injector rings causing hi idle?

While trying to hnt down a potential vacuum leak causing high idle after warm up, I ran across an unusual symptom: I was spraying brake cleaner on the tubing joints, then around the manifold gasket, and noticed a stumble in the idle. I pinpointed the source with the cleaner when I sprayed the injector boss on the manifold on 1,5,and 6.

I put in new takeout injectors two years ago from 5.0motorsports, and used the stock FORD green o-rings. They are much softer and were all I had left after destroying the Jeep 'rings outdoors in January weather.

Having paid attention in Tech Science class thirty years ago, I know that the injector bosses will grow larger in diameter as the engine warms up, especially being so close to the exhausts. This would cause an even bigger vacuum leak than when cold, and explains why the Jeep o-rings are such a tight fit. They have to compensate for the added expansion.

So, back to stock rings, and apologies to anyone who may have used the Ford rings reading previous posts they work.

so you replaced the o'rings and now it's fixed?

More likely it is the intake gasket that is right near by.

Well, could be. I did use the little red tube to precisely direct the spray at the injector boss. If the gasket did leak it was at exactly the same places. When I change the orings I will check the bolts and nuts.

Not that I don't want to replace the gasket with a new late model intake and Chinese "banks" exhaust, but tires and paint come first.

Keep us posted on the o-ring thing.

The spobi squad visited and awards old_man the "Golden Jeep" for the correct answer, "More likely it is the intake gasket that is right near by."

arty:

LOOSE INTAKE MANIFOLD BOLTS. Congratulations.

I was also awarded, but I don't want to talk about it.

They were the ones adjacent to injectors 1, 5, and 6, which is probably what tipped off the winner. Makes sense they would be, they are at the ends of a long manifold. Tightening the ones under was challenging, but I don't want to talk about it. There is still blue vapor trailing off the parking pad.

I did not change the orings as, once again in my old age, I discovered I had actually used Jeep rings on the manifold end of the injector, and the Ford rings on the fuel rail.

Idle is now stable at about 650 rpm, and no extra brake pedal is needed anymore. Thanks to all for their interest and concern.