*and torn down.

How's everyone doing??

So I've had problems with my '97 4L (not OHC) for some time now. I couldn't tell you where and when the trouble began but now I'm fairly stumped. So here we go.

I've always had to change the plugs every year or she wouldn't run worth a damn, would stall out idling in any gear, got me in a mess of **** a few times with that. Also threw codes left and right for misfire, O2 sensors, and MAF sensor.
I checked every sensor that I could with the help of this forum a while back, and not a bad one to be seen. And replaced the O2 sensors every time.
Somewhat recently the new plugs didn't do it anymore,
I was using NGK's but got away from them and went to Bosch plugs which seemed to hold up better, regardless....
And up to the last 100 miles she never back fired, up till...now...

I had a notion that i might have a bent valve or screwed up guide from a missing plug electrode a while back, after one of the few times it'd been to a shop to put new injector plate gaskets in.
Yet, when I did the compression check all cylinders were between 150-180. With one catch, the opposite side I thought my problem was... the 3 plugs were all oil fouled and I got a spit of oil when she turned over, from bad to worse, back to front. never had that before...

So... the underlying problem: I have more than 2mm of gunked up SHAT throughout the entire intake, almost all the way to the seats. It looks like this crap was coming from the EGR system. perhaps the evap return system also???

So....
Nothing has been scored that I've seen, or bent or overheated,
The coils where slightly over resistance, but evenly, getting a new one regardless,
I have done leak down tests before, and I'm still entertaining the thought that the rings one one side are bad.

Were did all the gunk come from? this truck has never burned oil, and there are no mixed fluids.

One last think... with the right performance parts and chips, can you effectively cut out the EGR system???? perhaps the evap too?

Thanks for taking the time for me, and the help if you can.

 

unlikely gunk would come from egr seeing only gases come through there.. and for the evap that also only takes fuel vapors from the gas tank and inputs it into the intake at crusing down the highway. even with good compression you could yes have bad oil rings on your pistons probally a good sourse of where the gunk in the intake is coming from. good luck. hope i helped some