I'm working on a 2000 4runner with the V6 in it.

A few weeks ago it started running terribly and the check engine light came on. p303 p306. I had done plugs and wires about 6 months ago so I immediately assumed coil pack(a little hastily it seems) I never saw it run bad but what the owner described and the code made sense.

I put a coil pack in and gave it back. A week later or so she said it did pretty much the same thing (running terribly, shaking, check engine flashing). I got in the car this morning and there was no check engine light on and running perfectly.

So I drove it for a while with no problems. parked it and called the owner to ask more questions, same story. got back in and BOOM misfire but no light. Driving around check engine light flashes but doesn't stay on and no code. It flashes while driving around but not stopped i.e. at stoplight. you can feel a misfire at idle and slight acceleration.

Any direction would be great!
thanks

 

Flashing CEL isnt good to take on the road for test drives. It has to be inspected. Usually, something like unburned fuel is being sent down and damaging the cat. What brand of plugs and wires? Other coil packs? Can switch good ones in and see if the miss goes away or changes cylinders. A scan tool to see the misfires is helpful to trace which cylinders.

Check before replacing..for instance try using a spark tester on each wire and see if you get strong arcing. Check ignition connections are all tight...

Any recent work besides the ignition components? More background?

 

mishinko wires and ngk plugs.

My scan gauge computer doesnt let me watch misfires.

my main question is, why doesnt it set codes? If I knew where the misfire was it would help

Can a fuel filter cause these problems? Or low fuel pressure in general?

It feels electrical to me but honestly thats an assumption.

 

Trouble codes can be pending in the memory if none light up yet. Better to park it for now until either a CEL stops flashing or returns solid. Damaged converters are expensive to replace.

How old is the fuel filter? If its time for a change, regardless of its affect on the symptoms, its good to change it. For it being the actual suspect, I doubt it. I hear others had issues with their fuel injectors with these codes...Were the old plugs carbon fouled?

Low fuel pressure typically presents with starting troubles or stalling.

Can at least check if the sparkplug wires were connected to the proper cylinders and coil packs. Cylinders 1,3,5 are the passenger side front to rear. 2,4, and 6 on driver side. The coil packs are 1 and 4 / 3 and 6 / 5 and 2. Of course, reading that you replaced them 6 mo ago, you would have had problems sooner. So perhaps not.

Coil packs refurbished, used, or new? Did they come with a warranty?

I went with a refurbished genuine coil pack that has given me good use over 18 mo ago and still going well since my P0300 and P0303 codes.

Any other history on that engine's maintenance and incidents can help clue on what else to look at. For instance timing belt work...

Electrical...can start with checking connections at the coil packs, wires, plugs are tight. I'd even check basic things like the batt voltage. Are there electrical issues aside from the main issue?

 

ANSWER:

Cracked vacuum hose going to the throttle body. I probably cracked it while replacing the #3 coil pack.

So original diagnosis was correct, moral for the story; "take your time, don't rush "simple" jobs."

 

I still don't understand why a CEL would flash and not set a pending code. If anyone can explain that I'd like to know for future problems.

 

Flashing light is usually serious. No more flashing?

I think there may be other stuff worth checking.