Zetec off idle miss - CEG Archives

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Originally posted is Zetec maintainance, but Im hoping I can reach a few more people here.

Hot or cold, the engine stutters really bad when I hold it just higher than idle, mabye 1/8" of pedal travel. Problem is, thats all I need to keep the car going at speed, so its getting really annoying. Any throttle position above that the engine runs fine. Throttle response in nuetral is great, unless I try to rev it slowly from idle, then it bogs pretty bad. In gear, once I get the pedal past that point, the car accelerates smoothly.

In the last few weeks, I have installed new Autolite platinum plugs (proper gap), new wires, and replaced the timing belt. The miss was there before any of this was done, but was barely noticable and has gotten worse since. Reset PCM with no change. No CEL. New TPS installed, no change.

What do you think? Coil? Now Im thinking it could be fuel realated.

Originally posted by CRZYDRVR:
.... Reset PCM with no change. No CEL...

IAC valve, fuel or air filter.

I've changed my IAC, fuel filter twice and my air filter is new as well. I have not changed the TPS as of yet. I have a slight bogging just off idle as well. My fuel mileage isn't great either. I have no vacuum leaks and new plugs, coil and wires. No CEL either.
I'm thinking fuel injectors? Fuel preasure?

Originally posted by SquareHead:
..
I'm thinking fuel injectors? Fuel preasure?

A real time scan should determine that. You may want to get a scanner with that capability.

I had a real time scan done. The tech claimed it was running rich and the IAC was constantly trying to adjust as well as the MAF. He suggested one or more of the injectors might be dripping into the combustion chamber. I have no cels so that is what the findings were.

MAF? Never had it happen in the Tour (while driving) but had it happen in my Evo. The MAF ended up being dirty.

Originally posted by SquareHead:
.... ... He suggested one or more of the injectors might be dripping into the combustion chamber. ...

But the tech could not pin point which injectors were doing it?

Clean the MAF sensor as suggested by Hector.

Originally posted by Loco4G63:
MAF? Never had it happen in the Tour (while driving) but had it happen in my Evo. The MAF ended up being dirty.

Cool, I can try cleaning the MAF this weekend. After that I will look into replacing the IAC like Tony suggested.

Funny you mention it might be running rich, my Dad said it sounded like a rich miss.

Originally posted by Tony2005:

Originally posted by SquareHead:
..
I'm thinking fuel injectors? Fuel preasure?

A real time scan should determine that. You may want to get a scanner with that capability.

Is this what you are talking about? If not, what should I look for?

"Real-time monitoring, plotting, and logging of sensors.
(Ignition Timing, O2 Sensors, Fuel System, Air & Engine Temp, more!)"

Yup, that sounds like it.

Edit. Feedback doesn't show excellent. And pretty slow in delivery.

Ok, I just wanted to know that I was looking for the right thing.

Thanks a lot for your help so far.

I cleaned my MAF and IAT last night and it really helped.
My new job has me driving about 1 mile up and down a dusty gravel road eveyday. I also washed out my filter box as it was disgusting inside.

Cleaned the MAF and put in a new fuel filter, still there.

Guess Im gonna have to stop ignoring the post to change the IAC and just do it.

I'm not so sure it's the IAC.When mine went, it would start idling high with no warning. Or, would idle so low it would stall out in D or R. Never in Park.
If your engine has a mis-fire, it sounds more like timing, spark or ignition.
How does the timing belt look? How is the tensioner and does the belt have any slack between the two cams? If yes, then here lies the problem.

New timing belt, tensioners, TPS, plugs and wires in the last month.

Timing belt is timed and installed correctly. Its starting to miss a little more now, so bad that at while idling the other day I thought for sure the CEL would come on. It didnt.

Im gonna start checkingv acuum lines in the next couple days. Im also going to hook up a vacuum gauge and drive it around and see what it does too.

I guess Im due, this is the first real problem the car has given me since I bought it about 7 years ago.

Ok, some more info that hopefully can help someone help me fix the problem.

Timing never drops below 38 degrees from idle to 3500 RPM. Nuetral, in gear, it doesnt matter.

Hot idle- timing should be 15-25 degrees, at 30, 19-30 degrees. WAY higher than it should be. That would also explain the pinging Im geting when pulling steep hills ever since I bought the car.

MAF voltage- .3 at idle measured, never passes 1.0 at any speed.

Hot idle should be .6 to .9

MAF voltage is way off. Need a new one perhaps? Cleaned the MAF several times, also cleaned MAF connectors with no change.

Hooked a vacuum gauge to the unused port under the throttle body. Vacuum at idle and at speed is within tolerance, but the slightest opening of the throttle at any speed drops the needle 0 and stays there. The needle also flutters quickly between 0 and 15 when the engine reaches 3500 in gear. With most of my knowledge based on older V8 engines, I know there should be SOME vacuum at any speed with the throttle open.

Everything else my scanner shows is good. Still no CEL. Also replaced the upper o2 sensor since unplugging it showed no change in the way the car ran, so I hoped it had something to do with it.

On the plus side, gas mileage is outstanding since this problem started

I had a lot of idle issues with my zetec. I had just thrown on a used CTA intake along with the MAF the guy sent me. I decided after the car gave me a ton of issues, to swap with the old MAF and see what happened. I swapped with the one that was originally on the car, and it worked fine.

Sounds like MAF. If you do get one. Check to make sure the calibration is right for the vehicle. Look at the tag in the driver's door jam for the code.
How badly is it missing? If your fuel milage is good is it that bad?

Originally posted by Tony2005:

Originally posted by SquareHead:
.... ... He suggested one or more of the injectors might be dripping into the combustion chamber. ...

But the tech could not pin point which injectors were doing it?

Clean the MAF sensor as suggested by Hector.

No they weren't sure.
I cleaned the MAF / IAT and it did help.