Thanks. I should have done the timing chain when I was doing the plenum, but I was in a rush and said ah I will have time to get it this spring (hard to find free time). I do here a rattle from the truck, where its coming from I have no idea. I always assumed it was the old Cat when that was in place but since I replaced that I still hear a rattle occasionally. The spark knock went away after doing the plenum.

Any ideas on the fumes? Where the Cat meets the down pipes, I was unable to weld the top of the pipes because of the tricky location. The exhaust beyond the cat is also a mess, could that be throwing the O2 sensor off making the gas smell?

On my 94 I also have the EGR tube, and I remember breaking a bolt on that so there may be an air gap in there as well. I'm just not sure how sensitive the electronics are to those things.

I think I will do compression test first, go from there and if thats good I may fix all other issues. Finally, I'm wondering if I'm just losing power through the transmission. My guess is its more engine related.

 

I would be tempted to simply replace the O2 sensor.....

 

If you're running rich, that will trip the sensor. It's what it designed to do. A timing chain rattle will sound like it's coming from under the water pump.Since you'll need to drop the oil pan to do it right, now would be a good idea to look inside and see if there's anything else loose in there. You CAN replace the timing chain without dropping the pan, but I find it's just easier to drop it rather than try to seal the cover and not have leaks.

 

I did that when I did the Cat, I was just wondering about exhaust leaks causing it to malfunction.

 

Only if they are upstream from the sensor.

 

Not meaning to hijack this thread, but these are the exact symptoms my 1997 5.2 is having. Low on power, heater is warm but not hot. The 5.2 runs smoothly, but my 2004 Z71 with 5.3 is much stronger, and gets better gas mileage. I’m unable to perform work like this due to back injuries. Does anyone have a general idea of the cost of having a timing chain replaced?

 

Parts are less than 100 bucks, its labor that will kill you.... Looking at 4 to 8 hours, and whatever the going rate is in your area.

 

My mechanic charges $65 per hour, so maybe it won’t be too bad. I’ve already bought new radiator hoses and a serpentine belt, is there anything else I should replace? I believe it still has the factory water pump.

 

Now would be a good time to replace the water pump (it has to come off anyway) and put a fresh thermostat and coolant in it. Heater hoses would be a good idea and especially the bypass hose on top of the pump. I've cheaped out and not replaced that three times and EVERY time it blew in really cold weather.

 

Thanks for the info. I’ve looked into replacing the thermostat, and can’t believe how complicated it is. I’ll go ahead and get a water pump.