Rough idle, Cyl 3 miss fire on 1996 Toyota Tacoma

Symptom: 1996 Tacoma 250,000 mi. Rough Idle- P0303 Cyl 3 miss fire. Adjusted valves- #3 was a zero lash- brought to spec. Cleared codes- Good drivibility several hundred miles, now P0303 is back along w/ Cat eff. below threshold. Vehicle runs ok in open loop, but when sensors come on line data is such: AFR- 20:1 at idle + 19% long term FT O2/1 .34-.55V O2/2 .34-.55 Injector resistance measured out at 15.4 Ohms- spec is 14.2 max- Cyl 1 inj. measured out at 15.2. AFR is very lean, ECU is Calling for lots of fuel. Maybe fuel press is low?

by in Phoenix, AZ on December 28, 2010
1 answer 1 comment
ANSWER by , December 28, 2010
the miss has put unburnt fuel into the cat and did it in. the cat is a result of the miss. start at basics. do a compression test first. do a second cylinder to compare pressures. yes, do afuel pressure check as well. adding 19% indicates either a vaccuum leak or a mass air flow. the injector resistance looks good but does not indicate spary pattern. just some ideas to follow up. Roy
COMMENT by , December 29, 2010
Thanks Roy, I'm going to do just that this weekend. Did the brake clean trick looking for leaking manifold...nothing. Now that I thinking about It I did have a few hot start issues this summer. Fuel again? (Arizona)- crank / no start. Wait 5 min fires right up.