Help with rough idle after Cat removal

[mc71454]

Removed my Cat Converter and installed a 2.5 test pipe. Also installed a ported oem elbow from the stock turbo to the stock downpipe.

Have a rough idle now. Spools up nice, have 17 lbs boost with 0.2 to 0.4 KR with 800 o2 . (I run 5 gallons of 100 with the remainder of the tank with 93). one 360 degree turn of the adjustable wastegate rod gave me 1 more psi of boost

O2 millivolts 750 to 800 at idle, TPS 0.44 off and 0.48 running at idle

IAC 44 in neutral, 65 in drive and 60 in neutral with AC on

I'm still learning this system, so go easy on me. if you want to talk BB Chevy and drag racing that is more my speed until I learn this car and it's electronics.

suggestion are really appreciated.

 

[phil_jordan]

Be sure to dbl check and make sure you didn't knock anything loose. Are your BLM's ok at idle?

 

[mc71454]

123 for BLM at idle. I'll drive it to work tomorrow and get some more data on the way in.

Yeah the down pipe was banging around a bit fitting it in and out with the test pipe. First thought was O2, but it cycling from 0 to 800+ with all kinds of crazy numbers in between is actually normal and was occurring prior to the swap.

Thanks for the reply..

 

[87_we4]

Lower the iac may smooth idle out a little. Just remember to rest tips afterwards

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[phil_jordan]

123 for BLM at idle. I'll drive it to work tomorrow and get some more data on the way in.

Yeah the down pipe was banging around a bit fitting it in and out with the test pipe. First thought was O2, but it cycling from 0 to 800+ with all kinds of crazy numbers in between is actually normal and was occurring prior to the swap.

Thanks for the reply..

Great. Can rule out vacuum leaks. Try the above post.

 

[mc71454]

Thanks, Will do...

 

[mc71454]

Have some new numbers. First 3 columns are idling in Park...The last column is idling in gear

AF 04 04 04 05
L8 32 30 32 38
lnt 128 128 130 128
bl 130 132 132 132
r 750 775 750 725
tps .48 .48 .48 .48
IAC 33 29 30 46

cc 0 to 255 and then back to 0 seemed to climb in 10 to 15 increments at a good rate.

If lowering the IAC anymore might help, I will try it some more.

If I power brake the car, there is no miss and it runs great at part and wide open throttle.

Loaded it real good up a hill and mashed pedal 17 psi 804 o2 with 5.4 KR with about 93-94 octane
Same thing with 96+/- octane 2.4 KR, going to mix 5 gal of 112 with 12-13 of 93 from now on.

Checked wires for burns and found nothing. all I did was change out the Cat and replaced the outlet elbow I banged the down pipe around a lot and had it all the way out.

Would a leak between the turbo outlet elbow and the downpipe cause this? I reused the donut gasket because it looked fine and it is tight. I guess I will take the turbo cover off and check for leaks around the donut.

Thanks for any assistance

 

[mc71454]

After being up to operating temperature..

decimel point between the O and O for KR is blinking, it goes away when I push on the throttle. Open Loop even after being warmed up, i guess this is normal for the TT chip I have. When the light stops blinking the motor feels smooth.

Should I reset the ECM for the heck of it? or are the IAC numbers still to high ?

 

[John Larkin]

Too high, they need to be about 10 hot in park. You'll have to adjust TPS to compensate afterward most likely. It's a dance.

 

[mc71454]

Too high, they need to be about 10 hot in park. You'll have to adjust TPS to compensate afterward most likely. It's a dance.

Thanks John, That sounds Promising...Will do over weekend and get back with results.

Appreciate it !

 

[mc71454]

Tonight I adjusted the TPS and IAC

at Idle in Park after a 10 minute flogging

tps = .40 could be .02 higher, 4.73 at WOT so good there.
IAC = 14

It seems a hair better, but still looks and feels like a mis-fire. Again a powerbrake doesn't reveal anything and it ran awesome at 3/4 throttle to about 15 psi and no KR.

I have a new 02 sensor, maybe put that in and reset ECM ?

 

[mc71454]

ttt

 

[87_we4]

Check the spark plugs and wires on passenger side. Might have knocked a wire loose or cracked a plug

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