1984 Stock Vette Hesitation

[Chuck McDonald]

I have a purely stock 84 with 85K. Purchased the auto three weeks agao and the prior owner did a complete tune-up (Wires, cap, rotor, plugs) the engine really misses and runs rough when it is cold, when it heats up the idle smooths out but there is still a very slight miss, on the road it is as smooth as silk, when driving in city traffic sometimes it will have a flat spot when starting from stop, other times it will be perfect. I replaced the oxgen sensor and I would like to know if anyone has any suggestions as what may be the problem, Oh, the fuel mileage is great at 16.1 in the city.

 

[JonM]

Any codes? Did you change the fuel filter? Get yourself a helms manual...its a bible you can't live without. Get the manual and the electrical supplement


http://www.helminc.com/helm/homepage.asp?r=


Let me also introduce you to the Crossfire site. Lots of info there in the tech section.
http://www.crossfire.homeip.net:81/cftest/default.asp

 

[Chuck McDonald]

Hi, yes did change the fuel filter, have a Helms and that directed me to the oxgen sensor, will check out your line. Thank you very much for the assist.

 

[Chuck McDonald]

Jon, how long have you had your 84? what type of problems have you had?

 

[tcolyer]

I have a purely stock 84 with 85K. Purchased the auto three weeks agao and the prior owner did a complete tune-up (Wires, cap, rotor, plugs) the engine really misses and runs rough when it is cold, when it heats up the idle smooths out but there is still a very slight miss, on the road it is as smooth as silk, when driving in city traffic sometimes it will have a flat spot when starting from stop, other times it will be perfect. I replaced the oxgen sensor and I would like to know if anyone has any suggestions as what may be the problem, Oh, the fuel mileage is great at 16.1 in the city.

I have an 82 Crossfire that had similar simptoms. Hope yours is not as bad as mine was. The camshaft had 3 worn down lobes & both cylinder heads were cracked. The car run really bad till warmed up then ran decent and got good gas mileage. Also it could be that the TBs need to be syncronized correctly.

By the way this was 4 and half years ago and now the car runs great (pushing 325 hp) and gets 21 mpg

Terry Colyer
TCOLYER012@aol.com
82 Silver blue coupe
86 Red 4+3 coupe

 

[Chuck McDonald]

Thanks for the information, I will run a compression test and see what I come up with, there is not any blow by and the exhaust is clean so I will cross my fingers and hope that it is a sync problem.

 

[JonM]

Jon, how long have you had your 84? what type of problems have you had?

I've had it for about 15 years...
and the only problems I've had is "all the above" I think I have replaced just about eerything.

 

[Chuck McDonald]

Well, I know now what I have to look forward too, hey your Vette looks great, good job.

 

[MoeJr]

If the TB's are out of sync they will act just like that. Also I had to replace my fuel pump at 80k so that may be a good idea too. Definitely get the TB's syced by someone who knows them well. I had mine done and my car runs sweet. Alot of Cross fire cars start and run a bit rough cold including mine but once mine is warmed up a couple minutes it runs like a scalded dog. Also may wanna install new tps. Keep us posted.


Moe

 

[Chuck McDonald]

Ho Moe, thanks will now be looking around for a decent shop.

 

[MoeJr]

You're welcome and make sure you find a shop that knows the Cross Fire well. If you have difficulty finding one you can always bring the car up here to the guy I had do mine. Good Luck and keep us posted.

 

[grey fox]

chuck, i too have recently purchased an 84 vette. i have the same problem with the flat spot from start. i also have an occasional stall problem.
i had it diagnosed because the check engine light came on.
they told me i had compression leaks in 2 cylinders.
my plan is to have the motor replaced with a rebuilt 84 crossfire engine. i can have one put in for 2K here at a local speed shop.
i still can enjoy driving it but would enjoy it even more with a new engine.
i think it would be worth the investment because the body and interior are in very good condition.
sorry i got off the subject. take care.

 

[geekinavette]

Your "stumbling" could also be caused by a vacuum leak. The intake lid is notorious for leaking, IAC valves are also a common source, as is the EGR valve (though it doesn't sound drastic enough to be an EGR problem).

grey fox: Cracked heads are all to common on '84s, make sure that's not where the compression is going else you may be buying WAY more than you need!

Good luck to the both of you.

Bill