1998 yukon Mystery p0300 and rough idle still

[OilBurner2003]

If it’s in the wiring, you may have temporarily “fixed” a marginal connection simply by moving the wiring around when you replaced the sensor.

Swap it with the other downstream sensor, see if the code follows.

1998 GM procedure below…

View attachment 385207
View attachment 385208
View attachment 385209

I appreciate it! But the code is gone already, if it comes back I will try that.

 

[OilBurner2003]

If it’s in the wiring, you may have temporarily “fixed” a marginal connection simply by moving the wiring around when you replaced the sensor.

Swap it with the other downstream sensor, see if the code follows.

1998 GM procedure below…

View attachment 385207
View attachment 385208
View attachment 385209

Hello sir, I wanted to point out something I found. I want opinions on this, My distributor looks kind of off center, doesn't it? It's a pain putting wires on, to the point where I threw up a video on seeing how other peoples distributor cap looks and it's nowhere near as close to the intake. In fact, My wire is rubbing against the intake because how tight of a fit this is. I don't know why I thought about this until now...The left picture is MY cap and rotor, the picture on the right is a video from someone on replacing their cap, see how far away cyl #1 from the intake? Mine rubs against it. I'm not sure if this means anything, but I wanted to run it by the forum.

 

[purp]

Hello again everyone, As most people know I have around 14 plus posts about this damn code, and I'm running out of ideas and options.

I have replaced, that I KNEW were bad:
Spark plugs
spark plug wires
distributor cap
Rotor
Ignition Coil
fuel pump
Fuel pressure regulator
Fuel injectors, upgraded to updated version
Fuel filter
upper Intake gasket

and much more. Mechanic of mine cleaned the MAF sensor and changed the PCV valve, stuff like that and it was doing well until I took it for a test drive. The only thing I could possibly think of is maybe the MAF sensor is going bad? I have no clue. At this point, It could be a valve, a rocker, a piston ring, or something else I have no clue about. Currently on a 30+ day wait time so I have a little while to keep troubleshooting. If you guys did all this work and were still having issues, What would your next step be? Any advice is appreciated. Keep in mind I have not done a compression test yet, I think I might get a few comments about that. Also, I have not done a smoke test for vacuum leaks. Let me know!

The 98 is before the AFM introduction I believe. It would lead me to criticize wiring to the injection system, or ignition system. Dirty grounds, and broken ground straps seem to be more and more common on the older models, especially if you live in a salty area, such as near an ocean, or somewhere it snows a lot, and they treat the roads.

 

[OilBurner2003]

The 98 is before the AFM introduction I believe. It would lead me to criticize wiring to the injection system, or ignition system. Dirty grounds, and broken ground straps seem to be more and more common on the older models, especially if you live in a salty area, such as near an ocean, or somewhere it snows a lot, and they treat

The 98 is before the AFM introduction I believe. It would lead me to criticize wiring to the injection system, or ignition system. Dirty grounds, and broken ground straps seem to be more and more common on the older models, especially if you live in a salty area, such as near an ocean, or somewhere it snows a lot, and they treat the roads.

It’s worth giving a look. The only other idea I have is the post above haha

 

[exp500]

What are your fuel trims at steady state cruise ? Try to test at several different speeds. Ex-35,45,55,65.And also if P0300 sets at a certain speed
Live data on your scanner is your biggest and easiest help here. Narrow which system is the problem.

 

[OilBurner2003]

What are your fuel trims at steady state cruise ? Try to test at several different speeds. Ex-35,45,55,65.And also if P0300 sets at a certain speed
Live data on your scanner is your biggest and easiest help here. Narrow which system is the problem.

I unfortunately do not have a scanner that can read live fuel trim data, been working on getting one that can. Got a lot of suggestions from the boys on here

 

[exp500]

2nd Best $40 you ever spent!^^^^^^^^

 

[OilBurner2003]

2nd Best $40 you ever spent!^^^^^^^^

Quick question for you. Let’s say a distributor cap has a really tight fit against the intake manifold, with the spark plug wire preventing it from sitting 100% all the way down, do I have to take the distributor out to re align it?

 

[east302]

Hello sir, I wanted to point out something I found. I want opinions on this, My distributor looks kind of off center, doesn't it? It's a pain putting wires on, to the point where I threw up a video on seeing how other peoples distributor cap looks and it's nowhere near as close to the intake. In fact, My wire is rubbing against the intake because how tight of a fit this is. I don't know why I thought about this until now...The left picture is MY cap and rotor, the picture on the right is a video from someone on replacing their cap, see how far away cyl #1 from the intake? Mine rubs against it. I'm not sure if this means anything, but I wanted to run it by the forum.

Attached is the distributor in my son’s 98 when he got it. I have two other 98s and all, with the CMP offset properly set, have that distributor cap screw tab nearly hitting the intake.



Your photo looks to be the reverse, but I’d think that you’d be off a tooth (or two) plus have the cam/crank sensor correlation code (P1245 or 1345, I forget which).

Is it worth restabbing it to confirm? Sure, but as soon as you loosen that hold-down clamp and touch the distributor, your CMP offset will probably change.

…which is easily set using a good scanner, so it kind of comes full circle.

But, there are at least two apps that will read the value - DashCommand and CarGaugePro. I’m sure there are others. Combined with an OBD2 Bluetooth adapter, you’d probably be under $100 for all of it.

Edit: Actually, yes, your distributor’s position would bug me and I’d be so tempted to pull it.

 

[OilBurner2003]

Attached is the distributor in my son’s 98 when he got it. I have two other 98s and all, with the CMP offset properly set, have that distributor cap screw tab nearly hitting the intake.



Your photo looks to be the reverse, but I’d think that you’d be off a tooth (or two) plus have the cam/crank sensor correlation code (P1245 or 1345, I forget which) and a really bad running condition.

Is it worth restabbing it to confirm? Sure, but as soon as you loosen that hold-down clamp and touch the distributor, your CMP offset will probably change.

…which is easily set using a good scanner, so it kind of comes full circle.

But, there are at least two apps that will read the value - DashCommand and CarGaugePro. I’m sure there are others. Combined with an OBD2 Bluetooth adapter, you’d probably be under $100 for all of it.

Haha I had someone say that it was reversed too, it’s not! That’s the way it was when we took the cap off a year ago. Although it’s not throwing a code, it does look off, do you think that could be a issue?