Digital Tuning New To Mustangs. 5.0 Sn95 Running Rich.

SnowRocker88 · Apr 10, 2012

It's not running so rich that it's fouling plugs or anything but there's a distinct (and strong) smell of gas while driving. I will attribute part of that to having turn downs under the trunk instead of tips extending past the bumper but it's still more than there should be I'm sure. That and the fact that I'm using an eighth tank of gas on my short commute to work and back...it has to be running mega rich. I don't have my odometer fixed yet so can't pin down an exact MPG number but it's not good. I used MAF cleaner and it didn't change anything so I'm going to assume it's not that. My coolant temp gauge shows it's running very cold but I'm pretty sure it's just a bad sender because the fan still comes on and the heat blows very hot. I also have an intermittent CEL that I have yet to check.

I'm going to start with pulling the codes to see if the computer will actually tell me what's wrong. If not I'll start by checking the TPS calibration. If that's not it I guess it'll be down to changing O2 sensors (but the computer should say if they're bad, right?).

VibrantRedGT · Apr 10, 2012

The rich condition is probably related to the coolant sensor / running cold issue. The ECC is reading that it needs to dump more fuel because the car is very cold. If the ECC reads this all the time it's going to continue to run rich until the sensor is fixed. Get the new sensor or you'll continue to throw money away in fuel.

Pulling codes is always a great idea. Change the O2's anyway. Most people don't change these and they are really important.

SnowRocker88 · Apr 10, 2012

VibrantRedGT said:
The rich condition is probably related to the coolant sensor / running cold issue. The ECC is reading that it needs to dump more fuel because the car is very cold. If the ECC reads this all the time it's going to continue to run rich until the sensor is fixed. Get the new sensor or you'll continue to throw money away in fuel.

Pulling codes is always a great idea. Change the O2's anyway. Most people don't change these and they are really important.

These engines run dual coolant temp sensors, right? One for the gauge and one for the ECU... If the fan still comes on that means the ECU coolant temp sensor is good, right? I could very easily be wrong. I'm VERY new to these motors. I will def be getting O2 sensors soon as well as a new thermostat and spark plugs.

Is there any way this could be IAT related?

ProKiller · Apr 10, 2012

agree with what Vib said. i would also recommend changing the o2s and checking your engine/chassis ground.

SnowRocker88 · Apr 10, 2012

ProKiller said:
agree with what Vib said. i would also recommend changing the o2s and checking your engine/chassis ground.

Yea, I read the ground straps are one of the first things to check. I forgot to mention that. I will be cleaning all the grounds and replacing them as necessary. I guess I know where to start and I'll update once some work has been put in. I appreciate the input.

1slow95 · Apr 10, 2012

SnowRocker88 said:
These engines run dual coolant temp sensors, right? One for the gauge and one for the ECU... If the fan still comes on that means the ECU coolant temp sensor is good, right? I could very easily be wrong. I'm VERY new to these motors. I will def be getting O2 sensors soon as well as a new thermostat and spark plugs.

Is there any way this could be IAT related?

Yes, the sensor for the ECU is in the heater pipe on the front passenger side of the engine. The fan will kick on at 210*(high at 220), and it should also come on if you turn on max AC or defrost regardless of temp.

I could be wrong, but I believe the IAT only effects timing. At high temps it will start pulling timing.

toyman · Apr 10, 2012

A cleaned MAF doesn't always mean a working MAF. The MAF and IAT signals allow the ECU to compute the air mass and thus adjust the fuel to maintain the programmed AFR. The O2's provides additional feedback to the ECU. If the MAF isn't reading properly the ECU will add extra fuel as that is the least risky strategy. The ECT sensor signal is telling the ECU the engine is cool/cold (from your description it appears to be correct though) the ECU will be adding fuel and will be running in open loop mode, ie. the O2's are turned off. The point I'm making is that you just cannot assume anything and you need to work through the diagnostics to resolve issues. What worked for someone else may not be your fix although the symptoms may appear identical.

SnowRocker88 · Apr 11, 2012

1slow95 said:
Yes, the sensor for the ECU is in the heater pipe on the front passenger side of the engine. The fan will kick on at 210*(high at 220), and it should also come on if you turn on max AC or defrost regardless of temp.

I could be wrong, but I believe the IAT only effects timing. At high temps it will start pulling timing.

Thank you. So, since my fan came on and I didn't have my air on at all (much less on 'max AC') then I can assume that sensor is good and the engine is running at the correct temperature?

toyman said:
A cleaned MAF doesn't always mean a working MAF. The MAF and IAT signals allow the ECU to compute the air mass and thus adjust the fuel to maintain the programmed AFR. The O2's provides additional feedback to the ECU. If the MAF isn't reading properly the ECU will add extra fuel as that is the least risky strategy. The ECT sensor signal is telling the ECU the engine is cool/cold (from your description it appears to be correct though) the ECU will be adding fuel and will be running in open loop mode, ie. the O2's are turned off.

So what is the method to testing a MAF? It's not just 'swap for a new one' is it? That game gets very expensive...

toyman said:
The point I'm making is that you just cannot assume anything and you need to work through the diagnostics to resolve issues. What worked for someone else may not be your fix although the symptoms may appear identical.

Oh, I know this all too well. My other car is a 1991 Toyota MR2 turbo...let's just say she requires a lot of attention.

99FiveOh · Apr 11, 2012

Or maybe it's not running too rich at all. First, we don't know what kind of midpipe/h pipe you have. O/R H pipe'd Mustangs tend to be a bit more smellier than catted ones. And the fact that you have it dumped right under the car isn't helping either. All those gasses are building up under the car and finding their way into the cabin.

