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2000 Deville DTS Misfire P0300


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So heres what happened. We had alot of snow here the past couple days. This morning I tried to drive through a big pile of snow and got high centered. After 10 minutes of (correctly) rocking it back and forth and digging it out I finally took the traction control off and I got out. Well the car stunk, not sure if it was tires or what. The SES light was blinking and it said code P0300. And yes it was misfiring. I cleared it many times but it still misfires and shows back up. It struggles in the lower RPMs to mid rpms but when floored sometimes it seems like all the power is there, not sure though. I dont think the car liked continually hitting the gas forward and back with the traction control limiting it. Because thats weird that all of a sudden that ruined something.

Ive done my research on here and people mostly say coil banks. Some say possibly injectors or plugs or cat converter but it usually ends up being coil banks. I looked at the exhaust it looks perfect. The rubber boot between the plenum and intake manifold looks just fine. I just cleaned my MAF and butterfly with cleaner a couple weeks ago, that smoothed the idle. I have 94k miles and am bout ready to do the plugs anyway. For fun tonight i took off both coil packs and cleaned the posts on them, they were pretty rough. Didnt help any though. Few of the boots and plugs looked pretty grimey.

So my questions are. How do I know which bank is bad? If thats whats wrong. And besides color arent both coil banks the same? So I can just buy a silver one and try it on either side to see which side was bad? I will do plugs and boots just cuz but Im just wondering about the banks before I buy one. I found some used ones at a junk yard for $75, not bad.

Am I going in the right direction???

Thanks

* 1966 Deville Convertible

* 2007 Escalade ESV Black on Black

* 1996 Fleetwood Brougham Black on Black V4P -Gone
* 1983 Coupe Deville Street/Show Lowrider -Gone

* 1970 Calais 4dr Hardtop GONE
* 2000 Deville DTS - Silver with Black Leather and SE grille GONE
* 1999 Seville STS - Pearl Red GONE

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side note:

not sure how many cars are like mine but i dont have that big air pump thing on top of my back coil pack. I have a friend that has a 2000 dts and he has it, it sounds like a loud vacuum when he starts the car in the winter. I think he got it fixed now though. My car has never had that part. Made it nice to get the back pack off though!! :D

* 1966 Deville Convertible

* 2007 Escalade ESV Black on Black

* 1996 Fleetwood Brougham Black on Black V4P -Gone
* 1983 Coupe Deville Street/Show Lowrider -Gone

* 1970 Calais 4dr Hardtop GONE
* 2000 Deville DTS - Silver with Black Leather and SE grille GONE
* 1999 Seville STS - Pearl Red GONE

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Did the P0300 begin while you were rocking it?

If I am not mistaken, when you rock the car, you need to take the traction control off and limit your RPMs as you will burn up your brakes. I believe proper procedure for rocking the car is covered in the owners manual. If the brakes can not limit the spinning the PCM will begin shutting down cylinders to limit torque. It does this by shutting down fuel flow to specific injectors.

Did the P0300 begin while you were rocking it?, or did you have it before the rocking incident?

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

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never had it before i got stuck this morning. And it probably happened towards the end of rocking it. I just think its gotta be hard on the engine to constantly be using the traction control being stuck and the tires just spinning. It usually is only used for a few seconds on a icy road...

So you are thinking maybe injector?

* 1966 Deville Convertible

* 2007 Escalade ESV Black on Black

* 1996 Fleetwood Brougham Black on Black V4P -Gone
* 1983 Coupe Deville Street/Show Lowrider -Gone

* 1970 Calais 4dr Hardtop GONE
* 2000 Deville DTS - Silver with Black Leather and SE grille GONE
* 1999 Seville STS - Pearl Red GONE

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I don't know how long you ran the car after getting stuck, but if you backed into a big pile of snow I would check inside your tail pipes to see if you packed snow into one or both of them that will cause problems until the restriction is cleared out.

no, just the front end got stuck. And Ive driven it 10 miles or more since. Ive checked over the exhaust pretty thoroughly.

I have a chance to go get that used coil pack today. Just dont know if I should. If its an injector or coil pack. I guess I could try the stethoscope trick to listen to the injectors...

