phresh_5

Ok so my friend and I are tryin' to fix this misfiring problem. Here's the specs on the guys car:
D16Z6, 14b, IC, DSM450, Uberdata.

The car boosts fine at 8.5psi all the way up to 4000rpm, then it beings in misfire and go lean. We have the WB hooked up and it shows 11.7-12.2 before 4k then all of a sudden around 4k to 4500 it begins to misfire and goes lean to around 13-14 a/f. Here's what we've tried:

Swapped known good distributor (from my car)
Swapped ignition wires
Swapped injectors
Swapped resistor box
Gapped plugs at 0.25 (ZFR6F-11)
Tried disabling vtec (same misfire)
Tried enableing vtec @ 3500rpm (same misfire)
Tried richening up the 3500 to 7k fuel range
Swapped known good ecu (from my car)
Tried leaving the wastegate open and WOT = no misfiring all the way to 7200rpm
Tried going part throttle boost uphill at 3500rpm @ 8psi = pulls hard
Tired going part throttle no boost upto 6k then going WOT = instantly starts misfiring
Swapped known good map sensor
Tried mild step retard (Total timing = 22)
Tried running it with no cat (same misfire)

I dunno, the car pulls hard down low untill it hits around 4000-4500rpm then it starts misfiring and looses power. Used to get an ELD code once we pushed it hard into the misfiring but I've since disabled it in Uberdata and it doesn't come back. Also used to get CYP code with old dizzy but the dizzy from my car took care of that.

Any idea's?

pornstarSR

i would have thought map sensor but you swapped that...

im gona say its tunning

load map need work

yellowturbo

just get a new set of plugs... it could be a fouled plug ??

Zer0DazE

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by yellowturbo &raquo;</TD></TR><TR><TD CLASS="quote">just get a new set of plugs... it could be a fouled plug ?? </TD></TR></TABLE>

or you may need to change the gap.

i am willing to bet that the issue is the plugs.

yellowturbo

no his gap is more than good... maybe he should change his plug and try another part number...

Just search here and you will find... I dont know but I do not remember anyone who use this kind of plugs ...

illusive

Almost still sounds like a problem with a map. Those are the same symptoms of a ecu seeing boost.

093turbo16

iTrader: (2)

possibly fuel pump?

blundar

not a bad call... I saw similar symtomns from a H22 swapped EG that had a bad fuel pump. Could *barely* get a 14 AFR at low RPMs/loads, but as soon as injector pulsewidth increased, AFRs climbed even with 2-3x as much fuel added to affected areas.

mattssi

I was thinking a possibly a failing fuel pump, Or a really bad fuel filter. Possibly never had been changed?

GEN2TEG

Distributor maybe?

ladysman

Plugs and gap look OK.


Modified by ladysman at 3:23 PM 12/9/2004

EKhothatch

Sounds like its either plugs, distributor or map.

93TurboSi

when you have a misfire no combustion takes place so clean air passes into your exhaust causing a lean A/F reading. this happens whenever i get missfires on my aem. so you <U> probably </U> only have a misfire not a lean condition

i'm pretty sure the ZFR6F-11 is a platinum plug right? try a copper plug like a bkr6e and gap it even smaller as a test to rule out plugs like maybe down to .021-.023.

verify your timing with a timing light to if you have not done so. especially after change out the dist.

the other possibilty is that the map coul be getting so super rich above 4k that its causing missfires but fool you because of the clean air fake lean condition. This one is scary to test though. cause basically the only way is to slowly lean it out bit by bit.

SOHC_MShue

i believe the zfr6f-11 plugs are just stock ngk's with one step colder heat range correct?

ladysman

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by SOHC_MShue &raquo;</TD></TR><TR><TD CLASS="quote">i believe the zfr6f-11 plugs are just stock ngk's with one step colder heat range correct? </TD></TR></TABLE>

Correct. They are not platinum.

phresh_5

Thanks for the suggestions.

I'm gonna try a new fuel filter next and swap over the known good spark plugs from my car.

I doubt it has anything to do with the map because we've moved vtec up/down and turned it off with the same symptoms. I've added fuel directly to the area that misfires and it still doesn't change anything.

But I'll keep thinkin' of other possibilities. Keep the suggestions coming.

SOHC_MShue

bump somebody help this guy

phresh_5

I gave the owner the car back and put a 4500rpm rev limit on it so he can't mess it up. Havn't had time to try my two idea's, but bump anyways.

phresh_5

Ok, so I finally got a chance to try out the new fuel filter and swap over the plugs from my car.

After changing the fuel filter the missing felt a little different. It's "sputtering" noise increased in speed and the car doesn't seem to loose as much power when it starts missing as it did before. But regardless, its still there and still happens at the same rpm range.

Next we ghetto rigged a fuel pressure gauge with a hose coming out of the hood through the passenger window to verify that the fuel pump was still supplying enough fuel at the problem area of the power band. It was. The fuel pressure continued to remain steady and slightly increasing as rpm went up (as it should).

So now we've completly ruled out any mechanical fuel problem possibility.

I then tried swapping in the ZFR6J-11 plugs from my Z6 into his, didn't help.
Put his plugs back in and gapped them at .020, didn't help.

So now we've ruled out any mechanical ignition problem since everythings been swapped with known good parts.

I also tried using a brand new chip with a new basemap, didn't help.

Next I might try upgrading the ground wires and adding a ground from the distributor to the chassis. Then try finding someone that has msd wires so we can test them out. I'm running out of idea's...

phresh_5

Bump for the morning crew

phresh_5

Bump for the night crew

blackeg

man, all my suggestions have already been said. i guess all i can do is give a bump . good luck

edit: did you verify you are at 16* btdc at idle with a timing gun??

i had a slight misfire with my z6-t. i never got around to fixing it cause the car was stolen, but thinking back on it id bet that was my problem

racinskittle

what's the base timing set at off of the distributor? Check it with a timing light. Was it retarded previous to running uberdata?

Snail Tuning

i had this problem with my last tune on a z6 engine

it would lean out near vtec.

you need to add fuel on the lower map, not the high.

because it won;t jump to the high fuel map until vtec engauges

the GSR i was tuning had this exact problem. 14-16 a/f and then would drop to 12 at 5k, but would sputter like a bitch until it hit 5k. so finaly i bumped up the low fuel table and alittle right at the vtec crossover and it started to fix it.

try that.

301am

kinda like this, but opposite?
http://www.mod-mart.com/car/MOV01435.MPG
its most likely a tuning issue