Random multiple missfire?

[vr4gto]

My '99 ES 2.4 is misfiring and the tach is bouncing all over the place. The engine runs fine and idles but the rpms don't match the sound of the engine. When driven the car misfires under a load but cruises fine. The code that pops up is P0300-Random Multiple Misfire. I've replaced the coils, wires, and plugs. It still misfires and the tach is all over the place still. Help. I'm lost. Thanks in advance

[Galant Evolution]

PO300-Random Misfire Circuit

http://img2.pict.com/ec/c4/a3/2576494/0/circut1.jpg
http://img2.pict.com/19/ad/2b/2576496/0/circut2.jpg


The injector power is supplied from the MFI relay (terminal 1).
The ECM or PCM controls the injector by turning the power transistor in the ECM or PCM "ON " and "OFF ".
TECHNICAL DESCRIPTION


If a misfire occurs while the engine is running, the engine speed changes for an instant.
The ECM or PCM checks for such changes in engine speed.
DTC SET CONDITIONS

Check Conditions:


Five seconds or more have passed after the engine was started.
Engine speed is between 500 and 6,000 r/min .
Engine coolant temperature is higher than 10 °C (14 °F) .
Intake air temperature is higher than -10 °C (14 °F) .
Barometric pressure is higher than 76 kPa (11 psi) .
Adaptive learning is complete for the vane which generates a crankshaft position signal.
While the engine is running, excluding gear shifting, deceleration, sudden acceleration/ deceleration and A/C compressor switching.
Judgement Criteria (change in the angular acceleration of the crankshaft is used for misfire detection).


Misfire has occurred in 4 or more of the last 200 revolutions [when the catalyst temperature is higher than 950 °C (1,742 °F)] .
or



Misfire has occurred in 20 or more of the last 1,000 revolutions (equal to 1.5 times the limit of emission standard).

TROUBLESHOOTING HINTS:
The most likely causes for this code to be set are:


Ignition system related part(s) failed.
Poor crankshaft position sensor.
Incorrect air/fuel ratio.
Low compression pressure.
Skipping of timing belt teeth.
EGR system and EGR valve failed.
ECM failed.
PCM failed.

DIAGNOSIS:
Required Special Tool:
MB991502: Scan Tool (MUT-II)

http://img2.pict.com/71/1b/07/2576503/0/circut3.jpg

CAUTION: To prevent damage to scan tool MB991502, always turn the ignition switch to "LOCK" (OFF ) position before connecting or disconnecting scan tool MB991502.




STEP 1. Using scan tool MB991502, check data list item 22: crankshaft Position Sensor.


Connect scan tool MB991502 to the data link connector.
Start the engine and run at idle.
Set scan tool MB991502 to the data reading mode for item 22, Crankshaft Position Sensor.
Check the waveform of the crankshaft position sensor while keeping the engine speed constant.
The pulse width should be constant.
If constant, go to Step 2.

If not constant, refer to DTC P0335 - Crankshaft Position Sensor Circuit Malfunction.




STEP 2. Using scan tool MB991502, check data list item 81: Long-Term Fuel Trim.


Start the engine and run at idle.
Set scan tool MB991502 to the data reading mode for item 81, Long-Term Fuel Trim.
The fuel trim should be between -12.5 and +12.5 when the load is 2,500 r/min (during closed loop) after the engine is warmed.
If within specifications, go to Step 3.

If not within specifications, refer to DTC P0170 - Fuel Trim Malfunction.




STEP 3. Using scan tool MB991502, check data list item 82: Short-Term Fuel Trim.


Start the engine and run at idle.
Set scan tool MB991502 to the data reading mode for item 82, Short-Term Fuel Trim.
The fuel trim should be between -10 and +10 when the load is 2,500 r/min (during closed loop) after the engine is warmed.
If within specifications, go to Step 4.

If not within specifications, refer to DTC P0170 - Fuel Trim Malfunction.




