This is my first post - so bear with me. I just rebuilt my 4.2L due to a bent rod because of a faulty intake manifold gasket breach - and it sucked water into cyl-1. Since the engine has about 180k miles, I decided to completely re-ring it while I was in there. It is back in in the truck, and idles pretty smooth (very little vibration, but not at factory timing of 10 BTDC with the Spout removed - its about 15-20 BTDC ?? First question - How do I bring this up to 10' BTDC? Second question (may be related) the passenger side exhaust is now noisy where it wasn't before. The rumble sounds like it's coming from the lower cat converter, but did not make this rumble before. Is it related to the timing? I had a spell with the Cam Sensor Sync Tool, but finally got that positioned - does that sensor adjust any timing after it's positioned? Any help will be appreciated !!!!

 

When I accelerate, the engine has a bretty large vibration, but is minimal during idle - also seems like it doesn;t have the power it should after being totally cleaned and rebuilt. Thanks!

 

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Wr,
Welcome to the 4.2 forum!
I wish I could give you some help on the timing, but I just don't know. There are a few threads here dealing with the sensor and adjustment. I'll do some looking and see if I can find them.

Not sure about the cat conv either. The guts inside are known to break and then rattle. My driver's side, downstream cat did that. Try banging it gently with a rubber mallet. See if you can hear the insides rattle.

Maybe somebody else will know more about the timing issue.

Once again, welcome to FTE.

 

Thanks, I may have figured it out. My passenger-side cat was plugged from water getting into the cylinder and coming out as steam in the exhaust. I temp bypassed the cat and the engine smoothed out great. I'll be replacing the cat shortly - but in the interim, had to bypass the driver-side as well so that both exhaust back-pressures were equal.

 

I've bypassed the lower cats, and now the engine idles fine. As soon as I give it gas, it shudders? When in gear (5 Speed - manual) I can drive if I barely press the accelerator. If I give it any pedal at all - it bogs down and barely goes. Once I get up to 40-50, it seems to smooth out. Any Suggestions??

 

I'm thinking bad MAF sensor.

 

It may have something to do with whether it was the upstream or downstream cat that you bypassed. There are 4 O2 sensors and the computer compares the signals from the upstream and downstream sensors to determine fuel control in the engine. At least, that's my understanding.

 

hi, the camshaft positioning sensor has to be lined up using the sync tool but it is critical that the timing marks (line up all the dots) are not moved out of position when setting up.
also check the vacuum pipes on the EVR soleniod have not been put the solenoid directly behind the EVR as these are the same type with 2 pipes into rubber boot. yes i did get them the wrong way around with my rebuild and it caused power loss etc.
good luck, hope this helps.