backtothe80s

I don't have the the underhood label and could not find it in the FSM. What are the stock timing specs for a 1989 5.7 TPI? I seem to remember hearing that it's 6 deg BTDC. Can anyone confirm? Is there a sticky somewhere I missed? Thanks!

backtothe80s

Anyone with a 1989 GTA 5.7 have a picture of the underhood emissions/tune-up label they could kindly post?

Thanks in advance.

rusty vango

they run best between 6-8 BTDC

Damon

6* BTDC is factory spec on all TPI engines. Set with the timing wire (temporarily) disconnected to establish correct base timing. ECM advances it from there per the programming in the chip.

Most of them you can advance the timing a little for some extra power, but don't go too far. 10* BTDC is where most of my TPI engines ran their strongest. This all goes out the window if an aftermarket chip/custom tune is used.

backtothe80s

I set base timing to 6 BTDC, but not using the method above. The factory service manual has you keep everything connected and jump the diagnostic port.

The car runs ok, but could run better and I don't want to alter anything from stock until I have everything right.

Thanks for confirming!

aliceempire

iTrader: (14)

Do it again with the EST wire disconnected. That stops the computer from advancing the timing. If timing is and issue then that will correct it. I'm not sure why the FSM would tell you differently.

mmadden55

I have a 89 tpi, 10 before runs good, set with EST wire disconnected per Haynes, manual which I highly recommend you get for your car if you don't have one. There is a very good diagnostic section in there as well as well written how to's for most repairs and wiring schematics. Next best thing to a factory service manual reasonably priced and can get them at bookstores and auto parts stores. I have one for everything I own.

backtothe80s

Wow. That's the second mistake I've found in the FSM. The serpentine belt diagram is also wrong. Once I disconnected the EST, I was showing 10 ATDC! I advanced it to about 8 BTDC. That goes without saying, it runs better.

Unfortunately, I didn't check the timing before replacing the distributor, so I don't know where it was. It sounds better than before.

eseibel67

The serpentine belt routing isn't "wrong", it's just that there was an update bulletin to route the belt a different way in order to keep the A/C compressor quieter. Either way will work the the correct length belt.

backtothe80s

That's what I would have expected, but following the diagram in the FSM left me with a belt that was too short.

I took a look this morning and the FSM publishing date is 8/88. That said, is there a source for FSM updates/bulletins?

paulo57509

I believe GM makes updates to repair procedures and the FSM through TSB's.

Full year TSB's were available in book form from Helm. I don't know if they still publish these though.

Years ago for a short time, GM made the TSB's available on CD-ROM for free on request. I still have my set but they no longer work with newer PC's.