Falling back into OL-1/Misfiring/Rough Idle No CODES - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


1992-1999 Series I L27 (1992-1994 SE,SLE, SSE) & Series II L36 (1995-1999 SE, SSE, SLE) and common problems for the Series I and II L67 (all supercharged models 92-99) Including Olds 88's, Olds LSS's and Buick Lesabres Please use General Chat for non-mechanical issues, and Performance and Brainstorming for improvements.

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Old 04-12-2005, 01:01 PM   #1
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Default Falling back into OL-1/Misfiring/Rough Idle No CODES

Hi

OK, have some wierd issues here. Anybody that could give a hand, I'd appreciate it.
I have a AutoTap Scan Tool on my laptop, I have all the data available, I understand a fair amount, but certainly not it all!

My 97 SSE Idles Rough
114K Miles, Newer Stuff since 70K:
Alternator, Plugs x2, Wires x2, Fuel Pump, Fuel Sender Unit,
UIM Gasket/UIM, blah blah all the typical stuff... Prob
new Water Pump this weekend, thou its not related to what I'm posting.

Saved a scan to a Excel spread sheet this morning on my way into work. In some free time, I was just looking at it. Noticed:

-Long Term Fuel Trim is mostly always hi(gher), above 7 or 8%, quite oven hits 15 and 16%, which I read in AutoTap MAY indicate a lean condition.

-Noticed It Falls back into Open Loop-1 for a second or two, then goes back to closed. I don't see any pattern to it

-Sporadic Misfiring. NOT EVEN across the cylinders, ranges from hitting 1 or 2 cylinders to 4 at once. Stays between 1-4 misfires on each current cylinder being hit.

-"O2 Monitoring Status" finally completes 10 minutes into my drive. ?

-If you just look over the numbers for O2 Sensors 1&2, Sens1 seems very erratic. Sens2, while the numbers very greatly and quickly, seems to flow better. Don't know if this is normal.

-Bank1 & Bank2 Crossover counts... Bank 2 stays mainly around 90, I read the range should be 0-250. Bank 1 However poll-vults over 250 up to 1,100 at times...???

Any other data to help me, I'll let ya know... thank you!

-Daron
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Old 04-12-2005, 01:07 PM   #2
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Not sure whats going on here... I hate it when these cars become unhappy....

I would be tempted to try another PCM.... But depending on the car it comes from( if a bonneville 97 model year then it shouldn't need to be flashed ) it may need to be flashed, or possibly need a crank variation lear sequence performed... I forget if its required on the 97 or 98 bonneville or both...

I'm just not sure what to tell you at this point...

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Old 04-12-2005, 01:13 PM   #3
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I hate it when she gets unhappy too... I really love the car, it runs strong despite running rough... I want it to last long, I'm afraid that won't happen with stuff like this happening.

I was kinda thinking PCM- how would I go about that? What about the Crank Variation Relearning?

What about this angle- what can I elliminate? How do I know it'* not an O2 Sensor, for example?
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Old 04-12-2005, 03:57 PM   #4
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You said something about one O2 sensor acting differently than the other. It'* my understanding O2'* are supposed to fluctuate repeatedly up and down. Tested my car recently with a brand new O2 and it did that. up down up down up down.

Maybe one is bad and causing you to dump fuel. How'* your mileage been?
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Old 04-12-2005, 04:47 PM   #5
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Actually quite the opposite.

I'm getting excellent gas mileage, which suprises me given this cars age.

I read a post in here about somebody finding the IAT floating about in the engine bay, and not plugged into the airbox. I have a custom K&N setup, without the IAT attached... Perhaps the problem?
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Old 04-12-2005, 05:10 PM   #6
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Not sure, on my 95 SSEi I forgot to hook it back up after having the airbox out to change front exhaust manifold... didn't notice any difference.
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Old 04-12-2005, 06:05 PM   #7
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First, the 95 Bonnevilles only had 1 O2 sensor... It was Position 1...

On the 1996 and later you have a Position 1 and position 2( might be called Position 3 so don't quote me on that one )

Now the Position 1 sensor is the one that the PCM uses for fuel perameters, The second sensor which is after the Cat is simply a sniffer for the cat to make sure its functioning properly...

You could have the exahust system tested for backpressure... But I'm not sure that will be the problem... Yes a good functioning O2 will swing up and down in terms of its voltage, a sensor that does this quickly should be good... On some scantools you will also be able to see the PCM go from lean to rich very quickly...

Not sure what the porblem may be... Its hard to say without actually being there to look at it..

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Old 04-13-2005, 07:59 PM   #8
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Sounds like it could be a plugged fuel injector.....very common on GM cars up here in Wisconsin...the gas is crap up here....too bad you dont live by me...I have a good spare pcm....its for an SE though.....good luck!
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