Hello, fellow Bonneville lovers!

I have a good problem for you!

The story:

My dad recently purchased a 1995 Bonneville (SE) for $400. It wasn't running, so he towed it to our house. We spent the next month working on replacing the engine. The check engine light was on, and my dad tried to read the code. It wouldn't read. Took it to some other places, and even they couldn't read the code. For the past 15 months, I've been driving the car with the check engine light on.

The reason we got it so cheap was because the previous owner seized the engine. It now has 134,000 miles on it. (As of Feb. 11, 2014 the mileage is about 137,200)

The Problem:

We also had to replace the oxygen sensor. About nine months later (about April this year), we replaced it again. Three months later, we had the same symptoms of a bad sensor (Engine sputtering, stalling, etc.) and replaced it again. Now it's having the same symptoms (sputtering, stalling, jerking). My dad thinks that the ECM could be having issues.

Sometimes when I'm driving (anywhere around 50-65 mph), it jerks once, maybe twice. Occasionally (once a week or so; in freezing temperatures), it starts, then coughs and stalls. Then I usually warm it up by revving it leaving it in park and pressing the gas). A couple times when I've done this, it acts like I haven't pressed the gas at all, then suddenly acts like it gets the signal and starts revving.

The Question:

Should my Bonneville be going through oxygen sensors so quickly? Or is it the ECM that's having issues and causing the sensors to go bad?

Updates:

It is not the ECM.
It is not the Crankshaft Position Sensor.
We are going out on a limb and trying the Knock Sensor.This did not solve the problem.

HOWEVER!

We took to a diagnostic place and they pulled out the code. PO325, the Knock Circuit. Looked under the car and guess what? Two knock sensors. One is in the Antifreeze, the other is about 18' down from the place to put oil into the engine. One's a '95 Knock, the other is a '98 Knock. The '98 is a new sensor. Going to run with the '95 unplugged to see if it gets better, worse, or the same.

Update (2/19/15):

Now running with two 95 knock sensors, check engine light went away. Ran well for summer, but she's decided she hates cold.

When the cold weather hit, she went downhill, and not in a nice way. She now refuses to start until the Mass Air Flow Sensor is tapped when it gets below 50. The other day, when it went below 40, she refused to start. Period.

My car starts up, runs for a few seconds, then shudders and dies. The only sensors that have not been replaced are the Temperature sensor and the Idle Air Control. Tapping on the Mass Air Flow sensor works most of the time (before and after replacing with a rebuilt). This only happens when it's below 50. It is not throwing a code. The Fuel pump is still functioning (I can still hear it whirring), and I have not been able to test the pressure.

When I am driving, she will hesitate, then jerk and act as if I have added to the throttle when I have held it steady. She will also stumble hard at speeds over 25 (Prefers above 50. Has done it around 45, and on rare occasion, 30).

Sputtering doesn't sound like a bad oxygen sensor. 95 pcm's aren't known for being rock solid. If they are scanning it correctly (94/95 is an odd scanner/connector combo) and not getting anything, I'd bet on the PCM being wonky.

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WHITE WHINE - 1992 SSE Supercharged 236.26 ci (.040 Over) 15.090 at 90.2 MPH on old engine w/ slipping trans & melted O2 sensor - Gen 3 M62 and matching TB, Gen 2 Pully, Zillamotorsports Ported LIM, YT 1.72 Roller Rockers, SII FPR & Injectors, Hypertech Thermomaster chip w/ 160 Thermo, TransGo Shift Kit, Infinity/Pioneer Speakers & a 10" Alpine Type R Sub, all the watts, 140 amp Alternator, Ricepipe CAI w/ heatshield, Pilot Angel Eye Foglights, Clear Corners, '02 17" Chrome Bent 5's, Magnaflow F-Body Muffler and Hi-flo Cat, Ceramic Coated Ported Exhaust Manifolds, Fan Override, Monroe Reflex struts, red calipers
2009 G8 GT - Sport Red Metallic, loaded, SOLO Axlebacks, Rotofab Intake, Tuned, autodim mirror, removed intake manifold cover, HSV GTS triple gauge pod, two tone red-hot shifter and HSV SuperSport steering wheel, GXP rear sway bar and diffuser, 3.45 diff and various Camaro suspension bits, LED Taillights

We just replaced the oxygen sensor, but it's not better. The connector is a funky one (OBD 1 1/2), and my dad just thought it could be a wiring issue that's interfering with the code reader.

So what you're saying, J Wikoff, (from what I'm understanding) is that I need to get a new ECM?

If the PCM won't communicate, then that is the most likely suspect.

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WHITE WHINE - 1992 SSE Supercharged 236.26 ci (.040 Over) 15.090 at 90.2 MPH on old engine w/ slipping trans & melted O2 sensor - Gen 3 M62 and matching TB, Gen 2 Pully, Zillamotorsports Ported LIM, YT 1.72 Roller Rockers, SII FPR & Injectors, Hypertech Thermomaster chip w/ 160 Thermo, TransGo Shift Kit, Infinity/Pioneer Speakers & a 10" Alpine Type R Sub, all the watts, 140 amp Alternator, Ricepipe CAI w/ heatshield, Pilot Angel Eye Foglights, Clear Corners, '02 17" Chrome Bent 5's, Magnaflow F-Body Muffler and Hi-flo Cat, Ceramic Coated Ported Exhaust Manifolds, Fan Override, Monroe Reflex struts, red calipers
2009 G8 GT - Sport Red Metallic, loaded, SOLO Axlebacks, Rotofab Intake, Tuned, autodim mirror, removed intake manifold cover, HSV GTS triple gauge pod, two tone red-hot shifter and HSV SuperSport steering wheel, GXP rear sway bar and diffuser, 3.45 diff and various Camaro suspension bits, LED Taillights

Your car sounds exactly like the problems I had with my SE when I bought it. It had a CEL, sputtering, stalling, random no starts. Bad misfire as well. Turned out to be the PCM. Real easy to change out, and only cost me $60 at a junkyard.

