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1996 Toyota Tacoma Question: Rough idle, Cyl 3 miss fire



, 2.4L 4 Cylinder, Phoenix, AZ, December 28, 2010, 18:58

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?

1 Answer
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  • Answer #1

    December 28, 2010, 19:47

    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.


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  • Reply

    , December 29, 2010, 09:48

    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.

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