idle drops to 500...
02-14-2006, 08:09 PM
#1
idle drops to 500... ok ive been tuning a car for a guy i just put a cam in.... its a 224 cam and it runs perfectly fine then all of the sudden it drops down to about 500 rpm for 5-10 seconds then comes back up and runs fine again......i tried changing the IAC and a few other things..... has anyone seen this before and can help me fix it ..... i have ls1 edit to tune with.....
02-14-2006, 09:20 PM
#2
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DO YOU HAVE HEADS ON THE CAR.. THE REASON WHY IM ASKING IS BECUASE I JUST PUT HEADS STAGE 3 AND THEN TUNED (LS1 EDIT) AND KNOW ITS DOING THE SAME DROPING DOWN TO 500 RPM ESPECIALLY WHEN ITS COLD. 
02-14-2006, 10:12 PM
#5
ok if u start it and its cold..... and just let it sit there and idle it will be idling fine then out of the blue it drops to 500 then comes back up...... but it also does it when its warm..... and the customer said also when u come to the first stop after it warming up it does it again.... and its throwing a 506 code which is system idle too low..... and it also throws a lean code when it drops that low.......
02-15-2006, 05:40 AM
#7
Hey guys I am the customer. The drop occurs several times during my daily driving. It drops twice during the warm up period, usually at 125 and around 175. Also as Fran stated, it drops when I come to my first complete stop after the initial warm-up period, if it's a stop sign I have to give it a bunch of gas to get it back up to 1000 RPMs or so to get it going again. Also if I slow to a half *** stop in second gear it will drop down. 2 other times it dips to 500 RPMs are when 1. After initial warm-up, the FIRST time I put it in gear to go, it dips down to 500-600 RPMs, and 2. after a long drive on the expressway to work(25 miles) going through all the gears and all kinds of driving as soon as I come to a stop at the exit it dips down again to 500. During the ride in stop and go traffic on the expressway it will also pick and choose when it wants to dip down to 500 and then if I let off the clutch it will surge to around 1500 RPMs and then back down to idle(900).
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02-15-2006, 05:55 PM
#12
if you could send me a file i can look over it, budchevy358@yahoo.com 22* should be fine for that cam, i would think you could maybe go 24* and it might help. send me the file over and ill take a look
02-15-2006, 06:55 PM
#14
Sounds like a RAF issue. The cells are probably not correct in those temp instances when it drops. As it moves through the RAF table it hits a "bad" cell and the sudden change in desired vs. delivered airflow upsets the idle. Do a cold start RAF log and use the spreadsheet to calculate a good RAF table.
Otherwise what are your warm IAC counts like?
Otherwise what are your warm IAC counts like?
02-15-2006, 10:26 PM
#17
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Some basic info needed;
* What is the desired idle speed set at?
* What are the exact code(s) you are getting and can provide the freeze frame history data (if available)? I assume PO171 and PO174
* Have you tried to reset the TPS?
* What exactly did you adjust besides the IAC?
* Have you logged data during a full drive cycle?
* Did you install the ported TB the same time as the cam?
From the GM manual>Conditions for setting code PO506:
ECT more than 140 F
IAT is greater than 14 F
Vehicle speed is no more than 1 mph
Actual idle speed is 100 rpm less than the desired idle speed
Above condition occurs for more than 5 seconds.
It could be a vacuum leak, faulty PCV, parasitic load on the engine (i.e. transmission)
or a faulty IAC valve (pintle valve stuck).
* What is the desired idle speed set at?
* What are the exact code(s) you are getting and can provide the freeze frame history data (if available)? I assume PO171 and PO174
* Have you tried to reset the TPS?
* What exactly did you adjust besides the IAC?
* Have you logged data during a full drive cycle?
* Did you install the ported TB the same time as the cam?
From the GM manual>Conditions for setting code PO506:
ECT more than 140 F
IAT is greater than 14 F
Vehicle speed is no more than 1 mph
Actual idle speed is 100 rpm less than the desired idle speed
Above condition occurs for more than 5 seconds.
It could be a vacuum leak, faulty PCV, parasitic load on the engine (i.e. transmission)
or a faulty IAC valve (pintle valve stuck).
man after being spoiled with hptuners 2.x I don't think I could do edit anymore. 
