Cadillac Owners Forum banner

1 - 20 of 33 Posts

·
Registered
2000 deville
Joined
·
57 Posts
Discussion Starter #1
Just got this code a few days ago. Car ran fine and the next morning it idled a bit rough and this code popped up. Gas milaeage was down 3 mpg as well.

Could this be a Mass Air flow problem? I replaced that 6 months ago with a used part, and have had no problems until this. It ran much worse with the MAF code.


Any short cut ideas?

Thanks
 

·
Master of the Dark Art of Diagnostics
2003 DHS - two-2002 DHS, 2003 SLS, 1995 Sedan DeVille, 1989 Coupe DeVille
Joined
·
19,854 Posts
Re: P0301 CADILLAC - Cylinder 1 Misfire Detected

Just got this code a few days ago. Car ran fine and the next morning it idled a bit rough and this code popped up. Gas milaeage was down 3 mpg as well.

Could this be a Mass Air flow problem? I replaced that 6 months ago with a used part, and have had no problems until this. It ran much worse with the MAF code.


Any short cut ideas?

Thanks
===========================
Could this be a Mass Air flow problem?the MAF sensor is monitored and should set a DTC if it was malfunctioning -

it COULD be lots of things -
dirty TB -
vacuum leak -
bad spark plug -
carbon arching at the spark plug boot -
bad/plugged fuel injector - etc -

MOST likely it's a bad coil cassette -
 

·
Administrator
2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
Joined
·
69,854 Posts
MAF also affects general performance, not just one cylinder.

I'm with basscatt​ - coil cassette (right, rear), boot(s), injector sticky, plug/boot dead or tracked.

Both cassettes and their ICMs are identical except for color. If a cassette has any - any - cracks or discoloration at the high tension terminals or insulated area that the plug boot slides onto, it's toast. Junkyard.

Inspect the boots for carbon tracking. You WILL find some oil in one or more plug wells - normal. DO NOT try to bend that steel pipe on the rear AIR check valve assembly - remove the assembly correctly. Two 10mm nuts on the flange on top of the exhaust manifold - magic words.
 

Attachments

·
Administrator
2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
Joined
·
69,854 Posts
A torn/cracked intake manifold connector plenum normally sets P 0171/P 0174 lean mixture codes, not a single miss code.

P 0301 - cylinder 1 miss detected - is the farthest away from the intake manifold plenum.

2000 - 2005 intake manifold, plenum end.
 

Attachments

·
Registered
2000 deville
Joined
·
57 Posts
Discussion Starter #8 (Edited)
I took the coil cassette off and there was no cracking or charring. The posts were rusted and had a bit of carbon. Last fall I had the plenum gasket replaced after a leak was found. When I took off the cassette I noticed all 5 plenum bolts on the backside were loose and 3 were backed almost all the way out! Could this be the misfire code? and do I need to prep the posts, or just steel wool then and put the coil pack back in? I also cleaned the soot out of the TB, it was filthy! I also ran a bottle of injector cleaner. Thanks
 

·
Registered
2000 deville
Joined
·
57 Posts
Discussion Starter #9 (Edited)
I took the plug boot out for cylinder 1. There was a little rust on it. Will replace and put Dialectric grease on and put it all back together and see if the was the reason for the code and misfire.
 

·
Registered
2000 deville
Joined
·
57 Posts
Discussion Starter #10
I put it all back together and the code came back and it still runs rough. I thought the loose bolts on the back of the Plenum may have caused a vacuum leak. The only thing I am worried about it is pulling the plugs. They are original and have been in there for 130,000 miles and 17 years. Any hints on how best to do this without breaking any? Thanks
 

·
Master of the Dark Art of Diagnostics
2003 DHS - two-2002 DHS, 2003 SLS, 1995 Sedan DeVille, 1989 Coupe DeVille
Joined
·
19,854 Posts
I put it all back together and the code came back and it still runs rough. I thought the loose bolts on the back of the Plenum may have caused a vacuum leak. The only thing I am worried about it is pulling the plugs. They are original and have been in there for 130,000 miles and 17 years. Any hints on how best to do this without breaking any? Thanks
=======================
use a spark plug socket -
do it on a cold motor -
 

·
Administrator
2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
Joined
·
69,854 Posts
AC Delco #41-987, pregapped to .050".

You will find some oil in one or more plug wells. Normal, not to worry. Because normal maintenance apparently has been severely neglected, you'll have some cleaning up to do.

Plenty of tutorials and pictures in here, Seville, Northstar.

Google "cadillac forums northstar spark plug change" and you'll get enough to study all night.
 

·
Registered
2000 DTS
Joined
·
29 Posts
My 2000 DTS was running perfect, then I parked for 30 no idea, came out to leave and as soon as I started it, it was running super rough. I drove home and the CEL was blinking the entire time. I instantly knew it was a misfire, and since the plugs had never been changed (155k Miles) I went to it. Got A.C. Delco plugs, and got both new coil cassettes since I didn't bother finding out which cylinder it was. Figured I might as well change everything since I would have had to take it apart anyways. Spent around 300 total on everything, and now it purrs like a kitten!

Make sure you get A.C. Delco plugs, nothing else. Get a plug socket, and a 5 inch extension (6 was a tad too long on the firewall side) and make sure you have a elbow adapter because you can't go straight down on the back side.

All in all, took about 2 hours of work. You might get frustrated at times, but just be patient and don't rush it. I've never done my own work, but it saved be almost a grand doing it myself.
 

·
Registered
2000 deville
Joined
·
57 Posts
Discussion Starter #15
How hard was it to get the plugs loose? It was recommended to me to have a cold engine. I have a torque wrench for the new plugs and am getting them from Rock Auto in a few days. I will report back after it's finished. Thanks for your input.
 

·
Registered
2003 Deville Base
Joined
·
71 Posts
I had the same code a last week. It was a bad coil. But you can always swap plug #1 with #7 and reset the code and see if you end up with a P0307, then you find the culprit. If the code stays on P0301, replace coil.

Another way, swap coils from front to back. If its the coil thats bad you'll get a misfire on #8.
 

·
Registered
2000 deville
Joined
·
57 Posts
Discussion Starter #17
I changed all 8 plugs with the recommended Delco platinum. Followed all directions closely, and had no problems. Car still runs rough. The rear coil cassette had carbon on the posts. I cleaned them all, but maybe it is still bad. Or it's a clogged injector.

I will order a coil cassette and try that next. I'm glad I changed the plugs they were rough looking especially number 1, where the PO301 code originated from. Thanks in advance for any more suggestions.
 

·
Administrator
2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
Joined
·
69,854 Posts
If there was any appearance of carbon tracking on the coil posts then it's toast. Hard to tell on the right (rear) black cassette. You should have changed all 8 plug boots, too, and used a small smear of silicone dielectric ignition grease in the top and tip of each boot. Dielectric grease at any parts store - cheap.
 

Attachments

·
Administrator
2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
Joined
·
69,854 Posts
Good stuff ​when used in moderation ............. < $2.
 

Attachments

·
Registered
2000 deville
Joined
·
57 Posts
Discussion Starter #20
I checked plugs and boots for tracking, found nothing, but the coil cassette had heavy carbon on all 4 posts. Front was clean, no carbon. I will get new boots while I wait for the cassette to get here. I did use dialectric grease as instructed. Thanks
 
1 - 20 of 33 Posts
Top