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random misfire on start up 2003 Seville


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I would pull your coil modules and look for cracks in the housings of the coils. Classic symptom of bad coils. Another thing to look at is if the cam cover gaskets are leaking you will find oil in the spark plug holes where the wires go.

GM FAN FOREVER

Nice, clean, luxury= fine automobile

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On your car the coils are grounded through the ignition modules, upon which they are mounted. The ignition modules are grounded at G108, which is a stud in the rear of the right (firewall side) head or engine block on the driver's side below the ECT. It may be hard to reach because, like the ECT, it is under the EGR valve.

The drawing in the 2008 FSM does not make it clear whether the grounding stud is in the head or block, but it shouldn't make any difference for the purposes of checking this ground. I would check the resistance to ground of the BLK/WHT wires coming out of the ignition module to verify the grounds.

We still have not established conclusively what the cause is. The essentials for good engine performance are air, gas, spark, compression, and timing. There are few conditions that will not throw a code. We still haven't found the miss counts and established whether this is just one or two cylinders or a random miss. Thus we are going by experience and indirect observation online.

Please find out how to get at the individual cylinder miss counts with your scan tool and get at them. This is just about the only hard data that we know is there but we haven't accessed.

<future hope>Existing technology will allow detection of spark waveforms as current and voltage profiles for each cylinder, and similar data for fuel injector waveforms. Oxygen sensor waveforms are already available, but would be enhanced by the use of wideband oxygen sensors on the manifolds; I have been told that narrow-band oxygen sensors are still being used, probably for reliability and longevity, and possibly for accuracy. But given this data, along with ECT, TPS, MAP, and MAF sensor data, it's not hard to see how spark, gas, air and compression problems can be determined by software which can then throw a code that would be very helpful in cases where existing OBD systems don't throw a code. </future hope>

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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'm wondering if it's electrical cause randomly sometimes it will click when trying to start or it will turn over half way then stop.I did get the battery light and check charging lights along with a code for the generator L Terminal (I think) but I figured that was due to my iac plunger broke and wouldn't let the car idle past 500 rpm.I never got those warning lights or generator code after changing the iac but the the p0300 has gotten worse since then.a lot of time with key on my volts will read 11.9-12.2 but I had my battery tested and they said it was ok , can't they test the alternator too?I really do thank y'all for your help.

sts03

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A very low idle speed can cause an alternator charge light to flicker or even come on, and possibly there will be a code thrown in that circumstance. If the alternator codes don't come back with the IAC fixed, you are probably OK there. If you have been driving the car, the battery is probably more or less fully charged now.

The battery should read at least 12.0 Volts when the engine off; any less means that it is dangerously discharged. With the key on and the engine off, it may drop a tad below 12.0 Volts if it is low. It should *never* drop below 9.0 Volts even when cranking the engine; if it does, you will have several module throw "low voltage" codes and possibly malfunction, and lots of bogus codes will be thrown. When that happens, charge the battery (by driving it, a trickle charger, or disconnecting the battery and charging it), clear the codes, and see what comes back.

What other codes to you have, if any, other than the P0300? Have you figured out how to scroll the freeze frame data and get to the miss counts?

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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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the p0300 is the only code for now ,the scanner i borrowed from advanced auto and im still trying to learn how to use it fully .i will try to get the miss counts .also im not sure if this related but it started doing it around the same time and its not as random as the misfire but sometimes when i turn the key to start the car it will click one time each time i turn the key (not a fast clicking but one click for each turn)after a few tries it will start or other times when i turn the key it will turn over half way then stop and when it does finally start after a few tries it starts ruff like theres not enough juice.i had the battery tested and they said it was good.the battery terminals are clean and tight .maybe that has something to do with the starter though?my battery volts have been more than a few times 11.9 even a couple of times 11.8 but it still started .today the car started and drove fine so i went to the store and when i came out and started it it wanted to cut off and as i started driving the ses light flashed for a few seconds and when i push the gas peddle it woud studder then like it was going to die then it would start to take off then studder again.it did that a few times then it smoothed out and drove fine on the way home.i dont know if its the coil or some other electrical problem?

sts03

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The click-but-not-turn-over on start means, most likely first, that you have a bad battery, a bad battery cable to the starter, or something wrong with the starter solenoid or starter. I would go after that first because it could leave you stranded.

I don't have time to bring up the SI DVD and look at your battery cable, but the earlier Northstars had three positive cables, one to the Maxifuse block, one to the alternator, and one to the starter. The ground cable had two wires, one to the engine and one to the radiator cross-member.

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 it might be a loose cable cause i had the battery tested at aap a few weeks ago ,ill check the connections .my dads 2001 caddy had similar issues with itnot wanting to start and i think it was the neutral saftey switch .sometimes it clicks other times it will start to turn over then die .

sts03

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yea it might be a loose cable cause i had the battery tested at aap a few weeks ago ,ill check the connections .my dads 2001 caddy had similar issues with itnot wanting to start and i think it was the neutral saftey switch .sometimes it clicks other times it will start to turn over then die .

If your car has the multiple cables... pull back the red cover and separate the cables and clean each one.

Corrosion gets in between the cables, sometimes causing erratic connections.

If your cables don't connect TIGHTLY, you may need to put a spacer washer in between the cable ends so that it will be nice and tight.

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I didn't read the full post. But, if your thinking a head gasket be careful once you get home at night and the car is sitting till the next morning, loosen the radiator car to release pressure. If its smooth in the morning your kinda know what your facing.

