1996 Buick Century rough idle/stall

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Greetings and good evening to all in the land of all things Bitog! So, my son-in-law brings me his 1996 Buick Century station wagon (known as "Tighty Whitey"). It's running rough and stalling. It might run good for about five minutes and then starts to idle roughly. Periodically, it will stall both in park while in the driveway and in drive during exciting moments at stop signs and stop lights. Sometimes it accelerates like a scalded dawg and other times, bucks like a roped bull. So far he has replaced, the EGR valve and the MAP sensor. He also cleaned the MAF sensor and the throttle control sensor. He pulled a couple of the plugs and said they look nice and clean and from what I can tell, the ignition wires look good. He's frustrated and brought it to me thinking I could fix it. But before I starting wrenching on this bad boy, I thought I would come to wise motor guru's here at Bitog and get some guidance. "Tighty Whitey" is a 1996 Buick Century Wagon with a 3.1 V-6 mated to an automatic transmission. Said vehicle has 200,000 miles on it, burns no oil and uses no water, (so I don't think it's an intake gasket issue). I'm thinking it could be - Fuel Pressure regulator, (although, I ran it for about half an hour in the driveway with the vacuum line removed and the regulator spat no gas out the top. However, the fitting where the vacuum line joins the Fuel Pressure regulator does smell strongly of gasoline. However, with the vacuum line disconnected, the motor still ran rough and stumbled periodically). Fuel filter. I have no idea when this was changed. Fuel Pump. Could it be getting weak? Coil pack. Could this be going bad? O2 Censor. I think it's original. Thoughts, opinions, words of wisdom - Thanks.
 
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My regal was running rough for a few weeks. It started every morning running fine, then once it got warmed up it ran pretty rough. Starting it up after i t was at operating temp was a pain, problem was coolant temp sensor causing it to run very rich when at operating temp.
 
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Throttle position sensor and iac valve come to mind here. I thing the crank position sensor usually either works or it doesn't so i don't think thats it. Has he replaced the fuel filter?
 
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Check for corrosion at the coil packs and plug wires junction. If it has any can cause issues. Get dremel steel brush and dremel them back to shiny and clean.
 
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Quick, cheap and dirty things to do: Pull the plug wires off and look for rust/corrosion at the coil terminals. Disconnect the mass air sensor (wire harness) Failing success at those, then: Check for codes, and read sensor values. If none, check fuel pressure. GreeCguy- I'm surprised you don't own a code reader yet. As cheap as you are, I would have figured you'd have jumped on one in an attempt at saving money by not going to the mechanic.
 

GreeCguy

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Originally Posted By: The_Eric
GreeCguy- I'm surprised you don't own a code reader yet. As cheap as you are, I would have figured you'd have jumped on one in an attempt at saving money by not going to the mechanic.
Yes, I hang my head in shame, (picture, if you will, a GreeCguy shame head hang). I actually had one a few years back - a really nice one too. Then, in a spirit of automotive repair brotherhood, I "loaned" it to a friend. Then the friend "lost" said nice scanner. He didn't know where it went or what happened to it, but he assured me he'd get me another. I'm still waiting . . . . Meanwhile, I've been too cheap to buy another one. I've been taking my cars to Autozone and having them scan them for free, but this Buick is running so poorly, I'm afraid to take it back on the road, (I can't express the relief I felt when I pulled it back in the drive way after the initial test drive. I did make a lot of new friends though. Every time it stalled at a red light turned green, people blew their horns at me as a sign of support and encouragement. Some even waved at me with one finger in the air - I took this as a sign, obviously they wanted me to keep my spirits up). Maybe a trip to Harbor Freight is in my future. Does anyone know if the 96 Buick is a OBD II?
 
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Originally Posted By: GreeCguy
Originally Posted By: The_Eric
GreeCguy- I'm surprised you don't own a code reader yet. As cheap as you are, I would have figured you'd have jumped on one in an attempt at saving money by not going to the mechanic.
Yes, I hang my head in shame, (picture, if you will, a GreeCguy shame head hang). I actually had one a few years back - a really nice one too. Then, in a spirit of automotive repair brotherhood, I "loaned" it to a friend. Then the friend "lost" said nice scanner. He didn't know where it went or what happened to it, but he assured me he'd get me another. I'm still waiting . . . . Meanwhile, I've been too cheap to buy another one. I've been taking my cars to Autozone and having them scan them for free, but this Buick is running so poorly, I'm afraid to take it back on the road, (I can't express the relief I felt when I pulled it back in the drive way after the initial test drive. I did make a lot of new friends though. Every time it stalled at a red light turned green, people blew their horns at me as a sign of support and encouragement. Some even waved at me with one finger in the air - I took this as a sign, obviously they wanted me to keep my spirits up). Maybe a trip to Harbor Freight is in my future. Does anyone know if the 96 Buick is a OBD II?
If your lucky, my 95 is obd 1.5 good luck scanning that, at least for less then $80 even then its not always correct. I do believe tho it is obd2 only way to truely find out is go outside and count the pins 12 pins=obd1 (possibly obd1.5) and 16 pins=obd2
 
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Yes, 1996 was the start of OBD II. Does it run better, worse or the same when you floor it? Have you gotten a chance to investigate any of the suggestions yet?
 

