4.0 V6 idle miss just at start up.
06-30-2018, 10:07 AM
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Join Date: Dec 2012
Location: WI
Posts: 1
4.0 V6 idle miss just at start up.
Usually a quick search of the forum has always given me an answer to any issue on this 2005 Mustang V6 with 130,000 miles. This has been a great car with very few issues over those miles and the 5 years of ownership. Many thanks to those who post problems and solutions. Not so lucky this time.
Symptoms: Upon initial start up with a cold engine there will be a light miss which gets worse if the transmission (automatic) is put in gear and brakes on. It will miss and shake but not steady. It will come and go for about 20 seconds and then goes away with no issues from then on. If rpms are increased it goes away. No codes are registered. Idles perfectly at 750 once through the initial start up.
Done so far: New air filter, Motorcraft spark plugs gapped correctly, fuel filter. Cleaned air flow sensor, throttle body, and checked EGR and PCV valve. Vacuum at 14 to 15 upon start up with 1200 rpm but it does very a little along with the rpm, settles in at 20 when idling at 750, and responds nicely after throttle blips. Listen test on fuel injectors has them all clicking well and the same. A can of techron injector cleaner has been used. No corrosion at the coil pack terminals. I have done the idle relearn process and upon the first start up the next day it did not miss. I moved the car a few yards to wash it and when restarted the miss was back. Once in a while it will not do it at all.
I would think if it was ignition a code would be thrown but maybe not. So before I throw a coil pack, wires, or injectors, at this problem that is intermittent and only at start up, I thought I would ask for opinions. What do you all think?
Symptoms: Upon initial start up with a cold engine there will be a light miss which gets worse if the transmission (automatic) is put in gear and brakes on. It will miss and shake but not steady. It will come and go for about 20 seconds and then goes away with no issues from then on. If rpms are increased it goes away. No codes are registered. Idles perfectly at 750 once through the initial start up.
Done so far: New air filter, Motorcraft spark plugs gapped correctly, fuel filter. Cleaned air flow sensor, throttle body, and checked EGR and PCV valve. Vacuum at 14 to 15 upon start up with 1200 rpm but it does very a little along with the rpm, settles in at 20 when idling at 750, and responds nicely after throttle blips. Listen test on fuel injectors has them all clicking well and the same. A can of techron injector cleaner has been used. No corrosion at the coil pack terminals. I have done the idle relearn process and upon the first start up the next day it did not miss. I moved the car a few yards to wash it and when restarted the miss was back. Once in a while it will not do it at all.
I would think if it was ignition a code would be thrown but maybe not. So before I throw a coil pack, wires, or injectors, at this problem that is intermittent and only at start up, I thought I would ask for opinions. What do you all think?
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