Severe Engine Misfire
Severe Engine Misfire Hello guys....new to the post, just got my Z a couple of weeks ago.
Anyways, my engine has an insane misfiring problem and keeps setting trouble code P0300. I have changed all the spark plugs, the fuel filter, and the 02 sensors. I have also checked the plug wires and the ignition coils and they are fine. Any ideas on what is cuasing this? I would really appreciate opinions from you guys before I have to shell out the big bucks to good ol' chevy.
If it helps the car is a 98 Z28 with the 6 speed.
Thanks
Joe
Anyways, my engine has an insane misfiring problem and keeps setting trouble code P0300. I have changed all the spark plugs, the fuel filter, and the 02 sensors. I have also checked the plug wires and the ignition coils and they are fine. Any ideas on what is cuasing this? I would really appreciate opinions from you guys before I have to shell out the big bucks to good ol' chevy.
If it helps the car is a 98 Z28 with the 6 speed.
Thanks
Joe
Re: Severe Engine Misfire No, I have not pulled the valve covers to check the springs. The misfire is random on all cylinders and is not apparant all the time. Since it is not apparent all the time I figured it would be more along the lines of something electronic or a fuel pump going out. Could either one of these cause a misfire situation? The engine seems to run fine when it is not under load and during the first minute or so of startup, when the engine is cold.
Teching In
Joined: Feb 2003
Posts: 18
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From: Schererville, In
Re: Severe Engine Misfire YOU MIGHT WANT TO CHECK YOUR CRANK POSITION SENSOR. I HVE THE SAME PROBLEM AND IT HELPED QUITE A BIT WHEN I CHANGED MINE, ALSO CHECK YOUR THROTTLE POSITION SENSOR. THATS WHAT IM GONNA CHECK TODAY OR SOMETIME THIS WEEKEND. GOOD LUCK...
Re: Severe Engine Misfire </font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by chino_man279:
The engine seems to run fine when it is not under load and during the first minute or so of startup, when the engine is cold. [/QB]</font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">So I think it's safe to say you only have a problem under a load right? Does it chug under accel? Is it stock/unmodified? Have you tried wetting wires under hood with water at nite & idling & looking to see if any wires are arcing out?
The engine seems to run fine when it is not under load and during the first minute or so of startup, when the engine is cold. [/QB]</font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">So I think it's safe to say you only have a problem under a load right? Does it chug under accel? Is it stock/unmodified? Have you tried wetting wires under hood with water at nite & idling & looking to see if any wires are arcing out?
Re: Severe Engine Misfire The problem does only seem to happen under load, but it also happens at idle with no load.... What kind of signal should I be checking for from the crank position sensor? Also where is the sensor? I have checked the TPS and it is operating correctly. The car is basically unmodified, only a lid, filter, and minor porting of MAF. What plug wires should I get to replace the stock ones? I plan on making this a 500+ horse motor within the next year or so, what would be the best wires for the application?
Also, today I had the scanner plugged in and I happen to pick up a cylinder #3 misfire before the multiple cylinder misfire code was set....I replaced the ignition coil on #3 and it seems to be sparking about 15,000 volts higher than the other plugs. Should I replace all the coils now? Give me some opinions....
Also, today I had the scanner plugged in and I happen to pick up a cylinder #3 misfire before the multiple cylinder misfire code was set....I replaced the ignition coil on #3 and it seems to be sparking about 15,000 volts higher than the other plugs. Should I replace all the coils now? Give me some opinions....
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Joined: Feb 2003
Posts: 18
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From: Schererville, In
Re: Severe Engine Misfire IF YOU WANT TO CHCK THE CRANK POSITION SENSOR, IT IS IN THE ENGINE BLOCK DIRECTLY ABOVE THE STARTER. THERE SHOULD BE A SILVER BRAKET WITH ONE BOLT. THE SENSOR IS INSIDE THE BLOCK, SO BE VERY CAREFUL NOT TO BREAK IT OFF IF YOU REMOVE IT. ALSO YOU MIGHT WANT TO CHECK AND COMPARE HE VOLTAGE ON ALL OF YOU COILS. I HAVE THE SAME PROBLEM, AND I THINK THAT THE CAUSE OF MY PO300 IS THE IDLE AIR CONTROL VALVE, SO YOU MIGHT WANT TO CHECK THAT OUT TOO.
GOOD LUCK CHINOMAN
GOOD LUCK CHINOMAN
Re: Severe Engine Misfire Thanks Formula26, I will check the Crank Sensor and the IAC. I have new plug wires on the way. I checked all the ignition coils and they seem to be putting out the same voltage except for the one that I already replaced. It is higher than the others now. Is this bad? I also changed the MAF, but it only seemed to help with the problem slightly...it made the computer quit setting a code for running too lean. GM also suggested to me to check for loose wires to the injectors, so I will check that tonight also.
Right now though I have another problem to fix....my intake manifold blew a bolt out the top of it.... <img border="0" title="" alt="[Confused]" src="images/icons/confused.gif" /> <img border="0" title="" alt="[Eek!]" src="gr_eek2.gif" /> <img border="0" title="" alt="[Confused]" src="images/icons/confused.gif" />
Right now though I have another problem to fix....my intake manifold blew a bolt out the top of it.... <img border="0" title="" alt="[Confused]" src="images/icons/confused.gif" /> <img border="0" title="" alt="[Eek!]" src="gr_eek2.gif" /> <img border="0" title="" alt="[Confused]" src="images/icons/confused.gif" />
