1996 LT-4 manual transmission starts and idles very rough for a few seconds then smooths out and increases RPMs for a few more seconds total run time about 10 seconds then shuts off.  Things already replaced: fuel filter, fuel pressure regulator, spark plugs, fuel pump, and fuel injectors. Dashboard shows service ASR and check engine light is on. Any ideas where to look from here?

Hi, I am not a fix it kind of giy but you have troubleshooter a lot already.  Maybe O2 sensor(s) or plugged line somewhere.

God bless,

BooBoo421!

Joseph Booher

Maybe consult with Gordon Killibrew?

http://www.corvettebuyers.com/killebrew/index.html

CorvEddie

Got a buddy with a Tech2 or even a OBD2 scanner? You should be able to pull some codes to get you started and you can log your startup to narrow down what's causing the issue.

My first guess would be MAF or throttle body related, IAC or TPS may need to be adjusted. Have you isolated any of your add-ons that may be causing the problem?

Just spit-ballin' here...

Before just replacing more expensive parts, I would suggest checking for vacuum leaks.  Are your hoses 20+ years old? Vacuum leaks are a PITA to find sometimes but can cause lots of idle related issues. Spend some time looking carefully and it may very well solve your idle problems. 

I have a similar problem but I don't stall runs rough on the low idle but doesn't stall. SES light comes on the low idle mostly, once cruising speed on the highway SES goes off. I have a code of 44 with the OBD1 scanner and that is a lean code left bank. 

I have changed the following: fuel filter, fuel pressure reg, fuel pump, Fuel Injectors, Spark plugs, Throttle Pos sensor, EGR, EGR Control Valve Sensor, PCV, PCV Valve Hose, Vent Grommet for PCV Hose, Manifold Air Temp Sensor, Air Intake temp sensor, Ignition Coil, TPS sensor, Sent the ECM out to be checked and that was fine. I cleaned the throttle body and replaced the air filter. All of these items were original to the vehicle with 58k miles so I figured they should be changed and will help my cause. The Opti Spark and Spark plug wires are probably a winter project and don't think they are causing the problem. So with that said I think a smoke test is in order because it appears there are a lot of vacuum issues with the LT 1 corvette plus they are 30 years old. Any other recommendations.