k then suddenly ur car seems like jerking rite? my problem was the O2 sensor...changed it and everything become ok..but he say it might also be the spark plug or the cable...he checked my O2 sensor using some tool to check the error code from ecu...

 

[guest]

same happens to my friend's car....evo2 engine with walbro fuel pump,fuel regulator and AFC 5 button...when reving till 4k rpm...car start tu jerk...what he do is i think he set the FR to be mo rich and tune back the AFC 5button...when we race along the high way can see fire came out from his car exhaust....huuu cun ahh?over rich ka that?

 

[fazid88]

that backfire can be caused by running to rich...but mostly due to carbon deposits in the exhaust due to incomplete burning in the engine..or if ur fren running on straight street pipe with no converter also can cause the backfire

 

[Wilson13B]

i have the same problem before..my mechanic says its not knocking...its misfiring...when u accelerate under load like u say till 4k then suddenly ur car seems like jerking rite? my problem was the O2 sensor...changed it and everything become ok..but he say it might also be the spark plug or the cable...he checked my O2 sensor using some tool to check the error code from ecu...

But the CEL never lit up .... if the 02 sensor kaput dy wouldn't the CEL will lit up?

The thing is like this,when the car jerk,there is popping sound coming from the exhaust and the engine just won't rev just like stuck with rev limiter,if i continue to accelerate hard sometimes knocking will happen "sound like a diesel clattering sound" ....

Another this is,last time when ever i accelerate hard and shift to other gear,there will be pop from the exhaust and fire ball shoot out from the exhaust,if no fire also got black smoke,every single shift,but now there is no pop sound from the exhaust even when i accelerate hard .... i suspect it running lean,but the Fuel Press still ok,as there is no AFR gauge or anything that can see the AFR directly,any thing i can do to diagnose if the engine is running lean or rich?

Thanks =)

 

[fazid88]

well...if u dun have afc i think the only way to know is bring it to a tuner who knows and have the equipments to read ur ecu...from how u describe it most likely ur running lean...the pop sound when u accelerate hard if im not mistaken is usually when u use street pipes...no converter and hence ur exhaust is rich with unburned hydrocarbon...but if u havent changed ur piping, popping sound means ur running rich...quite contradictory..hmm...well, im no mechanic..maybe any sifu out there can clarify things?

 

[Wilson13B]

well...if u dun have afc i think the only way to know is bring it to a tuner who knows and have the equipments to read ur ecu...from how u describe it most likely ur running lean...the pop sound when u accelerate hard if im not mistaken is usually when u use street pipes...no converter and hence ur exhaust is rich with unburned hydrocarbon...but if u havent changed ur piping, popping sound means ur running rich...quite contradictory..hmm...well, im no mechanic..maybe any sifu out there can clarify things?

Im running Turboback pipe straight to rear straight through muffler,there is no resonator/cat converter =)

I have some picture of the spark plug,i ill post it up later,hope the expert sifu's out there can help me clarify my engine condition =)

---------- Post added at 07:33 PM ---------- 6 hour anti-bump limit - Previous post was at 07:22 PM ----------

Thanks for any advice =)

 

[Izso]

Dude, go for a dyno and see where the lean/rich is happening or get yourself a wideband sensor. I kept fouling one plug (cylinder 3) and even changed the plug cables and all.

My own dyno showed I ran super duper rich at 3.5k rpm.

After some diagnostics I found the problem was with my AFPR being set to 5bar pressure. Reduced it to 3.5bar and voila, free power!

 

[Wilson13B]

Where you have the Dyno? how much does it cost?

Not dare to dyno,scared the dyno result will be very disappointing and malu.... =P

 

[AD_EG]

dyno rental i think between rm50-100.

tuning cost depedns what ECU/piggyback u using.

dont be malu bro..hp is just a number. not important...and that is malu? or having a BLOWN engine cause continue to drive on lean setup is more malu?

 

[guest]

what happen if set to rich ah?

 

[chek_corolla]

if not mistaken, white spark plug is lean.

 

[AD_EG]

not so bad la if too rich, but FC will be bad, puffing black smoke, and plugs will foul up earlier, performance a bit sluggish

in short better to be running rich than lean.

 

[kumar22mostwanted]

not so bad la if too rich, but FC will be bad, puffing black smoke, and plugs will foul up earlier, performance a bit sluggish

in short better to be running rich than lean.

yeah safety should always be first
thats why no matter what running rich is always better than running lean

 

[guest]

oh..as my previous post...my fren is using 86mm piston, got AFC5 button, fuel regulator and walbro FP and nissan turbine r33 or 32 fogot the code like 38v dunno wat haha....as fazid88 said...causes of backfire is because engine running too rich...well my car is standard evo3 engine...lastime wen we go back home..about 85km...both constant speeding...but my fren do more and faster speeding than me(as i sometimes only tarik2 and speeding up)...before we go back home..me and my fren got same half tank fuel as in the indicator.....cun2 the needle shown half tank fuel...wen we both at home...we compare our fuel consumption and the result is my fren fuel meter shown just nearly the last line..as mine already ngam2 or a bit lower then the last line...arr how this ah?is it mine that running rich?but my car got no backfire...he got backfire...oh ya....he boosted around 1.3bar...as me..heheeh standard 0.8 only....btw for all he done to the car...at 4th gear i can tapau my fren car and at 5th gear bye bye to my fren...haha y ah?he said at 4th gear to 5th hear..the rpm drops rapidly thats y he said cannot tapau my car...clutch problem?slip?