Hey Guys,
New member First time poster
I just got my first vette about 2-3 months ago. its a 1990 6 speed. 143k miles.

It has seen better days but I got it as a project me and the old man could work on together.
When we first got it the car would start but smoked like crazy and just stunk of gas. Also the car wouldnt move

So we hunkered down and got to work. Symptoms we knew were that the tranny would go in to gear but the clutch pedal was limp - seemed like the clutch was stuck in the engaged position. Ended up dropping the whole transmission and everything down there was ok so we went to the slave cylinder, it was fine too. Next stop - master cylinder. Turns out the plunger in the master had snapped, replaced that bad boy and boom the clutch is back in working order!!

We did a little video on it
Part 1:

Part 2:

Next stop was the smoking. The car wasnt really running that great either but we swapped out all the injectors with the bosch III's and the smoke cleared up while we were in there we went ahead and put a new fuel pressure regulator too.

Video to come soon =]

Now we have a rough idle, almost seems like a cylinder is missing, after driving it around it seems to smooth out in the higher RPM's, but at idle its pretty rough. and On startup it really fidgety to even start. Seems like you have to pump the gas a bit for it to get anywhere. Maybe the cold start injector?

If you have any ideas im open, but otherwise, look forward to seeing some cool projects and tips!

Kenny

 

Instead of guessing and purchasing unneeded parts and wasting time you are best advised to purchase a Field Service Manual (FSM) which will give you expert steps to diagnose your problem.
You can find them on places such as Amazon and eBay.
Purchase both sets and get the latest editions (red cover).

 

Thanks corvetteronw,
We do have the service manual ( not sure if there are better versions than others - we have a haynes) but it seems like some of the troubleshooting methods in there describe problems but dont really explain much. It does do a great job at instructions to remove parts and whatnot. It seems like when a rough idle it can be a few different things ( fun fact, our troubleshooting section in the book mentions vacuum leak as one, but then never mentions anything about checking or ruling out certain parts, or describing the vacuum system
but we havent shot-gunned parts at it yet, only spent 160 for a master cylinder and injectors so far . Been doing som reading on here to get a good idea on the next steps =].

Kenny

 

Cold start injectors were discontinued as of 1989, so you don't have one.

"Pumping" the gas does nothing. There is no accelerator pump. That said, if you hold down the gas pedal while cranking the ECM turns off the fuel injectors (known as "clear flood mode").

A rough idle is almost always a vacuum leak. It could also be a dead cylinder. Another possibility is that two spark plug wires are crossed. These engines run amazingly well on 6 cylinders.

I have never seen the inside of a Haynes manual, but I've heard that they are basically worthless. The big red book is the only way to get detailed, reliable (well, mostly) information.

 

Thanks for the videos. You do a very good job of explaining the small tips & tricks that help a lot.

 

Thanks cohocarl!


Cliff, thanks for that information - had no clue about the clear flood mode. Thats good to know. We were thinking vacuum leak as well (from just looking under the hood i can see that the cruise control vacuum line is completely broken and i know its off a vacuum, but just to force a leak we unplugged the vacuum to the brake booster and there was a significant degradation in the idle at that point.) but I will double check those wires. Thanks for the tips!

And just to give info - the hanes is ok for general stuff. But it is missing a lot of info besides just replacing something. Ill have to find one of those big red books.

Appreciate all the info guys!
Kenny

 

I'd start with a general tune up, now that you have the engine running.

Change the plugs, wires, cap, rotor, IAC valve (Idle Air Control valve, located on the throttle body), O2 sensor, fuel filter, air filter and set the base timing to 6* btc.

This should eliminate or fix a lot of the rough idle problems.

Also, don't forget to disconnect the EST timing wire (tan wire with a black stripe) located near the brake booster along the drivers side firewall, Before adjusting the timing or the computer will not keep the new setting. Reconnect the EST timing wire After setting the timing.

You may also, want to add some SeaFoam to the engine to clean out any carbon deposits on the valves and in the combustion chamber. With the engine running, remove the brake booster line and let the engine suck the seafoam from the can a little at a time. The seafoam will dissolve any carbon deposits in the engine and you'll know because A LOT of smoke will blow out of the exhaust pipes!...

When the smoking stops, you'll know the engine is clean!...






.

 

Kenny, i have a set of the Red Books for the 1990 Vette..Volumes 1 and 2.. Let me know if you want them. e-mail me a charlie2015@wildblue.net $70 + Shipping

 

GKK, thanks for the tips, thats the method I was going with atm, ordered a new set of plugs, a cap, rotor, will have to look in to the IAC. Havent heard of that seafoam trick but its worth a shot, thanks!

Charlie, thanks man i will keep that in mind, if the internet fails me - your my next plan of action =]

Kenny