Does everyone's V6 idle rough? Injectors?

pixapusho

Member
I've got a rough idle... usually idles around 680-730rpm. It will noticeably miss at idle. It drives fine, wouldn't call it fantastic. Does everyone experience the rough idle at least? Found a TON of threads about it when searching. Some claim it's just the essex V6. My OBD2 bluetooth scanner will not read Ford's misfire PID's... so i've got to find a different scanner.

At any rate... newer engine < 50k, I run premium gas, new oxygen sensors, lower/upper gaskets replaced.
Cleaned MAF. Changed IAC. New plug wires, plugs. No exhaust leaks anymore. Fuel trims indicate it's lean. Have not installed a new fuel filter yet... I know.

Long term fuel trim on bank 1 & 2 can be up to +4% to +7%, respectively. When averaged over the course of a few trips they are at +4%
Short term is -3% to 0% usually on either bank
I'm not sure what to make of it, but it seems that it is running lean, and is adding fuel to compensate. Log available.

250K on fuel injectors I think, at least that's what's on the body. Can't find any good source for affordable fuel injectors. I have a set from a '99 with low miles but spray pattern is different and the plastic injector bodies are cracked. Came from a running vehicle... not sure if they would begin to leak, but I don't want to give it a shot either. When I had the fuel rail out, I cleaned the injectors best I could and replaced o-rings.

I'm pointing my fingers at the injectors or coil, since they are essentially the only things I have not replaced when I did my engine swap. The previous engine idled just as rough with 250K on it. In fact, I notice very little performance gain so that engine must have been in good shape.

Any input is appreciated. Fuel trims are something I've read about and analyzed, but still not exactly sure what to make of them. I do have the spreadsheet for the datalog if anyone is interested in comparing.
 

fasterthanyou

Active Member
I know the shimmy you're talking about. It's not like its a dead miss, but isnt totally smooth. Your fuel trims seem good. Maybe its the injectors or maybe do a compression check and cylinder leakdown test on all cylinders.
 

SixPackSurprise

My lil Turd
I have that same issue. been trying to trace it since I got my car. I'm thinking about getting a MSD or Accel Ignition Coil. Buddy of mine put one in his car and it cleared his right up.
 

pixapusho

Member
Was thinking about a good coil / MSD. That's worth a shot for $100. With the glasspack and headers it sounds a little lopey at idle. Funny part is the car doesnt shake like any other shaky idle i've had... Just nit picking :) Glad to know I'm not the only one. I think I've got to bite the bullet and put some new cats on it. Offroad x pipe is interesting, but this v6 can't stand to lose ANY low end torque!
 

Phil II

Cone Destroyer
Small vacuum leaks can do this. My friend picked up an SVT focus. You could hear at idle when the eec went to open loop operation due to a dead pcv valve. Just enough unmetered air was causing a momentary lean condition.
 

Suek

Member
I had a problem with idle and I found on my 2002 the huge hose that goes from next to( Sort of down a little) the throttle body to the wheel well, to the charcoal canister was falling apart. I didn't take the wheel off and the shield. I was able to unscrew a couple bolts and git my hand in there and get it. I used a razor blade to cut the old one off the canister. To get the tube on I used just a tiny bit of Vaseline. Do you have a tune on it? I ask because your running premium gas. I also had idle with a DPFE4 Exhaust gas recirculation pressure sensor. It as to do with the Egr valve. This part can make it run lean if it's shot. Amazon.com: Motorcraft DPFE4 Exhaust Gas Recirculation Pressure Feedback Sensor: Automotive
 
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KirkComer

1999 3.8L 5 Speed
Mine has idled a little funky forever. I put MSD coil, MSD ignition and iridium plugs in it... none of that made a difference.
 

KirkComer

1999 3.8L 5 Speed
Its not a miss... but rather a "surge" sometimes... rpms don't really bounce around... I wish I could explain it better. No one would notice it but me... I'm just too picky for my own good sometimes. lol
 

KirkComer

1999 3.8L 5 Speed
I need to invest in a tuner at some point. I'm just a little hung up if I want to throw any more money towards this 3.8 or if I want to install a pushrod carbed 5.0 or just sell it and buy a GT (which are selling cheap) lol Decisions, decisions... I really like the look of the 99-04's and I like the rumble of a v8. Okay, okay... I know this is the v6 forum so I'll shut up about the v8's. haha
 

Suek

Member
Its not a miss... but rather a "surge" sometimes... rpms don't really bounce around... I wish I could explain it better. No one would notice it but me... I'm just too picky for my own good sometimes. lol
I need to invest in a tuner at some point. I'm just a little hung up if I want to throw any more money towards this 3.8 or if I want to install a pushrod carbed 5.0 or just sell it and buy a GT (which are selling cheap) lol Decisions, decisions... I really like the look of the 99-04's and I like the rumble of a v8. Okay, okay... I know this is the v6 forum so I'll shut up about the v8's. haha
So the car goes ahead a tiny bit ? I notice EVERYTHING with my car also. Lol I know I had a surge when I bought mine. I changed the IAC, That thick hose that goes to the charcoal canister from the intake manifold, near the throttle bottle, and the DPFE4 Exhaust gas recirculation pressure feedback sensor all in one day. So I don't know which one fixed it. Lol It was a noticeable surge. Say if you were at a drive through she'd go ahead a bit. That hose was collapsed in one part. I won't tell anyone you said V8. LOL
 

KirkComer

1999 3.8L 5 Speed
Thanks for the tips. It's not a big deal to me but I might work on it sometime... if I decide not to do anything with that last sentence you mentioned. ;)
 

oldfox

Member
Ok make fun,,,,,, I had a rough idle and over revved on accident it and now it is smooth at an idle. Carbon maybe?
 

Captain Max Silver

Captain Max Silver
Was thinking about a good coil / MSD. That's worth a shot for $100. With the glasspack and headers it sounds a little lopey at idle. Funny part is the car doesnt shake like any other shaky idle i've had... Just nit picking :) Glad to know I'm not the only one. I think I've got to bite the bullet and put some new cats on it. Offroad x pipe is interesting, but this v6 can't stand to lose ANY low end torque!
Go With A H Pipe. Just Have A Piece Of Pipe Welded In After Cats In Front Of Mufflers. Just Pipe 2" To 2.5" Depending On What You Have Installed, Mine 2.5". Did That To Mine When Installed Shorty Headers. Keeps The Torque, Even Sounds A Little Better. X Pipe High Speed Open Highway Stuff. Just Thought I'd Add My 2 Cents!!
 

pixapusho

Member
Thanks for the input. Still have my ancient coil. I did fuel filter and it helped my hard starts oddly enough. I assumed a "performance" coil wouldnt help. As Kirk said, I am also looking for perfection. The idle isnt shakey enough for concern. I have learned to accept it. It runs great otherwise. I am lowering it this weekend. It is a great reliable daily, but Ive recently put all of my money into my turbo DSM and havent touched the Mustang since I installed the headers 4 months ago or so. The DSM is not capable if being a daily! With 190k and a boost leak it is much faster than the V6 Mustang. It is apart and at the machine shop now. 252K on the Mustang body, hoping to drive it til its death. Love the Mustang for its parts availability, ease of service and reliability
 
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