Roy

I am hoping some of you guys can help me with my 2nd car. My other vehicle is a 1993 S-10 Blazer with the Central port fuel injection. I cant really say that it runs terribly or misses, it just feels sluggish, and inconsistent, seeming to have considerably more power at some times than others. (Maybe its just a big slug?) It is in a good state of tune, and it is a GM replacement motor with only 10,000 miles on it. The information off my X-Ray that seems relevant to me is the following. Not being familiar at all with this system I may be all out to lunch however. Most of the rest of it appears as what I percieve to be normal. There are no codes set or lights on.

My integrator numbers seem normal, but block learn tends to hover in the 110-115 range.

A/F ratio is normally right at 14.7, when floored it drops to about 12.5

Spark timing at cruise is around 30, as soon as I mash down on it (even partway) however it will drop way down to around 10.

After about a 10 minute drive I had over 30 hits on the knock sensor.

Any ideas where to start looking I would appreciate.

Thanks,
Roy

Greg

Is this the same engine that is in a 94 Blazer with the 4.3 Multi port. Looks like a minature TPI system? Is it running hotter?

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'89 Formula 383 TPI

Roy

Its not a multi port, my understanding is that it has 4 injectors all located in a central plenum. Some sort of valve system controls which one fires and when. It is sort of like an enclosed throttle body. Im not 100% clear on it myself. Only had it about 2 weeks and havent taken it apart yet. It runs right around 200 degrees.

GMTech

When it is acting up, check your desired EGR against your actuall EGR position. These engines are great for the EGR getting hung open. Also, earlier CPI has one injector and six poppet nozzels, making it a batch fire system. In '96, it went to sequential, wich meant six injectors and six poppets.

Anyway, another common problem with these is the CPI unit itself starts to leak fuel, and it may be starting to leak in your case looking at your fuel trim. They aren't to bad, but remember anything below 128 is rich. When it starts going around 80, your CPI probably is gone for good. I hope this helps.

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