Ok...

#1 the MAF that came with the car.

#2 Junkyard hiested one.

#3 Out of my friends 87 LT

#4 Pepboys: Borg Warner Rebuilt

#5 Pepboys: Delco Rebuilt.

I know #'s 1 and 4 checked out to be bad I have yet to check # 3 out... I get an intermittent code 34 on start-up... happens more often in warm weather. (Like today, Tuesday for those local guys here in NJ)...

I get an occasional hesitation without the code, very occasional and not bad at all...It seems to be random and nothing like my experiences with a bad MAF, or no MAF at all...

WHY WHY WHY?! Could a bad relay do this? Or is it a bad computer? Once I started the car with jumper in place, but it was running worse then than it is now...

Can anyone shed insight?

 

Oh, man, isn't today great outside? (sigh) First we had winter, then summer, then winter again, and now it's spring. Go figure.

If you want to spend the rest of today tracing wires, here's the code 34 chart. I had a bad MAF connector; you'd wiggle the thing, and you'd set a code. (Or, hit a bump while you're driving- oops, code 34!) The wires aren't that bad to trace. Oh, try wiggling the wires while your car is running (be careful of your fingers & clothing, of course...)
-----------------------------------------------
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've read this before, and I always shuttered that some day I'd have to do this...

The connector is not bad, no amount of beating or shaking will set a code or cause the engine to stumble...

It's so odd because I can shut off the car after no code, and turn it on 10 seconds later and it'll set a code after about a second of running... not even... How in the world could something be so flaky... I'm thinking the relay is "dieing" not completely dead... sometimes it switches on, others it doesn't...

I'll go do some checks and get back to you...

 

Ouch, I hope you find a problem, and it's not an intermittant wire somewhere. I actually replaced my whole MAF harness with one out of a junkyard car. Pep Boys wanted like $15 for the stupid connector, I walked away with the harness for $5. I took everything at the MAF end; including the fuse holder, power ring terminals, relay & connector, and MAF connector. Only two wires go "back" into the main engine harness- the black ground wire (step 5a) and the brown/white MAF signal wire (step 1a). The rest terminate near the MAF.

 

Tom, I'm going to shoot my car, or myself...

Step 1a, I can't even get a ****ing signal. I can't get continuety between the wires, I can't even get a steady reading to tell what I'm going to do next. I fluxuated between 0.0 and 72 mV... But it does that when you hold the probs apart in the air also...

The DMM checks out though, sees right around 2.3 volts on AA battery.

I think I'm gunna swap in that carbed 305 I've been talking about and calling it quits. I hate this *** forsaken computer ****.

 

Well, wait, 1a isn't giving you at least 4 volts? Did you probe the wire at the ECM? Maybe that's the bad wire! If you can't get continuity at the wire, try making a test wire. Strip a bit of the wire at the ECM, and strip a bit of the wire at the MAF. Then, connect the two spots together with a 10 foot piece of "new" wire, and see if you get voltage.

That's how an ASE mech patches a wire, instead of pulling the bad wire out of the factory harness.

 

The point I'm trying to make is that I couldn't get a difinitive reading... the DMM was jumping all over the place, no matter how I probed the connector, or what ground source I connected to, it was all over...

As for getting back by the ECM (cry) how the heck does one work under there? I get attacked by dust and dried up tape, have such a bad allergy attack/sneezing fit I have to go inside for a half an hour to recover... Ok so maybe not, but it's nearly as bad as the location of the distributor...

As far as replacing that wire... I'll bring ya a pack of brew and the car if you do it

 

Haha, don't forget the food & smokes! I knew that's what you were saying about a bad reading, that's why I wonder about the condition of the wire. No voltage on the wire would give you a weird reading (just like holding the probes in the air, or having the probe measure the voltage between your fingertips).

Two screws hold the ECM bracket to the underside of the dash. You remove the two, and drop the ECM down. Note the top of the ECM bracket (pointing to the sky), see that little "+" shaped arrow? That fits into a grommet right below the dash pad to keep the ECM from rattling around. If it's hard to get the ECM bracket back up, you might need to remove the dashpad. (I've been under my dashpad so many times that I put the screws in a ziplock bag and leave them in the house!)

I'd unhook the neg bat cable before disconnecting the ECM harness, I hear you don't have to, but better to be safe then sorry.

You should be able to swing a continutity test by probing that ECM connector. Double check for the proper position & wire color! And if the wire's bad, don't replace the exact wire, run one new piece of wire from the passenger compartment thru the firewall into the engine compartment. If you try to pull that factory wire out, you'll get gray hair

Did you try the rest of the test? Keep going as if 1 passed successfully. If you can't get a reading from that signal wire, but all the other wires test out, then it's gotta be that signal wire.

 

Another thing to check would be the frontclip that attches to the air box. If that clip is not secure, you could have an air leak

 

So when are all us Jersey guys gonna get together and fix each others cars? heh Or what will probably happen is TomP will end up with 2 30 packs and 3 cartons of smokes and someone pulling on each of his arms towards their car. lol either way, should be fun.

 

LOL! We should meet up at Englishtown one day!

 

Hey, food beer and all the cigs you can smoke works for me. I'll run the rest of the test tomorrow and see what I can come up with, and by the way, thanks for the tip about dropping the ECM down, it should help alot.

There are a last few things I want to do to this car... after that last couple hundred bucks, all the money I make this summer and during the following 2 semesters of school is going to go toward a new car. I'm thinking of getting a Monte Carlo SS... or investing it towards an SS R/T... I'll think about a black 89 TPI Iroc. I'm not going to settle for less the next time around, I'm going to do it again, and I'm going to do it right. When I'm rich I wanna own a v6 though, and screw with it and tinker... and own an I4... those things are just plain cool, it would be fun to make fast.

Oh, and Mdv6man, the computer only gets screwy when you have an air leak behind the MAF ... infront of it and all you have to worry about is pulling in unfiltered air.

 

Enlishtown is good, was just there during the swap meet. Damn, I'd have to buy a helmet just to see what my 1/4 mile run would be.

 

sounds to me like a burn-off relay maybe?
there are 2 relays for the MAF.
One is a power relay, the other being the burn-off relay for the MAF.
Try replacing them both at a price of like $20.

I've heard alot of these cases with the burn-off relay f*****g up.
Good Luck,

87GTA57L

 

Us V6's don't have burn off relays... We don't use a hot wire MAF.

both circuts for step 4 arn't giving me a light... I have a feeling circut 39 is gone...

I checked under the dash for a "GAGE" fuse, but all I found was a "Guages" fuse, and it was good... Where is the "GAGE" fuse? Are there more than one fuse box?

So what now, circut 39 being gone would explain no power from the signal wire, and would also explain an occasional "34"... maybe every once in a while the wire reconnects, the computer sees this and is like "woah, big numbers, I'm used to seeing 75 mV, not 4V!... code 34 here we come!".... That would explain the warm weather phenomena too...

Also, the wire for step 1a checks out to have continuety back to the ECM, I ran a test wire... Every other test checks out fine... though on the paper I have with me step 5 doesn't have anything checked, maybe that's fuzzy to, or I didn't get to it, I did this Friday and I havn't been able to get to a computer til now, so my memory is a little fuzzy.

So what do you think Tom, where should I start looking for this break in the wire, how should I go about checking this....?