surging idle?
Thread Starter
Racer
Joined: Apr 2002
Posts: 342
Likes: 0
From: new orleans La
surging idle?
I have a newly rebuilt 355 LT4 and I am expierencing a surge at idle but only in open loop situations as soon as it enters a closed loop the surging stops and idle stabilizes.
Mods include:
hotcam
ported heads
52mm TB
EM long tubes
30# injectors
air pump delete
cat delete
mezeirie water pump
corsa exhaust
ED Wright reprogram
LTCC
some scan data @ idle:
OPEN LOOP:--------CLOSED LOOP:
Map 27 in/hg --------14in/hg
IAC 122 steps --------50 steps
timing 25* -----------27*
cell 16 --------------16
Any ideas on what to look for in rooting out this problem?
Mods include:
hotcam
ported heads
52mm TB
EM long tubes
30# injectors
air pump delete
cat delete
mezeirie water pump
corsa exhaust
ED Wright reprogram
LTCC
some scan data @ idle:
OPEN LOOP:--------CLOSED LOOP:
Map 27 in/hg --------14in/hg
IAC 122 steps --------50 steps
timing 25* -----------27*
cell 16 --------------16
Any ideas on what to look for in rooting out this problem?
Team Owner
Joined: Aug 2000
Posts: 40,156
Likes: 45
From: San Pedro CA
hm... have you tried to reset the IAC? It's a simple procedure.
Turn off the engine.
Hold the pedal down a little, and start. hold the idle for 10 seconds. release the pedal. and shut down. Restart.
I think that's it. I will have to check my helms again to be sure.
Turn off the engine.
Hold the pedal down a little, and start. hold the idle for 10 seconds. release the pedal. and shut down. Restart.
I think that's it. I will have to check my helms again to be sure.
Melting Slicks
Joined: Jan 2002
Posts: 2,238
Likes: 4
From: Milan
Originally Posted by 99svrcpe
I have a newly rebuilt 355 LT4 and I am expierencing a surge at idle but only in open loop situations as soon as it enters a closed loop the surging stops and idle stabilizes.
Mods include:
hotcam
ported heads
52mm TB
EM long tubes
30# injectors
air pump delete
cat delete
mezeirie water pump
corsa exhaust
ED Wright reprogram
LTCC
some scan data @ idle:
OPEN LOOP:--------CLOSED LOOP:
Map 27 in/hg --------14in/hg
IAC 122 steps --------50 steps
timing 25* -----------27*
cell 16 --------------16
Any ideas on what to look for in rooting out this problem?
Mods include:
hotcam
ported heads
52mm TB
EM long tubes
30# injectors
air pump delete
cat delete
mezeirie water pump
corsa exhaust
ED Wright reprogram
LTCC
some scan data @ idle:
OPEN LOOP:--------CLOSED LOOP:
Map 27 in/hg --------14in/hg
IAC 122 steps --------50 steps
timing 25* -----------27*
cell 16 --------------16
Any ideas on what to look for in rooting out this problem?
bigger duration and lower lsa (if i remember is a 112 LSA) cams at idle can be at a completely differemnt vacuum level.(LOWER)
Since when you are in open loop the fuell supply is commanded by the stock calibration , you are running toooooo rich.
You are with less vaccuum , but you are at idle, less vacuum is the situation when you are NOt at idle. When tou go in closed loop the 14.7 AFR correction take place of your stock calibration.
With "bigger" cams you need to burn a new chip with LESS fuel at 600 700 800 rpm (where your idle is...) in the vacuum range (lower than usual with a stock cam).
You should also raise a bit your idle (chip speaking)
-Beppe-
Thread Starter
Racer
Joined: Apr 2002
Posts: 342
Likes: 0
From: new orleans La
Originally Posted by bogus
hm... have you tried to reset the IAC? It's a simple procedure.
Turn off the engine.
Hold the pedal down a little, and start. hold the idle for 10 seconds. release the pedal. and shut down. Restart.
I think that's it. I will have to check my helms again to be sure.
Turn off the engine.
Hold the pedal down a little, and start. hold the idle for 10 seconds. release the pedal. and shut down. Restart.
I think that's it. I will have to check my helms again to be sure.
Thread Starter
Racer
Joined: Apr 2002
Posts: 342
Likes: 0
From: new orleans La
Originally Posted by conv90
I think is the Hot cam.
bigger duration and lower lsa (if i remember is a 112 LSA) cams at idle can be at a completely differemnt vacuum level.(LOWER)
Since when you are in open loop the fuell supply is commanded by the stock calibration , you are running toooooo rich.
You are with less vaccuum , but you are at idle, less vacuum is the situation when you are NOt at idle. When tou go in closed loop the 14.7 AFR correction take place of your stock calibration.
With "bigger" cams you need to burn a new chip with LESS fuel at 600 700 800 rpm (where your idle is...) in the vacuum range (lower than usual with a stock cam).
You should also raise a bit your idle (chip speaking)
-Beppe-
bigger duration and lower lsa (if i remember is a 112 LSA) cams at idle can be at a completely differemnt vacuum level.(LOWER)
Since when you are in open loop the fuell supply is commanded by the stock calibration , you are running toooooo rich.
You are with less vaccuum , but you are at idle, less vacuum is the situation when you are NOt at idle. When tou go in closed loop the 14.7 AFR correction take place of your stock calibration.
With "bigger" cams you need to burn a new chip with LESS fuel at 600 700 800 rpm (where your idle is...) in the vacuum range (lower than usual with a stock cam).
You should also raise a bit your idle (chip speaking)
-Beppe-
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Thread Starter
Racer
Joined: Apr 2002
Posts: 342
Likes: 0
From: new orleans La
Originally Posted by mxw1
The O2 sensor is not used in open loop.
You might have a Lazy IAC motor. It could be gummed up and moving slowly, overshooting the target rpm. It's cheap and easy to replace and try.
You might have a Lazy IAC motor. It could be gummed up and moving slowly, overshooting the target rpm. It's cheap and easy to replace and try.
