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1996 Deville
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67 Posts
Discussion Starter · #1 ·
2000 Deville DTS, 122,000 miles. Bought at around 110,000 with no maintenance documentation, although it seems like it was very well taken care of.

The car has always occasionally stalled at red lights, but started back up. I had plans to clean the throttle body but hadn't gotten around to it.

A few nights ago, the engine began running rough, with the Check Engine light flashing. I drove back home as gently as I could (around 15 miles).

Pulled codes (with engine idling) and found the following:

P0300 Current: Random/Multiple Misfire
P0385 History: Crankshaft Position Sensor B Circuit Malfunction
P1106 History: Manifold Absolute Pressure/Barometric Pressure Circuit Range/Performance Problem
P1381 Current: Rough Road
P1599 History: Stall Condition
P1633 Current: Ignition 0 circuit

[NOTE: I discovered the P1633 was because of a wiring issue with my remote starter. I've now fixed this and the code went away.]

OK, NOW HERE'S WHAT I DID SO FAR:

PHASE 1. Replaced plugs and rubber boots. Used AC Delco plugs (gapped properly) and AutoZone boots. I figured the previous owner probably had never replaced them (and they did look old).

Cleared codes, road-tested car. Drives the same. Check engine light still flashing. However, I only have the following codes now:

P0300 Current: Random Misfire
P1106 History: Manifold Absolute Pressure/Barometric Pressure Circuit Range/Performance Problem

PHASE 2:

Replaced both upper and lower Crankshaft Position Sensors.
Cleaned throttle body, but it was barely dirty at all. Just a little black stuff on the throttle blade, but not much.

Cleared codes, road-tested car again. No improvement. Same codes and same rough-running engine.

QUESTIONS:

1. Should I try to gain access to a Tech2 and learn the new crank sensors?

2. From the P1599 code, it appears there's some type of MAP sensor issue. I certainly want to fix that and make my car perfect........but, could this be the cause for the misfire?

3. If I had a faulty coil or fuel injector, it would be only one cylinder misfiring, and therefore I'd also have a code ranging from P0301 to P0308, correct? The absence of this is making me think this isn't a coil or injector issue.
 

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Super Moderator
2010 DTS
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88,120 Posts
The onboard diagnostics will not give you a P0301 - P0308 code. It will only give you a P0300. You'd need a Tech II to get which cylinder is misfiring. Based on what you have done and the codes remaining, I'd replace the MAP sensor.
 

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Registered
1996 Deville
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67 Posts
Discussion Starter · #3 ·
Thanks for the fast response. I see the MAP sensor is both inexpensive and easy to replace. I'll go buy one in the morning.

I'm going to replace it no matter what, but I'm still curious if it's an item that could contribute to the misfire. I guess I'll find out tomorrow morning.
 

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1996 Deville
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67 Posts
Discussion Starter · #5 ·
Update: Replaced MAP sensor, cleared all PCM codes, went for test drive.

P1599 hasn't returned, but engine still has same misfire/rough running. You can hear that "spitting" sound from the exhaust at idle. Did a couple of WOT accelerations and P0300 and flashing MIL come right back.

I'm off to see some friends at a Chevrolet dealer and see what can be done with a Tech2. Probably will do CKP relearn procedure, check for any codes such as P0301 through P0308, and whatever other testing the Chevrolet technician thinks is a good idea.

Will post back later.
 

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1996 Deville
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67 Posts
Discussion Starter · #6 ·
IT'S NOW FIXED!

Tech2 showed cylinder #4 not functioning. Chevrolet technician said that CKP relearn procedure would only be necessary if a certain code were present, so he didn't do it.

He said the coil cassettes are generally reliable, and he suspected either a bad fuel injector or spark plug.

I didn't believe in the spark plug idea----after all, I had just replaced them. The chances of the old AND new plugs being both bad is pretty slim.

I used a long drinking straw as a sort of mechanic's stethoscope and I could hear each injector making the exact same clicking noise with the engine running.

Installed new coil cassette on front bank, and misfire completely disappeared. Cleared codes, went for a ride....runs like new! No misfire, no PCM codes.

Interesting that the tech I spoke with thinks the coil packs rarely fail, yet most AutoZone stores around here have them in stock. Then again, his experience is more with Chevrolet and Pontiac, not the Northstar.

Note to anyone who finds this post in the future using the search feature: I wasn't aware that codes P0301 through P0308 wouldn't show up on the cars onboard display. These are the codes that indicate that only one cylinder isn't functioning......this could potentially be due to a faulty coil, plug, injector, or maybe loss of compression. If your car is misfiring, find some way to get a Tech2 to read this information before replacing parts unnecessarily.

Ranger, thanks for all your help. I search and read these forums a lot more than I post, and I've already gotten lots of good information from your past posts. Thanks for taking the time to be here.

Well, at least my engine is back in running order and I got a tuneup done in the process......off to put the tools away....will be back here soon for help with ABS codes. Thanks again.
 

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04 Deville, 11 DTS Premium, 00 Deville (sold), 02 Deville (sold)
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2,691 Posts
FYI... Most people don't do the CKP relearn procedure after replacing the CKP's.
 

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1996 Deville
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67 Posts
Discussion Starter · #8 ·
FYI... Most people don't do the CKP relearn procedure after replacing the CKP's.
That's what I had read, too. I just didn't know about the individual misfire on cylinder #4 (because I didn't know I couldn't see it with onboard diagnostics), and after also seeing the P0385, I was running out of ideas and starting to guess.

It would appear that my CKP sensors weren't bad after all, and I replaced them unnecessarily, but still, $80 for the sensors plus $6 for the O-rings for the oil filter adapter, are still less expensive an an hour's labor for diagnosis at the dealer. Plus, I plan on keeping the car for a long time, and at least I eliminated another future failure point.
 

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Super Moderator
2010 DTS
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88,120 Posts
I was confused. Your profile says 1996 Deville. That engine does not have ignition cassettes. Then I went back to post #1 where it says 2000 Deville. Please update your profile for the sake of my sanity. :bonkers:

P.S. Glad you figured it out and thanks for the feedback.
 
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