86 2.5 Timing

quartermilecuda · 11-11-2009, 08:08 PM

I know this may sound stupid but I have just bought an 86 Comanche with a 2.5L. It has a slight knock and I knew about it before I had bought the truck. I think its the timing. But people tell me that the Timing cant be adjusted? I don't believe them. I am not familiar with these motors at all and I would appreciate it if someone could explain to me how I would go about setting the timing.

vaquaro · 11-12-2009, 01:46 AM

welcome to the mysterious word of " Renix " . Renix TBI .....Timing is controlled by ICM unit (otherwise known as "HAL" if you remember 2001 a space odessy ) which takes sensor readings to decide air/fuel ratios and timing requirements to meet EPA reg.s

quartermilecuda · 11-12-2009, 05:47 AM

So there is no way to adjust it?

cruiser54 · 11-12-2009, 08:34 PM

No. There is not. Describe the noise in more detail.

quartermilecuda · 11-13-2009, 09:13 AM

Its a low tone knock. First time I heard it It was somewhat loud. (Engine was cold) We couldn't tell where the noise was coming from. Just yesterday we went back to have another look at it and tried using a screwdriver to find where the noise was coming from. For some reason the noise wasn't as loud this time but was still low. (again the Engine was cold) The sound seemed like it was coming from the top right side of the motor. Previous owner says that he had rebuilt the motor and put all new bearings and gaskets in everything. When driving the truck it seems to have a power loss towards higher rpm. My thoughts on it is that when the previous owner put the cam back in and it was tooth retarded or something. (are these Chain or belt driven?)

cruiser54 · 11-13-2009, 05:35 PM

Chain driven. How long ago was it rebuilt? I have seen cases of carbon knock, where carbon builds up on the pistons and then gets hammered into the head causing a knock. Cam timing would not cause a knock. Is the vehicle still equipped with the original catalytic converter?

quartermilecuda · 11-13-2009, 07:13 PM

I think its a new aftermarket one. Looks new at least

quartermilecuda · 11-13-2009, 09:49 PM

I think the previous owner said it has been about 7k miles since rebuild

cruiser54 · 11-14-2009, 06:16 AM

PO might have replaced bad catalytic converter but left original muffler on which could now be filled with the old cat conv guts. That would cause a heck of a restriction and make it not want to pull at higher RPM and in higher gears.

quartermilecuda · 11-14-2009, 07:39 AM

I doubt it because I think the muffler is new to.