misfires whenever throttle is applied, no CEL help!

1993gsx · Feb 17, 2011

Hey everyone, I have spent over an hour now looking around online and on this forum trying to find a solution to my problem. Ive seen a lot of similar threads about misfires but none really like the problem I have. First let me give you a little information about my rig: 1993 gsx, its mostly stock, only modifications are a punishment radiator, and a punishment 3'' downpipe with MR 3'' cat-back. Everything else is stock. The plugs and wires were changed not long ago and are still in almost new condition. I pulled a plug just to look at it, and it seemed fine.

You must be logged in to view this image or video.

The turbo-back has only been installed for about 4 days now. yesterday I noticed that when I hit full boost (stock 9-11psi) it started to misfire on me. Now its so bad that it will misfire once in a while while idleing, and if I hit the gas at all it will start to misfire, and get severe backfires and misfires at ANY boost levels. If im cruising down the road and I hold it steady at 2500 just cruising it is fine, but if a hill comes I have to cross my fingers because the car basically wants to die

I changed the crank angle sesnor back when I first got the car in nov, and I tried messing around with the angle of it to see if I could get any change to happen. I couldnt get an improved result by rotating it either direction, so I left it where I knew worked. I did a boost leak test about a month ago, and I dont have any bad leaks. Im about to go talk to the shop foreman at the mitubishi dealership down the road to see what he thinks. I dont want to drive the car though because of how bad it is to drive. and it was just running fine yesterday

!!!! if anyone has any ideas that would be very helpful. thanks!!

TGST90 · Feb 17, 2011

Well your problem kind of sounds like my problem I have/had. It would misfire would trying to take off and I looked at it and saw my intercooler pipe came loose( big vacuum leak) check for any vacuum leaks. Im having a problem right now, I was driving yesterday and it started making this horrific rattling noise and backfiring bad and started drinking a lot of gas. But it would only do this if I was cruising, if I open throttle all the way it was fine.

GRAVEDIGGER · Feb 17, 2011

It still sounds like an ignition misfire to me. What kind of plugs are those? I would be running NGK BPR6ES plugs if it were mine.

brokedowntalon7 · Feb 17, 2011

GRAVEDIGGER said:
It still sounds like an ignition misfire to me. What kind of plugs are those? I would be running NGK BPR6ES plugs if it were mine.

check this first, always good to eliminate the possibility.

if that doesnt smarten it up check your base timing. should be 5 degrees before top dead center (BTDC), this could be the case especially since you were messing with the *cam* angle sensor.

1993gsx · Feb 17, 2011

They are bosch platinum, the guy before me had them put in along with new wires. I know its not what I would choose, If I did it I would def run NGK's. But they should still work fine right? Also, could an exhaust leak cause misfires? I couldnt get it tight enough where the downpipe bolts up to the 02 housing, and I dont think that this is the problem, but just a thought.

brownfinger · Feb 17, 2011

could be a bad MAF, too. Try a different one if you have access. Ditto on the coil pack.

1993gsx · Feb 17, 2011

thanks for the quick replys everyone, so far Im going to mess around with new plugs, checking the coilpack again, check the maf and double check vacuum leaks. thanks!

kchaazz · Feb 17, 2011

NGK BPR6ES plugs for your setup, gapped to .028, and NOTHING else. Bosch plats are junk for these cars. :thumb:

Also, check the plug wire connections at the coil pack by pulling gently. Number one doesnt like to go in all the way on these things and likes to pop loose. Also, be sure you dont have any oil on the wires at all, new or not. Places to check: spark plug wells; oil can also leak from the oil cap gasket and pool up in the area where the wires run across the valve cover. Cant tell in the pic, just thought Id mention it...

codeofdastreets · Feb 17, 2011

Id also check the injector plugs, had a simlar problem with a friends car

Dsm4lyfe12 · Feb 17, 2011

boost leak boost leak boost leak. Also check to see if your plugs are gapped correctly and i would switch to some ngks all day.

DSMTyson · Feb 17, 2011

codeofdastreets said:
Id also check the injector plugs, had a simlar problem with a friends car

Thats happened to me quite a few times. It would happen ~ 1/2 the time I hit WOT. My car would start running real rough(misfiring) and run lean.

But i'm 90% sure its either a boost leak or from those stupid bosch plugs.

Groundation · Feb 17, 2011

I would definitely do a boost leak test again. You say you did one a month ago, and your issues just started a few days ago. Also, switch your plugs to NGK's.

1993gsx · Feb 17, 2011

thanks for the replys everyone!! Im switching to NGK plugs and wires and ill see what happens. Also, the previous owner said that the car used to have misfire issues in cyl 2, but he had it serviced and fixed at the dealer. Don't know if its relevant, but ill try another boost leak test and try the new NGK's + wires. Thanks again!!

Put the NGK's BPR6ES gapped at .028 in and she's much happier. Now I can free rev as hard as I want without misfires. But still misfires when I go more than 7psi, and during idle. I found that when I mess around with the lower sidemount IC hose the misfiring was changing as I was wiggling the hose. So I think I have a boost leak there. neways

Heres the new plugs: still using the existing 7mm wires

You must be logged in to view this image or video.

Oldies:

You must be logged in to view this image or video.

few other pics: Heres what I have to replace the stock IC :]

You must be logged in to view this image or video.

this is the ugly underneath of a 17 year-old VT car =/

You must be logged in to view this image or video.

took this one while changing the timing belt, thought it was a cool shot

You must be logged in to view this image or video.

sorry for the off-topic pics, just figured I'd throw em up xD

alecstark · Mar 18, 2012

Im having the same problem with my 91 eagle talon tsi. Ive replaced the spark plugs (NGK copper gapped at .028) and wires, ive replaced the throttle body and soon ill be replacing the throttle body position sensor. Weird thing is though, when i cover part of the maf it runs strong until i uncover the maf. why is that? Also my car runs great when it is cold out until the engine get to normal temp.

zcoh2gdsm · Mar 18, 2012

codeofdastreets said:
Id also check the injector plugs, had a simlar problem with a friends car

x2, my STi would misfire at the most random times and i never knew what it was till i took it to a buddies shop and they told me it was the injector plug. i felt stupid afterwards. LOL

.

Spyderman7 · Mar 18, 2012

boost leak or Maf.But would check all connectors as well

The Top DSM Community on the Web

misfires whenever throttle is applied, no CEL help!

1993gsx

TGST90

GRAVEDIGGER

brokedowntalon7

1993gsx

brownfinger

1993gsx

kchaazz

codeofdastreets

Dsm4lyfe12

DSMTyson

Groundation

1993gsx

alecstark

zcoh2gdsm

Spyderman7

Similar threads

Latest posts

Build Thread Updates

Vendor Updates

Latest Classifieds