STEP 4. Check each ignition coil spark.

http://img2.pict.com/4f/2b/08/2576515/0/circut6.jpg


Check each ignition coil spark.
Remove the spark plug and connect to the spark plug cable.
Ground the spark plug side electrode securely.
When the engine is cranked, the spark plug should spark. If correct, go to Step 7. If incorrect, go to Step 5.


STEP 5. Check the spark plugs.

http://img2.pict.com/27/e4/91/2576513/0/circut4.jpg


Check the plug is not burned out, that the insulator plug is not damaged, and that there are no carbon deposits.
If cleaning is required due to carbon deposits, etc., clean using a plug cleaner or wire brush, etc.
Check the plug gap using a plug gap gauge. Standard value: 1.0 - 1.1 mm (0.039 - 0.043 inch) If within specifications, go to Step 6. If not within specifications, repair or replace the faulty spark plug. Then go to Step 13.


STEP 6. Check the spark plug cable.

http://img2.pict.com/55/30/de/2576525/0/circut5.jpg


Check the cap and coating for cracks.
Measure the resistance. Limit: Maximum 22 kOhms If within specifications, refer to INSPECTION PROCEDURE 34 - Ignition Circuit System. If not within specifications, replace the faulty spark plug cable. Then go to Step 13.


STEP 7. Check the injectors.




Disconnect each injector connector.




Measure resistance between injector side connector 1 and 2 at each injector. Standard value: 13 - 16 Ohms [at 20 °C (68 °F) If within specifications, go to Step 8. If not within specifications, replace the faulty injector
.
Then go to Step 13.




STEP 8. Check harness connectors B-17, B-19, B-21, B-22 at the injector for damage.
If harness connectors B-17, B-19, B-21, B-22 are in good condition, go to Step 9.

If harness connectors B-17, B-19, B-21, B-22 are damaged, repair or replace them.

Refer to Harness Connector Inspection. Then go to Step 13.


STEP 9. Check harness connector C-35 at the ECM or harness connector C-39 at the PCM for damage.
If harness connector C-35 or C-39 is in good condition, go to Step 10.

If harness connector C-35 or C-39 is damaged, repair or replace it.

Refer to Harness Connector Inspection. Then go to Step 13.



STEP 10. Check the harness wires between injector connectors B-17, B-19, B-21, B-22 and ECM connector C-35 or PCM connector C-39 .
If the wires between injector connectors B-17, B-19, B-21, B-22 and ECM connector C-35 or PCM connector C-39 are not damaged, go to Step 11.

If the wires between injector connectors B-17, B-19, B-21, B-22 and ECM connector C-35 or PCM connector C-39 are damaged, repair them. Then go to Step 13.

STEP 11. Check the following items.


Check the following items, and repair or replace the defective component.
Check for skipped timing belt teeth.
Check compression.
EGR valve failed. Then go to Step 12.
STEP 12. Replace all the injectors.


Replace all the injectors.
Carry out a test drive with the drive cycle pattern. Refer to Procedure 6 - Other Monitor.
Check for the diagnostic trouble code (DTC). If DTC P0300 is not output, the inspection is complete. If DTC P0300 is output, replace the ECM or PCM. Then go to Step 13.
STEP 13. Test the OBD-II drive cycle.


Carry out a test drive with the drive cycle pattern. Refer to Procedure 6 - Other monitor.
Read the diagnostic trouble code, and confirm that diagnostic trouble code P0300 does not reset

[vr4gto]

Has anyone ever fixed this problem without spending a ton of cash to get it done? I don't have access to a good scanner and I'm running out of cash to have someone else do it. My eclipse transmission blew and I have to get my 3000 running soon. What are the common things that cause this?

[Galant Evolution]

Did you read my post? If you dont have a plug in OBD2, you can still check most symptoms.

Ignition system related part(s) failed.

Poor crankshaft position sensor...You would prob be getting a check engine code.
Incorrect air/fuel ratio.....need a scanner for this...unless you have an accurate AFR gauge
Low compression pressure....You can check with a compression guage.
Skipping of timing belt teeth....check your timing belt for damage or loosness.
EGR system and EGR valve failed....You need a scanner for this.
ECM failed.....Need a scanner.
PCM failed.....Need a scanner.

