rustyroger

My '89 Buick LeSabre (3800 V6) is running rough, with the service engine soon light on.
The diagnostic plug has disappeared, the wiring under the dash has been hacked about, I dare say when the direction indicators were altered to comply with UK law and a rear fog light added.
However I found when I disconnected the MAF sensor it smoothed out again. So my guess is a bad MAF sensor, but before I commit to the $130+ it will cost to get one over here I would like to be confident I've nailed down the problem.

Thanks in anticipation;
Roger.

RROLDSX

Is there a way you can get the codes to read off the instrument panel for that Year?

76olds

A bad MAF sensor shouldn't make it run that bad unless the air filter was really clogged up for some time.
Have you tried some throttle body cleaner, clean the throttle body with a toothbrush really good?
How badly is it running?

Eric

rustyroger

The air cleaner is fine, I gave it a good work over with carb cleaner too.
It idles really rough, and smells like it is running way too lean, but I have checked everywhere I can think of and can't find a vacuum leak.

If I could identify the wires for the A and B terminals on the diagnostic plug then reading them will be no problem, any idea what I should be looking for?.

Thanks for the replies btw.

Roger.

Olds64

If your ALDL connector has been removed then you need a wiring diagram from a FSM to reinstall it. There's no reason an ALDL should be removed to install aftermarket cornering lamps and fog lights. Whoever hacked up your dash was an ignoramus.

I suggest you do that repair before spending money on a MAF sensor. Without reading the codes it will be a shot in the dark.

rustyroger

You should see some of the horrors I've come across with particularly wiring and emissions related equipment on American cars over here.
It's fair to say the car has run so well up to now I hadn't had a good look under the dash.

I checked out the MAF sensor with a frequency reading multimeter tonight, seems it is bad. I don't particularly mind paying for it, just didn't want to throw money at the car through guesswork.

Roger.

RROLDSX

If the MAF for your car is the heated filament type, you might try cleaning it with MAF spray.
When I ran a K&N filter on my Duramax, the oil in the air filter screwed up my MAF sensor and lit my check engine light. A couple of sprays with the cleaner and a trouble code reset and I was good to go. (also ditched the K&N).

rustyroger

I tried cleaning the filaments, with carb cleaner and very gently with rubbing alcohol.
Neither made any difference.
But thanks for your suggestion anyway.

Roger.

RocketRonnie

What do you mean by "rough" can u explain it more please

olds 307 and 403

Those year of cars were a crap shoot a lot of the time. I remember when apprenticing at a shop, my boss would narrow done issues to a couple of parts and put them on a 88 or 89 Buick with the same drivetrain. The car usually had to run awful forever to set a code, my Mom's 89 Taurus took forever to finally set a code. You are doing what mechanic's did with those cars when they were plentiful, test as best you can and hope for the best, good luck.

rustyroger

A rough stumbling idle, the ses light is on and the exhaust is probably putting as much hydrocarbons as CO2.

Roger.

RocketRonnie

Only durring idle.??
So your rpm at idle is going up and down?

Are u losing fluids.
Is this new to you..

Do you do regular maintenance on your car?
What's the last thing u did to your car before this prob. Started.

Do you know how to pull plug wires to isolate each cylinder?

RocketRonnie

What do u think olds307?

rustyroger

Idle all over the place, but if I disconnect the maf sensor it smooths right out.

Not losing any fluids, coolant, oil, transmission, brake fluid levels all fine.

I do all the maintenance, probably more frequently than necessary because of its low annual mileage. The problem started after I replaced the the transmission.

First thing I did was look for a misfire, each time I pulled a plug wire it made roughly the same difference.

I was wrong, it isn't the maf sensor, I put a new one on today and it made no difference.

Roger.

RocketRonnie

Don't replace parts on assumption, test you parts with a multimeter, it will hurt your pockets, been there.

Google this "Idle all over the place, but if I disconnect the maf sensor it smooths right out."

See where that gets you. See if all lines to your tranny are goings where they need to go. Take your time

What do you mean when you said about the hydrocarbons, do u smell or see anything new out the tailpipe

rustyroger

I tried with a multimeter, even bought an upgrade to try some checks before I even considered buying new parts.
Been fixing cars too long to throw money at guesswork.

The maf failed the frequency test, possibly I have more than one fault.

I already googled my symptoms, got plenty of well intentioned advice from people who seemed to know what they were talking about, sorting the wheat from the chaff is a tedious process.

With the maf plugged in the exhaust smell way to lean, like a major vacuum leak. But disconnecting it would make no difference if a leak was the cause.

Back to the drawing board I suppose.

I appreciate your input, thank you.

Roger.

gs72

Monitor the o2 sensor voltage. It should switch between .1 to .9 volts dc. Low voltage indicates lean exhaust high indicates rich. Figuring out how to get the self test to work would help you out a lot. If you can't. Then check voltages at coolant temp, inlet air temp, baro if it has one, maf, egr position, all at normal running temp. Disconnecting the maf puts the system into open loop. Since this smooths things out it indicates the the system is having trouble controlling a/f ratio, idle speed, poss. Timing. Sorry if all of these suggestions seem redundant, just hoping to poss. Point you to something that has been overlooked. Also check your sensor reference voltage at one of the three wire sensors. It should be 5.0 volts. If it is low start disconnecting sensors one at a time to check if one of them is shorting out. It the voltage is over 5.0 volts you have a ecm ground problem. Good luck!

rustyroger

Nothing redundant about your suggestions Gary.
Anything that might help me see what may be a very obscure fault or the elephant in the room is welcome. I swapped out the O2 sensor with the one from my '87 Olds 88 and it made no difference, I didn't check out the voltage though, I'll try that next weekend and post what I come up with.

Roger.