Jim Warman Posted September 24, 2012 Share Posted September 24, 2012 The prologue... 2003 Exploder, 4.0 SOHC. Has a bit of a rough run, lacks power, P0172 and P0174 in memory. Fuel trims are polar (one is pegged taking fuel away and one is adding fuel like crazy). Any time we have seen similar concerns, it has always been a plugged cat - no brainer. Apprentice slam dunks a cat and we are..... right back where we started from. At this time, I get a little bit involved. Had him swap upstream O2s side for each (of course he forgot to slime the threads when he transferred them) - so, one new O2 sensor later, we see the concern stay put - not following the sensors. Power balance shows all bank one cylinders way down on contribution... but all we have is a little bit of a rough idle. Certainly nothing as bad as the scan tool indicates. And then I inherit this puppy. Relative compression looks wonderful... but it sounds "curious" while cranking during the test. Mechanical gauge has bank two compression at 170ish and bank one at 105ish. Hmmmm, best guess would be cam timing? There's a bit of oil at the back of the right head - as I begin to remove the cam cover I notice the valve cam is cracked. Once removed, I can see some of the pieces of the chain guide and they don't look quite comfortable. Bear in mind this car didn't have any strange noises, rattles, pops or farts. Just another day in the life.... Now to determine if I have any bent valves. Quote Link to comment Share on other sites More sharing options...
mchan68 Posted September 24, 2012 Share Posted September 24, 2012 Jim, on any 4.0L SOHC engines where cassette failure has been observed, the engine itself is only five minutes behind. If I'm not mistaken, there was a TSB on those engines of that particular vintage for an updated jackshaft chain and tensioner intended to address a rattle noise under load between 2000 to 3000 RPMs (memory thing), not that it matters much at the point you're at with it now. Quote Link to comment Share on other sites More sharing options...
Brad Clayton Posted September 25, 2012 Share Posted September 25, 2012 Jim, be sure to remove the oil pump drive in the back of the block and give it a good look over (read that as REPLACE it). Those things are bad about locking up for second or two and causing mucho problems on bank 1 timing components, camshaft, valves, ect. Quote Link to comment Share on other sites More sharing options...
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