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2.2L ecotec (Vin F, 200K miles) has been generating P0300 random misfire code when idling. It runs fine at speed. I’ve replaced the following: upstream OS, ignition module, plugs, wires, EVAP purge solenoid and gas cap. The only things left I can think of is coil pack, vacuum leak or weak battery. Am I missing anything? This problem has only been apparent for 2 months.
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Where is fuel trim? Long term? Short term at idle? Course it could be mixture problem. You can see vacuum leaks from those fuel trim values among other things.
What kind of scantool do you have access to? I would recommend looking at mode 6 data to figure out what cyl is missing, and then go from there with a compression test to start.
I probably should have posted that I’m also a do-it-myselfer, not a professional mechanic. I understand what has been replied, but I don’t have the diagnostic tools. I was hoping to avoid the $250 diagnostic quote from the dealer.
Doesn’t need to be a dealer. Many local mechanics usually have a snap-on Modis or the like to do Mode 6, charging you for just a half-hour or hour flat labor fee. Just takes a bit of calling around.
Can certainly do it without this or even a basic scanner, but it will not be nearly as fast or easy to diagnose. If that’s the case, then I’d start with checking for a leak:
I would do a compression test anyway, might give you some insight. Have you ever performed a compression test? If not, you will need a compression test tool. They are pretty inexpensive, or you can even rent on from a local auto parts chain, pay a deposit, and get your money back when you return it.
You will want to take all the spark plugs out, disable fuel (remove the fuel pump relay, I believe on your car under the hood), and crank 5-6 crank rotations, record the numbers, and post them back.
I actually misspoke I believe. Ford has misfire data on mode 6, but GM I don’t think does. They have a misfire counter, but that is only if you have the enhanced OBD2 package for GM on your scan tool.
I would do the compression test, and you could also do a backyard power balance:
[video width=550 height=309 type=youtube]bAOmUjAjNjE[/video]The goal here is to find what cyl is misfiring, as the code does not say. I would highly recommend bringing the car to someone that has a scan tool capable of reading GM’s misfire count, otherwise, you can continue to throw parts at it, but that’s an expensive game. As Wayne613 said, call up some local shops and ask if they have GM extended OBD2 tools, and how much to diagnose a misfire.
Or you could also invest in a good scan tool yourself. If you have a laptop running windows: http://www.scantool.net/scan-tools/pc-based/obdlink.html
There are many options, but that software is pretty good, even if you don’t use their OBD2 interface.
see if this helps.
http://troubleshootmyvehicle.com/gm/2.2L/how-to-diagnose-misfire-codes-1
I have an Innova 3100 (OBDII) scan tool/code reader. Do you know if this is something that I can use?
[quote=”graphicfish” post=86730]I have an Innova 3100 (OBDII) scan tool/code reader. Do you know if this is something that I can use?[/quote]
it should work.
I’m working on an ECOTEC right now at work that had a P0300 and a rough, rolling idle. I diagnosed it last week with a worn timing chain and the customer picked it up. It returned with a loud rattle and a jumped timing chain and would barely run. This is common on those engines.
Since it now has 2 bent valves I’m replacing the engine with a used one.
At 200k I would be removing the valve cover to inspect the timing marks, chain slack and chain guide condition.
I don’t think that reader can read GM misfire per cyl pid’s, but you can try. Look through the live data PID’s on the tool and see if you can see misfire’s per cyl.
OK, so here’s the deal. First let me say I’m glad I found this site, it’s a much more pleasant way to talk car troubles than face-to-face at a shop (no offense, but everyone I talk to seems to want to retire on my repair job). So funny thing, I actually found a retired mechanic in my neighborhood that helped me do some troubleshooting. I told him about the idle issues, but I also noticed recently that some oil being blown into the intake looks like “coffee with too much cream in it”, and mentioned that to him as well. He said that can occur when a head gasket fails and coolant get into the oil. He also says this gasket failure can cause the type of idle issues I’m having. So my question to you guys is, does anyone agree with this? Should I bite the bullet and have a shop do the $200 compression check? And if it turns out to be the issue, do I go ahead and do a complete gasket kit replacement? (This car has been great, even at 210K miles and I want to keep it going as long as possible).
It’s not uncommon for condensation to form and mix with oil vapours and make white goo if the car is used for short trips in cold weather. If the oil itself is not milky I doubt if you have a head gasket issue unless you’re loosing coolant.
If you have a headgasket issue like you retired mechanic says… you have to confirm coolant loss, engine overheating problem, loss of ventilation heat.
A weak PCV can cause the same issue as a vacuum leak. If you look at the oil color which hapen to be milky, that can be cause by coolant… but you will rule this one out by looking at you coolant level and/or do an oil change and save the oil, it’s goign to be a pass or fail test.
In other hand, short running period doesn’t give the chance to the pcv system to extract humidity, so you can expect kinda the same color (i’m colorblind) You need to take your driving habid in consideration in this case.
At first view it seems your engine is not measuring proper air flow. If you are replacing PCV for instance. HAve a good look at the air filter and the piping from the air duct to the throttle body. The throttle body can be gummed up as well. giving no window for idle
Well then it’s just freaky weird. The air cleaner looks fine, and in fact the bad idling occurs with the intake tube completely removed. I don’t seem to be losing coolant because the level is steady. I recently had the oil pan gasket replaced and I’m not losing any oil. As stated before, the only place I saw the creamy oil was a small amount in the intake (near resonator). This engine does not have a PCV, it is built into the valve cover and non-replaceable. Let me tell you what I have replaced since the idling issue began: EVAP purge solenoid, gas cap, ignition control module, coil pack, plugs, plug wires, IAC, and upstream OS.
I drive this car 30 miles each way to and from work daily, mostly at highway speed. It runs normally cool, absolutely no smoke from the tailpipe, and RPM’s seem normal. All fuses are good.
I’m just trying to figure out why the idle is not good.
As many have pointed out it could be a mechanical issue. It could be a compression issue or timing chain slack as mentioned. Doing a power balance test will help you nail down an offending cylinder and does not require any special tools. Also, don’t neglect to check the basics like the plugs if you haven’t already. More information on solving performance problems can be found here.
http://www.ericthecarguy.com/faq/solving-automotive-performance-issues
Keep us posted
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