2000 Toyota Corolla | Misfire codes, Tune Up Needs

[Tegger]

Originally Posted By: Globalksp
I don't have a foolproof way of erasing the codes between coil swaps.

You don't need to.

You're currently getting P0301 and P0302. That means coils #1 and #2 are suspect. So you move those to cylinders 3 and 4.
If codes P0303 and P0304 are suddenly recorded, there's your problem. If P0303 and P0304 are NOT recorded, then the coils are NOT likely at fault.

But you're also getting a P0300. This code is what makes bad coils unlikely. P0300 would be more indicative of things like a leaky intake-manifold gasket, clogged EGR, damaged wiring, etc. A good garage will also check TIS for TSBs for known misfire-code issues with that model.

If I were you, I'd save my girlfriend's money and swap the coils before doing anything else at all.

 

[Globalksp]

I finally had a moment with the Corolla today.

Thanks for your input on the TSB's, Tegger. Here's what I found on this model, none associated with misfires: http://www.toyotaproblems.com/tsbs/Corolla/2000/

Today's results don't really tell "me" much, but here they are.

CEL was on when car arrived and returned a P0300, P0301, and a pending P0301 code. We'll notice that the P0302 code is no longer showing up.

I disconnected the negative terminal from the battery, flipped the headlights on to clear system of any remaining power, reattached the negative terminal, swapped coil 1 with coil 2, and restarted the engine.

CEL came on not immediately at start up, but after being driven for about 4 miles. These codes were: P0300, P0301, and a pending P0301.

Any thoughts?

 

[Vikas]

Assuming plugs have not been yet swapped, that would be the next logical step. If the codes stay the same, then it is time to measure relative compression of all cylinders

 

[Globalksp]

Even though the plugs are brand new? I installed them less than a month ago when I began this misfire journey.

 

[The Critic]

What are your short and long-term fuel trims at idle and at 2500-rpm?
Have you checked for vacuum leaks? On 1.8s I would definitely make sure the intake gasket is not leaking.
What is your MAF reading at idle?

 

[Globalksp]

Originally Posted By: The Critic
What are your short and long-term fuel trims at idle and at 2500-rpm?
Have you checked for vacuum leaks? On 1.8s I would definitely make sure the intake gasket is not leaking.
What is your MAF reading at idle?


These questions make me feel that this will be a great exercise in furthering my auto-repair knowledge. I'm aware of what fuel trims are, but am educating myself on how they can be interpreted to diagnose issues and what diagnostic tools are needed to recover such info.

A vacuum /intake manifold leak is very possible. After replacing the PCV, valve cover gasket, plugs, etc., I noticed a little whistle while standing over the engine and opening up the throttle. Had a video of it, but must have deleted it.

As with the fuel trims, I don't think I have the necessary tools to read the MAF values.

Any recommendations for a diagnostic tool on the affordable side of things? I've always worked on cars as a hobby, but of late have gotten more interested in perhaps taking that interest to another level.

Thanks

 

[Drew99GT]

Intake manifold gaskets are very common on those; does it have any kind of a miss at idle, or part throttle driving? Easy diagnosis is spray brake cleaner around all 4 intake ports of the intake manifold where it mates to the head. If you get any increase in rpms or it smooths out, it's leaking.

 

[Globalksp]

Good tips! Thanks!

 

[Vikas]

You installed new plugs a month ago? Which specific plugs did you install? Were they exact original plugs. Anything else and that might be the cause of your misfire.

 

[Globalksp]

Yep, Denso's. gapped and torqued to spec.

 

[The Critic]

Originally Posted By: Globalksp
Yep, Denso's. gapped and torqued to spec.

If you purchased the correct part number, the gap should not require adjustment. In fact, it is very easy to damage the electrodes when gapping plugs.
Why did you adjust the gap?

 

[Vikas]

Given that the code(s) came back in about month and half, you need to take out the plugs and check them again to check their condition.

 

[Globalksp]

Originally Posted By: The Critic
Originally Posted By: Globalksp
Yep, Denso's. gapped and torqued to spec.

If you purchased the correct part number, the gap should not require adjustment. In fact, it is very easy to damage the electrodes when gapping plugs.
Why did you adjust the gap?


Interesting, this is news to me. I've always checked the gap on plugs for the simple fact that I never assume they go from factory to my hand without ever leaving their box (returns for example) nor assumed that the factory properly gapped them.

That said, I put in Denso 4503's. I'll yank them out next opportunity I have and see what's what. For what it's worth, when I swapped the coils, I did notice a bit of oil on the coil boot. I just chalked it up to residual oil left in the valve cover's spark plug tubes.

-K

 

[chrome]

Originally Posted By: Globalksp
I disconnected the negative terminal from the battery, flipped the headlights on to clear system of any remaining power, reattached the negative terminal, swapped coil 1 with coil 2, and restarted the engine.

CEL came on not immediately at start up, but after being driven for about 4 miles. These codes were: P0300, P0301, and a pending P0301.

Any thoughts?


But wasn't #2 cylinder one of the suspect cylinders initially? I seem to recall it was #1 and #2 misfire codes, and the original advice was the swap coil 1 & 2 with 3 & 4. Why did you swap #1 with #2? Should have swapped them with 3 & 4 instead...

 

[Globalksp]

Originally Posted By: chrome
Originally Posted By: Globalksp
I disconnected the negative terminal from the battery, flipped the headlights on to clear system of any remaining power, reattached the negative terminal, swapped coil 1 with coil 2, and restarted the engine.

