data log question
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Junior Member
Joined: Jun 2010
Posts: 34
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From: lansing mi
Car: 91Z28
Transmission: 700R4
Axle/Gears: 3.23
data log question
I will start with informing you guys of my situation below.
Well over the winter i decided to put comp cams cc503 cam in my tpi as well as billet servo's and converter,car was tuned by "PCM FOR LESS".The problem that i am running into is a high idle at all time's closed loop as well as open loop.My idle stays constant at 1500 rpm's in park ….in drive im lucky to touch 1300 usually stays at 1500.Now i have gone through all of the normal procedures replaced my I.A.C. motor/coolant temp sensor/o2 sensor.The I.A.C. motor was set correctly and i have tried messing with the idle screw as well that did not seem to help my problem at all.Car has E.G.R. delete as well as smog delete.I am getting a constant vacuum reading of 13 in.Now i know i should be between 15-16 maybe 17 in. with this cam but can a couple in really cause me to have that high of a idle issue? I have completely torn down the tpi system and has all checked out fine new gaskets all that good stuff.My question to you guys is where would you guys maybe check and what would you do from here,any help as well as input would be appreciated thank you!:
Now after doing some data logging i know i have a problem but i dont know where my problem may be at…..i have a idle on the dash of 1500 rpm and a datamaster reading of 950 on both rpm gauges.Now here is where i am confused the car is indeed racing at idle at all times not doing 950 rpm like datamaster says.I have checked all the sensors they seem to be fine throttle body looks to be set up correctly this is where i am lost and do not know where to turn any experienced input is appreciated!
Well over the winter i decided to put comp cams cc503 cam in my tpi as well as billet servo's and converter,car was tuned by "PCM FOR LESS".The problem that i am running into is a high idle at all time's closed loop as well as open loop.My idle stays constant at 1500 rpm's in park ….in drive im lucky to touch 1300 usually stays at 1500.Now i have gone through all of the normal procedures replaced my I.A.C. motor/coolant temp sensor/o2 sensor.The I.A.C. motor was set correctly and i have tried messing with the idle screw as well that did not seem to help my problem at all.Car has E.G.R. delete as well as smog delete.I am getting a constant vacuum reading of 13 in.Now i know i should be between 15-16 maybe 17 in. with this cam but can a couple in really cause me to have that high of a idle issue? I have completely torn down the tpi system and has all checked out fine new gaskets all that good stuff.My question to you guys is where would you guys maybe check and what would you do from here,any help as well as input would be appreciated thank you!:
Now after doing some data logging i know i have a problem but i dont know where my problem may be at…..i have a idle on the dash of 1500 rpm and a datamaster reading of 950 on both rpm gauges.Now here is where i am confused the car is indeed racing at idle at all times not doing 950 rpm like datamaster says.I have checked all the sensors they seem to be fine throttle body looks to be set up correctly this is where i am lost and do not know where to turn any experienced input is appreciated!
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Joined: Oct 2002
Posts: 1,096
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From: Idaho
Re: data log question
Now after doing some data logging i know i have a problem but i dont know where my problem may be at…..i have a idle on the dash of 1500 rpm and a datamaster reading of 950 on both rpm gauges.Now here is where i am confused the car is indeed racing at idle at all times not doing 950 rpm like datamaster says.I have checked all the sensors they seem to be fine throttle body looks to be set up correctly this is where i am lost and do not know where to turn any experienced input is appreciated!
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Joined: Mar 2002
Posts: 18,432
Likes: 231
From: Chasing Electrons
Car: check
Engine: check
Transmission: check
Re: data log question
The ECM calculates the RPM from the time between distributor reference pulses (DRP). So if it is calculating and reporting a lower then true RPM, then DRPs are dropping out. This would also be accompanied with misfires.
Unless the actual code was changed, or the ALDL address list was changed, I would go with what the ECM is reporting for RPM.
If you are using the factory tach there is a sticky on the Electronics board here on how to fix it. Apparently it is common for our tachs to report a higher then real RPM.
RBob.
Unless the actual code was changed, or the ALDL address list was changed, I would go with what the ECM is reporting for RPM.
If you are using the factory tach there is a sticky on the Electronics board here on how to fix it. Apparently it is common for our tachs to report a higher then real RPM.
RBob.
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