Two minute over-rich fix ?

cstill88@hotmail.com · Feb 11, 2012

My 1986 B-2 has all new sensors, have new injectors coming Monday.
Map is new, O2 is new, Ign and ECM modules are new, fuel pump (Rail)
Battery is new, plugs, cap, rotor, air temp sensor is new but not ECT yet.

The vehicle starts and runs, but every appx 2 minutes runs rich. Does not want to idle, black smoke comes our the pipe, smells like gas.

Pick-up and running is much better now, but I have this one elusive glitch that I can't find, motor is '86 2.9 liter w/ 158k miles, no leaks, no drips.

Help, any ideas?

adsm08 · Feb 11, 2012

Could be bleed through on the plug wires. You didn't say that you replaced the wires.

With the engine at idle, stand away from the body so that you aren't touching it, and grab a hold of the coil secondary wire. If you get a good shock, go get some new wires.

jhammel85 · Feb 11, 2012

Have you tried checking the fuel pressure? Might be the fuel pressure regulator

sjr53 · Feb 11, 2012

Check for a loose orange wire that should bolt to the rear of the passenger side cylinder head. If it is bolted down, make sure it is grounding the orange wire.

cstill88@hotmail.com · Feb 12, 2012

Not plugwires, they are new as are the plugs. I think something in the main computer module (ECM) is calling for a full choke condition, but don't know what sensor calls for that. It used to only do this at warm start-up, now, at warm idle, it's every 90 seconds or thereabouts. I do have to check all the grounds though.

adsm08 · Feb 12, 2012

The IAT would give the signal that would call for the "choke" condition as you would understand it. But it shouldn't really make that happen.

I'm guessing you are more familiar with carbed systems.

big red 138 · Feb 12, 2012

adsm08 said:
The IAT would give the signal that would call for the "choke" condition as you would understand it. But it shouldn't really make that happen.

I'm guessing you are more familiar with carbed systems.

does the 2.9 even have an IAT sensor? ive personally never seen or read about one, but that doesnt mean it doesnt exsist. if anything i think the ECT would serve that function. at startup the coolant temp sensor is the highest priority sensor for fuel/air ratios ( as im sure you know) so hook a volt-meter up to it and check what its putting out, you can find the voltage=tempeture table on google im sure. { i do know that 3.52 is 50 degree F. and .28 is 248 degrees. 5 volts is shorted(-40degrees) }. but the higher the voltage the colder the fluid, so if its showing colder then what it is outside( +/-10 degrees), chances are its bad, try wiggling the wiring while testing, might have a bad connection at the sensor or pcm or corrosion/high resistance in the wiring/connections, scewing the reading and telling the pcm its colder then polar bear dick so it needs to dump fuel to make engine operation easier.....

another possibility is it might have a bad ground connections to the O2 sensor, causing the voltage signal to intermittently drop? ( sending a lean signal to the pcm). or some type of restriction in the MAP sensors vacuum line or reference, making it think the engine is under a large load and needs more fuel. but id start by testing the ect. if you dont have a volt-meter( analog ones are a couple bucks at napa.) you could try unplugging it then starting the truck.

hope this helps, gas is too expensive to waste!

sjr53 · Feb 12, 2012

The IAT is instead an Air Charge Temperature sensor & is in the middle intake runner with wiring next to the IAC valve wiring. If you just replaced alot of ignition parts, maybe 1 part was defective and you have no spark to 1 cylinder. The O2 sensor will see the O2 and richen up the fuel to cure a false lean indication.

CraigK · Feb 13, 2012

Try disconnecting the O2 sensor.
Yes, I know it's new.
Just might be worth two minutes to verify it's A-OK.

CraigK

Two minute over-rich fix ?

cstill88@hotmail.com

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