I changed my spark plugs 3 days ago and got an oil change the same day. Ever since then my car hasn't been the same. The car drives fine. No funky noises and no hesitance. When I am decreasing speed and in 4th gear (2005 2.3 auto) the rev needle starts to jump up and down, and the engine starts shaking. This starts happening at between 30-25 mph in 4th. The rpm's jump between 500 and 1000. The car starts shaking and sometimes stalls. I've been looking around at what may be the cause. I checked the coil on plugs, all 4 are fine. I saw someone on youtube having similar problems. It was worse than mine but still similar. He wrote that it wound up being his MAF sensor. My CEL isn't on, but i checked the MAF sensor and it was dirty. I bought some MAF cleaner and cleaned the MAF and IAT sensors. The problem still persists. I read about a "lean misfire." The symptoms seem to fit. Do I need a new MAF sensor? I am trying my hardest not to go to the dealership or spend a lot of money on a new part.

When changing the plugs, I disconnected the battery. I also disconnected the battery when cleaning the sensor. I bought Bosch Platinum +4 plugs. I also put fuel injector cleaner in the car.
Here's the video I watched. Mine doesn't jump as much at idle.

http://www.youtube.com/watch?v=ZOOAfumJiOY

Any input is greatly appreciated.
Thanks.
Lev.

 

Hmmmm? That experience makes me afraid to change my plugs??

Well, you know what they say, time to work backwards.

you say the only things you had done were oil and plugs, and an oil change is not liable to cause such a problem.
If you still have the old plugs, I'd try putting them back in to see if that's it.
Are all the connectors on the coils correctly and tightly? (though I'm sure you would've checked that already.)

When I was much younger than today, I helped a friend tune up his Saab. The car ran fine but he wanted to tune it up.
We put in all new parts, checked and double checked the dwell (points) and timing, and plug wires (only 3 on that engine) and everything seemed OK... expect the car would not start!
For 3 days we struggled with this car. Finally we started working backward and the problem turned out to be the "new" condensor... a "25 cent part." Put the old one back in and she fired right up.

 

Hey Richard,
Normally I would save something like my old plugs just in case. I saved an old pair of windshield wipers a few years back and wound up putting them back on a few days ago. Unfortunately, I threw the old plugs out. I did this on Thursday and garbage pick up was Friday. I was thinking it may be the plugs because it started after I put them in. I'm kicking myself for not keeping the old plugs. I'll try to return the plugs and see if new ones will fix my problem. Otherwise, it's off to the dealer :,-(

 

Two things, bosch plugs are garbage, second, make sure that the plugs are all the same thread length. But really i havent known one person near me to have any luck with bosch plugs at any level

 

I was originally going to get NGK iridium plugs but no place around me had them, and I didn't want to wait 4 days. I guess I should have waited. I thought Bosch would be good. I should have been a smarter shopper and read some reviews first. I'm going to go to advance now and get some Motorcraft plugs. I'll let you guys know if that fixes it.

 

Before I even got through your initial post I said to myself, "Ten to one someone sold him non-OEM plugs." Long story short, even if the replacement plugs are "good" (i.e. the work to the spec of the manufacturer), that in no way means they'll work in your car. Then again, there is definitely something in what Richard says regarding Bosch plugs.

Over the last couple of decades I've owned a number of cars built in Germany, the U.S., and Japan, and with the exception of a couple of the U.S. built cars which had Champion plugs from the factory, every one of them came with NGK plugs, the German cars included. I initially found it odd that the VWs, Audis and BMWs all had NGK plugs in spite of the fact that they contained plenty of Bosch parts (like the complete fuel injection system on at least three of the cars), but after years of hearing bad things about Bosch plugs, I'm no longer surprised.

 

Actually it was Travis that said Bosch is junk. I used to use Bosch plugs in my Volvo's and liked them. But that was then and this is now.
I too have read they aren't what they once were.
Wasn't the Robert Bosch Corp bought out by somebody? I'm sure the were I just can't remember by whom.
Or perhaps this is what happens to the quality of your parts when you begin selling them at Wal-Mart?

 

I switched the Bosch plugs for Motorcraft plugs. The jumping still continues. I guess its off to my mechanic. Damn it!

 

I know what you mean. Honestly it seems like your car just need to "relearn" after being reset. I used to have the bosch plat 4 plugs and they were junk in my car. I went to NGK plugs and they work way better than the bosch, less hesitation, better fuel eco. etc.
I seem to have the problem that you have when i replace my intake. I would check for small leaks in your intake tubing. I had a cracked intake boot where it connected to the TB and it was causing a small leak. My jumps were way erratic though basically from stalling and the jumping to almost 2000 rpms. I'm not saying that isn't a lean misfire but my similar problems happened all with my intake. (leaks, loose maf sensor etc)
Mine happened the same way. Driving and going was fine but when i laid off the gas and coasted or breaking around 25-30mph things would go nuts.

My jumping would go away after about 30-50 miles of resetting the battery though

 

That's exactly how it feels, like it has to relearn. It's been 2-3 weeks and it hasn't learned anything. Are your revs still jumping or fixing the leak solved the problem?

The car runs great. It has a lot more pep in its step, and the shifts seem a lot smoother. I haven't noticed any gas mileage increase. I've also been driving a little faster because of the improved performance. I was told by a friend that it may be my fuel filter. Is that a possibility?