ok i just got done putting a new head on my 91 Si and now when i drive it if i give it more than 1/4 throttle it starts to misfire really bad. the car is smoking pretty good too. i puled the brand new plugs after 5 minutes of running they are covered in black carbon it looks like. heres a picture. someone help me i tried everything i can think of. i tried a new dizzy, injectors etc.

 

oops was logged into a friends name^

 

i should add that i did replace the fuel filter as that was my first thought and i did a compression test. 180 across the board.

 

make sure there isnt any loose or broken wires on the distributor plugs. it happens

 

ok ill go check that right now.

another thing i noticed also the intake is abnormally loud. i mean like if im rolling in gear and i floor it, it sounds like vtec engaging on a B16 with a CAI. its really really loud.

 

check your map sensor!!

 

i did, i pulled the vacuum line and the car started to idle like ****.

 

i'm going w/ timing belt off?

did you set ignition timing right?

 

im starting to think timing belt also. i couldnt get the pulley off so i set it by getting the first piston TDC and looked at the mark on the crank pulley and cam gear but who knows if i got it right. im gonna try to get that stupid pulley off cause i got a brand new belt and water pump i want to put on. i dont know the age of the one on it now anyways. the ignition timing shouldnt cause this but i didnt have a timing gun handy today so i just fucked with the dizzy in diff positions and i didnt do anything.

i guess ill just have to get that pulley off tomorrow.

 

ok i just took the car for a longer ride to really see what it does. its not RPM based its throttle position based if i give it any more gas than just enough to move it starts to misfire. would a bad TPS cause this or something?

 

First, are you getting any codes?

If the tps is sending the ecu a wrong signal, the ecu will send the wrong amount of fuel to the combustion chamber. You might as well try adjusting the tps sensor to the correct voltage. When the car is idling, and the throttle is completely closed, you should have 0.45v volts. Since the car is backfiring when you give it gas, then turn the car off, and floor it with the key in the on position, you should get arond 4.5v.

 

def check your codes, thats the first step here in my opinion

 

its not throwing any codes, thats why im stumped.

ill try the TPS check, i was gonna do it last night but i couldnt find my multimeter.

 

did the TPS check, .5 at the sensor harness plug closd throttle, but its got .65 at the ECU plug. 4.5 at WOT though at the ECU.

 

this might sound simple but are you sure your firing order is right? if it is i would guess timing is off, or your dizzy is messed up.

 

lol yeah i already thought about that and checked it. i also tried another known good distributor and it didnt help.

the car is smoking pretty bad and it doesnt seem to be oil smoke it smells like its running really rich.

i was thinking about changing the o2 but i highly doubt thats the problem.

 

problem solved.

after i changed the timing belt, water pump, plugs, wires and set the timing it didnt change anything. my friend has been telling me its the cat since i got it and sure enough i unhooked the cat from the exhaust and the car runs good. loud but good