6SPDZ28

I have a 95 Z28 that seems to run just fine without the mass air hooked up, it even seems to start better without it. And another possibly related issue is that the diagnostic port does not work, I can lock and unlock my doors by jumping wires but when hooked up to a scanner it doesnt recognize that it is plugged in. The car runs fine but any advice would be appreciated.

BlackScreaminMachine

iTrader: (17)

With out the MAF plugged in the car goes to Speed Density Mode.

383_LT1_1295

i dont mean to thread hijack, but what is speed density mode?

i420tom

iTrader: (11)

a simple way to describe it would be that instead of measuring the air with the mass air flow sensor the computer has preset numbers of airflow that it uses for the situation.

i420tom

iTrader: (11)

are you trying to use an obd2 scanner? just casue it plugs in doesnt mean it ll work.

your car is obd1 and could have an obd2 style plug.

maybe2fast

iTrader: (4)

it uses the MAP sensor instead of the MAF sensor. because we have both

Formula350

iTrader: (3)

Yea, the 95 walks the line for OBDII, and even my friends 94 Vette has the OBD2 style plug. So don't let that fool you. 95% sure that is your issue. As to why it runs better, might be a bad MAF, and the car is already running like crap, so the Speed Desnity redundancy actually IS running better, but not as good as it would with a working MAF (just a guess, I've never had a MAF car yet)

siniSSter

iTrader: (2)

I have a 97 Z28 that won't even start without the MAF

383_LT1_1295

oh okay well that makes sense...speed density mode...well gm thought of some thing and did good on them...lol unlike the starters

Formula350

iTrader: (3)

MAP sensor toast then maybe?

6SPDZ28

If I do have OBD1 how would I check for codes, and how would I use an aftermarket computer modifier? The scanner I was using was a Snap-On scanner, would it automatically switch between OBD1/OBD2 or do you have to use a different card.... not sure cause it was my friend operating the scanner? And the last question... how do I know if my MAF is bad, is there a test?

Formula350

iTrader: (3)

Usually the test IS, if you unplug the MAF and the car doesn't change, but since LT1's have a backup, I dunno. I'd say it's bad. Got a friend with an LT1?

I don't know how Snap-On's work. The one I'm used to, you just pluged in the right cable to the scanner, and it was all on the scanner. So you selected OBDI GM, the 4th and 8th vin, and then away you went. I would assume if you can just plug in the correct cable, then you'd plug in the correct cartridge. So yes, it should all 'auto detect' that it's an OBDI car, regardless of the cable it's using. I doubt it has any sort of cable recognition software.

6SPDZ28

Thanks for all the info.

NovaTodd

My code reader is made by Auto X Ray. It reads the OBD1 codes as well as the standard OBDII scanners that you will find at Autozone (or Vatozone out here). I can pull code from my car as well as just about other car with a diagnostic port (and gives you the description of the code as well). I believe it is a mode #1000 that I got at the local Kragen Auto (Checker or Shucks for other parts of the country). Since 94 & 95 are different from anything else, you need the specific scanner for them.