Mass air flow (MAF) to intake air tempature(IAT)?

[americanz24]

I have an 87 Z24 with the 2.8...I'm getting codes 33 and 13...I have the speed density update and trying to wire in an IAT-i have gotten an IAT from a 94 3100 grand am-i spliced into the black and tan wires from the MAF harness and no luck?? The Car would run with a up and down idle...

[americanz24]

So i got the 60* chip that was to bypass the MAF...It helped the car run better because it sets the idle higher so at least it's not all over now...I have one of those testers where the light comes on when you hit power-well i tried all 5 wires on the MAF harness and none had power? Is there power suppose to be going to the IAT? Im now getting codes 23 33 34....could a bad MAP be causing these problems? The car has nothing to do with a MAF its all been updated/bypassed.....?
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[americanz24]

So i replaced the map-i guess it was bad since the codes are gone-i'm getting codes 23 and 45 which is the iat and running rich due to the iat so this iat isn't working for me...I'll take it to a parts store and have them test the ohms on the wires...

[3100 MPFI]

not 100% sure what is going on, but the 2 end wires (tan, and black) are the IAT wires. When I converted my 1988 Cutlass Supreme from MAF to speed density, I just cut those 2 and soldered on the IAT plug. I then just taped up the remaining MAF wires, and tucked them out of the way, and pulled the MAF fuse.

The only thing I had to do after that was replace the 1988 VSS with a 1989 VSS (they were calibrated differently).

What I think you might be doing wrong is using the IAT. In the 1988, if you convert it from MAF to speed density, it still has to have the MAF plugged in. It does not use it for readings as a MAF, but it essentially changes the whole MAF into a really big, and really expensive IAT. When I tried to do the conversion with a 1988 SD chip, but with a normal AIRBOX, I was getting some funny things too.

I think you shoud try to get a newer chip that is your same engine, and tranny, but didn't have the MAF in there at all, and not just an updated one. If you do that, it might work out better for you. I know it did for me, but once again, that was in a W-body, so there are differences.

[Superdave]

It's possible that the IAT you are using isn't right.. try one from a '88-94 Cavy. I have an extra if you need it... I may even have the harness.

[americanz24]

Wow surprised to see a reply after so long....well the previous owner did hell on the wiring harness-on all my relays the wire coating is completely stripped off so they were all toughing and i wasn't getting any power to the MAF harness-well i decided to check all the relays and find that theres a relay unplugged because the clip broke and also find that a hot wire was broke-so got that somewhat squared away...i tried the MAF harness with a light tester and bam all the sudden i have power now-The pink wire is hot not tan (someone else said tan too)...the car already had the speed update-i didn't have to do that-i came along the 60* chip for 20$ from a member on v6z24 who used it for a 87Z to bypass the MAF (he no longer has the car) so i said why not! i splice in the IAT and the thing melts so maybe had the wires back wards on the IAT..from the IAT i hooked org/blk into black and tan into pink :unsure: --usually any wire with a line through it is ground so i dun know-at least i have power now....Tomm i may take it to the parts store to test it....I'm hoping that i can get a cavy IAT from the store and it will plug into the grand am plug end -i'd hate to have that one melt though...i couldn't find a cavy in the yard and i needed the connector end and wires...So yea this has been crazy-multibale things at once go bad-had codes 23/33/34/45-most because the map went out...it's been over a month and took her for spin today at least since it's running a whole lot better-i'll pm ya Dave if i need that IAT-thanx

[86euro]

I think the black and tan wires are what goes to the IAT sensor.

[3100 MPFI]

It is the black and tan. I don't know where my 1988 book is, but my 1996 book (which is MAF, but not integrated like the 1988 was) lists this.

IAT:
A - BLACK - PCM to sensor ground
B - TAN - PCM to IAT sensor signal

MAF:
A - YELLOW - MAF sensor signal to PCM
B - BLK/WHT - GROUND
C - PINK - HOT IN RUN

[americanz24]

It is the black and tan. I don't know where my 1988 book is, but my 1996 book (which is MAF, but not integrated like the 1988 was) lists this.

IAT:
A - BLACK - PCM to sensor ground
B - TAN - PCM to IAT sensor signal

MAF:
A - YELLOW - MAF sensor signal to PCM
B - BLK/WHT - GROUND
C - PINK - HOT IN RUN

Instead of yellow mine is brown-pink is the only one that had power with ign on eng off
vetteracin who has a 87 cavy vert is using the pink wire with speed update...thanks for the replys...im getting code 23 still which is the IAT saying low temp indicated....well now i need i IAT since that one fried-i'll try an ohm meter, how do you that--with the harness wired or with the IAt hooked up....could i try just the wire itself?

[bszopi]

http://wiki.60degreev6.com/index.php?title=Detailed_Sensor_Descriptions#Intake_Air_Temperature_.28IAT.29_.2F_Mass_Air_Temperature_.28MAT.29_Sensor

To do a resistance check, separate the sensor from the harness and just check the sensor resistance.

[americanz24]

DONE! Turns out it was the tan and black...Brinky on v6 sent me another IAT since that one fired and said this-"The iat dont take any voltage. it works off resistance to ground....and the other sensors use a 5v reference. Thanks for all the input guys

[85_Olds_Ciera]

Im now getting codes 23 33 34....could a bad MAP be causing these problems? The car has nothing to do with a MAF its all been updated/bypassed.....?

I stumbled onto this thread, and am dealing with this issue now.

Three manuals left here...I just bought one...

1987-1988 GM-Wide Driveability and Emissions Diagnosis & Trouble-Code Manual for 2.8L VIN W Speed Density Engine #75841

When I receive the manual, I will read it over, and try to get back here...


Also found these tidbits:

1.

Ratings from GM show a 5hp increase in 2.8L equipped vehicles from 1988 to 1989 -- most would say that the MAF delete is the reason.

2.

They began manufacturing "speed density software" to update these vehicles. This speed density software consisted of a new prom, a new idle speed control motor, and a label to attach to the ECM (computer) that the vehicle had been updated with the speed density software. I am unsure of exactly what this corrected, but it told the ECM to ignore all signals from the MAF sensor. The MAF (mass air flow) sensor was still there, it just didn't do anything anymore. It presents problems for a repair technician if he is unaware of whether the vehicle has been updated or not. A scanner plugged into the ALDL link will give erroneous data and trouble codes if the vehicle has been updated and the scanner is not made aware of it!

[85_Olds_Ciera]

well the previous owner did hell on the wiring harness-on all my relays the wire coating is completely stripped off so they were all toughing....any power to the MAF harness...car already had the speed update

Who? The owner or the mechanic?

Upgrading your 1988 Beretta to Speed Density (Eliminating the MAF)
October 27, 2005

....Anyways, to upgrade your car to be 'Speed Density' which will delete the MAF and use only the MAP sensor, you will need to do the following:

1. Locate and install a PROM (memcal/chip) from a '89-'90 Beretta (to avoid issues with your EGR - auto or manual shouldn't make a difference)
2. Remove your MAF sensor (it was robbing power anyway)
3. Splice in an IAT sensor from most any other year Beretta model (they're pretty much universal in the GM world) in place of your MAF sensor.

.....
That's all there is to the upgrade. If you're having trouble locating a suitable PROM, your local GM dealership should be able to help them out -- just let them know what you're trying to do (there were service bulletins out about this). Ratings from GM show a 5hp increase in 2.8L equipped vehicles from 1988 to 1989 -- most would say that the MAF delete is the reason.