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Old 02-08-2013, 07:28 PM   #1
Schmilsson
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Default LW300 Misfiring; P0306; Vaccum Leak?

Just bought a 2001 LW300 V6 with 160,000 mi. on it three weeks ago when I got to college because it was all I could afford. Before I purchased, I went to a mechanic who said the SES light that was on was because of the MAF Sensor and the EGR Valve and would be a pretty easy fix. I bought the car, and then (2 weeks ago) changed the MAF Sensor, the EGR Valve, changed all 6 spark plugs, did an oil change and replaced the air filter and put a bottle of Seafoam in the gas tank for good measure, all to try and cure an existing rough idle problem. These fixes did nothing to help the rough idling, although the SES Light did in fact turn off for a week and a half after the fixes. The rough idling has gotten progressively worse over the past few weeks since purchasing, and is at it's worst the more the car heats up. In fact, after it is heated up I sometimes can't start it up unless I give it some gas while turning the key. But when the car is cold in the morning, it starts with no problem. Two days ago, the SES light came on again with code P0306 (cylinder 6), but like I said I just changed the plugs. I am thinking my problem is with a vacuum leak, and a mechanic I talked to said it was probably the hoses on the intake runners and to just replace them. I wanted to see what you guys thought before dropping $180 on those small hose pieces though. Sorry for the long post, wanted to be thorough to try to find an answer to this rough idling. Thanks!

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Old 02-08-2013, 07:55 PM   #2
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Default Re: LW300 Misfiring; P0306; Vaccum Leak?

Also should mention 2 days ago I had a SES code come up, which I believe was "P1406 EGR Valve Pintle Position Circuit", something about the EGR valve being 10% out of position, but I had the Autozone guy clear it because I had just replaced that EGR Valve and it hasn't come back yet, only the P0306 this time.

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Old 02-08-2013, 08:00 PM   #3
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Default Re: LW300 Misfiring; P0306; Vaccum Leak?

Find another mechanic. With 160k miles there are hidden issues that comes with age. One may be a possible partially clogged catalytic converter. There are three in your L300; one coffee can pre-cat in each exhaust manifold and the main one in the exhaust system. Find a shop or someone that knows how to test for blocked catcons. Search within these forums for suggestions.

Although not failure prone, ignition coil packs can fail. Examining the spark plugs can reveal if spark is missing. A compression test can reveal more.

Last edited by fdryer; 02-08-2013 at 08:08 PM..

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Old 02-08-2013, 08:15 PM   #4
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Default Re: LW300 Misfiring; P0306; Vaccum Leak?

Hey thanks for the quick response. Well, I guess I'll take it to a catalytic converter guy then tomorrow for diagnosis. Now that you say that, I'm looking at the Haynes Repair Manual for it and it does list "Restricted Catalytic Converter" under possible scenarios for "Engine Starts but Stops Immediately". I'll post an update when I know more...

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Old 02-09-2013, 08:13 PM   #5
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Default Re: LW300 Misfiring; P0306; Vaccum Leak?

Well I took the advice and this time took the car to Meineke, figuring maybe an established nationwide car repair service would be more reliable for diagnostics rather than the local mechanic. The Meineke guy first freaked me out after I told him the symptoms by telling me "I bet it's a blown head gasket- you bought a lemon buddy!" He then said he would check it out for me just to make sure, and an hour later he comes back with a self-assuring grin and tells me "Good news! It was just a bad ignition coil, so just replace the 2-4-6 igntion coil and it should take care of everything." The weird thing was, he didn't even charge me to diagnose this after an hour of looking at it, but I figured maybe they only charge for repairs and he was being nice. Anyways, I went and bought the ignition coil for $110 and put it in, and sure enough it didn't do diddly squat. I still have the same rough idling problems, and P0306 still came up after completing the drive cycle. So I've gone to three mechanics so far, and have changed out an ignition coil, MAF sensor, EGR valve, and all 6 spark plugs to try and cure this problem per the mechanics recommendations, and have gotten nowhere. Some mechanics refuse to even look at a Saturn V-6 because it's "nothing but problems." I bought the car half-based on the reputation of Saturns as solid cars, so I was surprised by this. I guess tomorrow I'll take it to Firestone where they rob you blind, and see what they think it is. After that, I'm about out of ideas for what this rough idling and P0306 could be. I'm due for the emissions test in 8 days, and have to figure it out by then because Louisiana doesn't do extensions

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Old 02-10-2013, 01:52 AM   #6
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Default Re: LW300 Misfiring; P0306; Vaccum Leak?

