2000 V6 Need Help Diagnosing

Htxgen

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Mar 10, 2017
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hey guys, new to the forum. Daily/work vehicle is a 2000 mustang with 85,000 miles. It was previously owned by my grandmother but she passed and gave it to me. It sat most of its life. First thing I did when I got it is change battery (wouldn't start) and fuel filter shortly after. I've been experiencing a rough idle for a while now. Feels like it's cammed lol. Anyways, changed camshaft sensor (went out) as well as spark plugs, wires. 2 weeks after I changed idler pulley and serpentine belt. Well the car is still idling rough. What is weird is (symptoms of fuel injector?) is on a cold start it starts up fine. No hesitation. Very subtle rough idle but no big deal. Once it's warm if turn it off then restart it, it will idle very rough until I give it gas and get going.

No codes, no stores codes. I'm at a loss. I don't wanna waste money on changing 50 different things and it not fix it which is why I'm here to ask you guys. I know it's hard to diagnose over the web. I get it. Just wanted to see if anybody can relate to these symptoms or give me a few things to try first that may help me get it fixed. Thanks!
 
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Get yourself a can of spray ether and start poking around the engine bay. If it sat for a really long time, there's a pretty good chance there's an old/cracked line somewhere that's sucking in unmetered air.
 
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Yeah I probably should have checked for leaks and stuff like that first but I just figured it would be plugs/wires kind of fix. Thanks for your help.

That's still a possibility but you usually get codes for that sort of thing. It may be a small leak if it's not tripping the CEL or generating codes for O2 sensors.
 
Yeah no codes or stored codes last time I checked. I'm going to connect my obd2 this Friday and drive for about an hour and see if any funky readings come up. I still need to check for leaks. Yesterday I had to clean my terminals and I noticed my engine has a noticeable vibration when on. I know all engines vibrate to some extent but this seems worse. Been looking into symptoms of IAC and EGR and it doesn't really seem like those 2. But it might be. Cheap enough to fix when I check for leaks or bad hoses. Any other suggestions other than leaks? Kinda wanna go through everything in one day and get this over with.

It's never stalled before. Starts up fine. Just has a rough idle with a random rough idle. Sitting in bumper to bumper for a period of time makes the thing almost stall on me (at least that's what it feels like). As long as I have gas im good.
 
+1 on looking for a vac leak.

If the car has sat for an extended time the fuel injectors could be gummed up. If a fuel injector problem is suspected consider an injector cleaning and flow test service such as InjectorRX.com. Once cleaned and tested they are as good as new. Cheaper than new.

If you have access to an ODB2 scanner, look at the ODB2 type 6 monitoring results under the misfire. This could give a list of the cylinders actually misfiring.

Not a bad idea to have the alternator tested for correct output and excessive AC ripple (bad diode). No excuse to skip this step as almost all auto parts stores will test for free. Note, a bad alternator COULD cause your symptoms. As well as "CAUSE" a false bad cam sensor symptom.
 
Going to try to get to it this weekend. Alternator is 2 years old. Not throwing a code and my torque app isn't showing a stored code but maybe a real reader will bring up something different. I've had time to think about what exactly is going on symptom wise and here it is in list form. Just filled up and used a carb/injector cleaner additive to my gas.

1). Cold start, the car runs fine. Some roughness but nothing bad. Sometimes it's 100% fine

2). Warm start causes a very rough start and smoothes out once I give it gas and start rolling

3). It idled rough when engine is at normal temps with an occasional bucking. That bucking happened frequent in heavy traffic last weekend.

It seems to be responsive to temperature. I would think if it's a vacuum leak it would always do the problem. Very rarely it has a perfect idle. But it has happened. Happened this morning actually. 65 degrees outside and on a cold start.

Thinking about flushing the radiator as well.
 
So I have something interesting to report. So I'm sitting at a light and my windows are rolled halfway down. I press the button to roll them down all the way. Once the window reached the bottom, the car started shaking like crazy (RPMs dropped to like 500). I let off the button and RPMs return to normal and no shaking. So I did it again to see if it was a fluke. And it did it again! Wtf lol
 
So I have something interesting to report. So I'm sitting at a light and my windows are rolled halfway down. I press the button to roll them down all the way. Once the window reached the bottom, the car started shaking like crazy (RPMs dropped to like 500). I let off the button and RPMs return to normal and no shaking. So I did it again to see if it was a fluke. And it did it again! Wtf lol
I suspect that if you monitored battery voltage you would find that the battery voltage dropped when the alternator is heavily loaded (say from locked motor amps from the window motor).

Bottom line: Today's cars simply will not run right without a STRONG battery and charging system. IMO EVERY problem should start with a review of the charging system. Ignore this advice at your own risk.
 
I suspect that if you monitored battery voltage you would find that the battery voltage dropped when the alternator is heavily loaded (say from locked motor amps from the window motor).

Bottom line: Today's cars simply will not run right without a STRONG battery and charging system. IMO EVERY problem should start with a review of the charging system. Ignore this advice at your own risk.

So are you saying my battery/alternator could be the issue? Battery is about 2 years old. Might have to check it. Alternator has been replaced but not sure when exactly.
 
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Think I found the issue.

My dashcommand found a pending code. P0133 02 circuit slow response. Never threw a check engine light. This code came on for a minute or two then went away then came back.
 

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So I changed the o2 sensor and so far that seemed to fix most of the rough idle. The only rough idle I'm experiencing now is starting it up after it's already warm. And its only rough while I sit in the initial idle. Once I start going it's fine. And even that seems to be improved/not as rough.
 
Update: Since I changed the O2 sensor, it seems to be running better, but there is still a rough idle present. Mainly when I first start it up for the day and then when im in rush hour. I haven't been in thick rush hour yet to see if I still experience hard bucking but it does idle fine in normal traffic now. It also struggles just a little bit when it has sat for a few days and I start it up.
 
Having a rough cold start now. Cranks a few times and then turns over. Fuel pressure is good. Unplugged this harness and it started up great. Maybe my MAF?
 

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