Please read thru the hole thread since there has been up dates and thanks for your Help !










Car: 96 Civic Hatch

Engine: Bone Stock H22A4

Code: p0304 ( Missfire Cylinder 4

Idle Air control Code


Problem:

Car started out of no where to Rev up and down between 1,000 -2,000 and when the car is driven it runs fine.

Sunday I took the car to the track and the car started to have a missfire code P0304 but onces runing the car feel fine but idle you feel a light vibration.


Check:

-All vacumm hose nothing loose or crack or broken
-Clean Air idle control (wasnt dirty at all but clean it anyways)
-replace all spark plugs



Found: So Here is what I found onces I pull out the wire for cylinder number four the car idles fine and the missfire goes away! there is spark coming out the wire has a new spark plug. But if i put it back it goes back rough idle and the miss fire.



HELP ! any ideas !

 

50 view and no help : (

 

what computer are you using? do you have access to a smoke machine?

cap look good? rotor? ohms test the coil?

 

Im using a prelude ECU everything out of a 98 complete harness, ecu etc harness was modified to work on the car dash board but its been swap like this for 3 years now so its has been running good before.

 

when i get home today im do a tune up wire, cap and rotor see what happens.

 

its your fast idle thermo valve, it will cause the idle surging. it's designed to keep the idle steady at cold starts until the iacv takes over. check out this link:

http://www.preludezone.com/diy-do-yo...em-thread.html

do it, fix your problems and be satisfied.

 

yea the surge is prop the FITV. fast fix is to just take the brass cap off and tighten the big white screw all thw way tight.

 

Ok so I did complete MSD setup wires, cap and rotor, NGK plugs and nothing car till had a miss fire cylinder 4 and idle up and down..

clean both the IAC and the FITV and nothing same thing...

re check all the hose to see if any would make a differences

I notice that onces i disconected the IAC it stop idleing up and down but would have a horrible miss fire.

 

Replace the IACV with a known good one and re-check, otherwise there's a good chance you have a vacuum leak somewhere. Leaks don't just have to come from vacuum hoses either, any gaskets going bad or parts shifting can cause a leak anywhere two parts come together and there is (or should be) a gasket (ie TB to intake manifold, upper manifold to the butterfly plate, plate to runners, runners to the head, etc).

Diagnose the idle problem before you move onto the misfire. The misfire could be a number of things; since you've already replaced the ignition components, I would try swapping the fuel injectors between 3 & 4 and see if it follows the injector.

 

are you using a msd coil? did you ohms test? did you tighten the fitv screw?
maybe your issue is solved? let us know

 

yes im trying to locate a IAC now because new there to expensive just to test it.

No MSD coil and yes the FITV screw is tight. but the problem was there even before the msd, cap, wires where use.

 

UPDATE on my problem

So I bought a new, FITV and IAC and didnt fix anything the rough idle was still there...

So i decided to take the Throttle body out and clean it. while inspecting it i found out the TPS sensor screw where not tight so i screw it back and tested it. just to find out the up and down idle went away but now the RPM's wont go down less then 2,000 RPMs and the miss fire still there..

also the ECU started to make this wierd noise like if theres was somehting grinding in there very wierd and in one corner it got really hot.

 

any one? jesus this thing driving me crazy!!

 

Ok Another update to my problem...

So i replace the MAP, TPS, throttle body, IAC, and FITV....

in the process i found out MAP sensor was missing the O ring.... So onces a new O ring was install the RPM's went back to normal. instead of reving up to 2,000... But the Up and down rpms came back and the miss fire went away... So I install a new gasket on throtle also clean and nothing same thing.. check hoses.. I even check coolant to make sure it was up to pressure and nothing
Damm RPMS are up and down..

I do get a check engine light but with the scanner i cant scan it any more for some reason it wont connect to the ECU... since it still has the OBD 1 plug i can jump it and get a code. The code that comes up is code 7 witch is the TPS... but then out no where it was throwing me a code 23 witch is knock sensor...

damm im confuse... what should i do next?

 

Sorry to hear you are still having issues. Any idle issues I ever had seemed to only be right at start up and went away as soon as the car warmed up. And it was only a slight idle surge nothing crazy. I NEVER saw a misfire code on this car and it is strange to think that it would be happening now.

Here are a few suggestions.

