Rough Idle After Crash, Searched Like Crazy

[Backroad_Beast]

So first of all, I've been using that search button for months and haven't found what I need. If you've found something you think I missed that will help please throw the link in here.

The car is a 2007 Mustang GT with about 80k on the clock.

What happened: Car took a header into a deep ditch at about 30-35 last October. Radiator, A/C Condenser, some power steering lines and the front bumper were the only things damaged and/or replaced as far as I know.

What's happening: The issues started about a week after I got the car back from the body shop, so sometime in November. The car runs completely fine on cold start up. Once the car has warmed up it starts running like shit any time the RPM's drop below 1200 and the motor will actually die if I don't give it some gas or jack the idle up with my SCT Tuner. The car bucks and misfires, throws the P0345 code, and has no power until about 15-1700 RPM when the engine starts running clean and everything returns to normal.

What I've done to try to fix it: So based off of some other threads that I've read I figured this was an alternator issue. Since the issue started I've replaced the alternator 3 times with no change in symptoms. One of alternators replaced was a PA, the other 2 were Ford, all 3 burned out and failed tests when I replaced them. Moving on from the Alternator, I figured it was a vacuum leak in my intake manifold since I had to sacrifice a couple bolts for a buddy's build. I replaced the missing bolts and made sure everything was tight, no change in symptoms. I added Charge Motion Delete Plates with a new tune, no change in symptoms. Today I removed the Throttle Body and MAF and cleaned both of those really well, no change in symptoms. I have checked all my grounds, all my vacuum lines, everything I can think of and haven't figured the issue out yet. I have ran multiple tunes on the car since the issue started, with no change in symptoms. The only thing I have found that somewhat helps is keeping my idle turned up to about 1300. That doesn't keep the idle from getting rough, but it keeps the RPM's from dropping low enough to kill the motor.


This issue has been going on since November and I'm at a total loss. I've tried everything I can think of, and everything that's been suggested by others with nothing but negative results. I'm about ready to put the car back in the ditch and leave it there this time.

 

[Fullboogie]

When you say you checked vacuum lines, how did you do it? Spray brake cleaner all around vacuum sources and see if the idle changes. If so, you've found a vacuum leak. You should also download the SCT Livelink software and do some actual datalogging. See if there's anything obvious, or send the logs to your tuner.

 

[Randy]

Will bama take a look at his logs? I'm pretty sure that's who he has for a "tuner" atm

 

[Backroad_Beast]

When you say you checked vacuum lines, how did you do it? Spray brake cleaner all around vacuum sources and see if the idle changes. If so, you've found a vacuum leak. You should also download the SCT Livelink software and do some actual datalogging. See if there's anything obvious, or send the logs to your tuner.

I wasn't sure how to properly check the vacuum lines so I pretty much just made sure they were all tight. I'll do the brakeclean method tomorrow and see if I find anything. I've got livelink on my laptop already, I've just never tried to use it so I'll have to test that out tomorrow too.

Will bama take a look at his logs? I'm pretty sure that's who he has for a "tuner" atm

Ya I'm still using Bama for now.

 

[07TGGT]

Tight doesn't mean airtight. A line could have a very small cut that is almost impossible to see unless the line is removed and inspected closely, or it could be dry rotted and cracked.

Anyways, email or call Bama. Tell them the situation, ask what PIDs they want you to datalog, datalog and send them the file for review.

 

[Randy]

Good luck Killian. Hope you get this thing running right, sometime soon. If you do decide to ditch it though, I'll take the 8.8, nawz, and front/rear bumpers.

 

[toorbeenee]

check your crank trigger connector, its a long shot but worth it

 

[itsslow]

Replace your spark plugs and run a compression test... When you say you let a buddy have a few bolts, please tell me you're not referring to the one's holding the intake manifold down?

 

[Backroad_Beast]

When you say you let a buddy have a few bolts, please tell me you're not referring to the one's holding the intake manifold down?

Sadly yes. His boost build needed them more than my car at the time.

 

[Backroad_Beast]

I checked all the vacuum lines the right way today, didn't find anything wrong. Going to check my spark plugs and do some compression tests here in a little bit. If that doesn't yield anything I'll do some datalogging and hope that unleashes some secrets.

 

[Misfit_5.0]

Did you check your timing? If it's off by just one tooth you will notice a rough idle and somewhat slughish performance. Possible damage to the ignition system or plug wires hooked up in the wrong firing order would be another guess

 

[Backroad_Beast]

Did you check your timing? If it's off by just one tooth you will notice a rough idle and somewhat slughish performance. Possible damage to the ignition system or plug wires hooked up in the wrong firing order would be another guess

No I haven't checked timing, but I don't think that's it. I've never had the engine apart enough to mess with the timing and the shop shouldn't have had any reason to do so either.

 

[itsslow]

Well if your car passes a compression test that's a pretty good sign it's nothing major. Replace the spark plugs and do some data logging before you start messing around with your timing chain

 

[JEWC_Motorsports]

Sadly yes. His boost build needed them more than my car at the time.

Have you replaced the bolts, if not you found your problem.

 

[Backroad_Beast]

Well if your car passes a compression test that's a pretty good sign it's nothing major. Replace the spark plugs and do some data logging before you start messing around with your timing chain

Walking outside to check the plugs and do the compression test now.

Have you replaced the bolts, if not you found your problem.

Yes I have. I thought for sure that was going to fix the problem but no.

 

[JEWC_Motorsports]

Did any of the gaskets get torn or damaged? You may want to check them again. If you removed the bolts and drove around like that it is possible you sucked one in.

 

[Barrie]

did any of the gaskets get torn or damaged? You may want to check them again. If you removed the bolts and drove around like that it is possible you sucked one in.

x2.

 

[BruceH]

Walking outside to check the plugs and do the compression test now.






Yes I have. I thought for sure that was going to fix the problem but no.

Hi Killian,

Did you retorque the intake manifold with a torque wrench and use a torque pattern?

You are describing a vacuum leak. It's very possible that the intake isn't properly torqued or has a defective gasket like previously mentioned. Unmetered air could be entering from somewhere else too. It won't hurt to physically go over all the lines again, pulling and tugging to make sure everything is connected.

 

[Backroad_Beast]

Did any of the gaskets get torn or damaged? You may want to check them again. If you removed the bolts and drove around like that it is possible you sucked one in.

That's something I was worried about, but a couple weeks ago I added Charge Motion Delete Plates (with a new tune) and all the gaskets looked perfect. Nothing has changed since before I added them and I double checked all the bolts for tightness a couple days ago.

 

[Backroad_Beast]

Hi Killian,

Did you retorque the intake manifold with a torque wrench and use a torque pattern?

You are describing a vacuum leak. It's very possible that the intake isn't properly torqued or has a defective gasket like previously mentioned. Unmetered air could be entering from somewhere else too. It won't hurt to physically go over all the lines again, pulling and tugging to make sure everything is connected.

Hey Bruce,
I used a torque pattern but I don't have a torque wrench so I just got them as tight as I could. I just tried the brakeklean method a few hours ago, spraying at different points around my manifold and attached lines but didn't get any change in idle. Any ideas of where else to check?