Swap the coil packs from 1 and 6 with others (take note of which ones) and see if the misfires move with them.

quote:

Originally posted by DonDraper:
Swap the coil packs from 1 and 6 with others (take note of which ones) and see if the misfires move with them.

Good advice.

Oh, this car doesn't have plug wires, then it's the coil packs and plugs.

Misfiring consistently on several cylinders is usually electrical. Bad fuel would be clogging injectors and is would come and go as they clear out.

A bad injector will misfire, but not give a rich code like a bad coil will.

quote:

Originally posted by rtquig:
It could be plugs, wires, or coils. Might even be an O2 sensor. It is somewhat common in the 5 & 6 cylinders, but you have to identify which cylinders are misfiring.

It's been my experience that anytime you get multiple codes the O2 Sensor is the first thing to look at.

A bad upstream O2 sensor will force the computer to run in open loop.
A bad downstream sensor will just fuss that it's not receiving voltage.

Misfire and rich is a bad coil pack/plug/wire.

Dumping unburned fuel into the cat will burn it up.

O2 sensors are not going to cause misfires on specific cylinders, they control fuel management per bank. You have two banks and a misfire from one cylinder on each bank.

First thing I like to do is check for any obvious wiring damage under the hood at the coils and fuel injectors. If nothing obvious, go with what DonDraper suggested. I would check the spark plugs for each misfiring cylinder just as a precaution. I would swap out the coils so that the two suspect coils are on the front bank on known good cylinders. So if the misfires follow the coils, then buy two coils and change them easy.

On your engine the rear bank starting from the passenger side to the driver side is 1-3-5, the forward bank starting from the passenger side to the driver side is 2-4-6. So take the coils from cylinders 1 and 6 and put them on cylinders 2 and 4. If the misfires follow to 2 and 4, replace those coils.

I would bet that it is the coil packs. Generally when 1 coil pack goes at that age and mileage the other coil packs aren't too far behind it especially after having the spark plugs replaced recently and disrupting them (pulling them off, pushing them back on). You could check the plugs but doubt it is them if they're pretty new, but will indicate if they're wet or not firing properly. It should be ok to run it 10 miles to the shop, provided there is no water in your oil and the engine wasn't overheated (blown head gasket)

Change your coil packs.

Awesome. Thanks guys.

So I watched a video and looked at the car. Seems like I can replace the front 3 (evens) pretty easily. And I think I can get to #1; I need to look at #5. The problem is #3. I need to remove a bunch of stuff to get to #3.

I was thinking about replacing all that I can but I'd still have to take it into the shop to replace #3. The shop doesn't really charge much of a premium for parts (in my experience - it's pretty close to the price if I ordered them online - so they must get a commercial / distributor discount).

I figure any real labor is involved in #3; shop should be able to do all the rest w/in 30 minutes.

Since this is the wife's car and since jimmy thinks the others are probably not too far behind, I'll just have all replaced at the shop. If it's not the coil, then it's problem troubleshooting something for which I'm probably not capable. So I guess either way it makes sense to just limp it to the shop at this point.

If only I felt comfortable doing #3,5 I think I could have fixed this just with buying parts.

At least in the future, if I get a bad coil (say, on my same age GS), then I'll know how to fix and am more comfortable doing it piecemeal (maybe keep a spare in the trunk). Maybe that one will be easier (in-line 6).

That little code reader is pretty handy after all.... Maybe I should keep it in the trunk.

If this engine has the spark plug tubes which go through the valve cover there is a seal between the spark plug tube and valve cover which can leak oil into spark plug tube and cause plugs to short out leading to misfires. I mention it since the vehicle is relatively old and seals are probably hard and brittle.

I just bought a van that the owners mechanic said the miss/stumble was plugs. I put in a rich mix of Lucas fuel and injector cleaner and it's coming out of it. Easy and relatively inexpensive to try. Dirty or plugged injectors make it run like it has bad plugs. I'm not sure if it would make it code that way but I haven't had the best luck with the consumer version of readers.

