Brotom

Just purchased a 95 Z28 and after assessment it appears there are mixed components on the engine. The car year is 95 however timing cover is a 94 model. The car runs good as we have replaced the optispark, coil and other related components however, the plumbing seems to be a mixture between 94 and 95 on the EGR system. Currently troubleshooting the EGR and finding no difference between engine performance with vacuum line disconnected. We will be replacing the EGR valve to see if this makes a difference. Does anyone have input regarding the OBD2 system with a 94 engine considering there are discrepancies between hookups on the optispark and EGR?

Injuneer

Both 94 and 95 use the same OBD-1 PCM. The only difference is 95 has a 16-pin OBD-2 "style" DLC. You scan it with an OBD-1 scanner, either using a 12-pin to 16-pin adapter, or jumping the pins as shown on shbox.com

http://shbox.com/1/xraycable.jpg

If you have a 95 PCM with a 95 auto trans program, it will not work with a 94 trans switched converter lockup. 95 uses pulse width modulated lockup.

Injuneer

With regard to EGR the only difference between 94 and 95 is which nipple the vacuum connects to on the driver side of the intake manifold. Makes no difference in the way the system operates.

EGR only operates under very specific driving conditions, primarily those that cause high combustion chamber temperatures, like lugging the engine while cruising at low RPM. Does not operate at idle, does not operate above 3,500 RPM, nor at WOT.

Brotom

Thanks for the info injured! I will follow up on your system information and post results

Brotom

Darn auto correct changed injuneer.......... sorry!