89 Coupe - Check Engine Light On

[Kingsley]

Trying to get through CA smog - diagnostics show code 34. Pulled MAF sensor - one filament bright/clean, other black /sooty. I know there is a specific MAF cleaner so is this usually effective or is a new MAF in the works?

[G Froelich]

I'd certainly try cleaning it first. Carb cleaner works if used gently gently. Some suggest a cotton swab. Not sure I'd be as daring. Good luck!

[Kingsley]

Used CRC MAF cleaner - when finished both filaments bright and shiny as well as vertical sections to which the filaments attached. Still code 34 so now checking circuitry per FSM. Reporting later.

[Kingsley]

No power at MAF cionnector so now running down circuitry. Grounds clean and tight. Only way to run down/identify circuits, as I see it, is to run through all of the harness connectors to find the circuit - anyone know of a single master list of circuits? Really not that much of a chore - welcome any comments.

[padgett]

Just a section 8 issue. Do not know any shortcuts.

[Kingsley]

Still tring to get beyond code EO34 - MAF Sensor. FSM Section 8 tests work down to bad harness connection or MAP sensor. As mentioned previously, both filaments clean/shiny as are the vertical section to which they connect. Woud appear some problem beyond the filaments. Trying to get good ID on replacement sensor and my Standard parts house says his book shows two part numbers. Curiously, the present part carries molded in number "AFH -50M - 02A and then imprinted below and a separation action the number "8520". Out of curiosity, any one recongnize that as a brand ID? I must be skipping over this sensor in the parts book - would someone let me know the OE number? Local GM parts dealer will not divulge parts numbers and I intend to go with Standard aftermarket part. Thanks.

[padgett]

I remember seeing somewhere that the originals came from Hitachi. Mine are the same AFH50-02A except 8802, 8420, 0402, & 9628 (date code ?)

[Kingsley]

This is in furtherance to Padett's comment above - Learned a bit about Hitachi today - they are, and been for a long time, a supplier of MAF sensors to GM and Ford. Carquest carries their products in this area and I was quoted a price of $170 which is a bit less expensive that I have been quoted on other brands. No mention made of core requirement which is generally a requirement from other suppliers but then who needs a bad MAF?

[Ronnie]

As info: My '88 model has the molded in number of "AFH -50M - 02A" and below that the number "8418".

[padgett]

MAFs are a good thing to pick up at a U-Pull-It when picking up Delco ignitions, (not on the same cars). Someday they will not be plentiful.

[DAVES89]

I agree. I typically pay about $5.00 each for them. They are still somewhat common. Also the yard I go to marks the car "engine good" which tells me for sure that it is good. I had 4 helped a friend out with 2, but am going out to the yard for other things today, will look for more.
Easy removal, 1 electrical connector, 3 screws, 5 minutes done.
Don't remove the whole housing, only the sensor goes bad, and the counter guy charges you more for buying the sensor and housing together.
Just look at the VIN tag to confirm "C" motor and you have the right one.
Olds or Buick they are the same...

[padgett]

Anyone had a MAF apart ? Is there electronics under the black cover ?

Someday we will look back and marvel at what we left behind in yards because was just "too common". Way off in 2050 a Magnavox that works will be a high dollar item. Have seen it happen before.

[DAVES89]

2050?
I am 53 with a recent bout of cancer. Don't think I am going to worry about obsolescence.

[Kingsley]

ECM Trouble Code Diagnosis - 8D1-47 - Circle 3 - Following that I am told "Faulty MAF sensor connection or sensor"". The male and female connections are good and the filaments are nice and clean so it must be the sealed inner workings. I will check to see if the '90 has the identical part on it and
if so will swap it out to confirm that my '89 is indeed bad. If so, will give Jim Finn a call! Just as info, just checked my parts book and the sensor carries the same number '88 through '90, changes for '91. '88/'90 P/N shows as 25532799.

[DAVES89]

'88 to '90 are the same. I don't believe I ever threw a code though. It was the black one. Started acting up shortly after I got it. Swapped out the MAF, all good since then.
Make sure you have an o ring to act as a seal for the sensor part that goes in the hole. I was missing one and had all the same problems of a failing MAF sensor...

