I have a 99 Accord EX Coupe v6, 113k miles, auto trans.

New timing belt @ 95

Adjusted valves 100k

This car runs good as long as you drive on the freeway. I drove it

When you lug it in the city the idle becomes irratic, the engine light goes on with PO 300, 301...306 no other codes than msifires accross all cylinders.

The motor makes a kind of intermitent "ticking" sound that it seems to come from the area of the rear exhaust manifold. The ticking comes and goes and seems to be more pronounced when you back off the throttle.

I thought it could be valve noise so I used a stephescope to listen for internal motor noises and can't hear any. If it were valve noise I dont think it would come and go. I dont know if a valve problem would cause misfires across all cylinders. I believe it be isolated to the cylinder with the bad valve.

I checked the vacume and had 21lb at idle but the vacume actually increases when you goose the throttle. It's my inderstanding that it should drop rapidly but it doesnt it goes up?

I used a heat gun to check the temp on both ends of the cat front 270 degrees front and 160 degrees at the outlet. I had a cat go out on another car and it make a pop corn popper noise

PS, I just cleaned the passage way under the intake manifold that periodically gets carboned up.



Anyone got any ideas?

 

For quite awhile, I've been hearing about the 6th generation Accords (1998-2002) having misfire problems. There was always people mentioning clogged EGR port, etc. possibly causing the problem. However, many times the misfiring still existed after EGR port(s) and EGR valve were cleaned. Recently, someone told me the problem may have to do with the distributors on the 6th gen. Accords.