Idle Surge
Idle Surge
747 TBI, almost stock 350. Idles at 40kpa, 575rpms, in drive when hot.
I'm having trouble keeping it from surging at idle. Sometimes shifting into drive stalls the engine.
It surges after sitting in drive for a minute or so. RPMs fall, MAP goes to 50 and then it revs up again.
Timing is the same from 400-1200rpm X 30-50KPA. BLMs aren't moving a whole lot, 124-128 pretty much. Changes to fueling made it worse in both directions (lean/rich).
Any suggestions?
I'm having trouble keeping it from surging at idle. Sometimes shifting into drive stalls the engine.
It surges after sitting in drive for a minute or so. RPMs fall, MAP goes to 50 and then it revs up again.
Timing is the same from 400-1200rpm X 30-50KPA. BLMs aren't moving a whole lot, 124-128 pretty much. Changes to fueling made it worse in both directions (lean/rich).
Any suggestions?
Supreme Member
Joined: Jun 2000
Posts: 7,554
Likes: 1
From: In reality
Car: An Ol Buick
Engine: Vsick
Transmission: Janis Tranny Yank Converter
<font face="Verdana, Arial" size="2">Originally posted by Brent:
747 TBI, almost stock 350. Idles at 40kpa, 575rpms, in drive when hot.
I'm having trouble keeping it from surging at idle. Sometimes shifting into drive stalls the engine.
It surges after sitting in drive for a minute or so. RPMs fall, MAP goes to 50 and then it revs up again.
Timing is the same from 400-1200rpm X 30-50KPA. BLMs aren't moving a whole lot, 124-128 pretty much. Changes to fueling made it worse in both directions (lean/rich).
Any suggestions?</font>
747 TBI, almost stock 350. Idles at 40kpa, 575rpms, in drive when hot.
I'm having trouble keeping it from surging at idle. Sometimes shifting into drive stalls the engine.
It surges after sitting in drive for a minute or so. RPMs fall, MAP goes to 50 and then it revs up again.
Timing is the same from 400-1200rpm X 30-50KPA. BLMs aren't moving a whole lot, 124-128 pretty much. Changes to fueling made it worse in both directions (lean/rich).
Any suggestions?</font>
Supreme Member
Joined: May 2000
Posts: 2,963
Likes: 3
Car: 1982 Z28
Engine: LS1
Transmission: T56
I had trouble w/ mine after advancing initial timing to 12deg BTDC. Idle was all over the place, you could see the IAC "chasing" it like crazy. I had burned a chip with the reference timing set to 12 also, tried this and my ARAP-base chip and both showed the same symptoms.
RPM would go up, IAC would go down to bring down the RPM...RPM would go down and nearly stall, IAC would go up to bring up the RPM...repeat loop.
Setting initial timing back to 8deg BTDC and clearing ECM memory did the trick. Check your initial timing.
-Kevin
------------------
1982 Z-28
See http://www.mycar.net/mafb/registry/detail.cfm?id=276 for details
RPM would go up, IAC would go down to bring down the RPM...RPM would go down and nearly stall, IAC would go up to bring up the RPM...repeat loop.
Setting initial timing back to 8deg BTDC and clearing ECM memory did the trick. Check your initial timing.
-Kevin
------------------
1982 Z-28
See http://www.mycar.net/mafb/registry/detail.cfm?id=276 for details
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