Need Help,engine started missing once it warms up.
Gentleman's Relish
Joined: Feb 2005
Posts: 13,189
From: AZ
RE: Need Help,engine started missing once it warms up.
ORIGINAL: RodGT35th
JGlisson, EXCELLENT CALL! What led you to your guess of #3 or #7 cylinder? That was great forsight man. My mechanic said he ended up hooking to his diagnostic machine. It was showing week ignition on #3. So he ohmed out the secondary and found it. He said it happens quite a bit on COP. Next time I'll know what to look for. PLUS I'll go to the salvage yard and buy repalcement COP. $97.00 each Ouch. Anyways, a big Blue Oval salute to your diagnostic skill.
Rod
JGlisson, EXCELLENT CALL! What led you to your guess of #3 or #7 cylinder? That was great forsight man. My mechanic said he ended up hooking to his diagnostic machine. It was showing week ignition on #3. So he ohmed out the secondary and found it. He said it happens quite a bit on COP. Next time I'll know what to look for. PLUS I'll go to the salvage yard and buy repalcement COP. $97.00 each Ouch. Anyways, a big Blue Oval salute to your diagnostic skill.
Rod
j/k
3rd Gear Member
Joined: Apr 2005
Posts: 607
RE: Need Help,engine started missing once it warms up.
Cylinder 3 & 7 seem to be the most common...not sure why, but they are. The way the engine is balanced...3 & 7 are more noticeable missfires as well. A #1 miss or # 8 is a much weaker miss.
$97 is a bit steep. Local dealer here charges me $65 a piece. If you have another one go...let me know.
And...right on about "octane" and its relationship to fuel.
$97 is a bit steep. Local dealer here charges me $65 a piece. If you have another one go...let me know.
And...right on about "octane" and its relationship to fuel.
3rd Gear Member
Joined: Apr 2005
Posts: 607
RE: Need Help,engine started missing once it warms up.
Here is cheap way to find which cylinder is misfiring (shade tree way...and a bit dangerous I might add).
Apply parking brake & start vehicle (engine needs to be hot of course).
Engage transmission in reverse and increase the idle speed to the common misfire range (1200-1500rpm). Easiest way to do this is to shim the throttle linkage stop screw with a coin or equivalent.
You should be getting a miss, if you have a bad coil that is.
Kill one injector at a time. You may also unplug a coil at a time, but you have to be quick. If you leave it unplugged more then a few seconds it will foul out the plug. It is easier to unplug one injector at a time. You will know when you have found the faulty coil when you kill the injector and the idle/engine balance remains unchanged. Of course if you have one faulty coil, 7 out of the 8 kills will result in a even rougher engine idle and rpms will drop when you kill each injector.
Did that make much sense? It is a little time consuming, but it works.
Apply parking brake & start vehicle (engine needs to be hot of course).
Engage transmission in reverse and increase the idle speed to the common misfire range (1200-1500rpm). Easiest way to do this is to shim the throttle linkage stop screw with a coin or equivalent.
You should be getting a miss, if you have a bad coil that is.
Kill one injector at a time. You may also unplug a coil at a time, but you have to be quick. If you leave it unplugged more then a few seconds it will foul out the plug. It is easier to unplug one injector at a time. You will know when you have found the faulty coil when you kill the injector and the idle/engine balance remains unchanged. Of course if you have one faulty coil, 7 out of the 8 kills will result in a even rougher engine idle and rpms will drop when you kill each injector.
Did that make much sense? It is a little time consuming, but it works.
5th Gear Member
Joined: Aug 2005
Posts: 2,638
From: Whitehall, Michigan
RE: Need Help,engine started missing once it warms up.
ORIGINAL: RodGT35th
Hey black01GT, thanks for replying. The problem actually was #3 COP (coil over plug) gone bad. See my last post.Car is running great now.
In reference to spark knock or detonation. You would actually increase octane levels if you were trying to remedy that type of situation. Using 89 or even 93 should help deter detonation. If I'm not mistaken and correct me people if I'm wrong. Octane raises the "flash point" of the fuel. This keeps the fuel or rather helps the fuel not to ignite because of cylinder hot spots or ....higher compression(dieseling).
Rod
Hey black01GT, thanks for replying. The problem actually was #3 COP (coil over plug) gone bad. See my last post.Car is running great now.
In reference to spark knock or detonation. You would actually increase octane levels if you were trying to remedy that type of situation. Using 89 or even 93 should help deter detonation. If I'm not mistaken and correct me people if I'm wrong. Octane raises the "flash point" of the fuel. This keeps the fuel or rather helps the fuel not to ignite because of cylinder hot spots or ....higher compression(dieseling).
Rod
Fuel burning too slowly will not cause a knock in the engine, it will end up with a lack of power. (This is why timing is advanced so the spark happens before TDC, the fuel doesn't all burn in an instant, if it did, a spark at TDC would be perfect). Switching to a lower octane to fix a problem with knocking/detonation will not help, it will make the problem worse.
The 4.6 PI GTs have 10.5:1 compression ratio, that's not exactly low. It's not high, but it's not low either.
5th Gear Member
Joined: Jul 2005
Posts: 2,387
From: Georgia
RE: Need Help,engine started missing once it warms up.
ORIGINAL: Jglisson
Blue04,
I dont' give a crap how long you been turning wrenches...you prove you don't know Fords, little alone Mustangs.
If you don't like the forum...click that little X at the top right corner of your screen...problem solved.
Blue04,
I dont' give a crap how long you been turning wrenches...you prove you don't know Fords, little alone Mustangs.
If you don't like the forum...click that little X at the top right corner of your screen...problem solved.
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