Catalytic converter = poor mpg/driveability?

[4x4exploder88]

Ok ,so I have been battling with running issues and mpg issues with this truck since I bought it. First it ran like crap, and got bad mileage. Then, it started running a little better after I did plugs, wires, fuel filter, air filter, cleaned the MAF, new IAC, new oxygen sensor, new crak position sensor, and seafoamed the vac. system.

Now, I drove it to work (about 100 miles round trip) for the past 2 days, without much a problem, other than some loss of power, especially going uphill. Well, today I left my wallet at work and ran back to get it about 10 mins after I stopped the truck, and at first, it wouldn't stay running, I had to hold my foot on the gas pedal to keep it running, then it smoothed out. It ran like crap all the way there and back, and when I got home about 5 minutes ago, my catalytic converter was glowing. Seems to drive great when it's cold.....

When I bought it I was told the PO had the heads redone, and I'm thinking maybe they got the timing 180* backwards? I think I read somewhere that when a CAT glows, it means either it's bad, or the timing is way off..... But I have no timing light (or the know how to use one) and no real way to check.

 

[ghosttrain2]

Any codes? Should also check fuel pressure. As for the glowing Cat.,it's possible that if it was glowing, that it was damaged(melted,etc) Start with the basics,pull codes,check fuel pressure, vacuum leaks, bad thermostat can cause it to run rich-think you'll get the idea.

Good luck!!

 

[4x4exploder88]

Pulled codes as soon as I got it home, didn't have any. No vacuum leaks, thermostat is good, don't have a fuel pressure gauge (yet, anyway) so can't check that yet. It was making a sound, like it was backfiring through the throttle body/air box, like every once in a while I would hear a very loud pop coming from the airbox area.

 

[ghosttrain2]

That could be a misfire/miss,or even a lean misfire-May want to have the fuel pressure checked. could try a vcacuum gauge hooked up to manifold vacuum port, run engine at half throttle(in park) , the vacuum will drop then should stablize and maintain. If it drops to zero, or shows a pressure,your exhaust is restricted.(works on carburated engines)

 

[ragajungle]

If the fuel pressure regulator goes it will, chug, and run sluggish... IT's easy to check --- find the regulator near the rear of the intake on the fuel rail - usually silver canister type joby. If you pull the vacuum kine off it and gas come outta the line - you found your problem.

If the regulator is bad it will dump gas - almost to the point of flooding - causing excess unburned gasoline to accumulate in the cats (glowing)

hope this helps

 

[4x4exploder88]

Sounds like some good advice, I will have to check the FPR.

If it drops to zero, or shows a pressure,your exhaust is restricted.(works on carburated engines)

I'm not sure I am following this one.... Either way it's going to show a pressure reading, or zero pressure, correct?

 

[4x4exploder88]

Removed the vac. line going to the fuel pressure regulator, the line did nothing but suck air, and the connection on the FPR did nothing, I assume it's good.

Now, on the vac. tree, where the hose connection that's labeled ccd in my manual, it was connected to the pcv valve. I capped the connection coming off the vac. tree like it's supposed to be, and capped off the top outlet of the pcv (the larger hose from the manifold is still connected - I think I have the wrong pcv). All the lines seem to be right coming off the tree and leak free.

Maybe I just have a clogged cat??

 

[ragajungle]

4x4 a lot of pcv valves are of the generic variety. They come with a T or and F or just one hole on the top, as long as the excess holes are capped you are good. if your cats where glowing there is a good chance they are cooked. BUT before you spring for cats (or delete them altogether permitting emissions regulations) you need to find out why they would have gotten plugged up in the first place. usually when cats get plugged its because unprocessed fuel finds its way in them and "cooks" the catalyst. Is the truck missing at all - or was it?

 

[4x4exploder88]

I'm not exactly sure what "missing" is...... I have an idea of what it means but not sure.

 

[4x4exploder88]

Maybe it was already on it's way out before the previous owner replaced the heads. I was told he did not drive it anywhere after the work was done, just a small test drive.

 

[ragajungle]

"Missin" Miss firing cyclinders. If one or more of the cylinders is missing (maybe from bad compression, worn piston rings or valve seats...) it will also allow unburned gas to go through and wind up in the cats.

 

[rogi]

Your "uphill" comment reminded me of a situation I had diagnosed on an '89 Toyota (RIP). It was also losing power whenever I went uphill, and it turned out to be only a very dirty fuel filter. When the mechanic asked if I'd ever changed it (it had 120K miles and I hadn't), I knew right off he'd nailed the problem. Well duh, I didn't even know where it was. Out 'O Sight, Out "o Mind!

 

[cjryan]

Maybe I just have a clogged cat??

I had similar symptoms to you except for the stalling at idle. I had to replace all my cats because they were clogged. No codes. A hose of my DPFE sensor (EGR related) kept blowing off because of the back pressure. A good exhaust should be able to tell you.