smog-guy707

iTrader: (11)

hey guys i have a 94 fd and it runs pretty bad

when i go full throtte it wont rev past like 5 1/2 or 6 and it will just backfire... but it only does it sometimes?

it sord of sounds like its bouncing off the rev limiter

(my mods are full exhaust, no cat, intake, walbro 255, fuel filter, bov)

just wondering if anyone out there has had the same symptom and what it was.

i know its not a boost leak or lack of fuel

anything helps... thanks

Rotary Potato

Have you done any kind of ECU tuning at all?

smog-guy707

iTrader: (11)

no im running a stock ecu

smog-guy707

iTrader: (11)

is sort of feels like a missfire... do fd coils ever go bad

smog-guy707

iTrader: (11)

or knock sensors

Mytelex22

iTrader: (10)

No ECU work huh? I can introduce you to a good engine builder, you'll need one soon

84 rotary rocket

could be the alternator, i had a simular problem and it was the altenator... get it checked at your local car auto store.

TT_Rotary

iTrader: (3)

i've heard a lot of people say, one of the main reasons for backfire is no cat, and thats one of the mods u have listed.. just my .02. =)

bladz311

iTrader: (1)

whens the last time you changed your spark plugs? fowled plugs can cause similar problems to what you are describing.

Tanjo

Actually, it is a lack of fuel, cause the stock ECU cuts fuel at 12psi. With your full exhaust and intake, youll hit 12psi. You say it only does it sometimes, I bet that when you wood it and let it build full boost, or when its cold out. Throw your main cat back in, or get an ECU, or you WILL blow your motor.

t-von

iTrader: (8)

LOL funny thread title!

XxMerlinxX

iTrader: (2)

Lol, what???

smog-guy707

iTrader: (11)

i changed my plugs and wires about 2000 miles ago

i thought if it was a lack of fuel i would have blown it by now... and i have been running with no cat for a while now and this was not a problem till the other day...

i have checked a lot of things and i will admit im stuck...

next to check is my alternator, coils?, and nock sensor

im saving up for a new engine regardless

EricRyan

iTrader: (4)

Well if you say it started happening only recently, I'm going to go ahead and say that with the colder climate changes, the air will be more dense and therefore already "boosted", bringing your boost levels closer and closer to fuel cut. Port your wastegate if you haven't already.

Trexthe3rd

What kind of plug and plug wires did you change to? I tried aftermarket plug wires at one point and it caused the same symptoms you are describing.

OneRotor

iTrader: (3)

It's fuel cut. Do as it was advised earlier and put your main cat BACK ON.

smog-guy707

iTrader: (11)

i got ngk plugs and wires off of rx7 store... will this backfiring/ 5grand redline make my car knock at all... just wondering?

XxMerlinxX

iTrader: (2)

Just put the cat back on, if it doesn't work, no big deal, but that's probably what your problem is.

sburkett

It is definitely fuel cut. You could put manual bleed valves in to lower boost. Otherwise you have to go to an aftermarket computer or like everyone hear says "put the cat back on".

The fuel cut is not fixed at 12 PSI, it's RPM dependent. My car is bone stock except downpipe, cat back, cosmo fuel pump, efini Y-pipe and intake. I was playing with wastegate pills and can push 15 psi with no fuel cut at 3500 rpm, but cut at 10.5 at 6000 PRM.

The fuel cut won't hurt your engine, it's not like going lean - there is NO FUEL at all during overboost cut, so there can be no preignition or detonation. With my mods above, I can go all the way to fuel cut without any fuel issues, runs 11.8 AFR at the tailpipe.

Plus even with the main cat you may still see it. My setup above with stock pills hits fuel cut once in a while on cold days in 4th gear and up at 5000 rpm.

Steven

BigWillieStyles

if your saving for a new engine then you probably have heaps of money to buy a new ECU.

Or just put the cat back in.

Rx72Heaven

iTrader: (2)

yep tis fuel cut, i had the same exact problem, either get a PFC and a fuel pump, or like above, put your Cat back in.

smog-guy707

iTrader: (11)

i have a walbro 255 and a pfc... i had the pfc in running the stock base map and i took it out because i thought it was the ecu so i put the stock ecu in...but... at work today i put my car on the dyno and drove it while my co-worker threw carb cleaner in the engine to see if it was fuel cut and rev up... nothing happend... i will put my cat back on though

Rotary Potato

Or you could just put the pfc back in and make the required changes......

And are you trying to say you confused the pfc with your stock ecu? The big A'pexi logo didn't give it away?

smog-guy707

iTrader: (11)

no i had the pfc in when it first ... drove wierd. then i put my stock ecu in and it still does it. my stock ecu is still in

jacobcartmill

iTrader: (6)

**** dog. my FD wont ROLL THE BITCHES UP. its BUSTED. WHAT DA HECK. SOMEBODY HELP ME FIX DIS PIECE