I'm not sure what to make of all this except that you've proven one Meineke mechanic doesn't know squat and another one knows even less - the one that claims Saturn V6's are nothing but trouble. Maybe its because this person doesn't know how to say "I'm not very well trained with EFI systems and cannot troubleshoot". There are mechanics that are "replacement artists", mechanics that don't know anything but follow others to replace parts, and then mechanics that actually have a brain between their ears and are booked forever because of honest repairs with a terrific business. Good mechanics are hard to find sometimes. I don't think you found a real mechanic yet.

I'm not a mechanic and learned about the two failure modes of crank position sensors from here, Saturnfans. Books and theory of operation is one thing but real world experiences matching theory goes a long way to a well trained mechanic/technician. All the smarts in the world don't mean squat without experience and all the experience in the world doesn't make a person smart. Combining the two rounds out a person. I wonder what the Meineke mechanic would say if you were to convey your disappointment of his recommendations that a new ignition coil pack wasn't the answer....................

Disconnecting pre-cats for examination to check for crumbling cat guts blocking exhaust flow is difficult and time consuming. Its not something to throw out as a possible problem without some thought behind the other possibilities like a coil pack. And then there's the main catcon that may be suspect too.

I hope my L300 lasts for as long as I need it. With just under 78k miles and close to 10yrs ('03), one O2 sensor, thermostat, and crank sensor have been replaced. Our L300's are no more troublesome than any other Saturn. Some members are well past 200k miles without issues. Others have replaced their body control modules more so than other Saturn models. Mine still works for now. Every car has its own 'quirks' that adds character to the model. Some owners faint when quirks announce themselves while others simply look past the minor flaws and deal with it. Some are horrified that a thermostat replacement requires major parts disassembly compared to most t-stat replacement. If one doesn't accept the quirks then maybe the car isn't what was expected. I didn't like the two day ordeal to replace my t-stat but its still cheaper than paying someone several hundred dollars to do it. I'm slow - four hours is a rough estimate for normal repair time.

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Old 02-10-2013, 02:06 AM   #7
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Default Re: LW300 Misfiring; P0306; Vaccum Leak?

yeah i totally feel you fdryer. my only issue is a rash of bad luck after being to three mechanics and changing a myriad of parts and still not being set to pass the emissions test. in louisiana, they only give you one month to pass, and no more extensions after that. so i've been fixing different things for the past few weeks but to no avail. that's why i say now is the time to go to the last line of defense, the firestone corporation, and have them tell me what is wrong with it. i'm not trying to be totally cheap, i'm just looking for a reasonable diagnostic to work off of, whether it be me fixing it from my haynes manual or them fixing it for three times the cost. mechanics are like doctors in that they have the ability to name their own prices. im just up against the louisiana emissions laws now (which are the strictest ive ever known, me being from illinois) and must get it fixed this week or else be relegated to not being able to make it to classes.

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Old 02-10-2013, 02:34 AM   #8
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Default Re: LW300 Misfiring; P0306; Vaccum Leak?

Other than Firestone, GM dealers are supposed to be expert on their own line of autos whether its a Corvette or Saturn. 'Supposed' is the key word.

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Old 02-10-2013, 01:47 PM   #9
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Default Re: LW300 Misfiring; P0306; Vaccum Leak?

K well Firestone was who I went with today, mostly because they are open on Sundays. I paid them $115 to diagnose the problem, and basically what they came back with for my money was "Codes that are pulling are P0300 MISFIRE RANDOM and P0306 MISIFRE CYLINDER #6; Advised customer to check timing to see if the marks line up and if not the timing needs to be changed. Recommend the dealer." So in essence, I just lost more money for what might be somewhat negligible information... BUT, they did do a compression test and checked the catalytic converts and said all are fine, hence the guy thinking that the only other thing it could be is the timing, so at least this is getting wittled down (although I'm spending too much money on wittling). He also said he wasn't very confident that it was the timing though, and that it would cost $200 to check to see that was indeed the culprit, and if it turned out not to be then he would be out of answers for me. Does anyone have an opinion on this timing suggestion, and is that something I can check myself with my modest set of tools and Haynes manual? I guess my only other option is to go to the dealer now, but I'm already so far in the hole financially with this whole scenario I'm trying to check here first. Thanks again for any info, especially fdryer!

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Old 02-10-2013, 01:56 PM   #10
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Default Re: LW300 Misfiring; P0306; Vaccum Leak?

Oh I should also note that he said if it wasn't the timing, then the ECM has to be fixed. But I'm not sure that would be causing all my rough idling...

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Old 02-10-2013, 03:27 PM   #11
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Default Re: LW300 Misfiring; P0306; Vaccum Leak?

You said you changed the 2-4-6 coil pack. That is the one in the front, (towards the radiator). Lots of people think Cyl 1 is in the front but it is actually in the back. Check for a vacuum leak by spraying carburator cleaner
around the rubber coupling for the #6 intake runner, you may have folded it over on the bottom or it may have cracked during access to the spark plugs.
A mis-fire may also be caused by a faulty injector or low compression on that cyl.

