Need expert repair advice - urgent

[Teamoatmealpie]

Ok- header nut popped over Memorial Day weekend - heard the pfffft- pfffft of an exhaust leak

Take it to local shop who had done work for me before. Well today they fixed the exhaust manifold stud and I had them put new cats on.

Drive out of parking lot van is stuttering and surging. Go right back they put it on the lift - they think spark plug wire is off- check it- nope

Instead one cat is welded on backwards? ******?

Ok they fix it- we start it up- still surging and stuttering. Guys says we are closing bring it back tomorrow. He says he "thinks the cats are too small and causing too much back pressure.

I say this is Effied- will the van make it home and back with out damage? He says it should be fine.

Ok so I drive it home - it stutters and surges- it won't accelerate -and the whole time i am thinking this cant be good to strain the engine like this. The van temp went a little past normal- not over heated - but went from about 200 to 210 or so right as I hit my driveway. The temp reading has always been static- even on long climbs.

My concern is the return trip has me climbing out of a valley for several miles. Could this cause engine damage - blow a head gasket - etc

Should I get it towed back? Or should I go get my grinder and cut the cats off tonight. Tell them I save them the trouble of taking them off.

Van drove flawless before exhaust guys touched it

1998 chevy 3500 -110k miles

 

[Stumpalump]

Did they hook up both O2 sensors? Get them to put free flowing cats on before you ask. If they are wondering about the cats then they put on some tiny 4cly units. I'd drive it slow if you think it's back pressure. It won't hurt it. I've had some bad luck with muffler shops over the years. Unless it's a custom hot rod shop they hire knuckleheads. Good luck.

 

[Bbasso]

CEL?
Codes?

 

[Teamoatmealpie]

No idiot lights illuminated-

Nor did i have access odbII tool.

Whole situation left me not happy.

 

[naterry]

Here's a few points, hope they help:

Drive out of parking lot van is stuttering and surging. Go right back they put it on the lift - they think spark plug wire is off- check it- nope

"Stuttering and surging" sounds like an A/F mixture issue. In other words: you have fuel, air, and spark or it wouldn't run at all. That leaves mixture, which points to a sensor >>> O2, IAT, TPS, etc.

Instead one cat is welded on backwards? ******?

The only thing "directional" about a CAT is the O2 sensor bung position, so that is half BS. If they welded the "post CAT O2" (note this O2 is usually only for detecting the efficiency of the CAT) on before the cat then it would throw a MIL but not affect the A/F mixture. The other scenario, where they might have welded (or switched the harness/plugs/etc) the primary O2 on after the CAT would make the ECU think the car is running too lean, which would lead to the ECU compensating by richening (sp?) A/F mix. You would smell and possibly see this in the exhaust.

The van temp went a little past normal- not over heated - but went from about 200 to 210 or so right as I hit my driveway.

Running hot means running lean. A lean mixture also sputters (more like pops).

Should I get it towed back?

I'd call them and make them tow it back based on how it ran leaving their shop, and document everything!

 

[Teamoatmealpie]

Unfortunately I am still here after 4 hours.

The cat put on backwards had a big *** arrow stamped into the metal on it. So you have 2 cats side by side - when up on lift it was pretty easy to see. The guy was all pissed he out it on wrong.


So today new high flow cats - the right ones.

Drive away - same problem.

The think they put the spark plug wires back on in wrong order- now miss timed.

They reset everything. Still messed up.

Now they have diagnosed bad rotor it's burned out say one spark plug wire is arching.

I looked - the rotor is burnt- would them miss timing it with wrong spark plug wire cause this?.

******- I had new rotor - cap- wires put on 2 years ago- and I had no issues prior to this shop. Now they say we didn't do it- it's another $400 to get your vehicle running.

 

[naterry]

Also, check the engine ground.

 

[Stumpalump]

Also, check the engine ground.

1998 Chevy. Good call. It needs extra grounds even if the factory ones are good. Add one from the body to the negative post on bat and one to the block. A bad batt can cause weird computer drivability problems. How old is it? The last guy put on typical inferior aftermarket parts. I'd be buying a cap with brass terminals an equal quality rotor and new plug wires. If a wire or plug is bad the spark can jump under the cap and arc. They messed with old junk and got burnt. I doubt they were out to get you. Can't you at least slap on a cap, rotor, wires, battery and grounds yourself or do you need help?

