2000 Elantra False Misfire?

Hello,
I have a 2000 Elantra with 134,000 miles on it. The problem is a misfire on cylinder 2 (autozone). Originally it was on 1 and 3 I think (autozone) but disconnecting battery has cleared code. CEL (check
engine light) stays lit, blinks and sometimes turns off for a while. When I first changed plugs it stayed of for about 100 miles or so.
Problem is I can't notice any performance issues when light is blinking or otherwise. Car runs as if nothing is wrong. The only slight thing I notice is at idle, the rpm's move very very slightly from say 800 down to 750. It does this in a rythmic pattern. Almost seems normal to me.
Here is what I have tried so far.
plugs - replaced with new wires - replaced with new coil - replaced with used coil acceration sensor - replaced with new injector cleaner - lucas and seafoam brand.
It seems like the light is coming on less and is blinking less often. Could be my imagination though.
FALSE MISFIRE?
I am not the original owner and have only had the car a few weeks.
Any advise is appreciated....
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WHAT kind of plugs did you use, If you put Bosch through them in the trash & get the recomended plugs
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Well I did at first. Autozone recommended Bosch platinum 4 plugs. $40.... After doing some reading I changed these to NGK plugs. They matched the number in the hayes manual except the last letter..... I think they had an extra letter on the end. Do you think these may be wrong plugs too......
sqdancerLynn wrote:

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I haven't seen any false misfires on the Elantra, and nothing as late as 2000, but there were some Sonatas around 1996 that were setting misfire codes caused by some sort of imperfection in the camshaft or head. In most cases, the cars ran flawlessly the entire time in the service department. Was really bizarre.
You might have a fuel injector issue. I again haven't seen this on your model, but I've seen several 2.5 and 2.7 liter V6s with partially clogged injectors. In those cases, the car typically ran well anytime except cold starts, and even then, the misfire was only barely detectable at idle, and not detectable at all off idle.
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Would this expain the light only being tripped while driving not at idle. Light has never tripped at idle but flashes while driving. It is starting to get cold here in Michigan. Haven't noticed a signicant difference while starting, I will observe this better in the morning.
Also is there a simple way I can check the injectors myself?
hyundaitech wrote:

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There's no easy way. Ordinarily, I'd recommend swapping with another cylinder, but your misfire seems to move around, so that may not provide any useful information.
Other possibilities I've come up with:
Defective crank sensor causing a perceived misfire when there is none.
Faulty chassis acceleration sensor (on top of left strut tower) causing misfire monitoring to not be turned off over rough terrain.
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Hello hyundaitech,
First of all I would like to thank you for your time and experience. It is greatly appreciated.
I stumbled on to something interesting on another internet page (carfax) about the crankshaft sensor. Here it is.
Engine    Occasional problems on this vehicle are failures of the Crankshaft Position (CKP) Sensor and the Evaporative (EVAP) Canister Purge Solenoid. These problems may cause the Check Engine Light to illuminate. The cost to replace the CKP Sensor is estimated at $80.10 for parts and $26 for labor. The cost to replace the EVAP Canister Purge Solenoid is estimated at $32.50 for parts and $19.50 for labor. All prices are estimates based on $65 per flat rate hour and do not include diagnostic time or any applicable sales tax.
Based on this and your advice it sounds like the CKP may be a very good possibility. I will the check the resistance between terminals 2 and 3 on the sensor. Should be between 486 and 594 ohms @ 68 F. At least according to Haynes.
I will let you know my results. Again thanks for the input as I am no mechanic and the closest dealer is about 75 miles away.
tj
hyundaitech wrote:

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Typically, the crankshaft sensor won't set a misfire code. If you're going to go the the trouble of checking its resistance, you may as well pull it out and look at the end that reads the wheel on the crankshaft. Check to make sure it hasn't been chewed up by the crankshaft wheel. Also check to see if the crankshaft wheel is loose by inserting a screwdriver in the hole and attempting to move it back and forth.
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Well I checked the resistance. I didn't remove it as you suggested as I just got back in and now it's raining and I have no garage.... The resistance checked at 944 ohms. The temp is not 68F out though. More like 45 but car was running a little while ago so probably more like 50 to 60 under the hood. I will check the other things tomorrow. Don't want to replace any more parts without being sure...
hyundaitech wrote:

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944 is enough different from the specified 486-594 Ohms that I'd replace the sensor. The problem is that resistance isn't a very good indicator of crankshaft sensor performance. You could still be replacing a good sensor.
The tach displays an rpm value based on a signal it gets from the ECM. The ECM determines engine rpm by reading the crank sensor. I could see a relationship between a momentarily bad sensor and both the misfire code and the tach issue. But it's also possible that you could have a loose wire in the tach circuit or that the tach is dying.
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update. I went to purchase a new crankshaft sensor. Tested new sensor resistance and it was around 850 Ohms. I didn't buy new sensor as I remembered that when I removed old sensor the bolt holding it in was loose enough to turn with my fingers. Since I put the old one back in and tightened the bolt the light has stayed off for a while now. I will drive a little longer and see what happens.
Do you think this could have been the problem?
hyundaitech wrote:

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I'd buy that for a buck. I've never seen it before, but I'm sure it's possible. The vibration of the sensor could cause it to misread the momentary engine speed.
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Just wanted to follow up. It's been almost 2 weeks and no engine light. The problem must have been a loose sensor bolt. Weird......
Thanks for all your help hyundaitech!!!!
hyundaitech wrote:

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I removed the sensor and it looks ok. Not chewed up. Wheel on crankshaft looks ok also. Do you think its worth replacing due to the resistance being off?
hyundaitech wrote:

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I forgot to mention. Sometimes the rpms seem to move a little jerky. Just the gauge not the engine. Don't know if makes sense or if its just my imagination looking for an answer..... hyundaitech wrote:

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Also there is a recall on the exaust manifold assy. For cracks in the weld I think. I haven't done the recall yet. Do you think this could be related?
hyundaitech wrote:

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No, the exhaust manifold wouldn't be related.
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