ramz003

Hello All,
First time Toyota Pick up and user here. I picked up a 80 truck (see pic) and had engine rebuilt and tried to bypass all the vacuum lines. Picked up truck today and i think its misfiring and truck doesnt have any power. Looking for mechanic in Dallas area to help out.

83

Boy that's a tough one. Looks like a nice truck. Only problem for us online is that we (and you) can't really know if the work was done right, by someone qualified. With a rebuilt motor and carb there are just so many things that could have been done wrong or hooked back up wrong.

I would look at timing first. Could be the distributer is off a tooth. That would be the most simple, "man I lucked out" fix.

gillesdetrail

iTrader: (1)

check for vaccum leaks at carburator base, intake manifold and vacuum lines too.

ramz003

After some testing i pull the #4 wire at distributor and it doesnt have an affect on the motor runs the same. i pulled the plug and it was black. Going to get new set and regap.

83

Would be good to make sure it's even sparking in the first place.

I had a similar problem one time when I did my head gasket. I guess I bumped the spark plug into something as I was installing it. I had completely closed the gap. Engine ran like crap and no power.

ramz003

Oh its sparking and i even replaced the spark plug with correct gapping.

83

So are you still having issues or did that solve your problem?

ramz003

Yes, still having misfire issues.

83

And still no change when you pull wire #4?

I'd still check the timing, and for vacuum leaks like gillesdetrail suggested.

If you're getting spark on wire #4 but nothing changes when you pull that wire, then either fuel somehow isn't getting into that cylinder, or you have bigger problems with compression...

kawazx636

iTrader: (3)

Any excessive valve chatter? You could have a worn/damaged lobe on that #4 cylinder. If the exhaust lobe is worn flat then the exhaust valve wouldn't be opening to let the burn gases out thus backfiring through the intake valve and up through the carb. Pop off that valve cover and scope it out. If the camshaft looks good, check the valve clearance anyway. With #1 at TDC the #1 exhaust, #1 intake, #2 intake and #3 exhaust rocker arms should be loose with the rest tight. Turn the crank 360* past TDC and the #2 exhaust, #3 intake, #4 exhaust and #4 intake rocker arms should be loose with the rest tight. Intake valve clearance is 0.008" and exhaust valve clearance is 0.012" - grab some feeler gauges and verify that this is correct.

Other than that, there are a few other things that could be causing your problem:
-Faulty plugs or plug wires (doesn't seem like the case from what you say)
-Weak coil
-Poor compression
-Bad timing (you really should check the timing)
-Timing chain jumped a tooth
-Vacuum leak (although this typically affects all cylinders)
-Poor valve seating
-Poor tuned carb (again, this typically affects all cylinders - what carb do you have?)
-Bad engine ground (check for loose or corroded ground wires on the engine. Even running a temporary 6-8ga ground wire directly from the battery to the block would help diagnose this)