I have had my SuperChip for about 2 years now, and have not had any major problems with my truck as long as I have owned it. However, I just recently noticed a rattle sound coming from my Gibson Exhaust. I have also noticed that my gas mileage has gotten considerably worse the last couple of weeks, and the truck did not seem to be running well. It took the truck to the local muffler shop to have a look at the Gibson Exhaust and he said the baffles in my muffler had burned up. He said this was likely because the fuel/air ratio was not correct and the truck was basically running too rich. This caused my exhaust to get too hot and burn out the baffle.

My question is this: 1)Does this sound legitimate? 2)could the fuel/air problem & truck running too hot be related to the SuperChip?

The last time I had my truck in for service, the dealership told me I should never put anything in the truck except 87 octane because higher octane burns too hot. Of course, I have continued putting high octane gas in the truck because of the SuperChip.

Please advise.

 

Hi lovemy4x4,

No, the Superchip did not cause your exhaust to burn up, my friend. There are literally thousands of F-150 owners using the Superchip and all kinds of exhaust systems, and that is not any kind of common occurrance. It is rather common to see Gibson exhaust systems have problems with blowouts, rustouts, etc., after a year or more on the truck, we here that on a fairly regular basis from owners who have had them on for a couple of years. There are also a number that don't have any problem with their Gibson exhausts as well of course, it's only fair to point out.

Your muffler shop doesn't have any knowledge about the air/fuel ratio from the Superchip, nor do they even have any equipment to actually test the vehicle for any kind of problem that would have anything to do with A/F ratio; they're guessing, based on what they saw in your old exhaust, that it's an A/F ratio problem, and they may indeed by quite right about that, but they have no idea whatsoever about the actual *cause*. It's not caused by the Superchip, nor is it caused by the Gibson exhaust, you've had the Superchip it on there for 2 years, as you say.

Here's an important fact to know: If you were running overly-rich, rich enough to clog an exhaust system, you'll get a check engine light from the DTC (error code) your ECU would throw from the feedback from your O2 sensors. The same goes if you were running dangerously lean, you'd get a check engine light for that as well.

However, it *is* possible that you are running a bit lean, or a bit rich, not lean or rich enough to actually hurt anything internally in the motor or you'd get a CE light, but lean enough or rich enough to cause some additional heat in the exhaust, and have that affect the exhaust over time. That is possible, we have seen that happen. We see that happen if certain modifications are done to the vehicle and are not tuned for, such as a changed MAF (mass airflow meter), if the O2 sensors are old, or if the vehicle is run hard or is used for towing, etc.

In other words, you could have a lean or rich condition from a mechanical problem, such as worn O2 sensors (which are 30K mile maintenance items, by the way), EGR issues, etc., **OR** you could have that condition as the result of a tuning issue, due to a particular combination of modifications.

Here's a key point: using a Gibson cat-back exhaust and a Superchip are not going to cause changes to the A/F ratios that would ever cause that kind of result. Something *else* has to be going on.

It could be an aftermarket MAF, as if one is installed with a Superchip that is not tuned for it, that *will* result in a lean condition, just for one example.

Your vehicle is a 1997 model, and it's an extremely heavy 4X4 with the Offroad package and the smaller 4.6 motor with 3.55 gears. That is very tall gearing for the ORP model's almost 32" tall tires, and that puts more of a load on the motor on top of it already being among the heaviest F-150's ever built. This makes a number of their owners naturally have to drive them harder to get them moving, which will put more heat into the exhaust. Being a 1997 model it's got some years and miles on it as well, so unless you have recently replaced the O2 sensors and fuel filter (a clogged fuel filter alone could cause a lean condition!), and kept on top of all other regular maintenance, this could very easily just be a maintenance issue in combination with the Gibson exhaust not being up to a lot of heat.

