Rough Driving

[slipping]

1999 2wd 4dr Tahoe
Happened a couple months ago and brought to the shop, thought had it fixed.

I'm going to try to describe as best as possible, I didn't have a SD card for my video to take. Started up in parking lot, sat for a few seconds and died. Started up again and drove out. Driving home from work tonight it started to stall/choke out. It would stumble and you could feel it decelerate then the RPMs would drop to zero. Took foot off the gas and moved to the side of the road and bam, RPMs back up to speed and was able kept going. Did this 3 or 4 times (30 minute drive on section of free way with no lights less those from few other cars and nothing around but desert). A few times it would stumble but not try to die out. Also smell from exhaust sometimes is strong, maybe unburnt fuel(not sure what that smells like)

Has 420 and 430 codes with CEL light
security light is lit, but has been since i acquired truck over a year ago
Has new Delphi fuel pump
has new ignition coil, starter relay, fuel pump relay, die hard battery
within last 6000 miles new cap, rotor, spark plugs, wires, heater control valve, kn intake, serpentine belt

Have not had the chance to do the fuel spider upgrade yet

thanks for looking

 

[great white]

Code 420 is cat converter efficiency and usually related to closed loop mode. The PCM is seeing a problem between the downstream O2 sensor and the upstream O2 sensor. This would be expected if you have a rich condition as the cat converter cannot deal with raw fuel puking from the exhaust ports. Keep in mind, raw fuel does not have to be running liquid, unburnt mixture is still raw fuel. Maybe meter your O2 sensors to make sure they're still in spec.

Code 450 I don't recognize off the top of my head....I think it has something to do with the evap system....

 

[slipping]

Ok, I will check them. That's one thing I forgot to list all 4 o2 sensors are less than a year old. 1 only a couple months.

 

[great white]

Ok, I will check them. That's one thing I forgot to list all 4 o2 sensors are less than a year old. 1 only a couple months.

It can be a domino effect:

A rich running engine (can be many things) can kill a cat converter and it can also kill an o2 sensor.

However, if they were dying/dead there would likely be a code for the upstream sensor being u/s.

Your issue sounds like rich running from the symptoms you've listed.

But it's pretty hard to diagnose something via internet connection...

 

[sewlow]

Defective/worn out/plugged cat?

 

[slipping]

It can be a domino effect:

A rich running engine (can be many things) can kill a cat converter and it can also kill an o2 sensor.

However, if they were dying/dead there would likely be a code for the upstream sensor being u/s.

Your issue sounds like rich running from the symptoms you've listed.

But it's pretty hard to diagnose something via internet connection...

I edited the OP because I just went to rescan, it was code 430 not 450. Yes it is hard to interweb diagnose, but its nice to have a starting point. Plus I like learning from you guys, I build aircraft so its a bit different.

Defective/worn out/plugged cat?

Mentioning the cats, Im pretty sure they are in need of replacing. Mech said they would probably need to be replaced last time I brought in (did not throw codes at the time). Ill probably bring it in this weekend if I have time. Appreciate the help!

 

[sewlow]

Not trying to hijack your post, but, aircraft? What type?

 

[slipping]

Not trying to hijack your post, but, aircraft? What type?

Started out F-35, then B2, global hawk, N-Ucas, Firebird, KC10 and a few other things cant go on about.

 

[sewlow]

Cool!

 

[slipping]

Yeah, its been a great time. Got a new position and will be doing even more.