GreeCguy

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Originally Posted By: The_Eric
Does it run better, worse or the same when you floor it? Have you gotten a chance to investigate any of the suggestions yet?
Better. On occasion, it will stumble when floored, but 9 times out of 10, that's how I got through red lights and stop signs - I simply kept my foot on the gas pedal keeping the rpm's up and when the light turned green, put the pedal to the metal.
 

GreeCguy

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First of all friends, thanks for the wisdom and advice. Secondly, I bit the bullet, went to Harbor Freight and purchased a "Cen-Tech" OBD II & Can Code Reader. Item #98568. (I'm keeping this one under lock and key next to my "lucky mood" ring - so no, you can't borrow it). According to my code reader, there were four stored codes: PO336 - Crankshaft position sensor A Circuit PO341 - Camshaft Position sensor A Circuit PO336 - Crankshaft position sensor A Circuit PO341 - Camshaft Position sensor A Circuit (Yes, I know it's a repeat, but that's what the code reader read and reported). I then did the "Freeze Frame" scan which said: DTCFRZF PO341 Fuel Sys 1 CL Fuel Sys 2 N/A Load - PCT (%) 3.1 ETC - 180 SHRTFT1 (- as in "negative") - 18.0 LongFT1 (- as in "negative") - 3.1 MAP (inHg) 14.4 RPM (min) 638 VSS (mph) 0 MAF (lb/min) 0.690 To ask the most Lutheran of questions - "what does this mean?"
 

GreeCguy

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Originally Posted By: dishdude
Sounds like a bad ignition control module, the one under the coil packs.
After reading countless articles this evening via the world wide web, I'm beginning to lean this way myself. One article I read stated that when you change the ICM, you should also change the coil packs as well as they could have been damaged leading to the failure of the ICM or, conversely, the failure of the ICM lead to damage of the coil packs which in turn could damage the replacement ICM. Is this common practice or just one opinion?
 
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I personally would be hard pressed to change out OEM coil packs if they don't show signs of damage; i.e. burnt, arc marks, corroded contacts, if they ohm out per procedure (I assume, I haven't checked the FSM) or compared to each other. I live in the high desert (serious lack of rust and corrosion), but I've wondered if the packs should be preventatively removed and new dielectric grease applied every 10 or 15 years, as they are past their expected service life.
 

GreeCguy

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UPDATE!!!! Okay ladies and gents, the weather here is a bone chilling 51 degrees, but determined as I was, I was compelled to brave this bitter winter weather and tackle the "tighty whitey" dilemma of the dancing V-6. First things first - bundle up. I wouldn't want to catch my death of cold and have to visit you good Bitogers via a spiritual medium. Second step - let's have a look at that thar coil pack. Terminals were rusty and corroded. My Chinese knock off dremel with it's tiny wire brush made quick work of making it all look bright and new. Likewise the inside of the plug boots themselves. I ran the tiny brush inside each boot and polished the metal connector to a mirror finish in less time than it takes to tell. The third step involves jacking up the rear of the car and replacing the fuel filter. A quick job since with the wheel removed, the filter is easy to access. The old filter was somewhat dirty, but I've seen a lot worse. (note to self, put the cigarette out BEFORE removing the filter - thankfully the fire demons were busy elsewhere and I escaped un-burnt). Now comes step number four which is the most exciting - the cam position sensor. Why the cam position sensor you ask? Because I had one that would fit this motor. Several years back I bought one for my daughters 1997 Olds Van with the 3.4 and just never got around to putting it in. Turns out, a little surfing of the internet revealed the 3.1 and the 3.4 GM V-6 use the same sensor. I dug it out still in it's box. It took some wrench twisting removing the power steering pump, but lo and behold, when I removed the pump, there was the old sensor living beneath, not only the power steering pump, but a pile of grease and dirt. Clean, clean, clean, then unbolt and remove. Upon close inspection, the turns out the old sensor had frayed wires right above the sensor. I'm not sure if the insulation was degraded by the grease and oil (which, by the way, I believe is leaking from the power steering pump), or if somehow over time, they simply wore for whatever reason. Popped in the new sensor that I've had for a few years and put everything back together. Now comes the moment of truth. With ignition key in the ignition switch, I shout out the drivers side window, "Clear prop," and turn the key. The engine barks to life. It runs GOOD! Still a tiny, tiny sputter and a tiny, tiny bit of roughness, but greatly improved over what it was doing. After allowing it to run for about 20 minutes, I shut it down and plug my nifty new OBD II code reader and the cam shaft sensor codes are gone. However, it still lists crankshaft sensor codes. I'm wondering if these are simply left over or if the crankshaft sensor is indeed faulty. I shut the motor down and decide to clear the codes and see if they reappear. So far, I've let the motor run for about 15 minutes and the check engine light has yet to come on. Maybe it will when I tool around the neighborhood, we'll see. For the moment, all is right in the GreeCguy world. I was hesitant to do this on Friday the 13th, being a fan of the Knights Templar and all - so we'll see what happens in the next few hours. Oh, and I did find where the crankshaft position sensor lives - way on the back side of the motor right above the oil pan beneath the alternator. If I must remove that one, I think I'll pop out the alternator and have a go at it as I can barely put my arm down there, let alone move a tool around. Even so, I'm very happy at the moment. I couldn't have done it without you guys - so thank you, thank you, thank you. Have an exciting night and a better day tomorrow. Remember to do something sweet for the one you love, (I'm heading to Lowes in the morning to buy a dishwasher - that's the way to a woman's heart).
 
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