onsight
New Member
Maybe check/inspect if you have any wires (including the 02 sensors) near the manifold or headers that might get hot and cause you fits as things heat up. Could also wiggle the wire bundle behind the valve cover (while idling) to simulate road conditions and see if you can influence the outcome.
My 99 died leaving the shop (once warmed up) because the shop improperly ran the crank position sensor wiring so the insulation melted and wire heated up. Once cool, it would start again (likely due to the resistance dropping). Just throwing this out there in case it helps.
On a gas getter car, I’ve used a shop vac to push air into the tail pipe (using lots of tape to seal it off) then sprayed soapy water on the manifold and all couplers. This exposed way more leaks than I expected to find. I used exhaust putty to seal it all up because I needed the car to drive the next morning.
Seconding this. My head was warped, which caused a cyl. 1 misfire. Rebuilt the top end (lifters, rockers, pushrods, etc) and the miss wasn't as bad, but the code would come back intermittently.
One day at work I taped the shop-vac to the tailpipe, set it to blow, and just used my hand to feel around the exhaust manifold. Two big hairline cracks. Replaced it with a $70 manifold from Amazon and a year later, no leaks or cracks, and the CEL hasn't come back.
It's a great test, takes 10 minutes, and is free.