Also, how far is your "short" commute? Without knowing for sure or doing an actual MPG test there's no way to be certain.

I know from personal experience that I put like 10-15$ in the tank and it "shows" a little more than I expected, but it's just an illusion. 3 gallons is still just 3 gallons no matter what the needle says! And if you get 16-18mpg in town driving, it won't take many miles to burn that up. Not to mention, an 1/8th of a tank is only 1.9 gallons which doesn't take long to burn at all! You have to fill the tank up (sell your first born to do so I know!) and do the test properly before you can say for sure you have a problem.

SnowRocker88 · Apr 11, 2012

NotA4.6 said:
Or maybe it's not running too rich at all. First, we don't know what kind of midpipe/h pipe you have. O/R H pipe'd Mustangs tend to be a bit more smellier than catted ones. And the fact that you have it dumped right under the car isn't helping either. All those gasses are building up under the car and finding their way into the cabin.

I know from personal experience that I put like 10-15$ in the tank and it "shows" a little more than I expected, but it's just an illusion. 3 gallons is still just 3 gallons no matter what the needle says! And if you get 16-18mpg in town driving, it won't take many miles to burn that up. Not to mention, an 1/8th of a tank is only 1.9 gallons which doesn't take long to burn at all! You have to fill the tank up (sell your first born to do so I know!) and do the test properly before you can say for sure you have a problem.

Yea, I'm def not just going by the smell. I have a odometer gear on order so I should be able to quantify my MPG soon enough. Until then, yes, it's just me saying "this looks like it isn't adding up". And I did take the added smell from the turn-downs into consideration. That's why I included that tid-bit of information on here. Maybe you're right. I'll see when I get to installing my gear (when it comes in).

NotA4.6 said:
Also, how far is your "short" commute? Without knowing for sure or doing an actual MPG test there's no way to be certain.

Roughly 6.5 miles each way. Also, this is with maybe 4 or 5 stop lights. That's only like 7 MPG... Best case scenario it's still something like 10 MPG, right?

I appreciate the input everyone.

99FiveOh · Apr 11, 2012

I remember driving my old Foxes with turn downs, they'd always smell pig rich!

Oh, and how much gas are you putting in the tank to get the needle to 1/8th? The lower half of the tank always runs out faster than the top half so the gauge isn't accurate as far as equal portions of the tank are concerned. For example the bottom 1/8th of the gauge will fun down faster than the top 1/8th of the gauge. This is why I say get your odometer gear installed, top the tank off and drive around a few days then top it off again. Then you'll have your actual MPG and you can go from there.

SnowRocker88 · Apr 11, 2012

NotA4.6 said:
I remember driving my old Foxes with turn downs, they'd always smell pig rich!

Oh, and how much gas are you putting in the tank to get the needle to 1/8th? The lower half of the tank always runs out faster than the top half so the gauge isn't accurate as far as equal portions of the tank are concerned. For example the bottom 1/8th of the gauge will fun down faster than the top 1/8th of the gauge. This is why I say get your odometer gear installed, top the tank off and drive around a few days then top it off again. Then you'll have your actual MPG and you can go from there.

Oh dear god...I've been looking at the top quarter/eighth. So far I haven't let her go down past a 1/2 tank just because she's sucking it down so fast...

SnowRocker88 · Apr 11, 2012

Oh, and to compare: I had my Toyota MR2 running an open downpipe (running pretty darn rich as they like to do) and this smells stronger than that.

99FiveOh · Apr 11, 2012

2 completely different engines with completely different engine management strategies. Really no comparison.

VibrantRedGT · Apr 11, 2012

When doing any repairs you start with the easiest stuff first. Right now I'd get that coolant sensor fixed then move on. Don't just throw parts on, that's throwing money away.

99FiveOh · Apr 11, 2012

He said his temp sender is bad, not the ECT. Until he pulls codes there's no telling if the ECT is bad or if it's even to blame for any of this. The sender only communicates with the cluster, the computer doesn't use it's signal for anything. Also, these gauges are just guides to let you know if everything is within parameters. Don't use the stock gauge as the "end all" of what you're temps truly are. You need an aftermarket gauge to find out for certain.

SnowRocker88 · Apr 11, 2012

Parts came in today. My odo will be fixed and my temp sender will be replaced. I'll be able to quantify my MPG. I still haven't had time to run it by my buddy's shop to pull codes but I'll get that done probably this weekend if I don't go out of town.

BANGERSTANGER76 · Apr 11, 2012

Nice paint color bro.

4.6 is right.

That gas gauge reads funny at the bottom. It seems like it goes faster.
Tighten up your Odo. Put your temp sensor & your plugs etc on.
Get your codes pulled to make sure your O2's & MAF are functioning correctly and go from there.

Banger.

SnowRocker88 · Apr 11, 2012

BANGERSTANGER76 said:
Nice paint color bro.

Thx. I'm loving the Deep Forest Green with the Bullett wheels. I never would have thought of the combination but I'm glad I got what I got. I'm loving the car.

BANGERSTANGER76 said:
4.6 is right.

That gas gauge reads funny at the bottom. It seems like it goes faster.
Tighten up your Odo. Put your temp sensor & your plugs etc on.
Get your codes pulled to make sure your O2's & MAF are functioning correctly and go from there.

Banger.

Thx

toyman · Apr 11, 2012

Two things are a must have in your tool kit. First an OBDI code reader like this ($25) and a repair manual (Haynes or equivalent). The code reader will let you know what the ECU has logged as sensors being out of the specified parameters and the manual will show you how to do the repair and/or test the electrical component that is suspect. This $50 investment will save you big $$$$'s compared to guessing and throwing new parts on in the hope it will solve the problem.

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