Please help!

Michael Riola

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04 Cobra 2.76 Eaton
340lph pumps pulse width modulated
Bolt ons
60 lb. Injectors

The car was tuned remotely and runs strong under wot. Tuned to lambda of 0.78 at wot and did all part throttle stuff. Week later I noticed an idle puls .

It happens if I clutch in and go into neutral at any kind of speed (like lazily approaching a light) the rpms dip and go between 750-950. Wideband showing lean pops like it is misfiring. New Iacv, tps, plugs, cam sensor, crank sensor. I cant seem to get it to stop doing this. Definitely embarrassing. Any thoughts all? I also tested vacuum. Reads 21 through the pulsation.
 

03cobra#2

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Are you able to datalog? Easiest solution would be to datalog and send to your tuner.

Did you replace plugs?

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01yellercobra

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Talk to your tuner. Sounds like the tune needs some tweaking. But it wouldn't hurt to check all the vacuum lines and intake clamps.
 

Michael Riola

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So I sent logs to my tuner and he thinks something is wrong mechanically. I have replaced all of the above indicated parts. Not sure what else it could be. Could this be an injector sticking?? Here is a video of my issue.

 

Michael Riola

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Are you able to datalog? Easiest solution would be to datalog and send to your tuner.

Did you replace plugs?

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Yes sir just did a fresh set last night. We are on AR93s gapped at 0.025 running about 16 degrees of timing. Plugs looked good on a fresh wot read.
 

03cobra#2

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How is the idle when the car is at a stand still? Does it pulsate like that when you are only coasting?

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01yellercobra

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My guess would be the dashpot decay needs to be tweaked. Might need to slow down the drop a little.

Although with you saying it pops I wonder if the coasting fuel shut off is a little aggressive? But I wouldn't think it's active at that point.
 

roy_1031

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My car did the same thing after tuning. I hit up my tuner and he revised my tune and said it was the air dashpot or something like that. He adjusted it and it ran beautifully after that and idled smooth.


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