CEL came on not immediately at start up, but after being driven for about 4 miles. These codes were: P0300, P0301, and a pending P0301.

Any thoughts?


But wasn't #2 cylinder one of the suspect cylinders initially? I seem to recall it was #1 and #2 misfire codes, and the original advice was the swap coil 1 & 2 with 3&4. Why did you swap #1 with #2? Should have swapped them with 3 & 4 instead...


This is correct... after replacing the valve cover gasket and putting in new plugs, the codes disappeared for a while. When they came back only cylinder 1 was reported (P0301) along with the P0300 code. So, I deduced that cylinders 2,3,4 were "fixed" and thus could be used interchangeably. In hindsight, would it have made more sense to swap with 3 & 4? Yea, totally. Would it have been easier to think to do that if not being rushed by the little lady who owns the car... mmm hmmm....

It's not the end of the world... if nothing else, I'm saving her money as her mechanic was going to replace all the coils first thing with the OEM Denso's for $287. She doesn't drive that much to begin with and until we started seeing each other, thought the check engine light was, you know, no big deal

 

[Tegger]

Originally Posted By: Globalksp
her mechanic was going to replace all the coils first thing

Somebody is not understanding what is meant by the term "misfire". That term has, in itself, NOTHING to do with the plugs or coils.

-- The crankshaft speeds up after every combustion event in each cylinder, and slows down between them.

-- The engine's computer monitors the crankshaft's speed/slow cycle. It expects each and every speed-up event to be exactly as strong as all the others, with a very slight variance allowed.

-- If some of the speedups are weaker than others, or they are variable, the computer illuminates the MIL.

-- If the computer is able to tie the erratic speedups to one cylinder, it will set a P030n code, where "n" is the number of a cylinder.

-- If the computer decides that erratic speedups are randomly distributed among the cylinders, it will set a P0300.

TL/DR: "Misfire" simply means that the crankshaft's speed isn't fluctuating within the allowed tolerance. That's all it tells you. It doesn't tell you which components are responsible.

 

[Globalksp]

Originally Posted By: Tegger
Originally Posted By: Globalksp
her mechanic was going to replace all the coils first thing

Somebody is not understanding what is meant by the term "misfire". That term has, in itself, NOTHING to do with the plugs or coils.

-- The crankshaft speeds up after every combustion event in each cylinder, and slows down between them.

-- The engine's computer monitors the crankshaft's speed/slow cycle. It expects each and every speed-up event to be exactly as strong as all the others, with a very slight variance allowed.

-- If some of the speedups are weaker than others, or they are variable, the computer illuminates the MIL.

-- If the computer is able to tie the erratic speedups to one cylinder, it will set a P030n code, where "n" is the number of a cylinder.

-- If the computer decides that erratic speedups are randomly distributed among the cylinders, it will set a P0300.

TL/DR: "Misfire" simply means that the crankshaft's speed isn't fluctuating within the allowed tolerance. That's all it tells you. It doesn't tell you which components are responsible.


This is why I love these forums. I've never heard a misfire code explained this way before and since you write with authority, I'm inclined to believe you. Thanks for furthering all our learning.

So, if a misfire isn't always contributable to plugs/cool/ignition... what else could be causing the "grossly" erratic variation in crankshaft slow down / speed up cycles? Where should I start looking / what's the 1st level investigations, 2nd level, etc.?

 

[Tegger]

Originally Posted By: Globalksp
what else could be causing the "grossly" erratic variation in crankshaft slow down / speed up cycles? Where should I start looking

You'd already been given a few areas to check, earlier in this thread. If you're posting from a telephone, you likely missed those replies. Telephones are for making telephone calls, not for learning how to fix cars.

Some possible causes of "misfires":
- intake air-leaks
- EGR passages clogged
- poor compression (which could itself have several causes)
- faulty injectors
- damaged electrical wiring
- fouled/damaged plug(s)
- weak coil(s)

There's no "magic bullet" solution. The order you would check would be to investigate the easiest stuff first.

Mandatory tools would include a proper scan-tool, and a vacuum gauge.

 

[Vikas]

Computer also "knows" when the cylinder is "NOT" firing. it tells you that by blinking the CEL. If that is happening, the the chances of dead ignition or dead injection are extremely high. Other type of misfires such as air leak or EGR passage usually don't start CEL blinking.

If you are a shop, you go for a remedy which will minimize customer comeback and incidentally will also provide a nice boat payment. So it would make sense that they would like to replace the ignition components. They figure if one coil is dead, the others are not too far behind.

But you as a car owner can follow different and cheaper path.

 

[Tegger]

Originally Posted By: Vikas
Computer also "knows" when the cylinder is "NOT" firing. it tells you that by blinking the CEL.

There's that misunderstanding again. Not even a blinking MIL necessarily means an ignition problem.

A blinking MIL just means that the variation in crankshaft speedups is great enough for the computer to decide that raw gas is being dumped into the cat, causing the cat to suffer damage. It still does NOT tell you which component is responsible!

It is very unfortunate that the SAE chose to call P03xx codes "misfire" codes. Every time folks hear the word "fire", they think "spark", which is misleading in the extreme. It might have been better to call them "inconsistent crankshaft impulse" codes instead.

A blinking MIL can be caused by such things as lean-misfires due to EGR clogging, or poor compression due to burned or misadjusted valves. And, in my limited experience, a blinking MIL accompanied by a P0300 can also be due to an failing ignition control module.