Hi all, I recently bought a 1985 C4 for my son's first car and I came across this forum while looking for info on the 85's. Our car runs rough and I'm looking for advice on where to start diagnosing/fixing our issues.

My son and I want to learn and do as much as we can, but are not opposed to taking it to a shop if that's what is recommended.

So far we checked compression (cold engine) 135-145 on all eight. Noticed the O2 sensor is hanging out of the exhaust and see a bunch of cracked vacuum lines. We'll fix those issues this weekend and see if that helps.

Can someone help us get a list together on what we need to check?

Thanks - Jon and Addison

 

Once that work is done, I'd do a good tune up. Cap, rotor, wires, plugs, oil change and oil filter, PCV, and air filter. I'd also do a scan for trouble codes. Good luck with the new ride.

 

My first purchase would be a factory shop manual. It sounds like you have some troubleshooting in front of you. The book will quickly pay for itself.

Also, there must be some reason the O2 sensor is not installed properly. That would be at the top of my list to check.

 

I agree with getting the factory shop manual.

In addition, rather than trying to lay out an exhaustive checklist for you, I would recommend that you go through each system on the car; check them; repair, renew and replace as necessary.

For example, the engine has the ignition system, fuel system, cooling system and vacuum system. For the ignition I would change the sparkplugs, distributor cap and rotor, sparkplug wires, and check the wiring for frayed and damaged wires. For the cooling system, flush and change the coolant, change hoses and thermostat, inspect the waterpump and change it if it is original or if there is bearing play, and change radiator cap. For the fuel system, new fuel filter, new fuel pressure regulator (old ones can leak and start engine fires), check fuel rail O-rings for leaks, if the injectors are original (they don't like ethanol in modern fuel)- change them for rebuilt from forum vendor FIC, pull and inspect fuel pump and lines in tank.

You can do this with each system on the car - engine, transmission, driveshaft and axles, rear end, brakes, electrical (I believe you may have the power junction terminal block behind the battery - check it for corrosion and damage), suspension, interior, weatherstrip and slowly go through the whole car renewing it and making it reliable.

Also as a separate note, after you get the Factory Service Manual (FSM), check and clean the grounds for the car - they are a source of many gremlins.

Good luck and have fun - I have found in the last few years that I seem to enjoy projects and wrenching more than anything else!

 

Hey guys, thanks for the advice. Taking one system at a time is what we'll do. This weekend my son and I knocked out the ignition basics- cap, rotor, wires, plugs and inspected wiring harness. We bought new O2 sensors but haven't put them in yet (my ramps won't work on the vette, need to find an alternative). We also inspected and replaced most vacuum lines (no difference in running yet). Fuel system is next... I'll search the forum, but any recommendations on where to get the Factory shop manual? Thanks-

 

This is a good time to get a set of new Race Ramps. The factory is offering a $20 Cash Back rebate on purchases of $200. Combine the factory rebate with our 10% Store-Wide discount and you can get a set of ramps at a great price.

 

FSM on CD - http://compare.ebay.com/like/400443171892?var=lv&ltyp=AllFixedPriceItemTypes&var=sbar
Paper reproduction - http://compare.ebay.com/like/230818277262?var=lv&ltyp=AllFixedPriceItemTypes&var=sbarHelm has it - http://www.helminc.com/helm/Result.a...ected%5Fmedia=

The FSM is the best thing you can buy for your vette.