It *could* be any number of things, we'd have to know more (and maybe see the exhaust for ourselves) to diagnose this. Bottom line, it sounds like it's time for some maintenance, and it's absolutely time to have that vehicle thoroughly checked by a good service technician, have any codes pulled, etc.

If you like, you can give us a call and we'll go over this with you, and see if we can make some sense out of what's going on there for you.

Talk to you soon,

 

I have been religious about my schedule maintenence, but I am not sure when the O2 sensors were last changed. The spark plugs and fuel filter have been changed within the last 20000 miles. I have a little over 92000 miles on the truck now, so I figured it was just caused by the truck getting older. I am not blaming the SuperChip in any way for the problems, I was just curious if you had seen anything like this before. Most of my driving is highway driving, but I do take it off-road a some during hunting season. Also, I just recently purchased a new boat, which I have been towing with my truck. I have not had to tow it much because it stays at the lake most of the time, but the unusual stress on an older exhaust and muffler could have been the problem. I am pretty sure the baffle is partially clogging the exhaust which is likely causing it to run badly.

I have not gotten a check-engine light because if this problem, but I can just tell the truck is not running at 100%. That is why I am not real excited about taking the truck to the shop so they can charge me $56/hour to run diagnostics on it and look at the truck only to tell me there is nothing wrong with it.

I think I will just replace the muffler (Gibson is going to warranty it), have the muffler shop examine the catalytic converters also, and then let someone check the O2 sensors. Should I check anything else....do you have any other suggestions, or should I just go ahead and let the shop run diagnostics on it? It is probably getting pretty close to time for a full service anyway.

 

heres a little lesson on A/F ratios with OBD-II compliant emissions.....remember the 14.7:1 air to fuel ratio (by mass). This means that except for cold startup and extreme, extended wide open throttle operation, the engine runs at 14.7:1 at all times it is in closed loop (feeding back mixture based on 02 sensors). It doesnt matter what you put on a vehicle, the PCM strives to maintain this ratio for the sake of the catalytic convertors-this is the ratio they work the best at. since superchips still allow a vehicle to maintain stock emissions the story you were fed should have been coming at you from the end of a shovel hope this sheds some light

 

Could someone expalin to me how running rich will cause an exaust to get too hot and burn the baffle out?

Kindest regards

Jean Marc Chartier

 

Hi JMC,

Good point! We normally associate a lean condition with causing additional heat, however, in the exhaust you can have raised heat from either a lean or a rich condition in certain situations. Ever seen a set of headers glowing cherry-red from too much fuel? It's a sight to behold and will scare you into thnking the vehicle is going to burn to the ground (and it can!).

Usually a too-rich condition eventually clogs the *cats*, but only after they cannot burn off all the residue. When the cats get too much fuel, they do attempt to burn it off, that's one of the reasons why we have multi-stage catalytic converters, the secondary cat is supposed to "store" additional oxygen to be used to help burn off the additional fuel that is always used in fuel enrichment (load) conditions. And that is exactly what the downstream O2 sensor is really looking for, though it's generally referred to as the downstream O2 sensors job is to check catalytic converter presence & function, in a generic sense.

So it's possible for a too-rich condition to cause additional heat in the exhaust in *certain* situations.

However, the "norm" is that a lean condition is thought of as the primary heat-producer in exhausts, as you're probably thinking.

Given what's going on with that particular vehicle, I'm guessing what the muffler shop observed was actually the result of a lean condition rather than a rich one.

 

Hi lovemy4x4,

No problem at all, I understand you're not looking to point a finger of blame, you're just trying to understand what you were told, that's only natural.

Glad to hear Gibson warrantied the exhaust and that you're on top of your maintenance, excellent!

I really don't think you have a major problem since you're not getting any CE lights (not that this is a 100% indication), but you can always have it scanned for any codes just to see if there may be any pending codes, etc. You might want to do that just for peace of mind. I certainly wouldn't give any shop a diagnostic carte blanche, just pull the codes.

Best of luck whatever you decide!