I recently bought an automatic 1985 corvette. It runs but it doesn't run well. It had old gas in it for about two years. I have new gas in it. I installed a new fuel filter, and I have new spark plugs, spark plug wires, a distributor cap and distributor rotor I plan to put in soon. I have driven it about 100 miles since I bought it. I am trying to learn more about cars and have help from a friend, but I am trying to find out what I need to do to get it running decent, doesn't necessarily have to perform top notch.

I have a hunch the problem lies with the fuel delivery. I was told the fuel injectors where replaced recently, the seller seemed honest. I would like to know what I can do myself to diagnose my problem to avoid taking it in.

My Problem:
I give it gas, it sometimes does not respond right away, sometimes it does. When it doesn't, it feels like all the gas is pushed in at one time as if I was flooring it. When I get it up to 55 and cruising it seems to do just fine. I know I am leaving out alot of information, this is my first post so please take it easy on me and any help is appreciated!

 

I recently bought a 99 convertible. I bought a Fob with a new battery and it worked for a few days and stopped. I heard if I hold down the lock and unlock button for 15 sec. the car would go into a learn new fob profile. I was wondering does the key have to be on?

 

under stering wheel you can find the aldl diagnostic link,put a paper clip between A e B terminal in the two upper right terminal,put ignition key on. On the dash you can see service engine soon blinking,it flashes 1-2,1-2,1-2-, 3 time 12, then it blinks for codes, pull codes if ECM has some trouble code stored.

 

Thank you, I had yet to find an easy way to check the codes. I can reset it by disconnecting the negative end of the battery terminal for a few minutes correct?

 

you want to know what the codes are, not to get rid of them. Autozone and Advance will do it free

 

I mean after I fixed them, or will they disappear on their own? Will advance do it fro a 1985? I called my local one a few days ago and they said they wouldn't.

 

Start with the basics.
The TPS (throttle position sensor) voltage is crucial for the ecm to calculate fuel delivery that should be set at 0.54 volts d/c ignition on engine idling or off. Measure the top and middle wire, also check it goes to 4.5 volts d/c with accelerator pedal fully depressed.

Check the fuel pressure, it should be around 30 psi on the 85 vette.

 

Most important tool for your corvette THE 85 SHOP MANUAL
This is a must have item.

http://www.ebay.com.au/itm/1985-Chev...item484d17544f

 

Yes, once you fix the problems identified by any codes you can disconnect the negative battery terminal for a minute and then reconnect it. This will erase any stored codes in the computer.

Just remember that the codes will give you the "system" that the error is in. It may not identify the exact part.

PM sent to you.

 

Thank you for the input!

I have the hayne's repair manual, but I should still get the shop manual?

 

You probably need new fuel injectors!

 

you need to finish installing you plugs, wires, cap, and rotor. Then see how it runs. If it's still lousy, call around to the auto stores I mentioned and see if they'll check for codes.
You can get your own scanner here. Easier than the old paper clip method
http://www.ebay.com/itm/Actron-CP900...9aec6e&vxp=mtr

 

Can someone confirm that autozone will check codes free for a 1985?

Ok plugs, wires, distributor cap and rotor installed. It still cuts off when I stop sometimes. And the same issue with an irregular power when I'm going slow. It does definitely run better now though, runs like a champ over 45.

Next step would be to check the engine codes I guess. I think that tool you sent me the link too I have actually, I'll give it a try tomorrow.
BTW, is the timing chain something I should be worried about with 154K miles? Not sure if it has ever been replaced.

Thank you guys for all the help so far!

 

Ceck fuel pressure during a driving test,you have to connet fuel pressure gauge to the valve on passenger side fuel rail,then route the gauge over windshield and attach it there with some adesive tape,run normally the car and see when cut condition comes if pressure is steady at 30 -32 or if it drops .I would change the fuel filter,may be clogged.As for the fuel injectors put some injectors cleaner in the tank,this will help.

 

That is incorrect. That will resync a current fob (maybe what you need). Both procedures are in the owners manual. If you don't have one you can get a pdf version free. I will post the link later.

Here's the link:
http://www.gmpartshouse.com/download...99corvette.pdf

By the way, what is this doing in the C4 section, posted in someone else's thread?

 

This seems to vary from store to store. Some stores don't have a OBD-I scan tool at their disposal any longer or they have lost the OBD-I cable or adaptor for their OBD-I/II scanner. It is hit or miss, so call around and see if you can find a store who can help you.

I can't help but think that the 2 year old fuel that sat in the engine left some gum and varnish behind. Unlike a carburator with a float bowl vent, the gas in the fuel rails, injectors, and fuel pressure regulator didn't evaporate, it just sat there and deteriorated. I'd run 2 or 3 bottles of Techron through the car. Advance has it on sale for half price right now. With 154 K miles, there is probably a ton of carbon on the underside of the intake valves and in the intake runners too. I am not quoting a TV commercial when I say the Techron will remove these deposits and get the gum out of the injectors as well. I have seen the results on high mileage engines I have treated then later disassembled.
I'd have done that first, but too late now. With that said, nothing you have done so far has been a waste of time or money, so no harm, no foul. If you get codes, just remember, all the computer can do is report that a sensor appears to be out of range. Often, mechanical problems can cause a parameter to be out of range and the sensor is reporting good data. For instance, dirty injectors and/or low fuel pressure can produce a code that says your O2 sensor is out of range (low). Replacing the O2 sensor is not going to fix the problem. Likewise, if your fuel pressure regulator is not regulating (or the fuel return line is blocked or pinched) then you will get a code saying the sensor is out of range high (rich). I have seen both cases, with injector dwell time reading long, trying to make up for low pressure or flow through the injectors or running incredibly short, trying to lean out an engine with 90 psi of fuel pressure at the injectors.
I would certainly avoid any high RPM excursions (even in neutral). I don't know about 85 Vettes (someone that know different, please weigh in), but for years, GM used a cam gear that had an aluminum core and nylon teeth. The teeth would age and break off until the chain was running on the aluminum nubs that the missing teeth attached to. The missing nylon would leave enough slack for the chain to slip a gear tooth or two at high RPM. As a minimum, if the gears and chain are original, there is enough wear and stretch that you are suffering from retarded cam and ignition timing. As a minimum, I'd check and set base timing to make up for that wear.

 

Thank you all, sorry for the delay I have been really busy with work so I have had to put work on the car on the back burner, but I should have some time starting tomorrow afternoon.

I have noticed an open vacuum line just in front of the engine, I will post pictures soon.

 

I went and bought 2 bottles of the Techron, I have one bottle in the tank should I put both in at the same time? Also, Is it possible that the car runs a little worse as the Techron is running through the system and taking care or the deposits?

I also found an open vacuum line, on one of the small lines that run underneath the top of the engine. I fixed those (after breaking and fixing two other similiar lines that were extremely brittle and probably needed it anyway), and took it on a spin and it seamed to run better at lower speads although it still stalls out.

Still haven't checked the engine codes :/ Maybe this afternoon.

 

Just do a Complete tune up and go through the entire engine to find all the problems. It sounds like the engine just needs proper maintenance.

Also, check for low fuel pressure (below 45 psi), at the fuel rail Schrader valve which could be a faulty Fuel Pump.

 

If your vacuum lines are that brittle you should check for vacuum leaks.

Have you cleaned your throttle body and IAC? (Idle Air Control Valve)


Dirty sticky TB or IAC can cause your idle issues,