Catalytic Converter Trouble???

[snowdogb77]

Alrighty then, guys, check this out. I pulled my MAF sensor, Throttle Body, and IAC off so that I could clean them (and found that they did have a bit of carbon buildup on them). I also installed a new K&N FIPK unit on my vehicle as well hoping that it would solve my hesitation problem. Here's the current status: upon hard acceleration I now get a backfire along with the hesitation/chugging.

With what I have done so far, this vehicle now starts quicker and idles like silk, you can barely tell the thing is running when you are sitting in it, but it still hesitates BIG when you hit the gas, along with the new noise, a loud popping and backfiring. This stuff, along with the carbon buildup has me thinking that I am not getting proper exhaust, and I was wondering if any of you had experienced this same thing. My XLT has 115k on it, and these are the original cats. Along with this, it seems that these cats are unique in CA, and I was wondering if anyone out there in Explorerland can give me a heads-up on where I can get these without going to the dealer.

Any Thoughts??

 

[TPLYNCH]

You may want to look at your fuel pressure regulator first... How does it run once you get past the hesitation/backfire? Does it feel gutless all the time?

 

[MrShorty]

If I thought I might have a bad cat, the first thing I would do is put a vacuum gauge on the engine. A plugged cat (or other restriction in the exhaust) will show up as low/no vacuum. At idle the vacuum should be ~20 in Hg at sea level. Accelerate the engine and watch the vacuum gauge. Vacuum should momentarily decrease, but then return to something near it's idle reading when the engine reaches a steady RPM.

 

[aldive]

How many miles is on your truck?

 

[snowdogb77]

You may want to look at your fuel pressure regulator first... How does it run once you get past the hesitation/backfire? Does it feel gutless all the time?

Nope, it definitely isn't gutless. Once you get past the hesitation it goes quite well, and it is now getting to the point where it doesn't do it all the time. There are times when I hit the gas and you can really feel the extra horsepower that the FIPK is giving it.

 

[snowdogb77]

If I thought I might have a bad cat, the first thing I would do is put a vacuum gauge on the engine. A plugged cat (or other restriction in the exhaust) will show up as low/no vacuum. At idle the vacuum should be ~20 in Hg at sea level. Accelerate the engine and watch the vacuum gauge. Vacuum should momentarily decrease, but then return to something near it's idle reading when the engine reaches a steady RPM.

Is there a specific port that you would recommend, or should I just make sure that it is one of the main vacuum trees?

 

[snowdogb77]

How many miles is on your truck?

Almost 115k. By the way, that Sea Foam stuff you suggested awhile back really is GREAT stuff! Even with the other problems that have arisen, I could really feel a difference in the idle after adding a can to my gas.

 

[expobronc]

maybe your TPS is goofing up your engines timing advance?

 

[MrShorty]

Is there a specific port that you would recommend, or should I just make sure that it is one of the main vacuum trees?

Any vacuum port will work.

 

[snowdogb77]

Any vacuum port will work.

Very Cool. I'll pick up a gauge today and check it out!

 

[snowdogb77]

maybe your TPS is goofing up your engines timing advance?

That was the very first sensor I changed, due to "quick and easy".

 

[TPLYNCH]

Running fine otherwise would rule out plugged cats in my book. Your FPR may be going, and when you floor it's dumping fuel and flooding the system causing your hesitation etc....

 

[snowdogb77]

Running fine otherwise would rule out plugged cats in my book. Your FPR may be going, and when you floor it's dumping fuel and flooding the system causing your hesitation etc....

That makes a lot of sense, now that I think about it. Too much fuel would cause a backfire, wouldn't it?