Hey Gang,
Just purchased 1987 IROC Coupe 5-speed TPI.
Came with receipts for motor rebuild (10k ago) Within the last 5,000 miles car had a Performance chip installed along with new Distributor and wire (red color.

Problem is the car is running rough... Really sounds like a bad plug or wire but reading this board also makes me think the chip may be faulty. No smoke from exhaust but it smell REALLY rich and car runs very cold - Below 1/4 mark on temp guage.

I will pull and inspect all plugs and wires tomorrow.

Do any of you have a stock chip for an 87 TPI that you would be willing to sell.. If not where can I find one????

Any other info would be appreciated! O am new at this!!

Thanks,
Sean
87 TPI with G92 (3.45)

 

Oh... One more thing!
A Code Scanner turned up No errors... Don't know if this means anything..

Thanks!
Sean

 

go to GM and get one, I think it's about 50 bucks.

 

this mite sound like a stupid comment, but an simple mistake may be your spark plug wires going to your distributor cup are mixed up??

 

If I were you I would check my timing and set it back to base time because the chip advances the timing for you

 

If the temp gauge isn't getting above the 1/4 mark, then the engine has a 160-degree thermostat. They're fine in TPI engine since in the summer it's hard to keep them below 180-200 degrees (depending on which radiator you have) anyways. I'd definitely check and replace the plugs and wires just to be sure they aren't the problem. If the problem was in the chip, you'd have an an error code set...

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Greg Westphal
'87 IROC 355TPI/A4

 

you cant get any codes from your car unless the stock chip is in the car. cause that is what its looking for stock settings not after market.

 

That is incorrect. It depends on the chip. SOME custom proms use unique code that does not conform to the GM standard for communicating with the ALDL. But they are few and far between.

On every "off-the-shelf" prom (ADS, Jet, Hypertech), they just modify some entries in the spark and fuel tables, and the ALDL works just fine.

As for the original question, on a stock engine, GM made the eproms so they were overly rich right from the factory. This was primarily for warranty claims as an overly rich eprom will just make it slower and burn more fuel. This allows for variances in the manufacturing process.

I found on my car that I had to pull a LOT OF FUEL out of the eprom to get the mixture right for maximum performance. They need much less fuel, and others are starting to notice this too.

Most of the "off-the-shelf" eproms just add a few degrees of extra spark in the mid range and more fuel...which is the last thing you need. To further compound it, most people as one of their first mods add an AFPR and crank up the fuel pressure...the LAST THING you need to do.

If you have acess to a prom burner, you can re-program your aftermarket Memcal with the correct BIN for your car. The BIN is readily available at www.diy-efi.org in the "download" section for the BINs. On MAF cars, the aftermarket Memcals have the same circuitry so you can just overlay the original BIN onto it. On SD cars, eprom writers use a "piggy-back" since so much more of the ESC circuitry is on the Memcal than it is on a MAF car. A piggy-back has a separate eprom on it and let's the ESC circuitry flow through.

 

well i guess i was wrong i know that it says in the instructions from hypertech that if you have to look for codes or take it to a shop for diagnostic test that the stock chip has to be in.

 

Bub, it MAY be true for your Hypertech Memcal. As I said, it really depends on the chip itself. The easiest way to see, is plug in a scan tool and see if it you can get readings.

As I said earlier, where I have noticed this, is on custom eproms and personally I think it is a pretty bad practice. What good is an eprom if you cannot hook up your scan tool to check out how it is performing?

Maybe they don't want you to see the information, because if you did, you might see how little (or how badly) it actually performs.

 

good point!