Gm Controllers

George M. Dailey gmd at tecinfo.com
Tue Oct 15 23:41:45 GMT 1996


At 10:33 PM 10/14/96 -0700, you wrote:
>Hi Peter
>
>Thanks for the infomation. My project is 74 chevy pu with a TPI unit out of
>an 86 Camaro. The pu has been running for 2 years with the TPI unit. The
>main problem is hot restarts on a warm day. Wanted to remove the cold start
>injector and replace software from a 89 calpak. Other big problem is the
>negative back pressure EGR valve sets a code 32 under loads. Also wanted to
>change curves to better suit a pu. Any help would be wonderful.
>
>Thanks Vance
>
High Vance, I've got an '89 TPI in my '58 chevy truck. Runs almost perfect.
Perfect if you don't count that annoying code 32 after 15 minutes at speeds
above 60mph. My EGR valve is known to be bad. I can't pull vacuum in it
unless the motor is running. Can't figure out the failure mechanism but I'm
sure it's bad. I disconnected the vac line to the EGR and called it FIXED.
BTW, bad hesitation with the valve connected.

Is the engine running rich or lean during the hot restart?  My first suspect
would be coolant and manifold air temp sensors. These are cheap and
available at the bone yards. The cold start injector is not used above a
certian temp (don't know specifics).

I can't help you with the cold start mods. Don't know enough too do you any
good.  It's hard to believe that the only difference between the two is
software. Think about it, 4 years and 1,000,000 units produced, when a few
lines of code would have eliminated lots of hardware and parts that could
break. One tight wad engineer said, "Parts you don't use never wear out!"
If an GM engineer (or who ever knows) would spill the beans on this, I"ll
ask the next sexy woman I see to dinner.  My ECM is 1227165 I DON'T THINK
you will damage any thing by swapping the Prom but be aware of VATS.

As far as changing "curves to better suit a pu", consider this. My rear end
is '75 chevy truck 2.73 - 1. The formula 1 Bird the TPI came from is, you
guesed it, 2.73 - 1. The 58 tips the scale at about 4600lbs, I think the
bird was 3,800 (if I'm off by a pound please don't torch me). Rather than
tamper with perfection, why not O.D. the truck? I'll be going 700R real soon.

GMD 




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