* 1966 Deville Convertible

* 2007 Escalade ESV Black on Black

* 1996 Fleetwood Brougham Black on Black V4P -Gone
* 1983 Coupe Deville Street/Show Lowrider -Gone

* 1970 Calais 4dr Hardtop GONE
* 2000 Deville DTS - Silver with Black Leather and SE grille GONE
* 1999 Seville STS - Pearl Red GONE

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How high did you rev the engine during this rocking?

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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How high did you rev the engine during this rocking?

well not high because the traction control was on. If the traction control makes the coils or fuel injectors intermittantly work to slow the engine down then all that abuse probably broke one or the other?

* 1966 Deville Convertible

* 2007 Escalade ESV Black on Black

* 1996 Fleetwood Brougham Black on Black V4P -Gone
* 1983 Coupe Deville Street/Show Lowrider -Gone

* 1970 Calais 4dr Hardtop GONE
* 2000 Deville DTS - Silver with Black Leather and SE grille GONE
* 1999 Seville STS - Pearl Red GONE

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How high did you rev the engine during this rocking?

well not high because the traction control was on. If the traction control makes the coils or fuel injectors intermittantly work to slow the engine down then all that abuse probably broke one or the other?

Yes, but you said you took the traction control off, how high did you rev the engine, could you have over revved the engine?

What do you mean by "all that abuse"?

Keep in mind that the traction control is in place to stop you from over spinning the wheels, to minimize the stress on the transaxle components from the forward and backward spinning of the axles, you can snap an axle going from foward to reverse

That said, explain what you mean by abuse.

The PCM shuts off injectors, but if you burned a valve or wiped a cam lobe or lifter in the process of the rocking, that could be the cause

It would seem odd that all of a sudden you would have a bad injector or coil or PCM driver, to me this is more related to a mechanical issue.

Is the engine ticking from a lifter?

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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How high did you rev the engine during this rocking?

well not high because the traction control was on. If the traction control makes the coils or fuel injectors intermittantly work to slow the engine down then all that abuse probably broke one or the other?

Yes, but you said you took the traction control off, how high did you rev the engine, could you have over revved the engine?

What do you mean by "all that abuse"?

Keep in mind that the traction control is in place to stop you from over spinning the wheels, to minimize the stress on the transaxle components from the forward and backward spinning of the axles, you can snap an axle going from foward to reverse

That said, explain what you mean by abuse.

The PCM shuts off injectors, but if you burned a valve or wiped a cam lobe or lifter in the process of the rocking, that could be the cause

It would seem odd that all of a sudden you would have a bad injector or coil or PCM driver, to me this is more related to a mechanical issue.

Is the engine ticking from a lifter?

I dont hear any ticking. Abuse i just mean its probably hard on the injectors or coils to be shutting on and off alot more than usual. Yes traction control protected the drivetrain but I just figured its probably hard on the engine to be using the traction control that much.

I didnt really "rock" the car. I pull forward, hit the brake wait a second, shift to reverse, hit the gas, once the car stops again then hit the brake, wait a second, then go forward again. I wasnt slamming gears forward and back, i used the brake and took my time shifing.

Once the traction control was off then yes the engine revved higher. But theres a limiter and it wouldnt allow it to go over red line. Also I KNOW I didnt floor it in reverse with the traction off. Thats not necessary, I just gave it some gas to back up. I KNOW I didnt floor it.

* 1966 Deville Convertible

* 2007 Escalade ESV Black on Black

* 1996 Fleetwood Brougham Black on Black V4P -Gone
* 1983 Coupe Deville Street/Show Lowrider -Gone

* 1970 Calais 4dr Hardtop GONE
* 2000 Deville DTS - Silver with Black Leather and SE grille GONE
* 1999 Seville STS - Pearl Red GONE

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Lets see what others have to say.

Its odd that you would spontaineously get a P0300 misfire code.

An engine will misfire for multiple reasons, compression low from various sources, fuel injectors, no or weak spark from various sources.

The injector pulses continuously, the PCM just shuts it off, the injectors dont work any harder due to the traction control turning off the electrical pulse.

If the plugs have high mileage on them they may be done and need replacing. Revving the engine could have fouled one with loosened carbon. Id pull the plugs and replace them, its not likely that you have a bad coil from that. Do the plugs have 94K on them? They are done much earlier than the 100K recommended change interval

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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Lets see what others have to say.

Its odd that you would spontaineously get a P0300 misfire code.

An engine will misfire for multiple reasons, compression low from various sources, fuel injectors, no or weak spark from various sources.