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I'm backkkkkkkkkkkkkkkkk!

Check all vacuum lines. I had to replace all mine. next change fuel filter, and check spark plugs and wires. do you have any coolant leaks?

cjski: The lines, wires, and plugs are good. Fuel filter's recently replaced. No leaks.
J Wikoff: Okay, thanks.
99BonnevilleSE: Thanks. I'll find out which ECM my car needs.

Update:

When I started my car a few days ago, the check engine light was off (for the first time in 15-16 months!). When I restarted it, the light was back on. Nobody that I told understands it.

(Sorry for the double post)

My dad just recently tightened the battery cables (as I also noticed the power was dropping, too.), and haven't had an issue since. But just in case it is the ECM, where would that little pain in the car be in this particular car?

You are in luck, it's probably one of the easiest things I've ever done. Disconect battery.Remove the black plastic cover underneath the passenger side of the dashboard. Like 3 or 4 bolts. Look up and to the right against the firewall. Pull back the 3 plastic tabs, holding up the PCM. Remove the three color coded harnesses. Now before you repeat the procedure backwards. Make sure to swap over the prom. On the PCM there is 2 bolts, remove those. On the circuit board there is a removable chip. Swap that from your broken one to the new one. That's it!

_________________
I'm backkkkkkkkkkkkkkkkk!

Oooh ... okay, thanks!

Well, just replaced the old ECM with a junkyard ECM. Same issue. Error reading code, nothing changed. Any other ideas? Or just live with it and hope for the best?

Okay, I've got some updates up. But I'm having a major problem now:

My car starts up, runs for a few seconds, then shudders and dies. The only sensors that have not been replaced are the Temperature sensor and the Idle Air Control. Tapping on the Mass Air Flow sensor works most of the time (before and after replacing with a rebuilt). This only happens when it's below 50. It is not throwing a code. The Fuel pump is still functioning (I can still hear it whirring), my dad is unsure when the fuel filter was replaced, and I have not been able to test the pressure.

When I am driving, she will hesitate, then jerk and act as if I have added to the throttle when I have held it steady. She will also stumble hard at speeds over 25 (Prefers above 50. Has done it around 45, and on rare occasion, 30).

Most of that is added to the original post. My dad and I have no other clues but a faulty rebuilt MAF or the ECM needs to be flashed so it can relearn the sensors.

Fuel pressure testers are cheap, and some places might even loan you one for a refundable deposit.

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WHITE WHINE - 1992 SSE Supercharged 236.26 ci (.040 Over) 15.090 at 90.2 MPH on old engine w/ slipping trans & melted O2 sensor - Gen 3 M62 and matching TB, Gen 2 Pully, Zillamotorsports Ported LIM, YT 1.72 Roller Rockers, SII FPR & Injectors, Hypertech Thermomaster chip w/ 160 Thermo, TransGo Shift Kit, Infinity/Pioneer Speakers & a 10" Alpine Type R Sub, all the watts, 140 amp Alternator, Ricepipe CAI w/ heatshield, Pilot Angel Eye Foglights, Clear Corners, '02 17" Chrome Bent 5's, Magnaflow F-Body Muffler and Hi-flo Cat, Ceramic Coated Ported Exhaust Manifolds, Fan Override, Monroe Reflex struts, red calipers
2009 G8 GT - Sport Red Metallic, loaded, SOLO Axlebacks, Rotofab Intake, Tuned, autodim mirror, removed intake manifold cover, HSV GTS triple gauge pod, two tone red-hot shifter and HSV SuperSport steering wheel, GXP rear sway bar and diffuser, 3.45 diff and various Camaro suspension bits, LED Taillights

I have wonderful news! My Bonnie is running just like a dream now!

The whole problem? The VATS was getting a skewed signal because my keychain was too heavy. The resistor pellet's frequency was being thrown off, causing every little problem I was having with her not wanting to start. Go figure!

Thanks to everyone that helped with my problem, and I hope you have a wonderful day!

Wow, that was one strange cause.
I never would have guessed the keychain.
Congrats on getting it figured out and thanks for posting your findings!

Please excuse my ignorance but what does VATS stand for or mean?

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https://imgur.com/yXMfKKC
2000 ssei
275,000 mi
Inherited from my grandmothers passing and was used to put 2 nieces thru college.
This car was built like a Tank!

Vehicle Anti Theft System

_________________
Andrew - owner/operator of Bonnevilles Unlimited

2004 Bonneville GXP | 60k | White Gold Tricoat | custom built supercharged 3800 hot rod | garage queen
1997 Corvette | 55k | Silver Metallic | Z06 wheels | Date-night Hauler/Parts runner
2014 Town & Country Limited | Cashmere Pearl | 95k | Family Hauler
2002 Ram 1500 Quad Cab Sport | Black| 260k | Official Bonneville Hauler

Did you keep the orginal throttle body with the 3 screw MAF when you did the engine swap?

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95 SLE... a keeper. 241k miles. Low and Slow.
97 BMW 528i
98 Infiniti vq35'd i30: 13.3@104mph, 30MPG Hwy (RIP)
02 Jag X-type
03 BMW M5
05 Chevy Cobalt LS
07 Infiniti G35s 6MT (Sold)
07 Ducati Monster S2R 800 with DS1000 swap
83 Yamaha IT175K
72 Yamaha DS7: '74 RD250 swap, JL chambers

Info on dropping a 92-99: Here.