Ok for starters the car had been sitting for a few years until recently, Replaced the MAF, plugs, wires, cap, rotor, ignition module, the piece under the module tested fine, new coil, tps sensor and pigtail. ECM is used from a corvette because the 2 reman ones I got the car wouldn't start.(original was bad) New fuel pump and filter and cleaned out fuel lines.


Car starts up and runs fine, plenty of power smooth idle, after it warms up or exits open loop it begins to idle up and down, I thought it was the temp sensor under the throttle body because if I unplugged it when the car was cold it would run the exact same way, plug it up problem gone until car was warm again.


Not getting any codes however the light does flash with every surge in the engine. At my wits end with this car any ideas would be greatly appreciated.

 

I have dealt with similar issues with my tpi. First thing I would recommend would be to check for vacuum leaks. Fuel pressure reg hose, egr, canister purge lines, and gaskets on the runners.
Another thing that helped me was resetting the minimum idle air on the throttle body. That made a nice difference with my setup. You can find this procedure in your manual.
Also check your pcv valve for proper operation.
Hope that helps. Let us know how you make out!

 

Ok got to play with at work today with our old scanner which I can read some data values. First off got these codes in order they are given from scanner, #42 EST, #41 Improper Prom, #34 MAF Sensor low input. Iroc-Zone lists the codes as #42 Bypass
or EST problem, #34 Mass Air Flow Sensor, #41 Cylinder select error. Confused to why scanner and website codes are written different and the only clue I have at this point is to test terminal C on the MAF to se if it is 0.5 volts closed throttle and 4.5v (aprrox) at WOT.


Any ideas or where to start would be great would really like to get this car running right.

 

Sounds frustrating. Did you try any of my suggestions? has the timing been set correctly?

 

Yes checked for vacuum leaks did find 2 very small ones and fixed. Timing was set years ago but I will check again. Hopefully I will get to play with it a little more today if not then definitely tomorrow. I will keep posting what I find. ALso I am guessing it says incorrect prom because the car has a hypertech chip in it?