Make sure all the wires are plugged in correctly, make sure you gapped the spark plugs correctly, check the wires with the spark plug in them to make sure they spark.

[vr4gto]

Thanks for the help. I'm having it scanned today. Hopefully nothing serious.

[Galant Evolution]

Thanks for the help. I'm having it scanned today. Hopefully nothing serious.


Np, report back after if you still need some help, and we will try our best! Good luck! :023:

[vr4gto]

So I checked the timing belt, it's good. Checked the ecm and the connections, the injectors, and fuel trims, they checked out fine. The tach is still bouncing around like crazy, does the crank sensor run the tach?

[Galant Evolution]

No but if you havnt gotten another code from the scanner and all your timing is within spec the crank sensor should be fine. Im at loss of what to say, hmmm this is strange. usually what happens for most people is the plugs or wires go bad causing it to studder upon acceleration but crusie fairly well. Im sorry bro im not sure on what it could be :104:

[vr4gto]

No but if you havnt gotten another code from the scanner and all your timing is within spec the crank sensor should be fine. Im at loss of what to say, hmmm this is strange. usually what happens for most people is the plugs or wires go bad causing it to studder upon acceleration but crusie fairly well. Im sorry bro im not sure on what it could be :104:

I'm at a loss too. Thanks for the help though. I'll keep you posted on progress.

[Galant Evolution]

Ok bro

[vr4gto]

Ok, so everything is checking out that's listed, is there any other thing that can cause this? Two shops have checked it and no success. The crank sensor is reading, the injectors are fine, new plugs, wires, coils, fuel trim is fine, no damaged wires. If the computer is shot I shouldn't be able to get readings correct? I'm completely lost and it's stumped two shops.
I forgot to add that the plugs for cylinders 2 and 3 keep getting full of oil.

[Galant Evolution]

^^ there is your problem man!! I have the same problem with cylinder 3 keeps getting some oil in there, im not sure how its sealed tho.

[vr4gto]

^^ there is your problem man!! I have the same problem with cylinder 3 keeps getting some oil in there, im not sure how its sealed tho.

does it affect your car having the oil get in? Is it causing a compression problem that isn't being picked up for some reason? My tach is still bouncing all over. It follows the gears at low speeds but when I let off the throttle it drops down to zero. At highway speeds it doesn't follow engine speed at all. On the scanner the rpm's are good until the many misfires. The other thing I noticed is the intake air temperature sensor was saying the air was 100 degrees. I also noticed there was no data for barometric pressure. Would my TPS or IAT cause problems with misfires if they were shot?

[97dsmturbogalant]

The oil problem is with the valve cover gasket. Autozone or any auto parts store should have one in stock. It comes with the valve cover gasket and the spark plug tube seals.

[vr4gto]

But would the oil problem cause this big of an issue with the way my car runs? It's weird how the car acts and its not being picked up on a scanner.

[97dsmturbogalant]

It could if the oil is fouling up the plug. If you take the plugs out and put new ones in, I knowit will smoke for a sec, but does it help the misfire? Valve gasket should be replaced anyways to prevent any other problems that might accour.

[vr4gto]

It could if the oil is fouling up the plug. If you take the plugs out and put new ones in, I knowit will smoke for a sec, but does it help the misfire? Valve gasket should be replaced anyways to prevent any other problems that might accour.
I put new plugs in again today and it's still misfiring. The other plugs were fouled but the new ones made no difference. My tach is still bouncing all over the place too.

[vr4gto]

Could a hole in my exhaust after the first O2 and before the cat cause a misfire? Everything else on the car is checking out fine. The only thing off is the O2's are fluctuating quite a bit. The hole is in the flex pipe.

[vr4gto]

I fixed the exhaust and the car runs and accelerates great now. No studders but the misfire code keeps popping and the tach is still bouncing around. Any ideas?

[Galant Evolution]

I fixed the exhaust and the car runs and accelerates great now. No studders but the misfire code keeps popping and the tach is still bouncing around. Any ideas?

