Extreme rich condition

[Hib Halverson]

You likely don't need to fuss with taping a pressure gauge to the windshield?at least not yet.

If you tested fuel pressure per the service manual and saw 45-psi peak after key off then the pressure drops. Your pressure is low. It should be 48-55 psi. If pressure drops after the pump shuts off you may have a leak.

A possible leak coupled with black sooty plugs tells me to investigate the possibility of a faulty FPR, faulty injectors, faulty ball check in the pump or anything else which can bleed off fuel pressure.

[-=Jeff=-]

Originally Posted by Hib Halverson

You likely don't need to fuss with taping a pressure gauge to the windshield?at least not yet.

If you tested fuel pressure per the service manual and saw 45-psi peak after key off then the pressure drops. Your pressure is low?should be 48-55 psi?and you have a leak somewhere.

A possible leak coupled with black sooty plugs tells me to investigate the possibility of a faulty FPR, faulty injectors, faulty ball check in the pump or anything else which can bleed off fuel pressure.

Considering this is the same with the OEM and Jerry's FPR, I am guessing that probably is not the case, but still a possibility.

[Marc Haibeck]

Hi Perry,

The engine will run very rich at idle if the MAP sensor vacuum hose is not connected or leaking.

The manifold vacuum reported to the ECM should be 40 kpa at idle. Since you don't have a scanner measure the voltage between pins A and B on the MAP sensor. It should be 1.7 volts at 40 kpa. If the voltage is greater than 4 volts the ECM will command the injectors to run full rich at idle.

[Perry Mitchell]

Thanks Marc. I will check that out and report back.

[Perry Mitchell]

Originally Posted by Marc Haibeck

Hi Perry,

The engine will run very rich at idle if the MAP sensor vacuum hose is not connected or leaking.

The manifold vacuum reported to the ECM should be 40 kpa at idle. Since you don't have a scanner measure the voltage between pins A and B on the MAP sensor. It should be 1.7 volts at 40 kpa. If the voltage is greater than 4 volts the ECM will command the injectors to run full rich at idle.

Marc. I finally got the plenum back on and after startup, the car still runs very rich and idles rough. I connected my mutimeter to pins A (Black wire) and B (Green wire) and got a 1.0 volt reading. Does that indicate a bad MAP sensor?

[Marc Haibeck]

That's at good MAP sensor signal at idle. The sensor is requesting idle fueling.

How does the engine run when you drive the car? It should run smoothly when accelerating. Even if it is running rich the engine should run smoothly but might be down on power because there is too much fuel. I'm wondering if there is a misfire?

Are the spark plugs carboned from the old fuel injectors? You don't need to get a new set of plugs if they are just dirty. The tips can be cleaned by spraying them with carburetor cleaner, letting them dry. Then heating them with a Propane torch.

[Perry Mitchell]

I should remind you that this motor has been transplanted into a 67 Camaro, not that it should matter. The car isn't drivable yet as it is being readied for paint and reassembly. I cleaned the plugs with brake cleaner, which were very sooty but not hard carbon, prior to startup and after I installed new injectors and removal of the secondaries and the installation of your re-calibrated prom. The SES light is on steady with no flashing codes. I can't let it run more than a 30 seconds as it will choke me out.

[XfireZ51]

If the SES light is on steady, then its in Limp Home mode which would dictate it to run rich. And you say you have no codes altho the SES would indicate there is(are). How are you reading for codes?
I would follow Jeff s advice on getting a scan tool like ALDLdroid.

[-=Jeff=-]

Or jumper pins a&b on the diagnostic connector and read back the codes, each code is 2 digits repeated 3x first one is always 12, it would be flash....flash..flash (does represent time delay) the is would repeat.. after 3 each code will appear.

What year harness did you use?

[Perry Mitchell]

It's an after market harness for a 91 LT5 made by Ron Francis Wire Works. It seems to be very accurate when compared to the original harness I removed from the wrecked ZR1. I had a code 66 that I detected by jumping pins A and B in the ALDL connector but that went away after installing a resistor as you and Marc suggested. I have no codes now, other than code 12, as detected by jumping the ALDL pins with a paper clip. I do not have a scanner YET.