Tailpipe juice?
Thread Starter
Senior Member
Joined: Aug 2008
Posts: 1,499
Likes: 2
From: Liberty, MO
Tailpipe juice?
Ok... this is gonna take a minute to explain, so please bear with me.
I have a 91 f150 2wd with a 302 and E4OD tranny. I've never driven it farther than about 15 miles at one time since I've had the truck, until recently. Of course you guys that have helped me over the last few months know that it's got a full tune up, EGR system is new, ignition is new, sea foam has been run through everything, etc., and it's been running great.
Since it's colder outside (well below freezing), I've been letting it warm up for about 10 minutes before driving. Earlier this week, I had to run across town on the way home from work, so my 11 mile drive turned into 30 or more. The truck ran fairly rough (mostly at idle) after driving for awhile, and I have been wondering why. Today, when I got back home from work at about 4pm, I noticed a small puddle in the driveway where my truck sits, right below the tailpipe (would have been there since 4am), and it was still a liquid puddle, not soaked into the concrete. My son and a couple of other kids were waiting for me in the yard, so I didn't look closely then, but just went outside a few minutes ago and it's still there, but soaking into the concrete.
This puddle smells like exhaust. It's not really 'oily', it's kinda brown colored, and must be thick stuff to sit for over 12 hours before soaking in (gas and oil don't take very long).
Between the rough running after several miles, and the mystery puddle, could this be a sign of a failing catalytic converter? I don't really know what visible signs (if any) that they give you. I think this truck has 2 cats - one where the two manifolds meet, and one back further but before the muffler? If this is the deal, is there any way to tell which one? I tapped both with a rubber mallet and don't hear anything rattling (aside from the heat shield on the rear one). I also have what feels like good exhaust pressure at the tailpipe - you can feel it pulse as the engine idles.
Sorry for the long bedtime story - and thanks in advance for any help!
I have a 91 f150 2wd with a 302 and E4OD tranny. I've never driven it farther than about 15 miles at one time since I've had the truck, until recently. Of course you guys that have helped me over the last few months know that it's got a full tune up, EGR system is new, ignition is new, sea foam has been run through everything, etc., and it's been running great.
Since it's colder outside (well below freezing), I've been letting it warm up for about 10 minutes before driving. Earlier this week, I had to run across town on the way home from work, so my 11 mile drive turned into 30 or more. The truck ran fairly rough (mostly at idle) after driving for awhile, and I have been wondering why. Today, when I got back home from work at about 4pm, I noticed a small puddle in the driveway where my truck sits, right below the tailpipe (would have been there since 4am), and it was still a liquid puddle, not soaked into the concrete. My son and a couple of other kids were waiting for me in the yard, so I didn't look closely then, but just went outside a few minutes ago and it's still there, but soaking into the concrete.
This puddle smells like exhaust. It's not really 'oily', it's kinda brown colored, and must be thick stuff to sit for over 12 hours before soaking in (gas and oil don't take very long).
Between the rough running after several miles, and the mystery puddle, could this be a sign of a failing catalytic converter? I don't really know what visible signs (if any) that they give you. I think this truck has 2 cats - one where the two manifolds meet, and one back further but before the muffler? If this is the deal, is there any way to tell which one? I tapped both with a rubber mallet and don't hear anything rattling (aside from the heat shield on the rear one). I also have what feels like good exhaust pressure at the tailpipe - you can feel it pulse as the engine idles.
Sorry for the long bedtime story - and thanks in advance for any help!
Senior Member
Joined: Jan 2008
Posts: 1,254
Likes: 4
From: Pablo MT
It could be water, are you losing any water from the radiator, even if you are not properly running engines will produce water in the exhaust as a byproduct of burning gasoline. The rough running might have been condensation in the distributor cap from not reaching the proper operating temp and staying there long enough. With it below freezing the water will stay in location longer than gas or oil due to freezing. To check the cats you will need a vacuum gauge and a tachometer, you attach the gauge and tachometer and then in neutral run the engine at 2000 rpm. The engine vacuum and rpm should not change or need additional throttle input to remain steady if you do need to add more throttle and or your vacuum drops you will need to repeat this test with the exhaust unbolted from the manifolds, if the second test comes out without changing your baseline your exhaust is plugged. The most common restriction points are the cats but occasionally the muffler plugs up so you can unbolt the muffler and try with just the cats installed, usually if you have to replace part of the exhaust after the cats you will damage other parts badly enough to need to replace them as well. The cats are in a stainless steel case with stainless pipes so it will not rot away as quick.
Thread Starter
Senior Member
Joined: Aug 2008
Posts: 1,499
Likes: 2
From: Liberty, MO
No coolant is being lost - I checked that last night. It does trickle some water out as it warms up, which I think is typical
When it's cold, I let the truck run until it's in 'normal' range before putting it in gear to go anywhere. It tends to run pretty well for about 10-15 minutes, then gets a little rough. I would think the distributor would be plenty warm after 10 minutes of idling and 15 minutes of driving.
I'll have to try the vacuum test - I have a new muffler to install, but decided to wait for warmer weather (the original 117k muffler is still on the truck). Maybe I'll get a new cat setup and replace the whole deal when I do the muffler. Everything from the muffler back is brand new.
When I was doing the sea-foam treatment, it was spraying black junk out the exhaust pipe. I had run it in the crank case, then later through the intake and fuel system. The intake/fuel treatment was when the black junk was coming out. I wonder if that black crap could have collected in the cats?
When it's cold, I let the truck run until it's in 'normal' range before putting it in gear to go anywhere. It tends to run pretty well for about 10-15 minutes, then gets a little rough. I would think the distributor would be plenty warm after 10 minutes of idling and 15 minutes of driving.
I'll have to try the vacuum test - I have a new muffler to install, but decided to wait for warmer weather (the original 117k muffler is still on the truck). Maybe I'll get a new cat setup and replace the whole deal when I do the muffler. Everything from the muffler back is brand new.
When I was doing the sea-foam treatment, it was spraying black junk out the exhaust pipe. I had run it in the crank case, then later through the intake and fuel system. The intake/fuel treatment was when the black junk was coming out. I wonder if that black crap could have collected in the cats?