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MsabyOffline
Post subject: Idle problem/ running rich  PostPosted: Sep 20, 2010 - 01:46 AM
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Joined: Dec 22, 2004
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I have a 91 stock sbc 305TPI motor (VIN F-7730 ecm)the only changes to the engine have been a high volume oil pump, a set of Sanderson headers, a heated o2 sensor and the cylinder heads have been rebuilt. The engine does have all the emmision devices bypassed i.e. egr, air dirvert etc. The ecm does not contain any trouble codes.
The problem is when I start the car it will idle briefly than the idle drops and the engine begins to surge. If the idle drops enoughy the engine will stall. If I hit the accelarator the engine springs to life and will try and idle again but the problem reoccurs.

I have checked the fuel pressure, fuel pressure at idle is around 38lbs. With the engine off it is about 42lbs.

I have measured and adjusted the new TPS switch and I have measure the IAC motor to ensure it is in specs. I tested each injector to verify resistance all injectors are 15.9-16.2. I have replaced the MAP sensor as well.

I removed all the spark plugs and regapped all the plugs, I did find one cylinder that the plug was black and wet. I assumed I had a bad injector, so replaced all my injectors with bosch III but the problem is still there.

I removed and plugged all non essential vacuum lines, I still have the same problem.

When I unplug the timing connector the engine will idle, it still surges but it does keep running. The engine is still running rich though. While the vehicle was running I reconnected the dist connector and the vehicle continued to idle and did not stall.

While the engine continued to run I sprayed a little carb clear around each injector, all the manifold gaskets, the vacuum lines and the idle did not change. I was hoping to find a vacuum leak somewhere

I checked the cap and rotor, the ignition module was replaced already.


I can't get the vehicle to idle long enough to adjust the valves, timing, etc.

Any assistance is greatly appreciated

Thanks
Mike
 
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jdinnerOffline
Post subject: RE: Idle problem/ running rich  PostPosted: Sep 20, 2010 - 11:21 AM
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Location: Toronto, Ontario, Canada
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It's a long shot but it could be the water temperature switch (for the computer). I had a few of them go bad, it thinks it is winter and floods the engine.
OR
Try cracking open any small vacuum line (not the MAP) and see if the idle increases. If it does and solves your problem, connect a micro switch to the throttle lever and electric/air switch to a vacuum port.

BTW, the best way to set the GM valves (IMHO after 30 years) is cold with the engine off. Bring #1 to TDC, crank down the rocker nut until you can no longer spin the pushrod between two fingers. Back it off until you can spin the pushrod. Perfect setting every time.
Watch the rotor and do each cylinder individually, 18436572.

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MsabyOffline
Post subject: Re: RE: Idle problem/ running rich  PostPosted: Sep 20, 2010 - 09:25 PM
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jdinner wrote:

BTW, the best way to set the GM valves (IMHO after 30 years) is cold with the engine off. Bring #1 to TDC, crank down the rocker nut until you can no longer spin the pushrod between two fingers. Back it off until you can spin the pushrod. Perfect setting every time.
Watch the rotor and do each cylinder individually, 18436572.


That is exactly the way I adjust my valves cold, i wait until I just see the exhaust valve move and i then adjust the intake. I usually go back over them once I have the engine running. These are the factory roller lifters and I have never adjusted a set before so I left them on the loose side. Do you recommend that 1/4, 1/2, 3/4 additional turn after zero has been established?

Thanks

Mike
 
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jdinnerOffline
Post subject: RE: Re: RE: Idle problem/ running rich  PostPosted: Sep 21, 2010 - 12:57 AM
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Are they solid or hydraulic. Roller does not matter or factor into the mix.

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MsabyOffline
Post subject:   PostPosted: Sep 21, 2010 - 03:01 AM
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They are in fact hydralic lifters
 
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MsabyOffline
Post subject:   PostPosted: Sep 26, 2010 - 04:31 AM
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Problem solved, When I removed the distrbutor to reprime the engine I must have installed it a tooth off and the ecm was trying to compensate for my mistake. I set the base timing and now the engine is running great


Mike
 
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