Cats clogged?

[callaway29]

Car is running real rough when it's cold, it gets better after I drive a couple miles. I
Also can't get better than 17mpg highway driving. (

 

[bluesrt]

ses light? usually a clogged cat gets worse as it gets warm, but if its running raw fuel throught it, they may be plugged too. could be a pooped plug or ignition cables

 

[EZ 2B Green]

You should be able to diagnose a clogged exhaust with a vacuum gauge.

 

[callaway29]

There's no light, it just runs rough when it's cold. If I goose it when it is doing this it will stumble for a bit then every thing clears up

 

[Jmch]

Any number of sensor malfunctions will cause this. A coolant temp sensor can malfunction with this result due to improper fuel/air mixture. Computer thinks the car is hot when it is not and leans the mixture prematurely. Once the car warms up problem goes away. It would also potentially be detrimental to fuel economy. May not trigger a light if it is still within a set range. I doubt the converters will be the cause but ya' never know. Possibly even a manifold or intake air temp sensor. Its hard to guess.. I would just hook it up to a computer and look for improper sensor readings or codes.

 

[dave6666]

A plugged cat is a mechanical problem. The engine is a mechanical air pump. Therefore the problem if it is the cats, would remain constant at any operating temperature or rpm. Plugged is plugged. Choking the engine is choking the engine. Put your hand over the tail pipe and see if one is pumping more air than the other. Unless both are neither are plugged.

 

[slysnake]

Put your hand over the tail pipe and see if one is pumping more air than the other. Unless both are neither are plugged.

That's what I was going to say.

 

[Paul Hawker]

Maybe spark plug wires...

 

[plumcrazy]

what dave said. its plugged or not. plugged wont get better

 

[Jack B]

If you can get access to an Infrared camera it will tell you everything. For some reason the car will continue to run with a dramatically plugged cat. I have some infrared pics of a plugged cat while the car is running if anyone is interested.

 

[callaway29]

it has to be a sensor of some kind, because it started stumbling while I was cruising on the highway at around 80MPH. Everything was fine then it started jerking a little, it feels like it is missing when it does this. Could it be a cam sensor?

 

[speedracervr4]

Hook it up to a computer and/or data log. It's hard to diagnoise issues over the internet with little facts other than "it feels like it is missing". How old are the plugs,wires, fuel filter, and 02 sensors?

 

[callaway29]

It has new plugs and wires, I had it hooked up to a scan tool while driving and everything looked fine, I did notice the TPS % would jump to a 23 to a 25 when it started to stumble. I will try and get some info off the scan tool and post it tomorrow

 

[slysnake]

it has to be a sensor of some kind, because it started stumbling while I was cruising on the highway at around 80MPH. Everything was fine then it started jerking a little, it feels like it is missing when it does this. Could it be a cam sensor?

I'm still saying clogged cat. That's how they start. Just had mine replaced. Started that same way, then went away for a while. Then it would run fine for crusing but wouldn't rev over 4500. Considerably less flow from one side than the other. Just put your hand down to the exahust and see if you feel the pressure and heat difference.

Replaced the faulty cat and now its back to it's old monster self. I went with stock cat from my dealer at 1100 bucks. High flows are considerably cheeper though.

 

[callaway29]

UPDATE: I checked the flow on the pipes and there is just too much air coming out to be clogged, so I replaced the upstream o2 sensors and that didnt cure it either. Now im replacing a TPS and I cant get it read below 20% at idle, at WOT it reads 78% is there something is there a trick to getting this down to the 4's like it was before?

 

[speedracervr4]

Do you have stock exhaust manifolds or aftermarket? Could be a leaking gasket or crack causing issues with the o2 sensors. Did you check all vacuum lines? BTW my TPS reads 16.9% at idle, but it's on a Roe motor with a VEC tune.

 

[dave6666]

Although I don't know what the correct reading should be, the TPS should read above zero at idle because at idle the throttle is open a little.

Also, does your logging tool read the TPS itself, or the PCM's interpretation of it? Meaning, it may not yet have learned the new TPS sensor yet.

Not the expert on those. Just food for thought.

 

[callaway29]

I was concerned because the idle was running around 1200 rpm but after driving it all day sunday the rpms dropped down to the normal 700, and last I checked the tps reading was at 19.8%. I never would of thought that the ECU need to learn a new TPS.

 

[callaway29]

The problem turned out to be my TPS, everything is running back to normal.

 

[ViperTony]

The problem turned out to be my TPS, everything is running back to normal.

How did you fix it? New TPS? TPS re-learn?

 

[SlateEd]

Hey All,

if there is a major difference in air pressure coming out of the exhaust from one side vs the other then would we say almost definitely a clogged cat?

my car has been tucked away for winter - took it out today and it sputters badly with anything more than 1/3 throttle (and it did get worse over the 30 minutes I drove.

I thought I might have a clogged injector or something on the right side related to 6 month old gasoline, but the air pressure at the exhaust tip is like night/day different.

no CEL, no codes. plugged in my SCT and returned to stock tune, didn't change anything.

 

[ViperTony]

Ed, maybe a family of mice took up residence in that side exhaust?

 

[SlateEd]

haha Thanks Tony... I would think I would have smelled something after they BBQed for 30 minutes though.. and more throttle just made it worse, didn't "blow out" anything

 

[Jack B]

Some cars have an H pipe, therefore, hard to diagnosis.

Hey All,

if there is a major difference in air pressure coming out of the exhaust from one side vs the other then would we say almost definitely a clogged cat?

my car has been tucked away for winter - took it out today and it sputters badly with anything more than 1/3 throttle (and it did get worse over the 30 minutes I drove.

I thought I might have a clogged injector or something on the right side related to 6 month old gasoline, but the air pressure at the exhaust tip is like night/day different.

no CEL, no codes. plugged in my SCT and returned to stock tune, didn't change anything.

 

[SlateEd]

Some cars have an H pipe, therefore, hard to diagnosis.

Good point - in my case it's stock exhaust manifolds, stock cats, Corsa 3" cat-back system directly out same side (crossover pipes gone)