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Old 03-10-2013, 09:20 PM   #1
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Shake at idle only

2000 V6 3.8
In neutral, I rev up the engine a little and coming back down, the rpm gauge stops around 1000 rpm for about 3 seconds, then drops to 700-800 rpm and starts to shake really noticeably. When you either take off or rev up the engine, the shake goes away completely.

I've replaced all spark plugs and wires, replaced the cam positioning sensor, new fuel filter, sprayed a mist of water on the thing that all the spark plug wires lead to(not sure the name of that but was told that if it was not sealed, I would see by misting it with water), and it was fine. I have taken out the MAF sensor and cleaned it with MAF cleaner.

I have a constant check engine light that throws the o2 sensor code. The mustang has straight dual pipes that have had the cats removed and no 02 sensors are plugs in to the two plugs toward the back. They have the two o2 sensors up front by the engine but not the ones toward the back that I think are suppose to go in front of and behind the cat.

Is missing the two back O2 sensors the reason for the shake only at idle? Is the rpm stopping at 1000 for 3 secs and then dropping to 700-800 range with shake all caused by no back o2 sensors?
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Old 03-10-2013, 09:43 PM   #2
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Try replacing your coil pack.. And make sure all the spark plugs aren't too tight and the wires pop onto the spark plugs all the way.
I replaced my coil pack and wires and everything and mines been running great! My cousin had that super shaky problem but that's cause his springs weren't touching the spark plug
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Old 03-10-2013, 10:11 PM   #3
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No the issue op is not with the rear o2 sensors...they are monitors and nothing more. However the o2 code could be thrown due to upstreams...the codes wouldnt happen to mention a sensor 1 does it? The upstreams help the car decide air/fuel mix...if you've replaced everything else that can throw an o2 code you may consider replacing just that..the upstreams. Had to do this on my GT was a fun time (not really lol)
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Old 03-11-2013, 11:16 AM   #4
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I always thought that the codes it was throwing had to do with the missing O2 sensor in the back. I'll have O'Rielly's run them again to pin point which O2 sensor it causing the light.

So, was your car doing exactly what mine is doing before you replaced the upstreams? and did that fix the problem completely?
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Old 03-11-2013, 11:46 AM   #5
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before you spend any money it may just be gunked up MAF sensor or idle bypass valve.

Get some electronic cleaner (spray cleaner) that is NO residue on contact cleaner. Hose down the MAF sensor (be careful accessing it). Then clean the IAC valve (idle bypass valve) if the MAF cleaning didnt fix it. Then after those two free mods look into other things.

Plugs may be an easy/cheap check as well

If you have a K&N the maf may be gunked from the oil they use as well.
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Old 03-11-2013, 07:01 PM   #6
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I cleaned the MAF with MAF cleaner already.

Lets pretend the MAF sensor is working fine and doing exactly what it's suppose to do. If I have the car at idle and shaking, like its currently doing, and I unplug the MAF sensor, should I tell a difference in the way the car is running?
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Old 03-12-2013, 10:49 PM   #7
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Quote:
Originally Posted by SpectorV View Post
before you spend any money it may just be gunked up MAF sensor or idle bypass valve.

Get some electronic cleaner (spray cleaner) that is NO residue on contact cleaner. Hose down the MAF sensor (be careful accessing it). Then clean the IAC valve (idle bypass valve) if the MAF cleaning didnt fix it. Then after those two free mods look into other things.

Plugs may be an easy/cheap check as well

If you have a K&N the maf may be gunked from the oil they use as well.
I believe the IAC is called the Idle Air Control and definitely try to clean that if you haven't already along with the MAF, as a start.
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Old 03-14-2013, 11:11 PM   #8
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I have this exact problem, i have had it for about a year now to no avail. I replaced my coil pack, wires, plugs, fuel filter, oil change, cleaned my air filter, cleaned my MAF, cleaned my PCV, cleaned my EGR.....the last time i fan a diagnostic with my SCT tuner and my laptop it showed a intermittent completely random misfire on all 6 cylinders. before i replaced my coil pack wires and plugs it started to worsen till it got to the point where it would bog down while accelerating (almost to the point of a stall), after i changed them (about 8-10 months ago) its been much better but the shake is still there, engine mounts are fine,


The only thing i can see is the gunk build up. I took my upper intake manifold off one day and noticed a lot of gum like substance on the butterflies, the only thing i can think is that there is some of that inside the cylinders/heads/etc. and the last time i did a seafoam cleaning it didnt really help it.

Some of those things might help you though, since each one did improve it a little bit.
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Old 03-16-2013, 04:11 PM   #9
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Exclamation

So, I just came across this while doing some research on a few other things. And apparently this guy says that if the EGR Ports in the lower manifold are dirty that it could cause a misfire. I'm going to try cleaning this once I get some off time and see if It helps any.

I've never heard anyone mention something like this, but if its possible that this is the problem then this could be the solution for many people that I've heard complain about this same issue.
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Old 03-16-2013, 04:39 PM   #10
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Please post on here if that fixed your problem when you get it done. I hope that will work for you and I. Thanks for the information.
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Old 03-16-2013, 04:43 PM   #11
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Will do, I'll try to include pictures before and after to if it helps
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Old 04-06-2013, 01:33 PM   #12
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UPDATE:

I'm not sure if it has completely gotten rid of it but if it hasn't it has damn sure smoothed it out. I wasn't able to completely clean it but what little bit I was able to do with taking the upper intake Manifold off and some carb cleaner has helped tremendously.

Also cleaned the IAC a bit too...

I did forget to take pictures, but I and the wife have decided that I'm going to do a more in-depth cleaning whenever i go do to a drain & flush of the coolant system (since i'd need it drained anyway) and also do a EGR delete and delete the hoses for the PCV system so we can eliminate the oil in the intake from the PCV and any unspent fuel that might be settling in the intake from the EGR
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