I just bought a 1987 Pontiac Firebird, 2.8 V-6, 82k original miles. The car just had a new MAF sensor, o2 sensor, air filter, belts and hoses installed. The spark plug wires are new, but I'm not sure about the plugs.

Today the car stalled coming out of Auto Zone, but fired right back up. Also, the Check Engine Soon light comes on every now and then (about 5 times so far in the past two days).

I am not very mechanically inclined, what would be causing these problems with the car? It seems to run good and idle very well. I am very confused.

Any help is gladly appreciated!

Thanks, Firebirdjoe (Joey Elsbernd)

 

The batt must be unhooked when you change a MAF, been told by many sources. Its a real common problem as soon as you buy a new one, you fry it. Batt should be unhooked before you unhook or install a MAF.

Matt

 

How many times in different threads do I have to say to check the MAF relay? It's right next to the MAF, tucked in the corner of where the air cleaner housing sits and the rad support. Mine went out on me and I had the same problem, until I switched the relay with one I bought brand new. Also, you may not have to disconnect the batt when you install a MAF, just disconnect the relay. (I'm probably wrong, ain't I?)

 

Probably about as many times as I have to tell people to follow through on my code 34 chart that I slaved over to type up.

The reason for disconnecting the battery is not about frying anything; the relay will prevent voltage going to the MAF unless the car's on. But- unhooking the battery after changing the MAF will (A) clear out old codes and (B) make the computer learn the engine from "nothing". That's faster then making the computer un-learn the engine (bad maf) and then re-learn the engine (good maf).

Code 34 chart follows; and I describe locations of everything, so you don't need to be mechanically inclined, just incline yourself to buy Radio Shack's cheapest $10 bright-yellow digital multimeter, and set the meter's switch to "VDC".

...................
-----------------------------------------------
DIAGNOSTIC CHART FOR CODE 34 (2.8L MPFI ENGINE)
---------------------------typed by Tom P------

First off, they want you to check out the air intake duct for being loose or
damaged.

Since you are getting the code 34, and no other error codes, we can kind of jump into
the middle of the chart:

1. Ignition off. Disconnect the MAF sensor wire. Connect a voltmeter between the
____harness pin "B" (center) and ground.
_______Less than 1 volt? Go down to "1A"
_______Over 4 volts? Go down to "2"

____1A: Disconnect ECM A-B connector. Check circuit 528 (brown/white, on connector
_________"B", terminal #6) for an open or short to ground. If it's not open/shorted,
_________it's faulty ECM connector terminal B6 or a bad ECM. By the way, this is the
_________MAF's "signal" wire.



2. Connect a test light between MAF harness pins "A" & "C".
_______Light on? Go down to "2A"
_______Light off? Go down to "3"

___2A: Faulty MAF sensor connection or sensor. So since you've tried two sensors,
________I'd imagine the connector's at fault. Try checking for corrosion on the
________connector's pins- I had that happen once. Also, try wiggling the connector,
________and seeing if you get a SES light. If I wiggle my current one, I can make
________a code 34 set, and the car almost stalls. I've gotta get another connector
________from a junkyard... Pep Boys sells new ones, but for an outrageous price.
---------update 10/2000: I replaced the connector (actually, the whole MAF harness!)
---------with one from a junkyard car. No more connector problems!



3. Connect a test light between MAF harness pin "A" and ground.
_______Light off? Go down to "4"
_______Light on? Go down to "3A"

___3A: The ground wire for your MAF, which is MAF harness pin "C", is open. Fix
________the problem with the black ground wire, either it's bad or burnt thru or
________it broke at the passenger-side-upper-frame-rail grounding point (a ring
________terminal on a screw).



4. Disconnect MAF relay, ignition "on" (not "start"). Connect a test light (at the
____relay connector) between CKT 840 (brown) and ground, and CKT 39 (black/pink) and
____ground.

____Okay, now, the MAF relay is located between your air filter box & radiator, on the
____radiator support, I believe. It should have one long black connector to the harness,
____NOT two connectors (one black and one gray)- that ones for your flip up headlights.
---------update 7/2001: For Camaros, you guys have a different location for your airbox.
---------But, the MAF relay's in the same spot, at the passenger side of the radiator, on
---------the radiator support. I believe it's the only relay you Camaro guys have down
---------there; just check the relay for the wire colors I mentioned for CKTs 840 & 39.