The injector pulses continuously, the PCM just shuts it off, the injectors dont work any harder due to the traction control turning off the electrical pulse.

If the plugs have high mileage on them they may be done and need replacing. Revving the engine could have fouled one with loosened carbon. Id pull the plugs and replace them, its not likely that you have a bad coil from that. Do the plugs have 94K on them? They are done much earlier than the 100K recommended change interval

I bought the car with 65k and i doubt they had been changed before that. The maintanence for this car says to change the plugs at 100k so Ive been waiting. Your right it could be a plug or two. Taking them out I will also see which cylinder is misfiring.

Whats the plug that has to go in these engines? Its like a delco platinum 2 or something Ive read?

* 1966 Deville Convertible

* 2007 Escalade ESV Black on Black

* 1996 Fleetwood Brougham Black on Black V4P -Gone
* 1983 Coupe Deville Street/Show Lowrider -Gone

* 1970 Calais 4dr Hardtop GONE
* 2000 Deville DTS - Silver with Black Leather and SE grille GONE
* 1999 Seville STS - Pearl Red GONE

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It was also -4 degrees out yesterday morning and the car had not fully warmed up. The gauge usually goes to dead middle on the temp gauge, it was at maybe 1/4. So not cold but not normal operating temp.

* 1966 Deville Convertible

* 2007 Escalade ESV Black on Black

* 1996 Fleetwood Brougham Black on Black V4P -Gone
* 1983 Coupe Deville Street/Show Lowrider -Gone

* 1970 Calais 4dr Hardtop GONE
* 2000 Deville DTS - Silver with Black Leather and SE grille GONE
* 1999 Seville STS - Pearl Red GONE

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The smell was probably (I am guessing) the catalytic converter...from excess gas being dumped in it from the misfire.

I doubt that you hurt anything mechanically from the way you described how you got it unstuck.

I kinda agree with Mike (Body by Fisher) that you probably fouled a plug.

I would start there.

At 94,000 they probably need changing anyway. :D

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excellent, I will change the plugs and boots today. Now i just need to find that part number for the plugs that this engine needs...

* 1966 Deville Convertible

* 2007 Escalade ESV Black on Black

* 1996 Fleetwood Brougham Black on Black V4P -Gone
* 1983 Coupe Deville Street/Show Lowrider -Gone

* 1970 Calais 4dr Hardtop GONE
* 2000 Deville DTS - Silver with Black Leather and SE grille GONE
* 1999 Seville STS - Pearl Red GONE

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For future reference, and maybe its an old wives tale for me, but I would ensure the engine is fully warmed up before pushing the RPMS way up, at that temp the oil is thick and may not reach the top of the engine as needed

What viscosity of oil are you using?

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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For future reference, and maybe its an old wives tale for me, but I would ensure the engine is fully warmed up before pushing the RPMS way up, at that temp the oil is thick and may not reach the top of the engine as needed

What viscosity of oil are you using?

the recommended 5/30

* 1966 Deville Convertible

* 2007 Escalade ESV Black on Black

* 1996 Fleetwood Brougham Black on Black V4P -Gone
* 1983 Coupe Deville Street/Show Lowrider -Gone

* 1970 Calais 4dr Hardtop GONE
* 2000 Deville DTS - Silver with Black Leather and SE grille GONE
* 1999 Seville STS - Pearl Red GONE

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Ok, tonight I changed the plugs and plug boots. Plugs i used the delco platinum professional ones. The plugs that came out of it were denso. Ive had the car from 65k to 94k not sure if those are originals. Every one of them the gap looked good so no fouling. 7 of them were white and 1 was mostly black. Not super wet but black and not white like the rest. This was a front plug. Hooked it all back up and still the exact same misfire. I put my fingers on all of the injectors I could feel each one ticking.

So front coil pack then? I ran an ohm meter across all of the coils front and back to each other and to the ground and they all read the same, doesnt mean one isnt bad. But the module inside the coil pack could be bad also and that is sealed up.

* 1966 Deville Convertible

* 2007 Escalade ESV Black on Black

* 1996 Fleetwood Brougham Black on Black V4P -Gone
* 1983 Coupe Deville Street/Show Lowrider -Gone

* 1970 Calais 4dr Hardtop GONE
* 2000 Deville DTS - Silver with Black Leather and SE grille GONE
* 1999 Seville STS - Pearl Red GONE

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Don't assume that the plenum is OK by looks. They usually rip on th bottom where it can't be seen. Spray some Brakleen and listen for an RPM increase.

