LT4 New LT4 owner with several issues, HELP!!

[BIG CTY]

Hello all,
I have been lurking and searching for quite some time now. This is my first post however. I bought a 96 Polo Green LT4 about a month ago. I'm a chevy guy at heart as I have 5 others! (In case you wanted to know, a 66 C-10, 69 Impala, 70 Monte Carlo, 91 GMC Sierra, 95 G20 conversion van) No wife and kids, so cars it is. The new to me Vet turned 100k miles on my way home from picking it up. The previous owner CLAIMED he did the following:

New spark plugs
New spark plugs wires
New distributor
oil change
New radiator
New water pump
New brakes

Well the car runs great with no misses or rough idles, but codes are popping up all over the place and its overheating. I dont hear the fan coming on and the temp climbs steadily at idle. As soon as I get going the temp comes back down where she should be. I also have a grind SOMETIMES going into first gear. Oh yeah, no reverse light either lol. I do hear a slight faint type ticking coming from what I think is the #3 spark plug, which might explain the p0303 (cylinder 3 misfire) code I have. But I also have p0305 (cylinder 5 misfire), and p0420 (catalyst efficiency below threshold, forgot which bank).

It strange because the car runs and drives fine, get exceptional gas mileage and seems to be in excellent shape. But codes come up for a reason. I thinking about changing the plugs and wires again, but I'm not sure which plugs and wires I should get. One may be cross threaded. I'm going to have a Corvette indy look at it this week, but I wanted to pos and get some info/opinions on what you all think the problems may be. I also ordered a reverse light switch. Any info you can give me would be greatly appreciated. Thanks in advance!!

 

[rmonty]

Welcome to the CAC LT4 forum! I don't personally have answers for you but I know there are some very helpful people out there on LT4's. They have helped me with mine more than a couple of times.

 

[Hib Halverson]

Well....let's assume the previous owners claims are true. With two cylinders sending misfire codes in spite of all that ign. work, I think I'd look for mechanical problems. Check the valvetrain for those cylinders and do a compression test.

The p0420 may mean you got bad cats.

Hope you don't have spark plugs which are "cross-threaded"

You also need to run the cooling fan diagnostic listed in the service manual.

 

[So Bay Vetter]

Having done most of those repairs myself, I might think your missfire issues are related to a hasty distrib/plug/wire replacement; unseated wires at plugs or optispark., insulation shields left off of plug wires. The missfires are on the left side and the wires go thru pretty tight quarters under the a/c pump and behind the p/s hose on their way to the opti. I remember having some difficulty seating the plug wires at the opti. as well.

 

[All-Ignition]

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