Glowing converters ,Possible cat blockage ?????

[Vince7]

Hello, I performed my 60k check R&R Intake& valve cover Gaskets,plug well seals and also replaced spark plugs and wires Motorcraft all the way also sprayed b12 carb cleaner into air intake at the TB also checked valve lash ok i miked the shimms they are good. 1991 SHO
3.0 yamaha 103k i wasn't sure if a 60k had been done but i had oil in the plug wells and low spark on cylinders 3 and 4 checked codes and replaced 6cyl coil pack, i'm not sure how long it was running on 4 cylinders and now runs smooth but low on power and low idle, i checked for codes and none just code 11 and after running at 3,000 rpm the converters started glowing and still has low power. it sounds like a clogged exhaust especially the cats. any thoughts or ideas will be helpfull... Vince7

 

[Yamaha V6]

Vince, I'd take the opportunity to replace that Y-Pipe ASAP. Give me a shout, I'll be at the shop tomorrow.

 

[89 black SHO mtx]

vince,
it sounds like a simpl;e case of dumping excess fuel into the exhaust. if the cats were clogged you would notice a drop in vacum(like the brake booster not boosting,etc...). you may have an injector stuck open. you can check this with a stethascope by touching each injector with the probe. their are other causes as well but they usually come with codes but not always. double check your spark and fuel. if you still think its a clogged cat take it to an exhaust shop and have them do a back pressure test on it.

 

[sdpatt]

The temperature rise across the cats after the engine has been run for a while is approximately 100F degrees. If your cats are glowing red, you may have a very rich mixture that is causing the cats to perform much more oxidation (burning) than designed. Have an exhaust shop check the system for heat rise and obstructions.

<small>[ May 10, 2003, 10:01 PM: Message edited by: sdpatt ]</small>

 

[projectSHO89]

Extra hot cats means too much fuel in the exhaust mixture.

A thermostat stuck open will also cause this.

Steve

 

[Vince7]

Hey thanks for the advice ,tommorow in the am i'm gonna check the injectors make sure none are stuck open, and the temp seems normal considering it wasn't running more than 5 mins or so.My main thoght is that if the previous owner ran the car with 2 cylinders not firing for a period of time i would tend to think the cats could be full of crap or collapsed.so i may try disconnecting the cats to see if theres an increase in power.

 

[Vince7]

Well its early on my end, started the sho up early to do a throttle reset and it ran like crap
misfiring and checked the plugs found cylinders
1 and 5 clean all the rest black carboned
what gives new day new probs heheh and if anybody has a plug wire specs, the car was different than what chiltons says on the right side of coil pack where the power connectors is 1/2/3 top to bottom on the left side is 4/6/5
seems odd the car was setup 1/2/3 4/5/6.....i'm gonna check for KEOFF codes.....

 

[HopefulSHO]

The Chilton's manual is wrong on the coil pack order.
(Painfully wrong, it was obivous when I tried to plug in the #1 spark plug wire & it wouldn't reach..)

Check out this old post for the right order for the wires on the coil pack. BeatDaSHO's got it right there.


Also..if your car was running for a long time w/ two cylinders dumping straight fuel to your cats, they're probably toast
Performance Y-Pipe time?

<small>[ May 11, 2003, 02:18 PM: Message edited by: HopefulSHO ]</small>

 

[Vince7]

Thanks much, i also found some ole stinky gas in the tank gonna pull the tank and dump it. I guess i have a new hobby gettin my SHO on the road my PC hobby gets the back seat......