I need some advice. I bought a 91 350 z28 back in the summer and I've had nothing but problems with the fuel system. 2 different shops couldn't fix it after months of trying. When I bought the car the previous owner told me it had an aftermarket chip in it. When I mentioned this to my current mechanic he looked into it and according to his research the chip that is in there is for quote "off road use only", which makes sense because the previous owner had mentioned that he was starting to build the car for racing but didn't get very far. I only want the car for style. It's beautiful on the outside. My mechanic tells me that there is a good chance that going back to the stock chip will either fix the problem or make it alot easier to fix, but a new chip is around 500 dollars. He told me he's talking to some people to see if he can find a used one, but I really want to do everything I can to get this taken care of faster. Should I:

a. Try to find a used stock chip on ebay or something. If so, what exactly should I look for?

b. Somehow get the stock data and program it into the chip I already have. I have no idea if this is even possible. I'm quite clueless.

c. Buy a generic used chip and program it like choice "b".

d. Shell out 500 for a new one and hope my football picks pan out this week to cover it.

Thanks.

 

If your current ECM has the broadcast code on it still, you should be able to find the stock file from someone on this site or at moates. It would be easy enough for your mechanic or someone with prom burning equipment to make you a new prom. Store bought or mail order chips can't come close to making YOUR car run its best. Good Luck!

 

new they have recently gone up in price by a huge amount. i don't know if you'll be able to find a used chip, or using the correct name for it, the MEMCAL or not, most who have one aren't likely to give it up. your best bet on finding a used one may be going to some wrecking yards & asking if
they have an ECM with the MEMCAL for a 92 camaro or fire bird with the same motor,trans, & fuel system you have.
for a 91Z with a 350 TPI & auto trans, you need AUJP which was the last update.

some of the aftermarket chips come on a carrier, of which you plug the stock MEMCAL in to. if you have this setup, you can just remove it from the ECM & then remove the MEMCAL from the carrier & plug the MEMCAL back into the ECM.
the carrier looks similar to this,
http://www.moates.net/product_info.p...products_id=32
i doubt you would have this, other wise i believe the mechanic would have said something.

it is possible to burn a stock bin file to the aftermarket MEMCAL you have, but more than likely the chip on it would need to be erased with a UV eraser, this may damage the chip where it can't be reburned or cause problems with the other 2 circuits in the MEMCAL.

if you can't find a used MEMCAL, your option C would be the cheapest way & probably the most reliable way to go. i would recommend getting a carrier & a flash chip, about $40.00 or so plus burning the chip & shipping.

do you know if the motor has had any mods done to it?

 

Ok now what is the difference between a PROM and a MEMCAL?

 

Wouldn't he be able to purchase an adapter, a Burn1, an EEPROM and download a stock .bin for his car? That would be less than $500. I did it for a TBI car but I'm not sure on a TPI car.

Gene

 

What kind of fuel problems were you having?
May/may not have been chip related.
People are always blaming the computer for any mechanical problems they can't find.

If you plan to keep this car for more than a year, invest in a datalogging cable and a chip adapter, chip and a burner.
Then you'll be able to diagnose and correct problems yourself without paying a shop.
If the car has been to two shops and they didn't find the problem, you've already paid more than the equipment would have cost you.

If the car will be resold, then buy a memcal for the combo you have and don't worry how far off the factory tune is.

 

firstly you can buy everything you need to datalog, burn chips and a couple extra EEproms (the actual chips) for 200 bucks. At which point you can get someone to send you a stock bin over the net and just program it in, voila and go.

Secondly if its an aftermarket chip from a name brand company your fuel problem probably has nothing to do with the chip.

all those do is pull a couple degrees of timing and get rid of the speed limiter. Kind of a joke really.

i know what its like to go to a shop that cant diagnose your problem. My advice is find another speed shop.

post ur fuel problem up in the tech section man. Possible culprits could be the fuel pump relay but in that case the motor would have absolutly no fuel.

any shop should be able to check the fuel pressure at the rail, that will let you know if its maybe a fuel pump issue.

and if both those check out, your ecm takes pulse reference from one of the wires coming off the back of the ignition control module, a wire goes right into the harness and back to the ecm. I had a problem with this wire and car kept randomly just cutting out and going dry. This wire would definitly be causing problems.
the ignition control module its right under the dist cap, kind of sticks out to the side and has a couple of pigtail connectors going into it, thats 100 dollar part but if it starts to be faulty can cause fuel system issues as well.

 

I can best describe it as 2 phases of stuttering. The first phase is on startup after being cold for 4+ hours it's pretty heavy stutering whenever I step on the gas until the car is warmed up. The second phase is lesser stuttering while driving. The problem has been "fixed" twice by my latest mechanic by messing around with the TPS and AIC. The problem comes back after about 1 and half to two weeks after being "fixed" and it gets worse over time.

Also it tends to get real close to stalling after letting off the brake at a red light, and on occasion, does actually stall. My mechanic says my problem might be caused by not having an O2 sensor.

 

youre not serious are you?

dude my car runs like a bag of poo until the 02 sensor gets warm enough to go into closed loop. No 02 sensor your car is just going to run in open loop, no wonder it runs like crap.

also sounds like you need to take a multimeter and measure the voltage at your tps, i forget the specifics but you shove the lead into the end of the black wire and either the blue or grey, and should get a specific voltage for your tps. tps is adjustable so if its off you rotate it until its correct.
Then again with a very modded motor mind you i have a horrible studder in open loop, get an 02 sensor man car needs that

on a seperate note if you have 90 dollars and a laptop its really cool just to be able to do datalogging, will give you a lot of information about how the cars running, and would be pretty easy to spot if its staying in open loop. can get the datalogging stuff from www.moates.net

 

this pretty much explanes PROM & MEMCAL,

https://www.thirdgen.org/forums/dfi-...om-calpak.html


i agree with JP, this may not be related to the chip. especially if you don't have a working O2 sensor.
doug is right, unless its been tuned to run in open loop, it will never run right without the O2 sensor. if a car comes into the shop i work at & is missing the O2 sensor, that is the first part it gets.