-The Blox TPS on that throttle body gave me some issues. The original was smashed when I bought that motor (typical for salvage yard pulled motors). You need to properly adjust the TPS when it is on the car in order to make sure the voltage is correct. This is hard to do with so little clearance to tighten the screw. I should have switched it to a bolt in order to help that issue. If you let the car idle while you adjust you will hear how much TPS effects idle.

-EVAP - because of all the complicated stuff I had to do in order to make EVAP work I always figured it would cause some vacuum leak.

-Vacuum box under the intake manifold - there is a black plastic vacuum box under the intake manifold toward the drivers side that is fragile. I already replaced it once and it is possible that it was damaged again.

-Maybe try to check the continuity of the wires for the coil and the TPS. Perhaps one of them has loosened up and it causing a short. That would explain the misfire and the heat in the ECU.

Hope this can help. Sorry to sell you a headache.

and P.S. make sure you check the oil levels frequently. VTEC seems to eat oil a bit on this car despite that there is never any smoke.

 

OK i give up trying to fix this.. does any one know a good shop/tech in the fairfield are in CT???

 

Try spraying brake cleaner on vacuum hoses and gasket areas, if you have an idle surge spraying brake cleaner on a spot, you found a vacuum leak.

$5 diagnosis, if it helps you find anything.

 

UP DATE ! ! !...

Ok so i took the car into a shop here where i live the guy been doing swap for couple years work at performance shop for some time. He spent 2 weeks with the car and did not find any of the problems im having. He check the fallowing

Harness wire by wire
Leak down test
valves adjustment
timming
vacumm hoses

Found bad knock sensor replace but just to find out now vtec wasnt working
and selonoid was the new code.

he couldnt find anything so i decided to take the car home

when i got home i started looking at the way the engine harness was done and also i keep having a problem where the battery keeps dieding. so after spending couple hour i find that the engine grounds where connect by those alen type bolts that come different colors password JDM sell these. Replace them with original 10MM bolts

also found the negative cable from the battery to under hood fuse box was 3 different type of wire and welded in a ghetto job. so one of these two thing could cause my ECU to get hot and make the noise and gone bad.

so i went and i bought a P06 Chipped with H22 chip and step down harness so it can work. result No more check engine light no more rpms surge BUT! rpms wont come down from 2000 rpms so tomorrow im going to buy new cable for the battery to the fuse box and re do all the ground cables.

Video 1
http://smg.photobucket.com/albums/v7...t=e6c2852e.mp4







after new ECU was install

Video 2
http://smg.photobucket.com/albums/v7...t=a6e6e4fa.mp4

 

SO the car has gotten

NEW:

TPS
MAP
IAC
FITV
Knock sensor
ECU
Step down harness
Battery (2)

after $1,200 In parts No problem found !! !!

ANy one wants to buy the hatch ?? LOL

 

Another update.

So battery problem fix there’s no more electrical problem hopefully…. I re did the ground cables to the engine/body. Also the positive cable to the fuse box and the negative cables on the battery as well. Car start right up battery hasn’t died yet. Vtec is working and hits hard it revs up to 8Gs now before only went up 6000 and bog out. Drove the car for a while everything seem good except the fact the rpms wont go lower then 2,000. I check the adjustment on the throttle body and nothing check tps sensor nothing. Thinking about replacing the dizzy see what it does. Timing is all perfect what else makes the RPMS stay high?

 

have you had this problem since you got it ? i know you probably have already checked this but have you checked the throttle cable adjustment ? its always the simplest things

 

Yeah re check it twice if change throttle bodies and nothing.

 

when you replaced the iac and fitv were they new parts or used parts? check the o rings on the fitv and iacv if they are old and crushed they will not seal properly and will let air jump from one port to another causing all kinds of idle problems. again make sure the fitv valve is screwed in. i believe there is a write up in the faqs on how to do this. i had this problem on my cd7. it sounds like an air leak.

if all the o rings on the valves look ok check the fuel injector seals. have you removed the intake manifold recently for any repairs or mods?

 

they where good working used parts.... o rings where replace with new ones. and yes FITV is screw all the way in.

 

look at the car over the weekend still no luck even check cable on the throttle maybe it would bring the RPMs down but no luck.

I really need a good tech that know there H series if you guys know some one please PM his info ASAP !! i live in Connecticut willing to travel to NYC or NJ if he can do it the same day.