CHRISPY

At the track last night I noticed a hestitation at light load. Almost like a bad plug wire or something?

Funny thing was the car ran great at WOT (11.6@121.7 full weight/full interior through cats on my M&H street tires)

If I revved the car with the clutch depressed or in neutral I'd get a slight miss that would seem to clear up.

Any typical cause for this? I am going to clean the MAF, replace the fuel filter and probably pick up a set of plug wires too.

Could a bad coil cause this? I haven't scanned for codes but will tomorrow.

Anything tuning wise cause this? I rescaled the injectors and did some tuning a couple of weeks ago and since the car feels kind of strange (soggy or dead) on part throttle and tip in but WOT is perfect (virtually zero knock, AF is 12.8:1)

Can a lean condition at part throttle produce these symptoms?

CHRISPY

Here are the codes I am getting:

P0153 - Heater circuit something error O2
P0135 - slow switching O2
P0133 - slow switching O2
P0507 - Idle control system rpm higher than expected

I am wondering if the O2s are dead or if the bungs need to be ground down to get more the O2 in the airstream?

Thanks for any assistance!!

MECHAM

iTrader: (4)

i know i had the high idle thingie and the iac plug wasnt all the way connected on my tb another friend of mine had his go bad but it was pretty evident there was in idle problem as it was idling at like 3k.

do you have any knock at part throttle/cruise speeds?

luv2spd

iTrader: (1)

Yeah, i'm pretty sure a lean condition could be a possible cause. Try adjusting the ve table.

383838

iTrader: (1)

Before making any drastic changes just unplug the 02's and run open loop and see if the hesitation goes away. If it does you just found the problem. 5 minute fix.

CHRISPY

good point, I'll try that

I am positive the IAC problem is the set screw, I'll adjust it again tonight.

I am wondering if I should just do an open loop tune and bypass the O2's all together? O2s are expensive and they **** me off.

If I do an open loop tune what should I shoot for AF wise at cruise? I know the mileage will suffer a bit but I dont really give a damn as I drive to cruise nights and drive to the track on weekends.

I do have cats on the car so that is a consideration. (Dont want to kill the cats)

Any ideas? I HATE the dead feeling and part throttle hesitation. When the codes arent there the car feels insane at part throttle. When they appear the car suddenly feels dead

jimmyblue

iTrader: (11)

If you tune open loop and the tune doesn't stay near
even, the cats are going to have a hard time. The AIR
doesn't run full time so rich products won't be burned.
I'd say if you are going to tune for full time open loop
you might as well just take the cats off and save them
for later rather than foul them out.

The variability in O2 output and occasional lack of it
makes low-flow tuning hard. Try the 'vette rear O2s?
Also I've been playing with the O2 rich/lean threshold
vs airflow mode settings (trying to force a lean idle
and cruise on my iron-logs exhaust car) but you
headers guys might find this is a useful "handle", you
could set the mode/airflow table up different and
put some lower switch thresholds onto idle and low
cruise regimes, especially if you could (say) hook up
a wideband, and look at what the real long-term
O2 average is to get 14.7 on the wideband (if it
even resembles closed loop in fact) or, if it idles
too rich, push those low-flow thresholds down to
like 300mV.

To really do this right you might have to break
the loop (like unplug the front O2s), instrument
them up to read raw voltage, adjust your VE
table until the open loop wideband says 14.7
and see the raw O2 voltage and the airflow
number (-> airflow mode value) at idle, and
dope out the map curve to represent. Then
you'd be close to right, to begin with, and the
closed loop threshold would also be kinda right
with regard to the exhaust induced O2 error
(though this is going to drift with sensor aging /
fouling on a pretty continuous basis, something
the higher-wattage heaters ought to help resist).

CHRISPY

whew...

Pulled the O2 sensors, cleaned them with electronic contact cleaner (they were black) wiped them down and let them dry

Then put ultra copper RTV on all the parts of the slip fit collectors were the weld didn't make it around. (corners and part of the top)

Tomorrow I'll ATAP and see how things look

Thanks for the help guys, I hope this fixes it!!