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Discussion Starter · #1 ·
Hey guys! Got a few slight issues with my Mustang.

Installed Gen3R, working well. No issues to my understanding with the install as it's been on for the last 6 months.

I've noticed:
-When driving normally, coming to a complete stop, my car drops into the 300-400 RPM range almost stalling out.
-When cruising around 30-60 mph range at a steady RPM, the car almost seems to stutter slightly, can't make it happen all the time, but it's fairly noticeable, almost as if it's "hiccupping" if you will.
-When warm (200-210 coolant temp) my idle is still sitting around 800-1000.

Unsure if this is related but I also have P0420/P0430 codes currently, more than likely due to long tube headers w/ high flow cats. I'm unsure on how to test and see if the cats are functioning properly, or if it's the sensors.

Any insight to these issues would be amazing!
 

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Does the car have working O2 sensors? The ECM is going to look for certain parameters. It also may not like the aftermarket cats. I remember the "old" days, when you could change just about any part you wanted. Not so, anymore. Have someone put a decent scan tool on it & go from there. Good Luck.
 
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Discussion Starter · #3 ·
Does the car have working O2 sensors? The ECM is going to look for certain parameters. It also may not like the aftermarket cats. I remember the "old" days, when you could change just about any part you wanted. Not so, anymore. Have someone put a decent scan tool on it & go from there. Good Luck.
It does yes, both sets of them are functional. With that being said, is it the ECM trying to overcorrect what it thinks is wrong?
 

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You'll need to get a scan tool with live data capability and learn/research how to interpret what you see.
The P0420 and P0430 codes mean that the upstream and downstream oxygen sensors are reporting readings that are too similar on both banks.
My guess is that the cats may be cooked from an overly rich condition. Note that aftermarket cats are not made anywhere as well as a factory cats are. Aftermarket cats won't last but factory cats will usually go for the entire life of the car. There are multiple possible reasons for these codes but bad cats are the most common.
 

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My understanding: it is a common problem with long tube headers, because the cats are farther downstream and don't get hot enough to function correctly. But the downstream O2 sensors only check to see if the cats are working, they do not affect the way the car runs at all.

I'm guessing your minor issues are tune related. Was it like this since the supercharger install, or did something change? Was it dyno tuned?
 
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Discussion Starter · #6 ·
You'll need to get a scan tool with live data capability and learn/research how to interpret what you see.
The P0420 and P0430 codes mean that the upstream and downstream oxygen sensors are reporting readings that are too similar on both banks.
My guess is that the cats may be cooked from an overly rich condition. Note that aftermarket cats are not made anywhere as well as a factory cats are. Aftermarket cats won't last but factory cats will usually go for the entire life of the car. There are multiple possible reasons for these codes but bad cats are the most common.
Are there any tests to be done to see how well the cats are working? I suppose I could data log & see the voltages of both upstream and downstream O2 sensors to see how they're behaving. Another theory would be temp testing inlet & exhaust (no pun intended) of cats.

My understanding: it is a common problem with long tube headers, because the cats are farther downstream and don't get hot enough to function correctly. But the downstream O2 sensors only check to see if the cats are working, they do not affect the way the car runs at all.

I'm guessing your minor issues are tune related. Was it like this since the supercharger install, or did something change? Was it dyno tuned?
The other issues have been present since I've purchased the car. Before: It was tuned by BAMA (I didn't do it). The vehicle is currently etuned by VMP. Maybe I'll send them a datalog & see if they notice anything.
 

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yep I think it is a good idea to talk with VMP about the issues, and send them a datalog if they need one to better understand what is going on

and I think i would try to ignore the codes coming from the rear O2 sensors, because I think that is going to be a fact of life with this system .... back in the old days they would turn the rear O2's off in the tune so this wouldn't bother you, but now I think it is illegal to do that .. you could ask VMP about that too.
 
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+1 for data logging and sending to VMP. This is absolutely your best bet to diagnose accurately your conditions. Helpful suggestions:

1) Set your sampling frequency (if you can) to 0.1 seconds. The data log files get real big, real fast - so that will make file transfers a lot easier. You do not need to datalog at higher frequency than that.

2) Break the data logs into separate segments. First segment is always from a dead cold start to normal engine temp AT IDLE. You may hold the throttle at 1000 RPM, 2000 RPM and 3000 RPM for ~10 seconds each with~30 seconds in between to shorten the warm up time and possible try to recreate the 'coasting to idle' hiccups. This data log should take about 5 mins depending on your ambient temperature.

3) Obviously, try to get a datalog segment when the car hiccups at cruising speed.

4) WOT throttle data logs, while extremely helpful when tuning for power, are ONLY to be performed at your local drag strip or on the chassis dyno (highly, highly recommended BTW). You do not want a speeding or reckless driving ticket, a wadded-up car, or anybody hurt.
- - - - -

* If you have the ability to do so, rack your 'Stang and remove and at least visually inspect your O2 sensors. Are they wet, black, and sooty? I believe you may be running a tad rich - and that would be a symptom. You may also wish to pull and inspect your spark plugs. Same inspection.

