P0304, P0302, etc cylinder misfire at idle.

[TrustGs-R]

Just curious if anyone has any thoughts on my current situation:

I installed ND 660 injectors, new o-rings, and my new turbo/ported manifold/ported o2 housing. I've been tuning the beast with my data logger and have idle and low throttle tuned fairly well now. Plugs are new and gapped properly, plug wires are new manecor, coil connectors are clean.

Here's what I notice now that I never had prior the the injector/turbo install:

-car starts fine when warm
-fuel curve, o2 voltages, datalogs look good.
-car runs perfectly fine.
-timing at idle around 5-6.5 degrees
-idle speed 700-760rpm
-fuel at idle max .81 volts, Short term fuel trim -1% average.
-requires about 6 seconds of cranking when the car is cold/has been sitting for 30+ minutes.
-every 2 days or so, I randomly throw a cylinder misfire code p0302, p0304 etc... only happens when idling and it doesn't happen all the time, only every few days or so.

sorry this is so long, just wanted to throughly explain my situation and I hope maybe someone has seen similar in their car before. ANy thoughts at all, please reply.

thanks!

 

[forcefed]

I had that same problem too, so someone answer this please.

 

[TrustGs-R]

had? hehe...or have?

any help?

 

[Rez90]

i have the same damn problem!!! if anyone can provide some info, please do

 

[TrustGs-R]

3 ppl with this problem...anyone out there have any ideas? it's very annoying.

 

[candela]

Well I cant tell you exactly what happens, but I would say that most all ecu's throw misfires codes even on brand new cars. When I used to work at the toyota dealer, people would come in with a CEL and we would scan it and find that on top of whatever was causing it, there was always a misfire code, and it didn't matter how new or old the car was.

I dont ever see any on my ecu, but maybe the obdII is more sensitve to that kind of thing. Although it doesnt show codes for it, I can feel my misfire at idle every now and then. And if I hold my rpm's steady at anything above idle I can feel the misfire as well. I dont know what else to do, as I hae all new/cleaned/checked ignition components...so I figure it's just part of the cars normal life. Because I noticed this after I upgraded my turbo/o2 housing/exhaust/manifold as well And I dont think it takes much to set them off either. Im sure you can read up on it, but I think if it misfires more than a preset number of times in like a few hours, then it sets the code. I know I didnt really help, but I dont think this issues is a really big deal, just annoying

 

[TrustGs-R]

ya...i think that's how OBD2 works.
Something like, if it detects the same minor problem after 3 warm up cycles it'll throw a code for it and if it doesn't for a few cycles, it turns the code off.

anyhow...ya...based on datalogs and other ppl i've talked to...I've decided misfires are common on modifed dsm's and dont affect performance (with just the presence of the code).

I come from a background of tuning heavily modified honda's....Many of the codes that honda's throw cause some sort of limp mode. I haven't seen such with DSM's yet (i like it).

I'll keep looking for the answer to my problem. Anyone else?

 

[TrustGs-R]

in case anyone cares (hehe)...

the code still comes up..
-only during idle
-not the plugs
-not the wires
-ALWAYS code p0302 cyl 2 misfire.
-all injectors are working
-injector o rings are new.
-coolant hasn't any bubbles.
-compression test shows good healthy motor.

any thoughts? PLEASE? hehe
TIA

-Jon

 

[TURBOSPYDER]

i have the same problem, and after doing some research, I found these two sites:

This site states the problem:
http://www.outreach.psu.edu/users/res122/DSM/


This site states the solution for Eclipses.
http://www.vfaq.com/mods/MCCC.html



Basically, someone mentioned that alot of carbon in the cylinders can cause misfires. The carbon soaks up the fuel momentarly delaying the ignition process causing misfires until its ignited according to the link.

But keep in mind, there are a ton of reasons that causes misfires, so cleaning the combustion chamber doesnt mean it will work.

Also, gapping of the plugs can play an role. The colder the plugs and the shorter they are gapped, the more chance of building carbon in your chamber because the spark cannot ignite all the fuel in the chamber(therefore causing misfires as the guy mentioned, but he could be wrong) But, the longer gap and hotter plug results into detonation.

I will let you guys know if theres any improvements on Friday.

Also, I just noticed most of you that have this problem have a 95 GST/GSX. I have a 99 GST, but I just swapped out my ECU to a 95 EPROM. Could it be the ECU??? But then again, I had this problem when I had the 99 ECU in.

 

[TrustGs-R]

interesting. Thanks for the reply.
Have you tried doing this MOPAR Cleaner method?

To this day I'm still trying to get rid of watever keeps bringing up this misfire code at idle. I get no bucking, just a stupid code that comes back after i get rid of it.

I've tried many things including a mild fuel system/combustion cleaner. I was going to try something I've been using on performance honda's for a long time with great success (cleaning out fuel/combustion system)...It's strong stuff and I'd imagine a lot like that MOPAR stuff. I'll have to give it a try and if it works, let you all know.

I'm thinking I should focus on cyl 2 as that's where the reoccurring code comes from. What cyl is your code pointing to?

 

[TURBOSPYDER]

The car is ready to be cleaned tomorrow. Ill have it fully done by Friday.

My codes was either Cylinder 1 or 3 or sometimes Multiple Cylinders. I do experience bucking and loss power sometimes and its very noticeable when my car misfires. I used the N0S Fuel treatment cleaner / Combustion Chamber cleaner, and it worked a little bit because now Im only getting cylinder 2 misfires and not too much of the stalling or bucking.

Im running 720cc injectors on my car and with 91 octane here in California, Im assuming theres alot of cleaning that needs to be done.

If your gonna try this method, Id say just do up all the cylinders so you wouldnt have to worry about doing it over for another cylinder.

I will let you know the results on Friday.

 

[TrustGs-R]

sounds good. i hate 91 octane btw

 

[TURBOSPYDER]

It works and Cars is running better. But I am getting cylinder 2 misfire still. But Idle is realllly smooth and car does die out any more.