99 Camry skips or missing when hot

:banghead: Help I have a 1999 Camry that run's great. The one issue I have is if you run for around 1/2 - 1 hour the car runs rough when you let off the gas. If you come to a stop the idle goes from around 400rpm to 700rpm's up and down. If you turn the car off and restart it, it will work good and start running rough after a while? No engine light comes on.

Which engine? There are several possibilities but, I would start with the coil. There's a few ways to do this. For a quick check, I like to connect a timing light to each plug wire to check for spark. If it doesn't flash while connected to a particular spark plug wire, it could be the coil or the wire. Another way is to remove the spark plug, ground it against the engine case, and watch for spark as you crank the engine. Another way to check the coil is to check resistance on the coil using a multimeter. Can be inconclusive if the coil isn't in it's fail mode. You would have to do the previous tests when the engine is running rough to be of any value.

This is your maintenance manual in the Factory Service Manuals thread at the top of the forum. Open the ignition file for test info. The rest of the files cover about everything you'll ever need. EDIT - http://www.camrystuff.com/index.php?page=Gen4_Manuals

I believe I have a very similar problem to this. I have a 99 v6 camry.

I have changed EGR sensor and o2 sensors and serviced TPS. Have just changed the Mass Air Flow meter sensor.

Problem sounds like missing but when idling the car idles very rough oscillating between ~ approx 500 and 800 rpm exactly. ie idle bounces up and down. When you put your foot down the car still has power and starts to run smoother. Problem goes away if you stop for 5 mins and restart.

I have managed to found someone to hook a diagnositc computer to the car when doing this and No error codes. The only issue now is that it shows that it injects 14% more fuel.

As I said this goes away after turning off for 5 mins and restarting. Reconnecting the computer shows that care running perfectly.

Really need some help with this. This car has only 125 000 km (~80 000miles)

Was really hoping that changing the mass air flow meter would fix but hasnt.

Even tried connecting a second hand computer. No change.

How about a vacuum leak or erratic fuel injector. Inspect all the vacuum lines (EGR, cruise, brake booster etc.) for cracks. Using disc brake cleaner with the engine running spray around the intake manifold gasket. If the idle jumps or stabilizes in a particular spot, you found a leak. Touch each fuel injector to see if you feel a click or use a noid light to test injector pulse from ECM.

Brake cleaner leaves no film. Make sure it doesn't list silicone as an ingrediant.

will do. good ideas. I have to wait to weekend to look into it.

I have a very good mechanic too working from home with his own diagnostics computer who has been investigating it too. I will pass these ideas onto him aswell.

I have suggesting to him that it seems like an air / vacuum leak from the beginning. We have fixed the error codes from the computer. Now we just have to work this problem through.

Ill report back soon.