I have a 1990 C4 conv., 107k miles, that Ive been restoring.I have managed some simple repairs and maintenance without problems. The car runs ok, but it seems to be skipping and does not have the power it should.
Not knowing the complete history, I want to perform a tune up.(plugs, wires,distributor, etc) is on the horizon. Replacing the plugs and wires looks to be a challenge because of accessiblity .

Can anyone share any tips or experiences that may make this endeavor to tune my 1990 C4 an enjoyable and successful effort? Or is it best to take it to a C4 pro?

thanks much,
jwardg

Howdy. If it's a stock '90 and the wires are in the stock location like in the photo and you want to keep it that way, it's a challenge. Same with the plugs. Do some searching.

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It's not hard... just fiddly...

Take your time, focus on one aspect at a time and you should be ok.

First off, plug access is not easy on these cars. You will want to have a number of extensions, a swivel socket, a regular plug socket and a 3/4" offset wrench.

The combo comes in handy with cylinder #8 (passengers side, firewall). It is a bitch... I use the regular plug socket and the 3/4" offset wrench to free it. A lot more room that way.

I suggest NGK plugs. You don't want to be doing this frequently.

Same with wires, I really have had good luck with Taylor. MSD I hear is also good.

Cap/Rotor, MSD or GM OEM.

Do this on a cool engine, the aluminum heads can get stripped on a hot engine when removing the plugs. Also, be sure to add a dab of anti-seize to each plug before putting back in.

Final thought, make sure the areas around each plug are clean before removal. This reduces the chances of debris falling into the cylinder.

@107k miles, do you know if the head gaskets have been done? This is a common failure with #8 cylinder failing. The gasket lets go at about 7-o-clock and that's about that. At the same time, I suggest the valve guides be replaced.

I have a 90 and did my own tune up last winter. I first took off the Air control divert valve at the front passenger side of the engine, and all the hoses and garbage that goes with that. That cleans up the engine bay and gives you a little more room to work.

I went with AC plugs and Excell wires which I found out nobody much likes but are working well for me and what I use the car for. I was alone most of the time while working on the bitch, I mean my car. That was good because on several occasions I turned the air blue with vicious cursing. I did use mechanics gloves which saved a lot of skin but sometimes I needed more feel and had to go without.

Eventually I got it all done and other than hard to get to it was not that difficult to figure out. I have a couple of repair manuals and checked them to make sure I had the right wire going the right places. It made me feel good to do it myself and I try to do all that I can with the help of the Guru's.

I have since taken off the Air pump itself and put in a air pump delete kit. Some guys make their own but I bought mine. TPIS has a good one and also Corvette Central. I also took off the Frisbee on the front of the motor which serves no purpose that I can see and wieghs a ton. Andy says that alone adds 5 h.p.

If you live where you have smog checks you may want to leave the Air equipment on but it's whole purpose in life is to warm up the Cat faster so it can do a better job when you start the car. Unbelievable amount of crap hung on the engine to accomplish that. If you do have to get checked let the engine warm up before running it through and you should have no problem.

Research the threads on Guru and don't hesitate to ask if you have a question. Don't be in a hurry or you will get pissed off.

I have an 87, pretty similar I think.

I did mine, and I'm not a mechanic by a long shot. First, a swivel socket is different than a knuckle. Do not use a knuckle! A knuckle will allow the socket to move laterally, and that will break the plug. Ask me how I know. Once the plug is broken, you're committed.

Passenger side is the challenge, driver's side is a piece of cake. Take off the fender skirts, and allow a bunch of time. #2 and #8 will be more than a little annoying.

Be sure to replace the ICM while you're doing the rotor.

If it's a 90 and not running right search the forums about the crappy fuel injectors that GM used on them. Mine were horrible!

Jon @ FIC is a great vendor to get new ones from.

1 8 4 3 6 5 7 2

Or just do one plug wire at a time.

For the hard to reach plugs, put a wrench on the end of your spark plug socket to break it loose.