Mike

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Old 02-10-2013, 03:48 PM   #12
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Default Re: LW300 Misfiring; P0306; Vaccum Leak?

Yeah I just changed the front (2-4-6 ignition coil) yesterday and it didn't turn the P0306 off. I talked to my buddy back home in illinois who is a pretty knowledgeable mechanic and he said he didn't think the timing would be the cause, since that would mess everything up really bad and not just cylinder 6. He told me to try what you (mikewiss) just said about the fuel injectors as well, so I went out and got myself a multimeter to check to see if the OHM's are off on that fuel injector compared to the rest of them. I've never done this before but hopefully I'll figure it out with the help of the Haynes manual. When I last changed that ignition coil I inspected the runner hoses and they all seemed in good shape except for the one over #2 (front side of engine, all the way to the right but before the big one) which had a small tear at the end. If this fuel injector test doesn't yield any answers, i'll start getting those hoses ($23 a piece from the dealer just for that small piece of rubber) depending on if the carb cleaner test shows me anything. I'll update when I'm done doing these, thanks again for your help

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Old 02-10-2013, 04:04 PM   #13
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Default Re: LW300 Misfiring; P0306; Vaccum Leak?

Carb cleaner test didn't show anything: I tried it on all the hose fittings for the intake runners and it neither sucked in to the runners or made the engine choke at all, so it doesn't appear that is the case. I'm a little confused as to where the fuel rail or injectors are but I'm still lookin...

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Old 02-10-2013, 04:29 PM   #14
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Default Re: LW300 Misfiring; P0306; Vaccum Leak?

Well after reading the Haynes Manual, it seemed like accessing the fuel injectors to check the OHM's would be quite a project, so I called the Firestone back just to verify that he checked those before I started taking my car apart. He 100% guaranteed me that my fuel injectors are fine, and said the fuel system checked out completely when he tested it including the pressure and the injectors. He also guaranteed me that it wasn't a vacuum leak after the compression tests and whatever else he did on it, and also not the catalytic converters, so I guess I'm just going to take it to the dealer tomorrow morning and if it ends up being any of those things I'm gonna take the receipt back to Firestone and have them refund my money for the diagnosis. I'm pretty much out of other ideas at this point

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Old 02-10-2013, 04:46 PM   #15
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Default Re: LW300 Misfiring; P0306; Vaccum Leak?

Unfortunately you inherited a problem from the place you bought the car from and the first mechanic either lied or covered up for the dealer. They had no intention of honoring something wrong with this LW300.

At 160k miles, the timing belt along with water pump and new plugs were needed back at 100k miles. Retaining the original timing belt is a risk anyone takes - any failure with this belt almost guarantees bent valves and/or pistons. While not contributing to this P0306 issue, examining the belt should be the minimum done so you can see if any wear dictates immediate replacement. Bearings and water pump are exposed for inspection once the cam cover is removed.

With plugs and coil pack replaced, this leaves the injector in question or possible cylinder/valve damage. The compression test, if it was done should provide numbers for each cylinder. Was it actually done and if so what are the numbers? Anyone can say anything behind our backs. A compression test requires removing spark plugs. You already know what it takes to get to the spark plugs or was this done by someone else?

When the main intake manifold is removed, all injectors are revealed. Removing spark plug #6 should have shown whether or not it shared the same color as the others. Spark plug reading is not rocket science.

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Old 02-10-2013, 05:14 PM   #16
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Default Re: LW300 Misfiring; P0306; Vaccum Leak?

fdryer: as i said before, all 6 spark plugs were replaced 2 weeks ago, and when I put them in they were all gapped properly. as for the compression test, as i said before that was done by Firestone, which is pretty much the most reputable auto service chain out there. the mechanic told me repeatedly that he did a compression test among other things, but no i did not think to get any numbers from him for this nor did anyone recommend me to get numbers from this procedure, otherwise i'd have them to post for you. i'm not a mechanic, so im not going to intuitively know all facets of this process. all i know is what i read in the haynes manual, hear from the mechanics i've brought it to (four soon to be five), and read on the internet.

as for purchasing a bad car, it obviously seems pretty apparent that i did, but at the time i had just been in a bad car accident and totaled my previous car, so i had little time or money to purchase a new one before school started. this one seemed to run great during the test drive, and the SES codes were verified by a mechanic before i bought it who gave me the impression all i would have to change would be the MAF sensor and EGR valve, and maybe the spark plugs, which i did. having the budget i had to work with, i took a chance on a reputable brand (it was either this or a chevy cavalier with similar miles) that needed a couple quick fixes, and it doesn't look good at the moment for me capitalizing on it.
i'm bringing it to the dealer tomorrow which is the final stop, and if that turns out a bust ill probably just drive it into the bayou and go purchase a bicycle

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Old 02-10-2013, 05:23 PM   #17
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Default Re: LW300 Misfiring; P0306; Vaccum Leak?

i think i see what you're saying though, that i should have looked the colors of the spark plugs before i threw them away for signs of injector issues, but i've never done that before (only checked gaps or replaced) so i didnt think of it. but again, the Firestone guy guaranteed me none of those were the issue, although i guess it's possible he just lied to me

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Old 02-11-2013, 06:04 PM   #18
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Default Re: LW300 Misfiring; P0306; Vaccum Leak?

