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Matt, Engineer
Category: Ford
Satisfied Customers: 21501
Experience:  BEng hons Mech engineering, in auto industry 22 years
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Have a 1985 rv on a Ford Econoline chassis with the 460ci

Customer Question

Have a 1985 rv on a Ford Econoline chassis with the 460ci engine. Can't get it to pass emissions. Replaced plugs, dist cap, air filter. Found a vacuum leak where the EGR plate mounts to the body and did a quick patch on it. Did better on the next emissions test, but still failed. Any ideas where to look next?
Submitted: 8 months ago.
Category: Ford
Expert:  Matt replied 8 months ago.


Incorrect fuelling due to a faulty water temp sensor. If this is the problem then the ECU will be leaving the car constantly ' on choke' and not reducing the fuelling as the engine warms - so unplug the sensor and clean the contacts on both sides with some switch / electrical cleaner (not WD40) and inspect the wiring for any signs of damage to the insulation especially where it runs over other components and through the bulkhead- if this doesn't help consider replacing the sensor as they're not expensive

Check for exhaust leaks before the O2 sensor as if this has been experiencing an exhaust leak then it will have been running very rich as the sensor will see the extra air pulled in as fresh / lean fuelling and be adding fuel to compensate.

this can lead to catalyst failure as the extra fuel can re-light inside and melt the catalyst

The best way to find an exhaust leak is to run the engine from cold and feel around the exhaust joints with your bare hands - you'll have about 30 seconds before it all gets too hot and you should feel any escaping gas blowing over your fingers

Expert:  Matt replied 8 months ago.


do you still need help?

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Customer: replied 8 months ago.
Sorry, I just realized that these were getting sent to my spam folder.The choke is opening up all the way after a few minutes of running. I have not been able to find an oxygen sensor anywhere on the pipes. Also, no cats and no leaks on the exhaust system. The original owner did install aftermarket headers. Carb is a four barrel Holley. I did just notice that it's leaking a bit of fuel somewhere near the front bowl/ inlet and another drip on the vacuum actuator arm of the rear bowl. I'm assuming that it's actually coming from the rod that holds the throttle plates and not the vacuum diaphragm on the rear side, but not sure about the front. Possibly stuck floats? Would be odd that both would get stuck at the same time, wouldn't it? This vehicle used to pass emissions with flying colors, so I'm confused about what could suddenly be causing an issue. Thanks
Expert:  Matt replied 8 months ago.


OK thanks for the extra information

I'd agree that it could be a stuck float or the float valve itself thats leaking and then flooding the chamber as the fuel will run over the tops of the jets and into the air circuit

so that's well worth checking out

I'd also check the state of the vacuum advance system on the distributor, if the diaphragm is split inside the actuator then you won't be getting the correct spark advance which will also hurt emissions