 

[Mwilliamshs]

...The only thing "directional" about a CAT is the O2 sensor bung position, so that is half BS...

THAT is BS lol OMFG you ever looked into a catalytic converter? The newer ones look less directional than the old rod-style I suppose but 98% of them ARE directional. A post-cat 02 sensor is a big giveaway but even a cat with no sensor bung is directional unless it's a very rare bird. I've never seen an aftermarket or universal cat that wasn't directional but they do exist.
.
RE: bad distributor rotor...
.
The stumbling condition sounds exactly like ignition stuff. Mixing up plug wires and running the engine out of time could cause a rotor to be burned due to the higher voltage passed through a larger gap. If you're 2 years into a cap and rotor they're likely hurting mileage anyway so replacement isn't a bad idea, depending on how much you drive. Brass will corrode slower/less overall than aluminum so if parts with brass contacts are available, I'd use them but OE parts typically weren't brass (Motorcraft often used brass coil contacts, aluminum everywhere else) so aluminum ain't the end of the world, just cheaper.

 

[naterry]

THAT is BS lol OMFG you ever looked into a catalytic converter? The newer ones look less directional than the old rod-style I suppose but 98% of them ARE directional. A post-cat 02 sensor is a big giveaway but even a cat with no sensor bung is directional unless it's a very rare bird. I've never seen an aftermarket or universal cat that wasn't directional but they do exist.

Wow, that's quite the intense response there. I'll skip your condescension and intvitation to your pissing contest and just say yes. Yes I have. Many. And yes, they are not all directional.

Type universal cat or racing cat in Google and take another look before responding next time. Do you know that the muffler shop didn't use a universal cat? I didn't think so.

Cats a bi-directional. You can mount them forward, backwards, or upside down if you really wanted. It doesn't matter which way the gasses flow in a cat.

They do mark stock cats with an arrow, but that is only because the flanges can be different sizes and the post cat O2 bung has to be down stream.

 

[Teamoatmealpie]

Yes cats mounted were directional and very small. He admitted the ones I needed were at other shop and he just used what was on hand.
So new cats on- verified they where correct for my 454.

Replaced all plugs wires rotor cap. Still running rough and missing.

Since I spent 6 hours at the shop i watched the "helper" guy who walked around complaining all day and saying ****** is ****** that. Which is what he said about 20 times when I showed up for day 2 of this saga. Great presentation for customers.

One of the things I did notice is helper guy would forget to connect the ground when welding on other peoples cars. Could that have caused the rotor to burn?

I will check the grounds. Other than that I am stumped.

Van ran perfect prior to going to this shop. Dissapointing experience. I am aware that stuff can happen that is coincidental and not necessarily the shops fault. But putting on tiny cats- one on backwards then the engine suddenly being nearly inoperable upon rolling out of the shop. Followed by hey were closing try and get home and comeback tomorrow. Followed by 6 hours of them trying to figure it out. And then no resolution isn't what I expect as good service. That's not even mentioning the meth head looking helper with the bad attitude.

Fun times for what should have been a quick and easy job.

 

[guidolyons]

I had a 1995 Chevy K1500 that would go through cap, rotor, and plug wires about every 18 months. I once had a set of plug wires go bad. At dusk with the engine running, you could see a halo around each wire as the plug fired.

Thought that might be the culprit, but since you replaced them and the stumble is still there...

My guess is that it's not related to the exhaust/cat work, but rather when they pulled the header to fix the broken bolt/exhaust leak.

I'm sure you double checked the firing order when plug wires and new cap and rotor were installed. Did you check the spark plugs?

My guess is they did not remove the spark plugs while working on the header and cracked the porcelain on a plug...causing a misfire.

 

[350outrage]

I had a 1995 Chevy K1500 that would go through cap, rotor, and plug wires about every 18 months. I once had a set of plug wires go bad. At dusk with the engine running, you could see a halo around each wire as the plug fired.

Thought that might be the culprit, but since you replaced them and the stumble is still there...

My guess is that it's not related to the exhaust/cat work, but rather when they pulled the header to fix the broken bolt/exhaust leak.

I'm sure you double checked the firing order when plug wires and new cap and rotor were installed. Did you check the spark plugs?

My guess is they did not remove the spark plugs while working on the header and cracked the porcelain on a plug...causing a misfire.

Or that they pulled the plug wires and then put them back on the wrong plugs...very easy to do.