Quote:
Originally Posted by Schmilsson View Post
Just bought a 2001 LW300 V6 with 160,000 mi. on it three weeks ago when I got to college because it was all I could afford. Before I purchased, I went to a mechanic who said the SES light that was on was because of the MAF Sensor and the EGR Valve and would be a pretty easy fix. I bought the car, and then (2 weeks ago) changed the MAF Sensor, the EGR Valve, changed all 6 spark plugs, did an oil change and replaced the air filter and put a bottle of Seafoam in the gas tank for good measure, all to try and cure an existing rough idle problem. These fixes did nothing to help the rough idling, although the SES Light did in fact turn off for a week and a half after the fixes. The rough idling has gotten progressively worse over the past few weeks since purchasing, and is at it's worst the more the car heats up. In fact, after it is heated up I sometimes can't start it up unless I give it some gas while turning the key. But when the car is cold in the morning, it starts with no problem. Two days ago, the SES light came on again with code P0306 (cylinder 6), but like I said I just changed the plugs. I am thinking my problem is with a vacuum leak, and a mechanic I talked to said it was probably the hoses on the intake runners and to just replace them. I wanted to see what you guys thought before dropping $180 on those small hose pieces though. Sorry for the long post, wanted to be thorough to try to find an answer to this rough idling. Thanks!



Okay after reading through this thread there could be a number of issues that are actually causing the problem that you are accepting the word of the various mechanics you took it to as the truth. Go to a local parts store and rent a compression tester for the day and test all the cyls yourself.

If they all come up roses then here are the following things that have solved issues with the same engine

Now one thing that may be happening is that your CPS or your CMP could be getting Iffy when it warms up it begins to fail. (this solved another rough idle car I worked on with the same engine) Sometimes it will throw a bad code and sometimes not. Get yourself a can of air and turn it upside down so it sprays
the liquid (warning it comes out at -40) . run the engine till it got to temp and began running like shait. Then stop the engine and spray the CPS for a little bit and restart the engine. If you are back to smooth running, TIme for a CPS.

These are the basics if you rolled it into my shop I would be looking at very seriously from the get go however. Air leaks in the 3.0 make this engine run like hell.

Check for air leaks in the Air Induction system (e.g., in the intake manifold)
Check for air leaks in the PCV system and in its related hoses and/or valve
Idle air inlet passage or throttle bore is dirty or full of deposits
IAC valve has failed
Throttle plate, throttle shaft or linkage is damaged or sticking
TP sensor is out-of-range or "skewed" high

If you have done all of that first, Then I would move on to injector(s) or another possibility that your valves may be sticking a little. I would put some top end lube in it and see what happenes.

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Old 02-12-2013, 02:36 PM   #19
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Default Re: LW300 Misfiring; P0306; Vaccum Leak?

Thanks again everyone for responses, this is a great website. My car is still being worked on at the Saturn dealership (they've been going through it for 5 hours now), and it sounds like they found a vacuum leak somewhere, and possibly another one in a different spot, but they're also going to retest the fuel pressure to make sure that's not an issue; sounds like they've got the problem almost solved. They're doing all this for $196 w/o tax, which I think is incredibly reasonable and if the problem is indeed fixed, I think is a great deal for that many hours of shop work, and am a bit shocked, but I'll believe it when I see it.
Also, if this is the case, I'll be going straight to Firestone to get a refund for their diagnostics which will have been 100% useless.
Wish I had more time to work on it on my own, but am up against the emissions test deadline so I had to pay someone, but thanks for all the suggestions. I'll post with the specific fixes hopefully soon

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Old 02-15-2013, 09:42 PM   #20
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Default Re: LW300 Misfiring; P0306; Vaccum Leak?

Well, finally "fixed", at least in the eyes of emissions inspection which I passed today. The Saturn dealership replaced an intake hose on the back side (1-3-5), and also cleaned out the throttle body which i guess was gummed up with carbon. I'd say it idles about 90% better than before now, with a hiccup every once in a while. But I guess that will do for now... Got a refund from Firestone too for their diagnosis which was completely wrong, and will probably just go straight to the dealership from now on in instances i can't fix myself. Probably written off Meineke as well... Thanks for all your suggestions, will probably have to get to things like the timing belt and your other maintenance suggestions in the near future when I get some more money.

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