1988 Buick Century, rough idle and stalls.

[THEFERMANATOR]

If it has the updated prom chip in it the MAF sensor is a waste of money. GM converted many of those from maf to speed density because the maf sensors were so problematic. Most left the maf inline as the intake air temp sensor in it was still used, but that was it.

 

[WarWagon]

@THEFERMANATOR Do you recall how to tell if this SD update was done to this vehicle? This tidbit is almost lost to history. After the long shop times with the 1988 3.1L FWD Olds I would be stunned the shop would have missed that. (It was the new body Cutlass Supreme with the 3.1 V6. Could have been an late 1988 or 1989 I forget now.)

A little on the 2.8L was all I could find...

Mass Air Flow (MAF) Sensor - A-Body.net - 1982-1996 GM A-Body Forum

Is something not working right? Learn how to fix it in our troubleshooting forums.

www.a-body.net

@MrMarty51

What engine is in this exactly? I was assuming it has the 3.8L V6. It could have the 2.8L looks like.

What does this have for an EGR valve on it? Possible it's sticking open (electric) or flapping full open if it's a vacuum and backpressure controlled unit. I have had the electric ones on other stuff stick full open stall me out when returning to idle or stopping.

Tap the ECM and see if the engine stalls. "Static Vibration Test" Aka "Thump It Twice" is looking for a loose connection in the device.

 

[MrMarty51]

It has the wee 2.8.
Yup, vacuum opened EGR but I believe there is wires to the vacuum valve.
I’ll have to give the ECM the double tap and see what happens.
Just being layzeee today. Had some running to take care of, got that done and hadda sammich, feels like snoozing time now.

 

[WarWagon]

If it still runs start it up, warm it up, drop in in drive. With the brakes on bring the engine up to 1200 RPM. This should kick the EGR vac solenoid on. If it starts running badly the EGR valve is flopping full open instead of moving via backpressure. (All electronic are just that without any vacuum to em.)

 

[MrMarty51]

I’ll be sure to do that, between returning from Alaska and before it goes to the shop for the rest of the items thats getting replaced.

 

[THEFERMANATOR]

The only way to tell if it is a speed density system is to check the PROM chip code and cross it to the TSB. I do know the ECM used on the 2.8l's were failure prone in the injector drivers. They use a batch fire injection system and over time the injector coils begin to short out creating extra current draw, and burns out the injector drivers. I fought one before, found the injector drivers were bad, replaced the ECM, but then had to do the injectors due to excess current draw. That was how I found out about the speed density update for them was I lucked out and found a PROM chip when I replaced the ECM.

 

[MrMarty51]

I will be showing this thread to the youngster that’ll be working on the car. Dig in and see if we can get an ID on the prom.

 

[MrMarty51]

No ID on the prom, He didnt dig that deep.
He pulled the injectors and tested them, only one was within spec.
He installed a new set and the car is run ing great, once again.
Then the next problem.
Wifey driving it, said there is a funny smell and it is making a noise.
I went out, engine running, no noise and no smell. Open the hood, nothing.
Yesterday she comes home and talks about the smell. I go out, engine is running, smoke from under the hood. Pop open the hood, have her shut it off. Compressor clutch must have shorted through. Disconnect the wire from that. Now it wont start. Seems the battery is low on voltage.
Have to wait until it warms a little more out there then go out and stick the charger on it. Determine if it is the battery and low voltage from the comp. clutch going out, or, if the low voltage wiped out the starter.
I do have a different battery that will work for test procedure if need be.

 

[WarWagon]

Check battery voltage before putting a charger on it. If it's like 10V you have a shorted cell and it's toast.

 

[MrMarty51]

Check battery voltage before putting a charger on it. If it's like 10V you have a shorted cell and it's toast.

Yup, 9.4 volts.
New battery, it then cranked slow.
Thinking the low voltage did a number on the starter, pulled out that starter, tightened the nut holding the battery lug to the solenoid. lifetime warranty unit. Took it over and got it tested. Tested just fine. Shoved that starter back in the hole, a battle getting it all buckled back up. Got in, hit the switch. Cranked over but a little slow.
Removed the serp belt. Tried to spin the AC clutch, not good. Hit the start mode. Engine cranked like it should. AC compressor is seized up.
Got the AC comp clutch to let the idler spin over free, hit the switch. Man she’s a sweet running little enjun.
Guess I’ll most likely try getting an AC clutch/pulley mechanism for it, if it is too much then might as well go for the entire compressor. Just leave the wires disconnected so it doesnt run at all.
Be nice if someone made an idler for these.

 

[MrMarty51]

Found a Dorman 34195 compressor by pass pulley. Stopped by oriellys, that just started closing up shop on Sundays.
Oh well, I’ll getter ordered tomorrow. Hoping they have one in Billings. It’ll be here Tuesday if they do have it in B-Town.

 

[MrMarty51]

I got that compressor by pass pulley on Wednesday. Today the temps got warm enough that with a long sleeve shirt I was inspired to work outside.
Got that compressor of and had to dig through and find some 3/8ths” bolts of a proper length. And nuts. Bolted that idler pulley on, got the belt put back on, fired the engine and WOW. How nice. Engine runs noise free. I had to roll down a window so I could hear it to be sure it was running.
I did notice that the belt tensioner is needing replaced aaaand, I forgot to tie up the AC compressor wires.
Tomorrow with the wires and RA for the tensioner.