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1988 Buick Century, rough idle and stalls.

MrMarty51

MrMarty51

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Location
Miles City, Montana
I hate this car. 😳😹😹😹😹
It was isdling rough and engine would stall.
Disconnected the O2 sensor and it idles and runs perfect. I guess it is taking readings from all the other sensors and coming up with a close enough equation of air to fuel.
Installed a new O2 sensor this morning, had battery disconnected, hooked up the sensor and battery, aaaand, it is right back to rough idle and stalling.
My next guess was going to be the coolant sensor, but, as good as it runs with the O2 sensor disconnected I’m thinking the coolant sensor must be okay.
Oh yeah, there is no CEL illuminated.
Anyone have any ideas what it might be ?
 
No O2 sensor = Open loop aka running off "tables" and ignoring most sensors. That, O2 failure, should turn on the CEL, but, the lamp must be burned out or the ECM is really toast. Primitive ECM that doesn't even reach the level of "Artificial Stupidity"!

Funny story I had a 1988 Olds 3.8L run like krap and turn on the CEL, but, no codes. Bad ECM and... 6 months later of fighting ignition module codes shop replaced the Fing Knock sensor and wiring plug that had oil dripping on it from the valve covers that had finally insulated the connection. No "Knock" sensed and the ECM's test (advance timing till knock dectected or max advance reached.) figured the ignition module for/behind the 3 coils wasn't responding to timing commands from the ECM. So it coded the ignition module timing failure NOT a no knock sensed code... And killed all advance to save the engine.

Pull codes.

"Static Vibration Test" Tap/wack the MAF sensor and see if it kills the engine. Clean the MAF as well as oil (ash) builds up on it.

Spark plug condition and wire age? (These, 1988, are not 100K plugs...) It's easy stuff and may not be it but it can be.

:facepalm: And quit throwing random parts at it.
 
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Does this engine still use the maf? GM removed the maf and went speed density on most of those early efi systems because the maf sensors were do problematic. Problem is you can't hardly find the chips to convert them from maf to speed density anymore. Most issues on those is either bad injectors(low resistance in the injector coils overloading the ecm), they only have 2 injector drivers and work in batch fire, and maf sensors. The O2 sensor in them is only a 1 wire iirc and is only used running down the road. 1st thing I would do is see if it is still a maf system, or if it was upgraded to speed density.
 
I am not all that familiar with the equipment on this engine.
It does have a plastic fitting between the air filter and the TB. There is a plug shoved into a receptical that has multiple wires connected to it. That must be the MAF or it could be a speed density unit. I’ll pull that hose back off and see whats within that.
 
The CEL did finally illuminate when the O2 sensor was disconnected. The wifey was driving it yesterday even with it stalling on her, and I dont know if the CEL ever came back on again.
I’ll take it for a drive this morning and see what happens.
 
Took the car tor a drive this morning. CEL illuminated. Went back to the garage. Probed the DL and got a code 13. That was the only code showing. It had tripped that yesterday when the O2 sensor was unplugged.
It does have the MAF system. The grate is discolored with some dirt, etc. I’ll try cleaning that and see if it makes a difference.
image.jpg
 
Again tap the MAF and see if engine stalls or stumbles. MAF failures like that do not code.

The sensor, heated resistor, is all that needs to be cleaned.
 
Yup, got a can of the genuine MAF cleaner. CRC brand.
I didnt get any more done to the car today. I got the new front brake calipers, a quart of DOT3 and the MAF Cleaner.
Old friend Bob came over. He was going shopping and needed some help getting his groceries up the two flights of stairs to his apartment.
He has COPD so bad he can barely make it up the stairs empty handed.
Always nice to help someone that needs it.
 
Probably dont want to use compressed air to blow through the MAF to, I would think.
There is a guy that has a scan tool that can hook into the OBD1 system and see what the sensors is doing. I made an appt to get it in to Him.
See how the cleaned MAF does for the drivability.
I did look for a coolant temp sensor, like on the 93 GMC I had but there is nothing I could see with two wires. One temp sender has one green wire so I am thinking the ECM must be taking reading from that. It has no temp gauge, only an idiot light:
 
I forgot to finish out this thread.
Took the Buick to the appt. he replaced the O-Ring on the oil pump drive adaptor, like a sawed off distributor, distributor less ignition. I figured thats where the oil was leaking from, I just did not want to mess with the dismantle process to get the drive out of its position. That stopped the oil leak.
He drilled out a plug to get to the idle adjustment screw, he found one vacuum leak and fixed that. There was also one bad coil so He replaced that.
Brought the car home and it was running real fine, until one evening the wifey took it to take the dog out for her run, the car died on Her.
I towed it home, it has been setting ever since.
I got on RA and ordered in a new Delco fuel pump/tank sender unit. A new ignition control module, the three new coils and a set of plug wires.
I called Rainey Day Repair and set up another appt. I told Him I was going to fire the parts cannon at that Buick. After I explained what that meant, He got a pretty good laugh out of that one. Car goes in the 17th of July to get the parts installed. I could have got an appt after the 13th but we will be in Alaska at that time.
 
Add a MAF sensor to the parts cannon.

How many miles on the spark plugs? It's a 1988 so 30K and IMO forget about exotic metal high mile spark plugs. Unless it's double tipped half the plugs fire in reverse wearing the side electrode rather than the the tip. I had bad luck trying to convert my 1985 V6 (distributor) to the "new" early Platinum. One plug came loose, melted down, quit firing, and the misfire melted the cat.

Frugal is rotating the spark plugs from one side of the coil to the other... 🤪
 
Looking on RA for a MAF sensor.
Has anyone ever heard of a reman MAF sensor ?
Only Delco unit I can get through RA is a remanned.
I really dont want to try out any other brand.
My guess, the reman has been sprayed out with some MAF cleaner, then may or may not have been tested to properly function the punched into a box and shipped out as a reman. 🤷‍♂️😹😹😹
 
Ask your local GM dealer if they have any new ones. Again the only reason I suggest one is they stall the engine when they crack a solder joint with no codes on the primitive 1980's ECM's. This old reman may be your only choice before reaching aftermarket.
 
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