I have this exact same problem, and I also posted in this forum and no one has been able to think of a solution.

 

Just know that your 5th gen IS different than the OP's 6th gen.....close but not really

 

Did the clean got carbon out of ports but gasket was crap so could be culprit i did add some silicone to it.but im the same boat only does it at idle runs great other than that.im assuming i caused a air leak possible at injector or gasket ,which i cant seem to be able to buy as its discontinued.im gonna do a co pression test today but since somone eles having this problem after the same cleaning i dont expect it to be an issue.btw its a 97 f22b.if anyone got ideas on the gasket please send em my way

 

The original post was from about 13 years ago, so you may not get help from the original poster. I'd think a vacuum leak would be more pronounced at idle as the engine vacuum is the greatest. Is your engine the f22b1 (ex) or f22b2 (lx/dx)?

 

Its the f22b.i pulled the plate again cleaned it wasnt very dirt.resealed the gasket as gasket is discontinued.cleaned injectors and checked and lubed seals.reistalled and drove it a couple miles and let it idle at home no light as of yet .i plan on bri gi g it to work tomorrow and thats a 31mile drive one way,so it should happen then if its going to happen at all.i also have a light for oxygen sensor heater ,i dont get that one all the time but every now and then itll pop up,ill be checking that today.its a 97 i bought a year ago drove as is slowly fixing issues as they arise.

Just painted

 

Sorry its a f22b2

 

Guess i got it must have been a vacuum leak i sealed it up with rtv and drove it that day and now 31 miles no light.wish they had that egr plate gasket available.thank for the response