DaveInPhilly Posted September 9, 2014 Share Posted September 9, 2014 So my 2006 2.3L just hit 105k so I replaced the plugs per the maintenance schedule. I used the Autolite Iridium plugs that I thought were supposed to be the same as the OEM plugs, but they were not actually identical the plugs that came out. The plugs came out fine, two of them had a bit of oil on the threads, but the tips were clean so I am not too worried about that. Ever since the new plugs went in the idle has been a little off. When I come to a stop the idle drops real low (about 600 rpm, then bounces back to ~900rpm, before settling down and constantly fluctuating between 790-830rpm. Otherwise the car runs great. It's not much a problem, and someone who isn't as familiar with car as I am may not even notice, but something is definitely going on. 0 Quote Link to comment Share on other sites More sharing options...
jeff711981 Posted September 9, 2014 Share Posted September 9, 2014 Are you sure all the wires are connected properly and connections are well seated? Didn't knock any sensor wires loose while changing plugs? Forget to reconnect anything? 0 Quote Link to comment Share on other sites More sharing options...
Noahfreak Posted September 10, 2014 Share Posted September 10, 2014 Sounds like you might have knocked a vacuum line off (or cracked one that's dry rotted from heat) or didn't seat the airbox properly. These engines are really sensitive to stuff like that. Even one clip unfastened on the airbox will make them run funny because it disturbs the flow over the MAF sensor. If it was a misfire condition due to the spark plugs, it would likely set off a CEL. Check all your vacuum lines and all of the fittings on the intake. Also, that many miles and 8 years old, could be something completely unrelated to your tune up job. 1 Quote Link to comment Share on other sites More sharing options...
DaveInPhilly Posted September 10, 2014 Author Share Posted September 10, 2014 (edited) Thanks, it didn't occur to me to check the airbox. I did also replace the air filter. I should also mention that mine is a manual transmission. I will check and report back. I also read that some folks in the F-150 forum have found that disconnecting the battery for 15 min and then going through the start up procedure a second time has resolved rough idle after changing spark plugs, so I'll give that a try too. I did double check everything except the torque on the plugs. Edited September 10, 2014 by DaveInPhilly 0 Quote Link to comment Share on other sites More sharing options...
BlackBetty Posted September 15, 2014 Share Posted September 15, 2014 Like Noahfreak said sounds like a vacuum leak! 0 Quote Link to comment Share on other sites More sharing options...
DaveInPhilly Posted September 16, 2014 Author Share Posted September 16, 2014 I checked the airbox and it is sealed properly. I checked the lines that I could see and everything looks proper. -Could an improper gap on the plugs be the culprit? This was the first time I used one of those wire loop dealies. -How much should the RPM vary at idle, is vacillating between 790-830 normal, or should it stay more consistently at a single RPM? -Since there is no obvious leak, how do I go about checking for a less obvious leak, or do I just start replacing hoses until it stops? 0 Quote Link to comment Share on other sites More sharing options...
jeff711981 Posted September 16, 2014 Share Posted September 16, 2014 I checked the airbox and it is sealed properly. I checked the lines that I could see and everything looks proper. -Could an improper gap on the plugs be the culprit? This was the first time I used one of those wire loop dealies. -How much should the RPM vary at idle, is vacillating between 790-830 normal, or should it stay more consistently at a single RPM? -Since there is no obvious leak, how do I go about checking for a less obvious leak, or do I just start replacing hoses until it stops? 0 Quote Link to comment Share on other sites More sharing options...
jeff711981 Posted September 16, 2014 Share Posted September 16, 2014 Or this... 0 Quote Link to comment Share on other sites More sharing options...
jeff711981 Posted September 16, 2014 Share Posted September 16, 2014 Sorry for the flurry of posts... but to answer your question about idle, here's some datalogs from my car, which does not have a rough idle. (Notice the biggest and quickest change in RPM is from about 788 to 754 - so a 30-40 RPM change in idle speed does not make for a rough running engine) 0 Quote Link to comment Share on other sites More sharing options...
DaveInPhilly Posted September 17, 2014 Author Share Posted September 17, 2014 Sorry, I can't view the videos at work, I'll take a look when I get home. But I should be clear, the engine isn't really running rough. Sometimes, when I come to a stop the RPMs will drop really low and then race back up before settling down. This feels a bit as if I have left the car in gear too long. Beyond that I can't really feel the engine doing anything out of the ordinary, I just see the tach ticking up and down a bit. When I plugged in my OBD reader, I can see the actual RPMs fluctuating. 0 Quote Link to comment Share on other sites More sharing options...
DaveInPhilly Posted September 29, 2014 Author Share Posted September 29, 2014 Well, I'm stumped. I pulled the plugs and double checked everything and everything looks good. I reset the idle trim strategy, no luck. I cleaned the throttle body, though it didn't really need it. I can't find any vacuum leaks. I just don't know. The problem is not quite as bad as it had been. For the most part the only symptom is the RPMs fluttering between 780-830 while sitting at a stop. Occasionally, when coming to a stop the RPMs will drop down to about 500 rpm, and then jump to about 1000 rpms, then settle down to that 780-830 range. I just don't know.. The car runs fine, and I am not getting any error codes, so I guess I'll just keep an eye on it and make sure it doesn't get any worse. 0 Quote Link to comment Share on other sites More sharing options...
FusionDiffusion Posted September 30, 2014 Share Posted September 30, 2014 Did you inspect the coil boots for signs of carbon tracking? Did you put a little dielectric grease on the inside of the boots? Is the engine any different under full load? 0 Quote Link to comment Share on other sites More sharing options...
DaveInPhilly Posted September 30, 2014 Author Share Posted September 30, 2014 The boots all look good. All nice and clean. I did use dielectric grease, and added a bit more when I pulled and replaced the plugs this last time. It does seem to do this a bit more when the AC is going, but that might just be in my head. Though the other morning I had the head lights, radio, and rear defroster on at the same time, and didn't seem to have any problem at all. 0 Quote Link to comment Share on other sites More sharing options...
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