2000 Camry 4 cyl engine check light code P0300

Check that ground wires are properly connected. Recheck wiring connectors. What's engine' vacuum like? Check the ignition coils and make sure they are good. Do a leak down test for each of the cylinders. A leaking cylinder will do it (but the cylinder head's was changed again!). A mechanically inclined friend and a $29.99 tool from Harbor Freight and an available air compressor will help if you want to attempt a leakdown test.

Free loan-a-tool program from AutoZone:

It should be something really simple during replacement. So look at the things the mechanic touched while taking off and putting on the cylinder head first.

Regarding MityVac and vacuum leak side of things:

If you have the MityVac free loaner, might want to check the operation of EGR valve as well.

Also, check the routing of the vacuum hoses to the vacuum modulator and EGR valve. Make sure the right ports on the throttle body is connected to the right ports on the modulator and EGR valve.

When does the miss happen? Accelerating or idle? Does the engine feel sluggish? (fuel delivery, timing)

Does the engine idle too fast or too slow/stall? (vacuum leak/EGR)

Check the 5SFE here, but Haynes manual of your year should do better:

Good luck.

I used a vacuum tester and on the intake manifold it reads 14 at idle. The instructions say it should read about 20.

I verified all vacuum hoses follow diagram for vacuum modulator and EGR valve.

It idles fine and has never stalled. It feels like it runs fine when idling and accelerating, it is only when I am trying to maintain speed when it starts choking and surging. Engine does not have as much power, but not a big difference noticed.

My gas mileage went from 38mpg to 34mpg after this original head work was done too.

I have an appointment tomorrow at the shop and he is going to verify the intake cam and exhaust cam are lined up for correct timing. I am assuming that the car will still run (at least run like it is) if the cams were put back together one tooth off.

snipped-for-privacy@hotmail.com wrote:

Yeah, 14" is low. So ECU thinks you're high altitude therefore inject less fuel (lean mixture) and you start random miss. Now that makes sense. You're about Denver or higher. (On a side note, I'm glad I have NGK Iridium plugs.)

Many 4cyls t-belts stretch and skip a tooth but won't set codes. Just sluggish and no power is all. But I hope it's just timing anyway, because during highway cruising if EGR is open it's least of your problems (usually they don't and engines knock).

If there are no leaks and a quick check on timing is fine then it's the valvetrain. Hindsight is always 20/20, it was probably better to just use your original cylinder head for valve stem seals, as I plan to do during the next timing belt job using Fel-Pro seals myself.

Who knows if your current cylinder head's cams have been messed with (e.g., racing cams, etc). See what the mechanic says, and see if you can get a warranty replacement and quit messing with this particular cylinder head -- unfortunately from the same rebuilder I guess.

Now you have to replace the head gasket too. #$%! I'd use Fel-Pro Multi-Layer Steel (MLS).

I mentioned retarded cam timing vs crank, but right, if the cylinder head reassembly went wrong the two cams may be off (the dots don't line up). (!)