T/C will use the ABS to control wheel spin. If that is ineffective, THEN it will disable injectors.

You can't over rev it. The rev limiter will kick in at 4000 RPM and disable the injectors.

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Don't assume that the plenum is OK by looks. They usually rip on th bottom where it can't be seen. Spray some Brakleen and listen for an RPM increase.

T/C will use the ABS to control wheel spin. If that is ineffective, THEN it will disable injectors.

You can't over rev it. The rev limiter will kick in at 4000 RPM and disable the injectors.

I will check the plenum with the spray, its free, maybe tomorrow

* 1966 Deville Convertible

* 2007 Escalade ESV Black on Black

* 1996 Fleetwood Brougham Black on Black V4P -Gone
* 1983 Coupe Deville Street/Show Lowrider -Gone

* 1970 Calais 4dr Hardtop GONE
* 2000 Deville DTS - Silver with Black Leather and SE grille GONE
* 1999 Seville STS - Pearl Red GONE

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It could something as simple as a bad plug WIRE.

Just a thought....

Remember the KISS principle...

I know your just being helpful, but i dont know how many times ive read someone on these boards telling another to change their plug wires on their 2000+ northstar. They dont have plug wires. I thought it was widely known? They have some rubber boots that connect the coil to the plug which are JUST AS expensive <_< I did change those with the plugs.

Looks like next step is checking the plenum connector boot thing and buying a used coil pack.

Though.... my friend has a 2000 dts as well, and if i could borrow his car for 30 minutes tomorrow i could try out one of his coil packs to see if thats really the problem... I may do this!

* 1966 Deville Convertible

* 2007 Escalade ESV Black on Black

* 1996 Fleetwood Brougham Black on Black V4P -Gone
* 1983 Coupe Deville Street/Show Lowrider -Gone

* 1970 Calais 4dr Hardtop GONE
* 2000 Deville DTS - Silver with Black Leather and SE grille GONE
* 1999 Seville STS - Pearl Red GONE

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....I know your just being helpful, but i dont know how many times ive read someone on these boards telling another to change their plug wires on their 2000+ northstar. They dont have plug wires. I thought it was widely known?

It is widely known among folks with a 2000+ Northstar powertrain.

But not everyone remembers exactly which model year the coil-on-plug (COP) change happened on Northstars.

High voltage plug wires was the standard for so long (six or more decades) that a "check the plug wires" response is burned into long-term memory.

Jim

Drive your car.

Use your cell phone.

CHOOSE ONE !

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It could something as simple as a bad plug WIRE.

Just a thought....

Remember the KISS principle...

I know your just being helpful, but i dont know how many times ive read someone on these boards telling another to change their plug wires on their 2000+ northstar. They dont have plug wires. I thought it was widely known? They have some rubber boots that connect the coil to the plug which are JUST AS expensive <_< I did change those with the plugs.

Looks like next step is checking the plenum connector boot thing and buying a used coil pack.

Though.... my friend has a 2000 dts as well, and if i could borrow his car for 30 minutes tomorrow i could try out one of his coil packs to see if thats really the problem... I may do this!

Sorry about that.

As Jim D noted...

I do not have a 2000 model, and I did not remember "EXACTLY" when they changed to COP.

I have been working on cars since the mid 50's and the VAST MAJORITY of them all had plug wires.

Even my 2006 Chevy van has plug wires. :D

I actually WAS just trying to be helpful...I thought it may have been something that just got overlooked, and maybe needed to be revisited.

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Everyone is trying to help here. The NS went to COP in 2000, I have made this mistake multiple times, among other year to year changes. Your problem acts like an ignition wire. You should check the compression in #8 since that plug looked different

It could something as simple as a bad plug WIRE.

Just a thought....

Remember the KISS principle...

I know your just being helpful, but i dont know how many times ive read someone on these boards telling another to change their plug wires on their 2000+ northstar. They dont have plug wires. I thought it was widely known? They have some rubber boots that connect the coil to the plug which are JUST AS expensive <_< I did change those with the plugs.

Looks like next step is checking the plenum connector boot thing and buying a used coil pack.

Though.... my friend has a 2000 dts as well, and if i could borrow his car for 30 minutes tomorrow i could try out one of his coil packs to see if thats really the problem... I may do this!

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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