____The test on CKT 840 checks to see if voltage is getting from your MAF fuse to the
____MAF relay.

____As for CKT 39, that's controlled by your GAGE fuse. (So that's what it does! Cool.)
____It comes on with the car's ignition- that's why you need the ignition "on". When this
____black/pink wire gets power, it flips the MAF relay's magnet ON, which basically switches
____the MAF on- that's how power gets from CKT 840 to the MAF.

_______Only one light? "repair the open circuit".
__________No light on CKT 840? See "4A"
__________No light on CKT 39? See "4B"
_______Both circuits are fine? Go see "5"

___4A: If no light on CKT 840, find the MAF fuse- it's under your hood, screwed down
________to the upper-frame-rail on the passenger side of the car, closest to the
________headlights. You'll see two little black boxes, each with two wires coming out
________of them, screwed down to the upper frame rail by one screw each. One of them
________has a red wire and a BROWN wire coming out of it- that's your MAF fuse holder.
________Pop the top off to see the MAF fuse. (The holder with red & orange wires is for
________your computer and fuel pump.)

________If the fuse looks fine, try replacing it anyway... I've had that happen to me-
________the fuse looks fine but's really shot. Perform test #4 again. Still no light?
________Probe the MAF fuse holder's RED wire with a test light to ground. This checks
________the MAF fuse holder's connection to the positive-junction-block, located on the
________passenger side of your radiator support. If it's bad, follow the red wire to
________the junction block & fix it. Do test #4 again- still no light? Check
________for corrosion on the MAF fuse holder's contacts. You should get a light by now-
________unless your test light's shot!

___4B: If no light on CKT 39, check the GAGE fuse in the fusebox. As I said up in "3A",
________if the fuse looks fine, try replacing it anyway. Do test #4 again. If you've
________got no light, you get to trace CKT 39 thru the firewall, so hopefully you get
________a light on this one. This one would be a bitch to fix. All I could tell ya is
________that the black/pink wire goes to the GAGE fuse, and the GAGE fuse gets turned
________on when your ignition switch gets turned to "on".



5: Connect a test light between circuit 840 and CKT 450 (black ground wire from the
____relay connector).
_______Light off? See "5A"
_______Light on? See "6"

___5A: Fix the bad ground wire (open on CKT 450) from the relay to the chassis.
---------update 10/2000: This is buried! It follows the wiring harness along the
---------passenger side lower frame rail. You'll have to trace it the whole way. It
---------joins with 5 or 6 other ground wires at one point. Then, after that junction,
---------one wire goes to a ring terminal on the rear driver's side head.



6. Check out the condition of the orange/black wire that goes from pin "A" of the MAF
____connector to terminal "E" of the relay. If this wire is fine (not shorted or open),
____then your relay's bad... you could get a junkyard one but I think a new one is only
____$10 or so from GM.

 

I was hoping I wasn't the only one who had to repeat thierself over and over again.

 

The problem has been fixed. The vehicle was only running on five cylinders instead of six. I dropped in a new set of plugs and wires, changed the oil and a new air filter. The car seems to run a hell of a lot better and put out more performance. I guess my next question is.... why did it stall on my when I ran over a speed bump... AT AUTO ZONE!!

 

You need to check your codes, man..

https://www.thirdgen.org/newdesign/faq/thirdgen.shtml .. click on the 'Miscellaneous' tab near the top of the page.. first item under that heading. You're running your jumper between pins 5 and 6, not 6 and 12.

And burning a MAF because of hooking it up with the battery connected is a myth... by the book, it's safer, but as TomP said, the main reason is to clear the ECU's blm table.

 

I got some time today at work and did a diagnostic check on the cars computer. I pulled up a code 32 (EGR Valve), took it to the mechanic who works on the cars from my job and he said the EGR was screwed up. So hopefull minor repairs is all I will need.

 

Haha, just do a search on TomP for "tuneup" and you'll come up with about a million messages. I guess in this case (spark plugs) the tuneup was the answer again!

 

Well, when it's time for me to do the TomP tuneup, I'll use the search button to save us both a few keystrokes.

 

Does this mean you're gonna sell the T/A? I know someone looking for a ride in Indy, & for some reason he keeps wanting to fix up his borken down f*rd vans, jsut cause they have 351Ws in them.