can somebody please tell me what is happening? short drive log and major miss

[mvvette97]

My car has done this ever since the tune. I have a comp 228 230 cam and other mods. runs and idles great but here is the problem. Been driving any length of time engine fully warmed up. If I turn the car off like to grab a soda at a store and let it set for a bit then do a hot start it will still run fine and idle, now just as soon as I pull out on the street and by the time I get to second gear under light throttle it will start to miss BAD and the wideband in the car will flatline lean. Step on the throttle harder and it will give a jerk and instantly come out of it. wideband goes back to normal and you can drive the car all day and will be fine. It only does it on a hot start and withing 20 seconds after the start or just long enough to get backed out on the road. Cold start is fine and after it has the fit it will be good to go all day until another hot start. Here is a short log of when it done it. what do you think is happening here?

[WeathermanShawn]

I take it you are running Closed-Loop..MAF Enabled?

I would suspect a 'bad' O2 sensor or worst case injector. If you look at the attachment (your log) you can see LTFT2 at -14.1% and LTFT1 at -2.3%. Perhaps you should log your Narrow-Band mv's.

Why it is doing it..sounds more mechanical than tune. Your Trims should be much more symmetrical.

Thats all I can spot on a real quick log check..

[mvvette97]

yes closed loop and maf. I also noticed that the trim was way neg compared to the other. If it was an 02 taking a dump I would assume it would be the bank 2 sensor?

[joecar]

Log HO2S11 and HO2S21... we want to see how quickly the switch, so reduce the pid channel count to no more than 24...

Try these:

VSS
TP
RPM
DYNCYLAIR
DYNAIR
MAF (SAE)
MAP (SAE)
IAT
ECT
AFR
SPARKADV
KR
LONGFT1
LONGFT2
SHRTFT1
SHRTFT2
HO2S11
HO2S21
MFTOTAL

[joecar]

Also: seems to be a lot of MAP for the small amount of throttle, but it might just be the cam... 228/230 what LSA...?

what does MAP read with key on engine off and at idle...?

[WeathermanShawn]

myvette:

Are your running stock ignition coils or aftermarket? What type of spark plugs and how old?

I am also curious about your MAP's. In your log were you going on a flat-stretch or road or a hill? AC on or off?

I know it is a lot of questions, but perhaps you are having an ignition/spark problem to a cylinder. Are you hearing a major misfire?

Thanks..

[mvvette97]

My cam is a 112 lsa. The coils are stock and the plugs are AC Iridiums. plugs have about 5000 miles on them. I can for sure hear the miss but it's more of a running out of fuel miss or possibly a flood out miss because if I step down a little more on the throttle it will pop right out of it's fit.. I'll get some map logs and of the pid secection above and post them

[WeathermanShawn]

As Joecar stated, keep your PID channel selection to 24 or less to insure accurate logging.

You can log Misfires, but perhaps we can keep that log separate or accomplish at another time. My hunch is a bad O2 sensor, but looks like it is involving fuel or fuel supply..so more logging is a good idea.

Keep us updated.

[mvvette97]

Here is a short log I did today. I noticed the IAT temps are way up, don't know if that would cause my problem or not..

[WeathermanShawn]

I am not sure what is happening..

It was hard to find a direct HO2 comparison log, but I tried. I don't think your narrowbands are switching that fast?. I thought I saw a lot of your Idle and your HO2's were flat and quite high.

Again, its hard to make a direct comparison. Sometimes they are just lazy at certain speeds. I use the rear Corvette-type O2's up front.

Anybody else have any ideas?