This is on the manifold pre-cat.

I had that banana in the tailpipe feeling and the manifold was cracking , so I figured it was getting hot/clogged.

Just puilled the mani and only 20% of the comb was visible. Lots of white coating....

Have a spare waiting to swap in, but was thinking I could use my weed flamer to heat it up fromthe downstream end.

Possibly it would burn off the deposits w/o damaging the catalyst?

more than likely, it is actually melted. Once they do that, theres not much you can do other than swapping in a new one.

Then, make sure you get the O2 sensors changed so you aren't running rich (which is what causes this)

Ok, It looked like a coating on the surface- actually stands above it. I've seen melted honeycomb on my other verter( long gone)..


Will hit up the Zone for some sensors.

thanks JOhn

you could try poking through the clogs with some coat hanger wire to see if they dislodge. When the catalytic converter melts, generally you'll see a blob of clogged honeycomb in the middle of the exhaust path through the converter.

Coathangers for mnchkins, maybe, those suckers are small, and I'd be pokn for months.

I'm glad I got a spare a few years back. I couldn't find squat for my truck today. Hit up 4 wrecking yards and all I could find was a front corner lamp for 20$ - local dealer wants 125$.. ABC would prolly be cheaper, of course, but still would be a new price.

Get this- local dealers want $25 for EACH exhaust mani gasket ( I need 4). Went to Kragen- $11 for the set of 4.. I could buy 2 full sets for the price of only one gasket.

I should have invested in exhaust manifolds
( w/ pre-cats included) years ago.

Can't find them in the junkyard anymore and dealer wants
$600 for a precat by itself. I got a manifold, precat, and the ppipe downstream for $150 4yrs ago.
Shiite is like gold now.

Well, might as well keep it up on the jacks and install new pads, rotors, bearings and seals.

I've had a "death wobble" for the last year- around 35-40 mph-.. It steadily got worse until yesterday when it was up on jacks and I noticed I could rock the front wheels side to side at the top and bottom. I thought it was just the steering box getting out of adjustment.

The bearings were loose and getting hammered.



I might even consider install new shoes in back to get the emergency brake functional again

I'm sweating the pounds off.

So a related semi-postjack question:

My back cats are dead, and have been for awhile. the SES code is to check the back 02 sensors, which we did, but it turns out the cats are useless.

I assume this will affect gas mileage, as John said, it will be running too rich?

That's a good question..

My back cat is gone( the shell is there- but no honeycomb).. At one point I had to replace my rear O-sensor.

The o-sensor ( on the manifold) that I replaced this weekend was original since new- no wonder I had problems.

When you say they are deAD whatr do youmean? clogged/ not there, waht?

Bille, how's the truck running now? Should run a lot better now with a new O2 sensor. The O2 sensors slow down when they get older. Because of this, the engine controls tend to run too rich (because they are not being corrected as often by the O2 sensor), which over time causes excess heat during burnoff in the cat, eventually melting the catalytic converter core. If you watch an Air/Fuel ratio meter on an old O2 sensor vs a new one, the difference is pretty amazing. Once the engine is warmed up and the O2 sensor is in feedback loop mode, the new one bounces quickly between rich and lean vs a slow bounce for the old one.

Robin.. how many miles do you have on yours? Have you replaced the front O2 sensors? The rear O2 sensors are just there to double check the readings from the front sensors. The front-most O2 sensors are the ones the ECU uses to calculate the mixture. With the older Nissan engines, I was told the O2 should be replaced every 60k miles or so. They may be able to go a bit longer now, but with use their readings do slow down...

quote:

Originally posted by datz510:
Bille, how's the truck running now? Should run a lot better now with a new O2 sensor.

I'm sure it will run better. trucks still up on blocks, Just have to put in new pads. Haven't even started it.

that cat was murderated.

I only replaced the front sensor..

The back O-sensor is at least 100K miles if not older- will it/could it cause a "tilt" in the ECU?

Maybe I should change it as well?

Well heres the deal.

The iddiot light came on indicating bad rear 02 sensors. I took it to a shop who tested the 02 sensors and determined the 02 sensors were ok. The next thing to look at was the rear cats. They did some type of temperature test measuring input to and from the cat, and thats how they determined the cats were bad.

I know have 50k on the truck, but the iddiot light came on about 10k ago.

Oh Robin . If the cat's are truly bad, be prepared for about a 1300$ parts bill alone!

Might want to hit up ABC for the cats., but I would be suspicious of the shop, as replacing a pair of 60$each O-sensors( kragen) isn't as lucrative as a pair of $600( each) cat's( local dealers).

And replacing the cat w/o the O-sensor might just get yhou another clogged cat in the near future.

FYI If I can pass smog w/ just a front cat, why can't you Maybe you could accidentally lose the honeycomb to a recycler for some$$$.

quote:

Originally posted by hillbille:

quote:

Originally posted by datz510:
Bille, how's the truck running now? Should run a lot better now with a new O2 sensor.

I'm sure it will run better. trucks still up on blocks, Just have to put in new pads. Haven't even started it.

that cat was murderated.

I only replaced the front sensor..

The back O-sensor is at least 100K miles if not older- will it/could it cause a "tilt" in the ECU?

Maybe I should change it as well?

The rear O2 sensor is only used as a failsafe to check that the front sensor is working properly. It isnt used to control mixture, so you should be fine leaving it alone.

Cats aren't that expensive. I had my entire exhaust redone with a new cat a few years back for $290

A few years back precious metal prices were half what they are now. Check local dealer for prices NOW.