Hello guys,

my SC 08 GT/CS has developed a rough idle. It runs up to about 1200rpm when I start it up and then after a little while it gets down to its normal ~750rpm, but then after a bit it will suddenly dip to about 400rpm and just start running pretty rough and erratic.

After a little research, I decided to clean out the throttle body (there was gunk) and MAF sensor. Didn't help.

I think my next step is to replace the fuel filter, which is probably overdue.

Just looking for any tips or suggestions on what else I can look at.

thanks

 

Check all your vacuum hosed one may have popped off somewhere and you might want to check your throttle position sensor also.

Also check your CAI intake to make sure there are no leaks after the MAF.

Have you recently installed any new mods? Do you had a tuner? Have you Checked for codes? Did you ever get a check engine light?

 

No new mods recently, and the CEL did come on after I cleaned the TB and MAF. I disconnected the battery and it went away, at least for the time being. I do have a Predator and plan to plug it in to look for codes.

 

The electronics in the throttle body can go bad and cause idle problems and deceleration problems. It happened on my car and it didn't throw any codes ...

 

Hey, so did you have to replace the throttle body? Does sounds like what I'm experiencing. Takes quite a while to reach normal idle speed at a stop.

thanks

 

Ok,

so replaced the fuel pump today and it's still not running right.

 

Yes I had to replace it , it's the fly by wire electronics that goes bad and I don't know if you find someone to fixed it , I'm pretty sure Ford won't. My idle wouldn't hold steady and would move up and down to around 400 RPM. On the highway if I put it in neutral at a high speed and let the RPM's drop it would drop down to 0 and stall. It never threw any codes , but Steeda was able to determine the electronics were bad. It may or may not be your problem , just something to consider.

 

Thanks, 05YGT, I'll keep that in mind...

 

Ok,

so I hooked up my Predator and lo and behold, it pulled up 3 trouble codes:

P0171 OBD-II Trouble Code
System Too Lean (Bank 1)


P0174 OBD-II Trouble Code

System Too Lean (Bank 2)

P1000 FORD -


On Board Diagnostic System Readiness Test Not Complete

I looked up the codes, and they pretty much point to what I've already looked at, but I guess I need to take a closer look for any vacuum leaks. Hmmm...

 

How about the O2 sensors ?

 

Yes, those are possible culprits, too, although I'm not sure how to check those. Guess I'll have to look it up.

 

TL;DR - I had same problem. Clean the air intake stuff.

The first time I cleaned my air filter with that special oil, my RPM went all wacky. Up to like 1200 and down and all in between. I read into it, turns out I "over oiled" the air filter. I took it apart again, sure enough there was oil everywhere lol. I cleaned the filter again. Also cleaned the Mass Airflow Sensor in the air intake because it was covered in oil droplets. I used brake cleaner as suggested and it works awesome. It sometimes idles 500-650 or so, but I'm fine with it.

After reading some other posts I might clean the throttle body now too. It makes sense for RPM to be all wacky. It's an air/fuel mixture explosion blah blah blah. If a foreign object/material gets inside (oil for instance) it won't explode right I guess? lol. I'm so not a car guy haha.