[RESOLVED] missfire and white plug tip on the 1st cylinder

[63tuner]

my car seems to missfire at idle, but it happened when i drive it for more than 30 minutes. And when i drive at about 60 mph using gear 4 and 5 and then push the throttle, the car seems to hesitate with the RPM moves slowly up. I noticed that my AFPR reading sometimes went down from where i set it (from 42 psi to 35 psi) but when i pull the vacuum line at the top of AFPR, the idle went up..I have a white plug tips on the 1st cylinder.

here what i did to overcome this problem

1 clean the throttle body
2 clean the PCV valve
3 new gasket at TB and BOV
4 teflon tape at sard AFPR ( @ adjustment screw, gauge) and @ the type s BOV
5 new plugs (NGK BPR7EIX) (gap @ 0.026)
6 check for boost leak using soapy water
7 used the injector cleaner

 

[63tuner]

Any idea guys? this problem happened before i put i the new spark plugs, but the problem in creasing after i change the spark plug. my wires are not more than 2 years. my AFPR is about 6 months old (unconstant gauge reading). the type s bov is 3 months old, the 255 Wlbro (rewired) is about 2 months (bought it because my older pump keep on making a loud sound).

 

[63tuner]

oh yeah it happened on all gears, not just 4 and 5, but usually when the weather is hot

 

[D20mobile]

oh yeah it happened on all gears, not just 4 and 5, but usually when the weather is hot

you might have oil getting into cylinder1 that or your using some really crappy fuel. They call this an ash fouled plug.

 

[Freerevving]

If it's injector related, injector cleaner wont help... Seafoam helps but it's too late for that... take your injectors out and have them professionaly cleaned and/or tested...

once you've ruled that out you will have saved yourself from a melted/pitted piston

 

[turboglenn]

The white plug on #1 is the only thing making this a tad peculiar. Have you looked at the other plugs to see what color they are? When running in closed loop mode and aiming for a perfect burn from the fuel/air mix you will often get a white burn on the plugs since when at "perfect burn"..(or stoich) there are no left over hydrocarbons to pollute the end f the spark plug nd combustion chamber surfaces turning them golden brown, brown or black (depending on your tune)

Well, there's always the issue of out-flowing the stock accelerator map programming. The ECU has a feature that squirts a bit of extra gas on quick throttle openings. The engine requires the most added fuel at 0 - 1500 RPM, a little less from 1500 to 3k and the least from 3k to red-line.

After a slew of upgrades (including simple fuel management) You can start to flow more air with a quick jab of the gas pedal than your ECU is programmed to support/keep up with. This will cause your hesitation when gassing it quick from a steady state RPM cruise.

4g63's are more "hungry" than a lot of other motors I've messed with tuning when it comes to the accelerator pump function, or at least that I've found when doing stand alone tunes on DSM's. Even on 1k cc injectors i still have a huge pulse width bump for the accel pump input, way more than I'd have on most Honda's and Porsche's.

 

[63tuner]

today, i started the car and the car was running 3 cylinder. i checked the wires that connects to the injectors and i can feel that it was pulsing. but when i moved the injectors a bit it seems to run on 4 cylinder back.I moved it again and it started to run 3 cylinder again. any idea how to fix it?

 

[Freerevving]

could be the injector seal or a clogged injector... there are several ways to do a leak test, the best being a boost leak test

 

[63tuner]

do i need to change the injectors ? any other way to fix this?

 

[63tuner]

by the way ,on cylinder 2,3 ad 4 , the plugs are black at the tip ,only cylinder 1 are white. do i need to change the injectors?

 

[Freerevving]

You have one cylinder running lean from either a leaky seal, or a clogged injector (both would be at that cylinder). The oxygen and knock sensor have both picked up the lean condition, retarding the timing and causing the other injectors to run rich.

the easy way to find a leak is with carb cleaner.. at idle, spray the injector seal at that cylinder, if the idle changes (stumbles then goes up, usually) then you have a leak there. You can spray around the engine to find vacuum/boost leaks this way, although it's less effective at finding boost leaks. Keep it mind there could be a leak near cylinder #1 at the intake manifold, or somewhere else.... also keep in mind that there might not be a leak at all.

The other thing to do, which I already suggested, is to take your injectors to have them cleaned and tested. It's really just one process where they test the pressure as they're running detergent through it. They should tell you before and after flow results after they're cleaned.

 

[63tuner]

i used soapy water on the intake manifold and found no leak. what is the resistance of 510cc injector? i want to buy a set of injectors

 

[63tuner]

do leak or clogged injectors make fuel pressure drop?

 

[63tuner]

i have changed the injectors to 510cc. the car seems to run great today. but i have not try it at full throttle . i will test the car for one week and inform all of you if there is any hesitation or missfire. thanks guys.

 

[63tuner]

today, i check the spark at all cylinder and found that cylinder #1 and #3 had less spark. if the coil pack are bad, the spark should weak at either cylinder 1 and 4 or 2 and 3, because #1 and #4 share the one coil pack and #2 and #3 share one coil pack. right?

 

[63tuner]

I have not change my coil pack, i think that if the coil pack is bad than it would hesitate in all RPM range, but it happened only at 2-4000 rpm. well I installed 510 cc injectors ( i found that 2 of the 450cc have a cracked at it's nozzle ) , Installed a new alternator belt, aircond comp belt and power steering pump belt ( the volt was at 12.8v at idle and increase to 13.8v after changing alternator belt). Then I bought a new AFPR and set the FP to 35 psi because i don't have any fuel management to get the A/F ratio right.