Rhensonsr

I need to do a tune up on my "NEW"1984 C4. This is my first vette and would like some recommendations and war stories.

Thanks,
Randel

aklim

KISS. You aren't going to get a huge jump in power unless something was wrong before. Stock cap and rotor and plugs would be great as would a set of wires if it hasn't been done recently.

billschroeder5842

Also, the best effort you can put your time into is making sure that all the sensors are within spec and adjusted correctly.

If your Coolant sensor, TPS, IAC, O2 and MAP are all doing their job, you will pretty much have the L83 dialed in.

Rhensonsr

Thanks guys. I plan to replace all of the sensors because the wires look worn at the connectors. It is running very rich and smokes upon start. Today I plan to pull the CEL code...provided this Nashville heat allows me to lol.

Rhensonsr

Code is a 42 so it looks like I will be checking the ignition.

aklim

Code 42, IIRC can be tripped when you time the car and disconnect the EST wire so I would check timing and adjust as necessary and disconnect battery for a minute and run it. If 42 comes back, lets look at it carefully otherwise we might be chasing ghosts.

Rhensonsr

I just got around to replacing the temp sensor, wires, cap, and rotor button and WOW at the difference in power. Still running rich and it looks like the injectors are spraying heavy so I ordered a new kit with O rings and gaskets. Timing is dead on 6 degrees. I am ordering the other sensors and plan to put them on over the next 3 weekend. By then, soccer season with the grandkids will be over lol.

Hot Rod Roy

Are you talking about the temp sensor in the front of the intake manifold? There are four temp sensors in this engine.

If it looks like it's running rich, and the fuel injectors don't dribble when you shut off the engine, it's more likely to be your O2 sensor than bad injectors. Saying "it looks like the injectors are spraying heavy" isn't very analytical! The injectors should have a nice smooth spray pattern. Point your timing light at them for a good look!



Setting your ignition at 7 1/2 to 8 degrees BTDC will improve your performance, with no negative side effects.

billschroeder5842

Your spray looks normal to me. Video is always better as it shows the pulse.

I messed around with my timing and settled at 12 on my '82.

aklim

Hard to say without a side by side comparison with a known good one. Kinda like saying "The bulb is bright". Well, compared to what? I would suspect after all these years they are crudded up.

What exactly is in this "kit"?

corvettenorway

try 10 deg timing

Hot Rod Roy

Bill, that photo is of the spray pattern (pulsed) from my '84, not the OP's. (Mine runs super!)

As you advance the ignition, the HC and NOX will rise. With more than 8 degrees initial advance setting, you'll probably fail smog test (if you care). The ESC spark control is pretty effective, so you will probably never hear a pre-ignition knock. I don't think our ancient L83 ECM's can count knocks like the later Corvette's.

For my techie friends: https://link.springer.com/article/10...544-013-0099-8

aklim

I'd wait till he has everything set up right before screwing with the timing. Either that or it might mask some other problem and/or exacerbate an existing problem or two till.... BOOM!. But on the bright side, the new motor will, more than likely, be good.

Rhensonsr

My spray pattern is nowhere close to that even. In fact, mine looks more like drops shooting out instead of a spray. Hope to get them in this week and will update as I progress. Thanks everyone for the advice and comments. I do want ot try the 10 degrees once I get the gas fumes down so my wife can ride.

Hot Rod Roy

Bill, is this true? Did you do this with your '82, or are you speculating that it would be better than a strobe light? I haven't tried the video trick, but with the un-aided eye, the pulses are so quick, it's just a blur. I don't see how a video would make it any better (unless you have a high speed [slow motion] camera).

With the un-aided eye, I can see the smooth cone spray pattern, but I can't see the pulses.

aklim

If you really want to know and not guess, that is the way.


In that video, it shows how they measure volume so they can see what the pattern is and what the volume is after a measured amount of time. That is how I know my injectors lose volume after a few years. Now, how far your service interval is, IDK. It loses enough that I prefer to schedule a shut down in the winter every 3 years so I can do my other stuff that requires the TB off for maintenance.

Hot Rod Roy

Both injectors dribble? That sounds like you may have low fuel pressure! That will certainly cause both injectors to malfunction. Have you changed your fuel filter? A clogged filter will certainly cause low fuel pressure!

Before you fix something that doesn't need to be fixed, by rebuilding your injectors, it would be good to know your fuel pressure is good.

It's a little tricky to check the fuel pressure on an '84. We don't have the handy schraeder valve, like our TPI friends do! If you've changed your fuel filter, that's the easiest place to test the fuel pressure. Remove the filter, and use short pieces of fuel line and a "T" fitting. Check the fuel pressure at the "T".

I'm sure some will say you need to test the fuel pressure in the fuel line between the throttle bodies. That's probably a more accurate test, but much harder to do. The filter location test will tell you if you have a bad fuel pump. Your fuel pressure should be 11-13 psi.

Rhensonsr

Well, it turned out to be the TPS and CTS causing the running rich. Once I got the TPS adjusted correctly, the fuel smell went away with the black smoke. Now the smoke is blue with a large puff at start up. Look out valve seals, you are next.

corvettenorway

trynge to change the pcv valve