Oxygen Sensor or ECM?

[LightningAclhemist]

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).

[J Wikoff]

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.

[LightningAclhemist]

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?

[J Wikoff]

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

[99BonnevilleSE]

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.

[cjski]

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?

[LightningAclhemist]

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.

[LightningAclhemist]

(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?

[99BonnevilleSE]

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!

[LightningAclhemist]

Oooh ... okay, thanks!

[LightningAclhemist]

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?

[LightningAclhemist]

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.

[J Wikoff]

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

[LightningAclhemist]

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!

[MKMike]

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!

[mcdavidhome]

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!

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

[harofreak00]

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!

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

Vehicle Anti Theft System

[95naSTA]

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