air leaks and CELs

I have been fighting two codes on my Rover for a few weeks now. Both refer to an airleak that the computer says it can no longer compensate for with the injectors. I did replace a few vacuum hoses, found a bunch that had no clamps, and replaced a connector, but to no avail. What gets me is the old gal runs great. The idle does not hunt, there is no hesitation, no misfires, and she basically purrs along like she did before the Check Engine light came on. Except for that light, I would never even know there was a problem.

I beginning to think there is no air leak. Last year when I replaced the exhaust system, I went with 4 recommended after market O2 sensors from Atlantic British. My Disco hated the downstream ones. The computer would not even talk to them and the truck went full rich until I replaced them with 2 oem ones from the dealer (ouch!). I beginning to think the two upstream ones are the culprit. With a new engine 15,000 miles ago, I just cannot see it being a bad intake manifold gasket. Even of the "mechanic" who did the work was shady, I just cannot see him reusing the old gaskets when I bought him all new ones. It could be the fuel pressure or a clogged fuel filter, but again, no symptoms at all.

What does the hive think, am I barking up the wrong tree?

If you clear the code, will the CEL come back if you just let it idle or do you need to drive it for the light to ome back on?

Not a rover, but I dealt with a vehicle that had codes indicating an air leak, and it ended up being a split in the intake tube. The split was in the bottom of one of the flex joints and hidden from view. 

At idle the split was  closed and didn’t leak, it was only under a load when the engine would move enough that the split would open up causing a leak would and set the CEL.  

If this is an obd2 vehicle and you can view fuel trims then i can tell you how to figure out if it actually has an air leak or not. 

Smoke test?

Bad check valve on the charcoal canister/ carbon in the iacv/ carbon in the butterfly are the common rover air leaks. 

I would look at the evap system. GM trucks have a similar issue. 

Vigo said:

If this is an obd2 vehicle and you can view fuel trims then i can tell you how to figure out if it actually has an air leak or not. 

I can, I have a reader that lets me view everything. I needed to get it to reset the airbag light. It also usually takes a good 20 or 30 miles till the CEL comes on.

Alright then. Vacuum leaks are powered by vacuum. Vacuum decreases at higher throttle openings. The fuel trim will show the system trying to compensate for the 'unmetered/unmeasured' air by adding fuel/positive fuel trim. As you increase throttle, the fuel trim should shrink back to a normal range as the vacuum, and thus the leak, goes away.  

most I have seen was 23%.. but I will give it a good drive in a couple of days and keep a good eye on it