Engine misfire from 4k+ (video)

[enjoi.this]

Ive been dealing with a boost related mis-fire, almost like fuel cut but not nearly as violent. The higher the boost I run the worse it pops. If it stays at 11psi its all good but any more is a no go.

Fuel + Air mods are: lex afm, 550s, walbro, AFPR at 34 psi (vac off), 6an lines, j-tube bypass and stock CT-26

Exhaust: full 3inch turbo back and no cats

Once at full throttle and boosting AFR drops down to as low as 9.8:1 sometimes. I noticed once it gets too about 10.8:1 is where it starts to pop. I have an SAFC-II to tune with but i was ripped off and it doesn't work.

I tested with a boost leak tester today and found 1 vac leak and noticed the EGR makes a gurgling noise. But unfortunately it still has the same problem. Things I'm going to do this week are put it new plugs (copper this time) and re-check ignition timing just because. It would be nice to figure this problem out so I can bolt on the 57trim.

At 23 seconds in the video is where I do a full throttle pull so you have to listen closely to hear the pop pop pop
[video]http://s19.photobucket.com/albums/b157/suzuki_mx499/?action=view&current=MOV02969.flv[/video]

 

[89supracrazy]

I thought with vac off that you should run about 40 psi. It seems 32 psi is a little low to me. Maybe somebody can chime in to correct me if I am wrong.

 

[enjoi.this]

33-40 psi vac off
23-30 psi vac on <---this is the one that matters - it's the normal ops condition. 25-27 psi is what I usually see.

I rechecked my fp and its about 34 psi vac off and 25 vac on. Forgot the correct value

 

[89supracrazy]

Also,
When setting the afpr to the right pressure, remove the vacuum hose.
You normally need to run a vacuum hose on to the afpr while driving but when you are setting the afpr you need to disconnect that hose.

With the hose disconnected, set the afpr at about 36psi when running stock. when runnin with the 550/lexus combo set it to 40 psi. Try to get a wideband meter and use it to finetune the afpr setting.

hope this helps

I don't have my afpr setup just yet but here is something that you might try.

 

[enjoi.this]

I tried adjusting fuel pressure like you say with the lex and 550's but it was even more rich at 40psi, hence going down to 34psi.

Checked the ignition timing today with the jumped pins and it read 10 deg BTDC and twelve deg with the jumper removed. With the timing light attached to #1 lead, I could hear a miss and see it in the flashes of the timing light. Also the degree mark on the crank pully isnt completely stable on 10 degrees, kinda almost like its bouncing back and forth between it.

Makes me wonder if there could be an issue with the coil packs or the plug leads? Still have yet to change the plugs which will come soon enough.

 

[89supracrazy]

Yeah. I watched your guage closer and realized that you are running rich. I believe you are on the right track. I would check my plugs to see how they look. It also could be a boost leak. Not enough air. I would go over my ic piping real good.

 

[enjoi.this]

I checked double time for boost leaks

On another note I put in new plugs today, BKRE7E NGK's gapped to .27

A lot of the popping is gone now but it is still present. Cars doing some really wierd shit...

Tested the coil pack along with the high tension leads. Only thing I did notice was an intermittent reading from one of the coils. I would measure resistance and the readings would jump around, then I would tap on the coil and it would stabilize at .5k ohms.

 

[enjoi.this]

Car is pulling hard now when its not blazing hot under the hood. Pretty sure Ive narrowed down a partially failed coil since I get scattered readings even when its cold. Once the car gets hot it has a very noticeable miss when idleing or holding it at 2k rpm.

89supracrazy you had the right Idea to turn back up the fuel pressure. My previous information was misleading. Once I turned the FP back up to 40psi the popping mostly disappeared. Then I turned it up again to 42psi and it is now completely gone. This makes sense since the last set of plugs was reading a lean burn.

The misfiring coil must be why my A/F guage was reading normal since unburnt fuel was making its way into the exhaust. THANK GOD IM ON A STOCK TURBO! This would have probably been the end of my fresh engine if I had something larger on right now. wew..

I did a compression check today just to see if I had done any damage but everything checked out A-ok! Now I just need to track down someone with a coil I can test with. Anyone know of a better after market replacement ignition set up for a 7MGTE?

 

[89supracrazy]

Glad to hear you got it going in the right direction. You might take a look at your afm. Mine was missing at idle and around 2k rpm. It never threw any codes until it got real bad. I luckily had a Lexus afm that I swapped it out with and it idle smooth and accel. real good. It took care of my problem. Maybe take it off and get some spray air in a can and spray the two little holes out. Make sure you don't tilt the spray can because they will be liquid come out and maybe ruin your afm. Makes sense if something is blocking the holes in the afm that is why it idles rough, until you flow more air. It might be going bad all together but I would try cleaning it first. Only air though.

 

[enjoi.this]

I just replaced my AFM with another actually since it did the same thing as yours haha. Im going to chuck the AFM here as soon as I get some more cash together and get maft-pro w/speed density. The K&N FIPK is whats wrecking the AFM's for sure since they are oiled. Im so tired of shitty AFM's.

 

[89supracrazy]

Yeah. They are a pain in the ass. Speed density is the way to go. I was going to go with the maft pro but they will dollar you to death trying to get all the accessories that go with it. It should be $400 and everything you need come with it. HaHa.