Runs Rough Under Load

[97Yukon4dr]

It fixed mine, apparently the computer wasn’t happy haha

thats interesting Ill try and check that

 

[97Yukon4dr]

The only time I recall my SES light flashing is when I had a misfire due to a damaged plug wire on my 4.3 Vortec. IIRC, the flashing SES light means you are risk of damaging your catalytic converter.

the cat's were supposedly replaced before i bought the truck could it be possible that they are bad and that is whats causing it?

 

[Revan73]

the cat's were supposedly replaced before i bought the truck could it be possible that they are bad and that is whats causing it?

Even a bad cat wouldn't cause running problems unless it was clogged up, you would be getting a lean o2 code from that at least. My bet is you have the opposite. And an empty cat would show SES but it won't effect performance.

Go to walmart and buy a $15 OBD-II scanner and report back with codes.

 

[Revan73]

the cat's were supposedly replaced before i bought the truck could it be possible that they are bad and that is whats causing it?

Did you figure it out?

 

[Erik the Awful]

Even a bad cat wouldn't cause running problems unless it was clogged up, you would be getting a lean o2 code from that at least.

A bad cat can run normal until you put a load on the engine, and then the backpressure bogs the engine down. You have to lift the throttle and reapply just to keep accelerating. BTDT. I don't follow how it would cause a lean o2 code. The quick way to diagnose is to split the exhaust right in front of the cats, hang the loose exhaust up with some wire, and test drive.

 

[97Yukon4dr]

Even a bad cat wouldn't cause running problems unless it was clogged up, you would be getting a lean o2 code from that at least. My bet is you have the opposite. And an empty cat would show SES but it won't effect performance.

Go to walmart and buy a $15 OBD-II scanner and report back with codes.

I had time to use my shops Autel scan tool on lunch today... there werent any stored codes, nor was there any freezeframe data. I allowed the truck to warm up and took a look at the live data. There wasn't a single misfire, Bank 1 and 2 was running rich, and it appears as tho all the sensors are operating within range. the fuel trim data was -3 for bank 1/2 long term, and -2 for short term bank 1 and -3 for short term bank 2. I noticed someone had mention CMP retard which is -11 on my truck.... according to my scan tool this is within the -20...60 operating range

 

[Schurkey]

I noticed someone had mention CMP retard which is -11 on my truck.... according to my scan tool this is within the -20...60 operating range

Spec is + or - 2 degrees at ~1100 rpm, not "somewhere between -20 and 60".

 

[stutaeng]

I had time to use my shops Autel scan tool on lunch today... there werent any stored codes, nor was there any freezeframe data. I allowed the truck to warm up and took a look at the live data. There wasn't a single misfire, Bank 1 and 2 was running rich, and it appears as tho all the sensors are operating within range. the fuel trim data was -3 for bank 1/2 long term, and -2 for short term bank 1 and -3 for short term bank 2. I noticed someone had mention CMP retard which is -11 on my truck.... according to my scan tool this is within the -20...60 operating range

Why do you say it was running rich? Those fuel trims look really good. That was while idling?

Does the Autel have a record function? You now should take the truck for a spin and try to replicate the problem. Either record the entire drive or have a helper drive while you monitor the scanner.

 

[97Yukon4dr]

Why do you say it was running rich? Those fuel trims look really good. That was while idling?

Does the Autel have a record function? You now should take the truck for a spin and try to replicate the problem. Either record the entire drive or have a helper drive while you monitor the scanner.

The scan tool simply stated bank one and bank 2 rich. Im not sure if it has a record function but its a $4000 dollar scan tool so it doesn't leave the shop for personal use sadly. ill have to buy a little scan tool and have someone look at it while i drive. The problem is it only throws a check engine when I'm in a bad traffic situation and pushing the truck more than I'm comfortable. ive owned the truck a year and a half and its only been that bad 3 times

 

[97Yukon4dr]

i

Spec is + or - 2 degrees at ~1100 rpm, not "somewhere between -20 and 60".

It may have been incorrect because I was idling at around 750 when I checked it. i don't understand how loosening that little screw can help change the cam retard... the distributor cap can only bolt down one way so how is it possible to change the degrees. wouldn't it just causes a bad connection temporarily between the cap and rotor