Check your wires are connected to the right plugs? That's what happened to me. I switched the plug wires.

quote:

Originally posted by Mikito:
If this engine has the spark plug tubes which go through the valve cover there is a seal between the spark plug tube and valve cover which can leak oil into spark plug tube and cause plugs to short out leading to misfires. I mention it since the vehicle is relatively old and seals are probably hard and brittle.

You have no idea how much those valve cover seals around the spark plugs will drive you up a wall. When they get brittle and crack pieces off, it can give off symptoms of a number of problems.
Mine got so bad, it was pumping oil straight into the combustion chamber and smoking something awful. All that oil will quickly cause a coil pack to go bad, as well.
Best money I ever spent (I usually do my own work) was having a mechanic friend replace the valve cover gaskets and seals on our FWD V6 Maxima last month. The rear bank of cylinders is a bitch to get to.

The shop said my Celica misfire was the O2 sensor. Didnt fix it. They wanted to check a few other things starting with fuel stuff.

I wasnt so sure, so I replaced the coils for $20 off amazon and it fixed it. I dont think the O2 sensor was still good - it needed replaced and was the “easiest” for the shop to fix. But it was also way more expensive for the shop to do. If id do it again, i couldve easily swapped the O2 sensor and coils myself and saved $200 or more.

But i got lucky i suppose.

quote:

Originally posted by konata88:

quote:

Originally posted by smlsig:
If the check engine light is on but not blinking it is ok to drive to the shop.

If it is blinking have it towed

Is that universal? Good to know.

Yes as far as I know with everything from a Ford Ranger to a Porsche GT3

As already stated by Shifferbrains, a bad O2 sensor is not going to cause a cylinder specific misfire. This is especially true at idle where the ECU is running in open loop mode(therefore not using O2 feedback for fuel trim control).

Pull the spark plugs to evaluate what's going on.

If the plugs look clean/dry, then it's likely lack of fuel causing the misfire and it is ok to drive a short distance to the shop.

Lack of fuel is either a clogged injector that may be remedied by a fuel system cleaner, a bad injector that needs replaced (internal coil failure), or an issue with the old/brittle wiring harness.

If one of the plugs is wet and drenched with fuel then it is NOT ok to keep driving it.

That means you likely have a bad coil pack and the cylinder is now filling up with un-burned fuel. If you continue to drive it you will wash the oil off the cylinder walls in the bad cylinder causing scoring/damage, along with diluting the oil for the rest of the engine as well.

quote:

Originally posted by DonDraper:
Swap the coil packs from 1 and 6 with others (take note of which ones) and see if the misfires move with them.

This is the quickest, cheapest test, just swap the number 1 with the one next to it, right on the front of the engine (transverse v6), clear the codes and start it back up.

If the problem moves to the other cylinder you know the coil pack is bad, if not then you have other issues. Lots of times you can get several codes, but some of them are related to the initial problem code and are ghosts.

Once you fix the main problem the others go away.

Still without spending a nickel swapping one coil for another tells you what you need to know.




Link to original video: https://www.youtube.com/watch?v=VlfqoGEECYQ

Could it be that a valve adjustment is needed? Couple of years ago, my Honda started throwing misfire codes generally when it was colder weather and I did the usual: took it to the mechanic for injector cleaner, checking the coil packs, plugs seemed fine, swapped coil packs...but finally, through my internet research, I went back to the mechanic and had them check my valves and they ended up having to do a valve adjustment; my mechanic did tell me that it was pretty rare to have to do a valve adjustment.

Had the same thing happen to me last year on my Chevy. Misfire with 125000 on engine. Drove to mechanic and he mentioned to replace one of the coils. I had him do that and at the same time replace the plugs. Now it was driveable so went to RockAuto and ordered rest of coils, read that when one goes the others will follow. Replaced the rest on my own and runs like a new vehicle.

Thanks guys. I swapped the coil between #6 and #4. Cleared codes and then started engine.

Weird - now I have misfire only on #1. #4 is not misfiring as I would have expected. Thoughts?

I'm passing by the dealer later this morning. I have about an hour to decide if I should buy 2 coils, 1 coil or none. Help?

I decided to try to replace just the coils that are bad, if any. I'm going to swap cars w/ my wife until we can buy something new for her (need to raise a little money). So, just want to fix the minimum for trade-in.