* This next suggestion will require some proper fitting and gauges (or pressure transducers) - but you may also wish to physically measure the actual back pressure of your exhaust. This is not for the faint of heart - all your fittings and gauges must be rated for the temp and properly sealed and connected - but it is an absolute way of determining if you have plugged or clogged cats. You should observe little or no (<1 psi) pressure drop across your cats and the upstream O2 sensors should be near zero psi.

* You may consider disabling the rear O2 sensors via a revised tune (or if you know how to use ForScan) - but as others have mentioned - this will result in an automatic emission test failure. On a similar note, I'm not sure this will resolve your drivability issues.

Good luck and keep us posted. Feel free also to upload your datalog files here (in .csv file format, please!) There are members here who can read them on LiveLink Gen2 software.
 

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Are there any tests to be done to see how well the cats are working? I suppose I could data log & see the voltages of both upstream and downstream O2 sensors to see how they're behaving. Another theory would be temp testing inlet & exhaust (no pun intended) of cats.



The other issues have been present since I've purchased the car. Before: It was tuned by BAMA (I didn't do it). The vehicle is currently etuned by VMP. Maybe I'll send them a datalog & see if they notice anything.
You didn't datalog and send VMP the results when you first got the tune? No E-mail tune is perfect the first time out.
 

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Discussion Starter · #10 ·
+1 for data logging and sending to VMP. This is absolutely your best bet to diagnose accurately your conditions. Helpful suggestions:

1) Set your sampling frequency (if you can) to 0.1 seconds. The data log files get real big, real fast - so that will make file transfers a lot easier. You do not need to datalog at higher frequency than that.

2) Break the data logs into separate segments. First segment is always from a dead cold start to normal engine temp AT IDLE. You may hold the throttle at 1000 RPM, 2000 RPM and 3000 RPM for ~10 seconds each with~30 seconds in between to shorten the warm up time and possible try to recreate the 'coasting to idle' hiccups. This data log should take about 5 mins depending on your ambient temperature.

3) Obviously, try to get a datalog segment when the car hiccups at cruising speed.

4) WOT throttle data logs, while extremely helpful when tuning for power, are ONLY to be performed at your local drag strip or on the chassis dyno (highly, highly recommended BTW). You do not want a speeding or reckless driving ticket, a wadded-up car, or anybody hurt.
- - - - -

* If you have the ability to do so, rack your 'Stang and remove and at least visually inspect your O2 sensors. Are they wet, black, and sooty? I believe you may be running a tad rich - and that would be a symptom. You may also wish to pull and inspect your spark plugs. Same inspection.

* This next suggestion will require some proper fitting and gauges (or pressure transducers) - but you may also wish to physically measure the actual back pressure of your exhaust. This is not for the faint of heart - all your fittings and gauges must be rated for the temp and properly sealed and connected - but it is an absolute way of determining if you have plugged or clogged cats. You should observe little or no (<1 psi) pressure drop across your cats and the upstream O2 sensors should be near zero psi.

* You may consider disabling the rear O2 sensors via a revised tune (or if you know how to use ForScan) - but as others have mentioned - this will result in an automatic emission test failure. On a similar note, I'm not sure this will resolve your drivability issues.

Good luck and keep us posted. Feel free also to upload your datalog files here (in .csv file format, please!) There are members here who can read them on LiveLink Gen2 software.

I appreciate the input & I did take the advice of yours as well as other members. I have recorded:

Cold start to 180F
Idle for 30 sec then slow rev to 6000RPM
Town drive for 8 minutes

I recently checked my spark plugs with the advice of a friend of mine with a boosted Coyote. I had my spark plug gap set at .030", I've switched to .025".

I have noticed, my exhaust is fairly sooty (black residue). I pulled my entire exhaust yesterday to check for obstructions and to seal a few exhaust leaks and noticed the interior of the pipes were black.

I have yet to pull the O2 sensors, but my suggestion now is that they may be fouled?

I did record said datalogs but it doesn't seem as though I can input them into the thread in .csv format.
 

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My guess is that the cats may be cooked from an overly rich condition.
I'm still thinking that there's a good chance that the old piss poor Bama tune was making the car run too rich and it wound up destroying the cats. Bama has such a poor reputation. I would hope that the VMP tune didn't do it but it probably depends on when the drivability and code issue started. If they tuned it so that the PCM made it run a little too rich and you drove it like that for 6 months then that might be what caused this. Or it could have been a combo of a bad Bama tune and a not so ideal VMP tune that put the final nail in the coffin for the cats.
Are there any tests to be done to see how well the cats are working? I suppose I could data log & see the voltages of both upstream and downstream O2 sensors to see how they're behaving. Another theory would be temp testing inlet & exhaust (no pun intended) of cats.

