Thread: 3.9 RUNNING TO RICH?

Can any one help me, my disco is running really rich and I'm wondering if I can adjust airflow to lean it out? Just serviced a month ago new plugs leads and timing done, it does need a new air filter though (could this be why?).

Possible sources of running rich:

Fuel pressure regulator failed or the vacuum hose has perished and fallen off. Check around the back of the engine where the fuel pipes connect for the regulator and see if there's petrol in the vacuum hose or it's got disconnected from the vacuum nipple on the back of the manifold.

ECU temperature sender stuffed, its a plug like an injector plug just behind the thermostat housing. Check the resistance of the sender is around 300 ohms when hot.

Mass air flow meter is stuffed or disconnected. Find a known working one to borrow and test by substitution.

Get a workshop manual pronto (so you're not working blind) from the "shop" tag at the top of the page.