1993 Ford Ranger failing NO(PPM) at 15mph only.

(15 MPH) NO (PPM): MAX: 533, AVE: 136, I tested: 815

(25 MPH) NO (PPM): MAX: 786, AVE: 124, I tested: 631

My CO is:

15 MPH: MAX: 0.70, AVE: 0.06, I tested: 0.04

25 MPH: MAX: 0.84, AVE: 0.05, I tested: 0.02

I am fairly certain that I simply need to clean my EGR system. The valve itself works, however, a vaccuum tester gauge does NOT change rpm or idle speed, which leads me to believe that the EGR lines are clogged.

Any other ideas? I passed the rest of the test just fine.

Answer:		We think you're right on the money. Disassemble the EGR, we're certain you will find the exhaust and intake passages to and from your Ford Ranger's EGR valve clogged. With some carburetor cleaner and a metal flexible rod clean the passages both on the engine and the EGR valve, reinstall the EGR valve and expect to see a decrease in idle when vacuum is applied to the EGR valve with your vacuum hand pump. posted by SmogTips Support