T O P I C R E V I E W
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twstd5o
Member # 1981
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posted
HELP PLEASE...I've got a constant misfire at 5000 rpms and I can't figure it out. It's been on the dyno and one other shop has yet to figure it out.
Here's what I've done so far:
Ignition: new 3924s gapped at 50 cap and rotor stator msd coil wires ignition module
fuel: 30lb injectors 255lph fuel pump fuel pressure reg recalibrated meter for injectors
I've also cleaned the IAC, IAT and ACT sensors.
The tuner said the injectors are now at 70% duty cycle and the air/fuel ratio is pretty much right on just like the one attached above.
He had a spare processor at his shop and we swapped that out as well as a different chip and nothing helped.
What should I check next??? PLEASE HELP
The h/c/i combo is as follows:
331 twisted wedge xe274hr track heat intake
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TRIXSNK
Member # 2844
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posted
Did you try closing the gap a bit on the plugs?
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AJBlackGT
Member # 3936
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posted
quote: Originally posted by TRIXSNK: Did you try closing the gap a bit on the plugs?
yeah, try that...i posted that over on the other post at the corral.
You dont have an MSD box do you?
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twstd5o
Member # 1981
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posted
I have a Crane Hi6 Ignition...what should I gap them to, 40 or lower?
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red GT black rallyes
Member # 4495
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posted
maybe try unplugging the crane box and see if its that, if not have fun finding out what it is cuz i had the same problem and i never could figure it out so i just changed my MSD box did another tune up and changed my timing chain, oh and i went with the A9L computer.
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twstd5o
Member # 1981
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posted
We bypassed the ignition and it still did it. I forgot to mention we also put a new fuel filter in there too.
I found this Ignition and Fuel specialty shop in Concord who says they can probably fix it but I need to bring information and installation instructions for every after market part I have on the car. Oh and the base price for diagnosis is 500.00
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jaybquick
Member # 4286
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posted
hey twstd, just realized I was on the corral forum with your same post. Maybe it is just the Dizzy screwin up.
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JohnB
Member # 969
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posted
It sounds like the pickup in the distributor is going out. A slight possiblity is the fuel pump cutting off, but I doubt it. I'd check the fuel pressure under WOT though.
Close the gap? The car isn't blown.
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twstd5o
Member # 1981
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posted
Isn't the stator the pickup...If so I just changed it last week. The fuel pump is brand new as of two days ago.
Fuel pressure was dropping at WOT but after changing the injectors, reg, pump, and filter it's not anymore.
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twstd5o
Member # 1981
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posted
I've heard on stroker you sometimes have to use a smaller gap...is that not the case?
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JohnB
Member # 969
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posted
What is your CR? Unless it's over 10-1, you have no need for closing a gap. And if it is over 10-1, and you're only making a lil over 300rwhp, I'd talk to the tuner, cuz sonething's wrong.
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Fostang
Member # 3752
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posted
quote: Originally posted by JohnB: What is your CR? Unless it's over 10-1, you have no need for closing a gap. And if it is over 10-1, and you're only making a lil over 300rwhp, I'd talk to the tuner, cuz sonething's wrong.
autos and dyno's don't always agree you should know that John.
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JohnB
Member # 969
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posted
LOL!! Well, I was trying to be nice. I guess I coulda went with something like this...
"I'd speak with the tranny shop first, cuz if you're only making a lil over 300rwhp with a 10-1 331 stroker, you've got a converter as loose as a whore in Thailand"
What I was getting as was he shouldn't need to close the gap. Period. I'm guessing all the normal stuff has been checked. TPS, Ignition module, stator, etc...anything that has to do with ignition and/or throttle position??
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AJBlackGT
Member # 3936
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posted
I was assuming that he had a little compression when I said close the gap, i mean why have an all motor stroker with no compression And its free, mine as well worth trying, .050 is a pretty big gap anyway. Find a dizzy you can borrow and try it out, and check your grounds
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2stangs69-91
Member # 1951
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posted
I would go to a AR autolite racing plug 1 step colder and close the gap down to .040. I have experianced plugs that glaze and cause high RPM misses that only show up under load. I think it is that simple.
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TRIXSNK
Member # 2844
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posted
quote: Originally posted by JohnB: It sounds like the pickup in the distributor is going out. A slight possiblity is the fuel pump cutting off, but I doubt it. I'd check the fuel pressure under WOT though.
Close the gap? The car isn't blown.
My bad for some reason i thought it was
Didn't mean to mislead.....
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98slowhoe 'FIFTYLX'
Member # 895
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posted
Sounds similar to the problem Yellow94GT(drew) is having. He can't find the damn thing either, and he has tryed a lot of different things. I wish you the best of luck cause it might be a while!
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HungryHippo
Member # 537
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posted
i'd try a .045" gap and check as many of the grounds as possible
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twstd5o
Member # 1981
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posted
Today was the first time I've drove it since cleaning the ACT, IAC and IAT and it seems to be much, much better... Before I cleaned the ACT, it was black with crud all over it.
The Thermactor vacuum hose wasn't on all the way too. I don't know if either of these could have been the problem but the car hasn't misfired yet in about 20 attempts. It use to do it all the time. It might just be my imagination but I'm getting a second opinion on this in an hour or so.
Thanks guys
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talaposa
Member # 2460
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posted
Looks like its time to go back to basics. I'm assuming from the threads that the ignition and fuel are O.K. I'd look into the spring rate on those heads. Weak springs could start to float at about that rpm with the hydraulic roller setup. Cam profile will make a difference. I'd look there.
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