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Decel/RPM Stablization failure. Car won't recover from RPM Drop (sometimes) - Ideas?

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Old 04-05-06, 06:28 PM
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Decel/RPM Stablization failure. Car won't recover from RPM Drop (sometimes) - Ideas?

This is the deal...

I am not sure if it's an engine issue, tune issue, or whatever... but here is the situation.

My engine has 2000 miles on it, and since I removed the methanol I've been driving it pretty easy. It doesn't see over 7psi (read sig for mods, etc etc)

Lets say I am on the highway doing 70mph, and I am in 4th. I want to shift into 5th so I press the clutch in, and go to shift. Obviously when you push the clutch it, the car assumes a neutral state... and the RPMS will drop until the car is in gear, and clutch released. So I decide to hold the clutch in like a grandma... and watch the RPMS fall. IT is supposed to catch at low RPMS and the injectors begin to spray again. Well, half of the time (notice I said half, and not always) - my RPMS fall and do not recover... it tries to recover.. but doesn't make it. Sometimes it will recover (barely), and other times it will be just fine. If the car dies, I simply dump the clutch and it picks back up where it should be.. but its a real PITA if you're at a stoplight, or sign, etc.

I had recently fixed a vacuum leak in the elbow... I don't know if this would cause it. I also decided to riched up the N1 Row on the Power FC (400-800RPM area) - I upped it a buttload and that helped a little, but I've richened it up so much that my injector lag settings wont allow me to add more fuel in that area... but ANYWAY.

I know there is a setting somewhere int he power FC that allows you to set the delay that the injectors come back on when the car drops RPMS and has to be caught in the idle area so it doesn't stall.

My fuel pump is wired for a constant 12.5VDC, and my fuel pressure is 36psi base.

I am not sure if this is a tune issue (because the map has worked just fine before), or mechanical issue, engine issue, etc. I would just like some input.

I've also adjusted my idle screw. The idle sits around 1200RPM, but right now it bouces up and down and I am currently adding and removing fuel in certain areas to stabilize the idle since I don't have an idle control solenoid (maybe i should put one back in eh?)

Well, any input would be great. If my description wasn't clear enough, please let me know so I can try and better explain it.

Thanks
-Darren-
Old 04-05-06, 06:47 PM
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well dh i think your problem has something to do with no idle air control solenoid. u see one of the tasks that your IAC handles is to "catch" the set idle speed while your moving and while your stopped. as your rpm drop to a certain target spedd the IAC opens up quickly to catch and maintain the target idle. in short.... get an IAC
Old 04-05-06, 06:51 PM
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check your dashpot, it could be sticking

located on the front (bumper) side of the throttle body...trace the throttle cable

it is a round top like device...with a plunger on one side
Old 04-05-06, 06:54 PM
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Whats the IAC look like so I can dig it out of my box of ****? LOL

David - received the datalogit today, thanks.

Hrmm, IAC goes where?

Going to get a pic of engine, maybe i can find it.
Old 04-05-06, 07:02 PM
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Here is a video, this is the dashpot correct? It's barely making contact, and it doesn't move. I can move it with my finger though.

http://videos.streetfire.net/video/6...4788F7565C.htm
Old 04-05-06, 10:43 PM
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After reading up.. the dashpot is supposed to make contact UP TO 2800rpm. Looks like mine isn't even making contact at idle.. lol. Seems I'll have to replace it... ugh.. $85 from malloy =/
Old 04-06-06, 04:03 PM
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Well I bought a used one from Fritz... oh well, waste of $37, lol. I adjusted mine and things work fine now. I had a friend hold the car at 2800RPM and I screwed it over to make contact. Everything is working well.

I guess i'll have an extra dashpot if anyone needs one... beats the $85 price though, I am not too worried about $37 =)

Thanks for the help guys!

-Darren-
Old 04-06-06, 04:27 PM
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Thanks for the follow up. My car does the same thing. I just thought it was a the 850s having problems at low revs. I'll take a look at it next chance i get. CJ
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