The other issues have been present since I've purchased the car. Before: It was tuned by BAMA (I didn't do it). The vehicle is currently etuned by VMP. Maybe I'll send them a datalog & see if they notice anything.
Looking at the voltage of the upstream and downstream sensors is a good idea but taking a temp gun to the front and back of the cats when the engine is fully warmed up will definitely divulge if the cats are even doing anything at all anymore or just barely working depending on the temp differential. If so, they could be melted or just ruined by too much unburned gas being forced thru for too long.
 

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Datalogging with laptop? Import CSV file into Excel


Which aftermarket cats do you have and what RWHP level are you at (approx).
Some talk here on higher power levels and if cats can handle it or not.

 

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Datalogging with laptop? Import CSV file into Excel


Which aftermarket cats do you have and what RWHP level are you at (approx).
Some talk here on higher power levels and if cats can handle it or not.

I'm currently running BBK high flow cats w/ their long tube headers. I'm unsure of the state of them but I did remove the X-pipe and look at them, they didn't seem to be fouled but I also have no idea what I'm looking at in regards to cats.

Approx RWHP is in the 650ish range
 

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I'm currently running BBK high flow cats w/ their long tube headers. I'm unsure of the state of them but I did remove the X-pipe and look at them, they didn't seem to be fouled but I also have no idea what I'm looking at in regards to cats.

Approx RWHP is in the 650ish range
Probably OK with those. Would concentrate on the tune. Here is a vid of a guy that melted a stock cat @ 720 WHP. Go to about 7:20 if you don't want to
watch the entire thing (kind of boring).
 

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Which aftermarket cats do you have and what RWHP level are you at (approx).
The HP is really not going to matter. It's not the amount of power it's the tune and how rich it allows the fuel/air mixture to get under various conditions/at various times. Too much fuel in the exhaust is what usually burns up a cat or renders the ceramic matrix ineffective. Bad tunes are usually to blame for that on a modified car and being a Bama tune here sends up red flags.
I'm currently running BBK high flow cats w/ their long tube headers. I'm unsure of the state of them but I did remove the X-pipe and look at them, they didn't seem to be fouled but I also have no idea what I'm looking at in regards to cats.

Approx RWHP is in the 650ish range
The brand of aftermarket cat for the most part doesn't matter. None of them will have anywhere near the same amount of precious metals in them that a factory cat will. This means that they won't last as long or be as effective as a factory cat. They just have a better chance of failing and in less time.
Test your cats as I suggested. The temperature test is easy and definitive.
 

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The HP is really not going to matter. It's not the amount of power it's the tune and how rich it allows the fuel/air mixture to get under various conditions/at various times. Too much fuel in the exhaust is what usually burns up a cat or renders the ceramic matrix ineffective. Bad tunes are usually to blame for that on a modified car and being a Bama tune here sends up red flags.
I see what you are saying, ultra rich tune will kill them faster, but when you take a cat designed for 400 HP NA, and put 7-800 (gross) HP FI to it,
you have to run richer by default. Combine that with higher EGT's that comes with the FI (unless you run meth or water injection, which very few do in
the domestic V-8 world, anyway), and I can see why some guys are killing the stock one's after a blower, even with a decent tune.

Makes sense though that the aftermarket one's would hold up, since like you say, they have less to fail to begin with.
But even with that said, some of the brands seem to be holding up better than others.
 

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One thing I am surprised nobody has mentioned yet with regard to the P0420 and P0430 codes. With long tubes and high flow cats you will need to install defoulers on the rear o2 sensors. This will pull the sensors out of the direct flow and correct the readings to prevent those codes. This is assuming that the cats are good and there are no exhaust leaks, and is only necessary since tuners are no longer able to turn them off without risking massive fines. Defoulers are cheap and can be found all over ebay, etc. What style you go with will be determined by your clearance needs based on where the sensors are located in your new exhaust.
Now this isn't going to solve the issues you are having, as these codes are specifically for after combustion. I would definitely data log and have VMP look at what is going on. Good luck.
 

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Makes sense though that the aftermarket one's would hold up, since like you say, they have less to fail to begin with.
But even with that said, some of the brands seem to be holding up better than others.
No, it doesn't make sense that aftermarkets will generally hold up. I didn't say they had less in them to fail to begin with. I said they have less precious metals in them to last.
Less precious metals to catalyze the exhaust gas makes aftermarkets less effective right out of the box and also decreases their overall lifespan since there's less metal to react as they degrade over time. Aftermarket cats exist because they're cheaper replacements but definitely not better replacements. Not many people would buy an aftermarket catted mid pipe if it cost the same as a Ford mid pipe. With fewer precious metals it makes the cat less effective at converting the CO, NOX, and hydrocarbons so compared to a factory cat that puts it closer to triggering a trouble code even when it's brand new.
Running richer in a forced induction car will be harder on the cats in general but if you have a less efficient cat then it will just degrade faster. The life of an aftermarket cat will be much shorter since there's less elements to make the reactions in it as the cat slowly clogs or gets damaged. The PCM calculates that there's little happening inside the cat due to the sensor voltages being too similar and the PCM registers the codes.
 
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