Outer Limits 4x4 Board

Does anyone know what would cause my 90 US Rocky to idle erratically? The check engine light came on with a code of "12," which is not listed in my online manuals. I checked it three times to make sure I was not just able to count, but that's what I keep getting ... a 12. I do have a major exhaust leak on a bracket after the O2 and before the cat. Would that affect it?

Ok, evidently it has something to do with the EGR system. apparently the US version has 15 codes i suppose because of emissions. Anybody know if you can bypass or take off the egr system? Do the Ferozas have an egr system? When i turn on a/c the idle speed levels out at 1000. Any ideas?

Ferozas don't have EGR (at least Aussie spec ones I've seen don't)

Your's has a different EFI system with more sensors- see the Service Manual for more details. If you do a search on Google you should find a site that details how to clean out the Rocky EGR system.

I would imagine that you can't remove the EGR system if you still have to pass an emissions test.

Code 12 trouble area:

EGR valve
EGR modulator
EGR VSV
Water temperature sender

What do you mean "idle eratically"?

Kickingback99 wrote:When i turn on a/c the idle speed levels out at 1000.

Turning on the aircon will increase the idle speed (as will turning on the heater fan or headlights). There are two solenoids that open up and bypass air into the inlet manifold, they are controlled by signals from the ECU. The aircon one is adjustable and hangs off the outer side of the inlet manifold.

Idle speed can be adjusted on the throttle body. Try playing around with your ignition timing and you might be able to cure the erratic idle.

Pull the EFI fuses for a couple of minutes (or disconnect your battery) and reset the ECU's memory too. See if that helps.

Without the air on the engine idles between 900 and 1600 every other second. Turn the air on, flat 1000. When i reset the ecu by disconnection of the battery, the light will stay off and the idle problem does not happen for about a day or two. Usually if I am carrying more than one person.

Check your air bypass valve in the throttle body. My bet is it's jammed open- it should close when the coolant warms up.

Exactly the same thing happened to mine about 18mths ago. It was continually revving up and down- got strange looks at traffic lights! People thought I wanted a drag.

Check the coolant is flowing through the pipes up to the valve housing and also try levering the valve with a screwdriver to free it up. I think I may have sprayed silicone spray into mine to help free it; but thinking back that wasn't so smart as it can poison oxy sensors....

If you search you'll find more info on it.

ok, apparently the person that worked on this before me decided not to attach vacuum hoses to bottom of distributor...just found it while replacing hose clamp on water hose underneath distributor...

Make sure you get the two of them around the right way or your advance curve will change.