Low/rough idle in gear, cleaned throttle body and MAF, still present

Hey all,

I've been doing some forum sleuthing and haven't found a fix yet. My 07 4.7L SR5 has a rough and loud idle while in gear (D, 1-5, R) and like 500-600 RPM, if I change to park or neutral the RPM's go up to about 800/900 and it smooths out. But when in gear at a stoplight or stopped at a drive through (can really here it there since it bounces off the building).

I cleaned the throttle body and MAF sensor with the cleaners made for that, tried a couple different "idle reset" procedures. nothing. still have the same low/rough idle in gear. Any help would be appreciated.

Thanks in advance!

 

This sounds more like a transmission issue to me than an engine issue. I'd start looking there. What's your fluid level etc? Also, idle IS normally rougher and lower in gear than neutral park, but yours sounds a little worse than normal.

 

Check all of your vacuum lines. Number one cause of idle issues is poor air control. Cleaning the MAF and throttle body was a good call. Vacuum lines would be my next stop.

 

I'll try and check vacuum lines and get the transmission fluid drain and fill done again. Thanks @Aerindel and @KNABORES

 

I don't know if you need a drain and fill just yet, but I would take a look at the fluid level, quality etc.

See, when your in park or neutral, the transmission is disconnected, and free-wheeling...when you go into drive etc, your not in gear, but the transmission is engaged and slipping. If its not slipping as cleanly as its supposed to, that would bog down your engine MORE than usual. I emphasis more, because there is always a drop in RPM, and a little roughness in Drive, but not moving, compared to park and neutral.

Also, keep in mind, if your climate control is set to Defrost, or Defrost/floor mix, regardless of your heat sitting, the AC system is running, wether you the AC button pressed or not.

And when the AC is running, that also draws down the RPM.

 

Agreed. Strategically spraying parts of the vacuum lines with a can of brake cleaner with the straw attached can help identify a leak.

Have you pulled your spark plugs to see what condition they are in? They could indicate a potential issue. Also, when was the last time you changed the timing belt? Could be stretched an messing with the timing. I had a Honda that would throw itself out of time and the engine would shut off. I had just purchased the vehicle from a private party who told me the timing belt had just been changed. It had not. And it was due for it's SECOND timing belt change.

 

Sounds like an IACV is dirty.. My 02 Celica had similar issues.. if it has it, I'd buy a gasket and crack it open and clean it out with brake clean.. have some coolant on hand.

 

ok updates. I found the noise, it is the muffler. at low idle it vibrates more and it sounds like the inside metal pieces have broken loose. From all my research it seems my idle numbers are pretty normal for the 4.7 in drive or rev vs in park/neutral, and idle goes up a little with lights on. I also did the carb cleaner spray on all vacuums and didn't have any idle changes. Truck runs great besides that noise that was annoying me. Its really hard to find that by yourself when it is only in gear.
In the process I also changed my spark plugs and my pcv valve, both looked original to the 07 with 165k miles. I also did a transmission pan drop and drain and fill of the WS ATF and changed out the atf oil strainer. All of my maintenance is up to date so i'm happy about that though. Truck is running in tip top shape just need to eventually get a new muffler I think.

Speaking of mufflers I kind of just want OE equivelant to keep costs down and keep OE performance and towing. Should I have a shop weld on something or get something bolt on like the ansa ty42405? I have the reg cab short bed 126.8" wheelbase. I would like to not have it louder or drone more than stock, I am one of few that hates loud exhaust systems..... (awaiting haters)

 

If you are still looking to replace your muffler try contacting Dirty Deeds for a BAM muffler exhaust they are handmade and bolt on