[padgett]

OBD-I is pretty crude. To set a code pretty much means you have a short or open somewhere (of course it might be inside the module)..

[Kingsley]

Voila! Jim Finn promptly supplied me with a nice, clean MAF sensor at a very reasonable price and Code 034 is no longer an issue. Now on to the California SMOG station with "no code - no light" confidence. Filaments on the old sensor identical in appearance to the new one so the problem had to be in the sealed internals. I am going to get inside of it just for the heck of it to see if I can find anything of interest - reverting.

[Kingsley]

In post 12, Padgett expressed an interest in knowing what was on the inside of the MAF and I can sum it up first by saying "one heck of a printed circuit board". The black plastic cover has the male three connectors plus, in the bottom of the socket, a metal female opening which ties in to the C (positive) connector within the plastic housing. The cover is glued to the die cast base which does not appear to play any part in the electronics other that to house the black plastic part holding the two filaments which are exposed to the air flow. Inside, there is a thin gauge copper "tray" (well fastened to the die case base) with a bendable top in which the circuit board (2"x1 5/8") rests and which is thoroughly covered by a soft gel. Only pictures can do justice to the minuteness and detail of the circuit board and I will come up with some just a soon as I can.

[Kingsley]

Secured a good used MAF sensor from Jim Finn and no code 34 or any other code showing thereafter. Nevertheless, failed second California SMOG test. Replaced O2 sensor with new one and passed with flying colors so can now title this former NJ car in CA.

Just as info, I will outline the SMOG readings which met or exceeded minimum requirement if there is a desire for it on this Forum. This was not just a "coincidence" after installing a new O2 sensor as have used this mechanic for many years and he runs a strictly straight up shop.

[G Froelich]

Yes, I'd like to see the readings. Also, was wondering how exactly your EGR was failing. Thanks!

[Kingsley]

Please note the correction to my previous post. Turns out, as I talked again with my mechanic with respect to picking up the car, it was the O2 sensor instead of the EGR. When he quoted cost this morning he was in the range of about $30/$35 and it was AC Delco brand. In my elation over getting it passed I mis-understood the nomenclature. I had previously tried to replace that sensor but could not budge the old one using a crow foot and was going to try the plumbing tool but, time being short, decided to take it in with no codes. I should have the car back later this PM and will gladly post the readings.

Good luck to you as you pursue the demon.

Kingsley

[Kingsley]

Please note my edit of my previous post in which I referred to "EGR" valve. In my elation over getting it passed this morning I misunderstood the part nomenclature and when arranging to have the car picked up I asked about the part brand and it was then I found out that it was the O2 sensor. I now have an extra one as I had tried to replace the one in the car prior to taking it to the shop but could not budge it using a crowfoot. Was going to try the plumbing tool at about $15 but, with no codes showing and all readings being in line, thought I would take it in as time was running short. All's well that ends well.

Good luck with your pursuit of the demon!

[Ronnie]

... I found out that it was the O2 sensor. I now have an extra one as I had tried to replace the one in the car prior to taking it to the shop but could not budge it using a crowfoot. Was going to try the plumbing tool at about $15 but, ...

There is a socket made just for removing the O2 sensor. $9.99 at Autozone. I think they will loan you the socket as well.

[Kingsley]

Ronnie - thanks very much. Appreciate the info and nice to know that it is appearing on the Forum for all to see and take advantage. I should have known!

This '89 will wrap up my qualification as "redneck" as the only asphalt it will see is that leading up to my house. My gosh, everyone is entitled to have a "putterer" car! It was a New Jersey car and necessary to get it smogged for a CA title.

[Kingsley]

Here are the results of a 'PASSED' CA smog test - '89 - 107K. Test results are at 15 Mph (1700 RPM) and 25 Mph (1651 RPM)

MAX AVE MEAS

%CO2 14.7/14.8
%O2 0.0/0.0
HC (PPM) 76/58 23/17 47/32
%CO 0.50/0.40 0.05/0.05 0.02/0.08
NO (PPM) 537/494 62/60 0/0