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random misfire on start up 2003 Seville


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Hi, I've been getting a random misfire usually on cold start that last maybe 30 seconds or so then the idle will smooth out.it has happened after driving to the store.sometimes the ses light will flash and if I turn the car off then back on it's fine, used a scanner from aap and the only code is p0300.so far no issues while driving it's only at start up and usually goes away when the idle comes Down to normal.my fuel pressure is 34psi at idle.any ideas?

sts03

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Not sure if 34psi is too low or not normal I believe is ~40psi

Are you losing any coolant?
If so it could be small amount is filling the cylinder while it cools off and causes the stumble on startup until it's all burned off.

Could be a leaking injector is wetting a cylinder overnight as well

I just went through this in a thread below here mine was either a bad plug/boot/injector as I ended up changing some parts around.

To see which cylinder is misfiring you need a Tech 2 scanner (my idiot self didn't go this route)- not sure if AAP or AutoZone's etc have this capability and you'd have to have it hooked up when it happens - some one may chime in if the cylinder misfire stores the value.

Your DIC will display only the P0300 code when active - it will not tell you which cylinder is the problem child

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The only two things that will do that and not set a code are a leaking FPR and moisture or arcing at the spark plug boot.

With the 2003 Seville, you can get *all* the codes from the dashboard by turning on the key and, on the A/C buttons, pressing <Off> and <Pass Warmer> together for a few seconds until all the dash lights come on like you just turned on the key, then releasing both buttons. The codes will be presented on the driver message panel.

When a miss happens on a given cylinder regularly, you will get a code P030n where n is the cylinder number that has the miss. You will NOT get the P030n on the dashboard or an inexpensive code reader, but a laptop-based or professional auto tech grade code reader will show the P030n codes. Autozone can get that code for you. It can tell you which cylinder is the problem, if you have an ignition arcing issue or some such.

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-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

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Yea I did get the p0300 code and my ses flashed a few times (only at idle when first starting the car) I went to advanced and still only showed p0300.this usually only happens when cold staring and will Smooth out After car runs for a few.I need to check the fuel pressure when it's actually misfiring maybe pump is pooping out.it's totally random some days it is fine.

sts03

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With the 2003 Seville, you can get *all* the codes from the dashboard by turning on the key and, on the A/C buttons, pressing <Off> and <Pass Warmer> together for a few seconds until all the dash lights come on like you just turned on the key, then releasing both buttons. The codes will be presented on the driver message panel.

On the '98-'04 Seville and 2000-2005 Deville, to access the onboard diagnostics, the ON/OFF and INFO UP buttons are the ones to press and hold. ON/OFF = "Yes", INFO RESET = "No". Info up/down is the toggle to scroll through the system.

Kevin
'93 Fleetwood Brougham
'05 Deville
'04 Deville
2013 Silverado Z71

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Yea I did check the codes on the dash and got p0300 random misfire, so I went to advanced auto to see what cylinder was misfiring and using their scanner it still only showed p0300.

sts03

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That may be an indication that the miss isn't from spark or anything particular to a given cylinder, such as a vacuum leak or a fuel problem. I would think that there would be another code for mixture unless the problem was of short duration, like just a second or two.

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-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

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  • 2 weeks later...

Yea it's only when starting the car and usually on colder starts, but it will smooth out when the idle comes down.the ses light also flashes sometimes when it misfires but never when actually driving only when first staring it up.every time the ses light flashes if I cut the car off then back on the ses light goes off then it is idling smooth.idk I might have to take it to the Goodyear by my house and get a diagnostics run on it but knowing my luck it won't misfire when they check it.the guy there claims they scanner will pull up everything even if it doesn't misfire when they run the diagnostics is this true?

sts03

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The dashboard will not display all the codes. There is no such thing as a P0301-P0308 on a 2003. Just P0300.

You then need a capable scan tool to see which cylinder is missing. A GM Tech 2 certainly can do it...I don't know of any other scan tools that can.

As for codes...there has to be code written for the PCM to detect a problem and turn on the SES lamp. Bad coil? Sure...bad engine ground? Maybe not. Codes are not a fail-safe cure all. They are really there to be in Federal OBD compliance.

If not...every car out there would have a SES lamp on all the time.

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my 01 eldo just had similair problem. was coil module. Both my scantools told me o304 (cylinder 4 misfire). If yours is only a 0300 it may be fuel related. your Caddy should have the same setup as my eldo. 2 coils, one for even bank. one for odd

GM FAN FOREVER

Nice, clean, luxury= fine automobile

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Most scan tools will not show a P0301-308 on the 2000-2003 models. Hence the AutoZone problem....They have to be reverse engineereed to do it.

There is no P0301-308 in the service manuals for the 2000-2003.

2004 with the new coils design do have these codes.

