engine dieseling when shuting down
Thread Starter
On The Tree
Joined: Feb 2007
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engine dieseling when shuting down my carbed LS3 has wants to diesel when i turn it off from driving it sometimes.only does it when i drive it for more than 10 miles straight without shuting the engine off.its not real bad dieseling just does it for a second maybe two.gets on my nerves though...any ideas?it has the GMPP intake on it with a 750 edelbrock.im not running any timing advance with the MAP sensor but i got the base timing at idle set at 9* right now ramping up to 31* at 2500rpm.think i need more timing at idle or put advance in it at idle?main reason i havent messed with the advance is im not used to the whole psi thing.
thanks for any help
thanks for any help
deiseling is caused by having the throttle blades set too far open at idle. if you are running not enough timing at idle it will force you to open the throttle blades to compensate to get idle rpms to where you want. crank up the timing to 15, or 18* at least. then you can reduce throttle opening back to the right position. this should cure the deiseling.
I run my timing at 20 initial 0-600rpm, 38* 600 -3500rpm, dip down to 35* at 5000, then back to 37* from 6000 on. My engine has 9.5:1 compression though, and yours will probably like a couple degrees less since it has 10.5:1.
my $.02
I run my timing at 20 initial 0-600rpm, 38* 600 -3500rpm, dip down to 35* at 5000, then back to 37* from 6000 on. My engine has 9.5:1 compression though, and yours will probably like a couple degrees less since it has 10.5:1.
my $.02
How many miles on the motor?
Reason I ask is carbon build up in the combustion chambers contributes to this. Thus engine needs to be hot.
The cure back in the 70's was to use higher octane gas. That and a few high speed runs to "blow out the carbon". Worst case try leaving it in gear when you turn it off.
If our timing is wrong the engine could be running hotter than normal.
What 3pedals says makes sense also.
Reason I ask is carbon build up in the combustion chambers contributes to this. Thus engine needs to be hot.
The cure back in the 70's was to use higher octane gas. That and a few high speed runs to "blow out the carbon". Worst case try leaving it in gear when you turn it off.
If our timing is wrong the engine could be running hotter than normal.
What 3pedals says makes sense also.
Thread Starter
On The Tree
Joined: Feb 2007
Posts: 156
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thanks for the input...i will try adding some timing and closing the base idle screw to get the rpms down.im gonna take the car to the track this coming up fiday for the first time and try to get the timing dialed in better.
its brand new...only has maybe 300 miles on it now.
How many miles on the motor?
Thread Starter
On The Tree
Joined: Feb 2007
Posts: 156
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Mine does it if i run less than 93 octane, mine is a stock LQ4 with 317s milled ,030. I need to check it out as well
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Joined: Jun 2011
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From: Lincoln, Nebraska
A new product called CarbShot can help. Even though the YouTube video shows it being used on a boat engine, it will work on any carbureted engine.
http://www.youtube.com/watch?v=gV0Antm1Wl8
http://www.youtube.com/watch?v=gV0Antm1Wl8
Last edited by Wiese1; Jun 23, 2011 at 07:03 PM.