Even after you cleared it?

[vr4gto]

Even after you cleared it?

Yes. But the car runs awesome now. Feels like brand new. No studders at all now. But the code keeps popping.
What runs the tach? Would a bad ground wire connection cause it to bounce around? It works when the accelerator pedal is pushed, but when you release your foot it starts going crazy again.

[vr4gto]

Any ideas?

[Galant Evolution]

Yeah check all the fuses and the grounds and wires, if you still cant come up with anything, go to a junkyard and get a new speedo for likeless than 20 bucks, maybe its just your RPM gauge is just messed up. Or go to autozone and buy an actual aftermarket tach gauge, hook it up and if it reads normal RPM and is working normal, your stock one is messed up prob.

[vr4gto]

Yeah check all the fuses and the grounds and wires, if you still cant come up with anything, go to a junkyard and get a new speedo for likeless than 20 bucks, maybe its just your RPM gauge is just messed up. Or go to autozone and buy an actual aftermarket tach gauge, hook it up and if it reads normal RPM and is working normal, your stock one is messed up prob.

Thanks. Any idea why the P0300 code would keep coming on when the car is running great and not misfiring? I'm thinking maybe the computer isn't clearing the code out of it or maybe the rear O2 is acting up. Fixing the exhaust made the car feel like new again and the misfire went away but the code won't.

[Galant Evolution]

^ That im not sure about why it wont erase...thats odd!

[vr4gto]

^ That im not sure about why it wont erase...thats odd!
Maybe clearing the code with scanner isn't clearing it from the ECU's memory? Maybe unplugging the battery for awhile will clear it?

[vr4gto]

Ok, put new O2's in and it runs awesome but its still popping the same code. It pops only at higher speeds. I had it cleared and the car idling and wiggled the wires near the injectors. The tach stopped bouncing around when I did this but it started again when I took my hand off the wires and popped the code again. No misfire was heard. But I took it for a ride and it misfired again. If I release the gas pedal it stops. So I'm guessing the tach is fine but is connected to something that is causing the tach to bounce around and the misfire. So the tach's issues is an indicator of a certain problem. Any ideas? Any wiring diagrams available?

[Galant Evolution]

intrument panel, gauges, and wiring indicators:


http://img2.pict.com/01/be/ae/2748168/0/800/wiring1.jpg
http://img2.pict.com/20/c7/bb/2748151/0/800/wiring.jpg

if you need more let me know.

[vr4gto]

Thanks.

[Galant Evolution]

NP!

[vr4gto]

If my catalytic converter is plugged, would it cause a misfire?

[vr4gto]

So I gave up and dropped it off at the shop. Now the tach has completely died, the car shifts hard from first to second and there is something drawing power that almost stalls the engine. But now there's no CEL. All fuses, relays, and grounds are good. New O2's, wires, plugs, coils, and battery. The injectors, egr, crank sensor, mass air, tps, iac, map sensor, coolant temp sensor are all good. I'm thinking there's got to be something with the computer that's acting up. It's checked out fine by two other machanics besides myself though. I'm at a loss. I hope this other guy can figure it out.

[Galant Evolution]

So I gave up and dropped it off at the shop. Now the tach has completely died, the car shifts hard from first to second and there is something drawing power that almost stalls the engine. But now there's no CEL. All fuses, relays, and grounds are good. New O2's, wires, plugs, coils, and battery. The injectors, egr, crank sensor, mass air, tps, iac, map sensor, coolant temp sensor are all good. I'm thinking there's got to be something with the computer that's acting up. It's checked out fine by two other machanics besides myself though. I'm at a loss. I hope this other guy can figure it out.

wow thats crazy dood. It could possibly be the ECU hope he figures it out bro

[vr4gto]

So the misfire problem is solved. The grounds were either severed or slightly cut. Don't know why, but the car runs mint. Now the tranny is having clutch flare. The clutch plates are worn. How long do you think it will last if I just replace the plates?

[rjs32]

Which grounds are you taliking about vr4gto?