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youi might have the common ground cable going bad from the alternator to the right front frame rail. If your coming home at night and the car is running fine and when you start the car in the morning cold and its running rough and SES light is flashing with a rough idle that goes away sounds like a head gasket. Are you loosing coolant?Do you smell coolant?

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1. If you have a head blown, you will see white smoke from the exhaust when you idle and GAS ON IT. You have 8 coils and plugs, where they changed out? Came in on the in of the forum. I kept getting a rough hesitation at start up and code 0300 for random misfire. I started with each coil: as the engine was running, unplug one at a time. When you see a change in the engine, that will be a good coil. When you see NO CHANGE that would be the one to key on. Can you hear any air or a vacuum leak?

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Are you still having problems? I have a 2005 deville and I went through the same process with 0300 code and found my problem

Which was??????

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

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Now the ses light flashes after starting it up after it's warmed up and and it acts like it's going to die completely then it will smooth out.I am loosing coolant for a few months and I thought it was the crossover cause I saw coolant leaking from the gasket,I changed those gaskets a few weeks ago but I'm still loosing coolant with no visible leaks.I did a block test and the fluid changed colors so I guess the block test doesn't lie.I'm pretty sure the coolant was low enough not to taint the test(it was 1-2 inches below the proper fill line).it's never ran hot, the highest the needle has gone is to the first tick past the middle mark and that was sitting in traffic I've put it 2nd gear and wot to redline a few times lately and the needle doesn't budge.any recommendations what studs serts etc.. to use .which kit is more reliable and comes with most of what you need (user friendly)i know jakes studs come with the drills ,taps ,the plate thing to drill it in straight etc.. but it is kinda pricey does any of the other kits come with the extras ?

sts03

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The TimeSert inserts come with a kit that includes all you need to drill and tap properly. You can buy a used kit and new inserts. You may even be able to rent or borrow a Timsert Northstar alignment and drill bit kit.

If all you have so far is coolant loss with no overheating, you have time to plan the repair. If you drive the car every day at highway speeds, you have a few weeks. If you drive around town, a few months. Eventually overheating will force you to do the repair.

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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If you purchase a new Timesert kit I believe it comes with 10 inserts but verify that with the person at Time Fastener Co. You will need to purchase 10 additional inserts. A used kit will need all 20 inserts.

You will need to make sure you buy the correct insert kit for your car as the threads and length of the bolts have changed over the years.

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

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Yea I was reading that that it only comes With ten inserts not sure why.what's y'all view on the the other products like ccc,suregrips,normserts?

sts03

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Timeserts or Norms. you can sell the norms kit after on CL for good money. Or, if your in a pinch you can check uship and ship the car to me and i can get it done for you.

B & B automotive LLC 46250

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There are 10 head bolts to a side. Some people would want to pull only one head. :glare:

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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im set on either the time serts or suregrip studs ,ive noticed nobody so far on here recommends the studs ,whats the reason?what about using big serts ,from what i read that they are for if the time serts fail but can you use them in the first place ?ive read on some othe sites atleast for pre 2000 northstars that the crankshaft and water pump pulleys have to be removed when doing this job,would this be the same for 2000+ ?

sts03

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Here's my opinion. Others may differ.

Any head bolt repair will require that new head bolt threads be drilled and tapped. The threads are deep in a well that allows long head bolts to stretch in tension so that the aluminum engine can heat and cool without pulling the head bolts or releasing the clamping force on the heads. This requires that an alignment plate be bolted on the block that provides a way to keep the drill aligned, and the tap aligned. Both drilling and tapping need to be done carefully, with proper lube, and slowly, to avoid overheating and weakening of the new threads in the block. Failure to properly align both the drill and the tap, and lack of patience in drilling and/or tapping, will result in weaker threads and possible failure of the job.

TimeSerts: Lowest cost, repair for keeps if done properly. Factory recommended by GM, Ford, VW, Porshe, and others.

BigSerts: Bigger hole, for use when another repair fails. Some people try Helicoils or fail to drill and tap properly, and need a BigSert. Or, if a TimeSert pulls out when the head is pulled again, you need a BigSert for that hole. If the BigSert fails, the block is scrap. Done properly, this repair is also for keeps.

Studs: Repair is for keeps if done properly. Disadvantage is that you can very easily scratch a head mating surface in assembly, which can cause head gasket failure. Advantage is that you can pull the head again without disturbing the threads at the bottom of the bolt hole well. If a stud *does* unscrew, you will need to use an insert in that hole, which can get complicated. Another issue for me is that the torque-and-twist specifications are a function of the bolt/stud diameter and alloy or a given clamping force and performance when the engine is heated and cooled, and who figures that out for the studs?

The whole argument for studs is that the head bolts pull because they are weak or the threads are weak, which isn't the case. For a good time, see

http://chrfab.com

and browse lots of 1993-1999 Northstars that are modified and turbocharged for sand cars and for racing; all of them with head work are Timeserted because you can't trust the threads once a head bolt has been pulled in any aluminum block. They use stock head bolts.

Either a stud or an insert repair, done carefully and correctly, is good for keeps. Just use red coolant and change it every three or four years.

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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No need for studs. Never used them and hopefully never will. Of the 20 + years working on these cars I have perfected a method and I have no want or need to perfect my method. Timeserts, Norms, a smaller version of Norms, what else do you need. The item listed below works well too.

ebay

131001300509
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If you used Bigserts as a first repair, you will need to drill out the holes with a drill first which means you'd need a second drill bushing for that operation. You would also need to purchase four step dowels from Timesert since the Bigserts will open up the dowel holes enough that the factory dowels won't stay put in the block. Unless you already had the Bigsert kit, I don't know why you would want to use them for the first repair.

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

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