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Yea cause I use the scan tool from advance auto and all its giving me is p0300.this is the freeze frame from the last misfire.abslt tps%0: engine speed 1221:calc load %6.7: maf(lb/m)2.72: map (Hg)14.8: coolant °f 41:iat °46: ign adv °5.5: snd air upstre: short Fuel both banks 0.0: long fuel trim bank 1 -3.9 bank 2 -5.5 fuel sys 1 both banks open 1.?

sts03

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There should be a miss count on all of the cylinders in the freeze frame. When everything is OK, all of them will be zero or very small. When there is a miss on one cylinder, the count will be in the thousands on that cylinder.

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-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

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I took a freeze frame with the car running at 1500 rpm , absolute tps% 0: calc load 3.1:maf (lb/m) 1.26: map (Hg)7.1:iat °79 : coolant temp °201 :ign adv °15:short Fuel bank 1 0 bank 2 1.6: long fuel both banks -4.7.shouldn't the tps% be more than 00 if throttle was applied and I read online at normal operating temp the iat temp should be right below the coolant temp ?

sts03

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The data and the order it is presented will depend on your scan tool. Scroll down and look for the miss counts.

The IAT is the intake air temperature, and should be near the ambient temperature once the car has been moving for a few minutes. The ECT is on one of the cylinder heads and has nothing to do with the IAT.

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-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

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oh ok ,cause i was reading on 1a auto and they were saying the iat temp should be just under a few degrees of the coolant temp when the car is at operting temps .im starting to get exhaust smoke its like a drak gray,is the smoke more than likely related to the misfire?idk i might have to break down and go to the dealership. i would be nice if i knew what cylinders were misfire .would a bad coil pack cause the symptoms plus the smoke from exhaust?

sts03

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Please give me a link to the 1A Auto web page that says that IAT should be near a hot engine coolant temp. Saying that IAT is near coolant temperature of a hot engine tells me that what they are calling IAT is not the IAT that I am thinking of, intake air temperature, from a sensor in the air cleaner housing. "My" IAT will be about the same as the outside weather temperature, the coolant temperature will be about 200 F.

A good code reader that can read the "latent" codes can, on some models, read a P030n code where n is the cylinder number with the miss. A code reader that reads the PCM memory can read the miss counts of the cylinders, which should all be zero or just a few, unless a cylinder is missing which will result in a miss count in the thousands. This is well worthwhile to get your hands on because if only one or two cylinders are missing, troubleshooting becomes far simpler if you know which ones they are.

CTS-V_LateralGs_6-2018_tiny.jpg
-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

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oh ok ,cause i was reading on 1a auto and they were saying the iat temp should be just under a few degrees of the coolant temp when the car is at operting temps .im starting to get exhaust smoke its like a drak gray,is the smoke more than likely related to the misfire?idk i might have to break down and go to the dealership. i would be nice if i knew what cylinders were misfire .would a bad coil pack cause the symptoms plus the smoke from exhaust?

You should not take what you read at face value...

Kevin
'93 Fleetwood Brougham
'05 Deville
'04 Deville
2013 Silverado Z71

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if your IAT is close on cold startup it is normal, but if it is when up to temp either it is either very hot outside. (too hot for people) or your air intake is pulling air from by the exhaust manifolds lol

GM FAN FOREVER

Nice, clean, luxury= fine automobile

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http://www.aa1car.com/library/air_temp_sensors.htm .my bad it was aa1car.com.its toward the end of the page . how do coil packs fail on these cars, do they fail slowly and randomly or do they just go? The link may not work but it is aa1auto.com website.I googled iat sensor symptoms and there page should come up. Edited by sts03

sts03

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There is some extraenous text at the end of the link. When you delete that, the link works OK.

Others that have the two-coil-pack cars or have worked on them will give you the benefit of their experience. I can say that most coils fail gradually.

CTS-V_LateralGs_6-2018_tiny.jpg
-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

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Yea cause it's usually When starting the car doesn't matter anymore if it's a cold start or not but normal highway driving is fine only some wot are sluggish at times.the ses light so far only blinks when first starting the car or When I first take off after starting but so far it hasn't blinked at faster speeds.could a coil fail in this way or is this maybe a failing sensor?

sts03

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I really doubt that your problem is being caused by a sensor. When a sensor fails, you will get an OBD code that tells you so, and you aren't getting that; you haven't put up an OBD code list but you seem to know what the codes are.

Things that can cause a miss that varies with driving conditions and give you a P0300 include coils, plug wires, plug boots, the plugs themselves, and problems with the fuel injectors or the FPR. I would check the grounds on the ignition modules; they have two, and both must be good.

CTS-V_LateralGs_6-2018_tiny.jpg
-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

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Where are the grounds for the ignition modules? It's getting worse but still random the car drove ok for a day and Half but a few times in the couple of days when I started the car it was about to cut off and When I start to drive it will shudder bad and the ses starts to flash, if I cut it off then back on it's usually runs fine.maybe it is a loose ground or bad coil if that can cause the randomness of my problem even though it's starting to happen more often.

sts03

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