2014 rough idle in Drive (109K miles)

[wsteele]

The test for a bad mount is pretty well described in this video, if not the same kind of vehicle, the principle is the same. It takes two people, one in the drivers seat and one watching the engine movement (you can do it yourself watching the engine through the slot in the opened hood, but you won't be able to see the movement down by the mounts, takes a little more experience to judge how much movement is too much).

You can also take a close look at the mount itself, you may be able to see a crack in the mount. Our OE mounts are liquid filled, so a tear pretty much makes them toast.

 

[Bill 1960]

My 2014, 5.3L Tahoe has recently developed this problem where every several seconds I feel a rough idle just for a second or so. At first, I thought another car had bumped into me at a red light, then realized it was happening whenever I was stopped in Drive. Any thoughts?

That’s the same symptom I had, although mine was happening at irregular intervals and gradually became more frequent over a lot of miles. Turned out to be the fuel pump.

https://www.tahoeyukonforum.com/threads/stumble-hesitation-and-stalling-solved-fuel-pump.128547/

 

[JBravo1977]

My 2014, 5.3L Tahoe has recently developed this problem where every several seconds I feel a rough idle just for a second or so. At first, I thought another car had bumped into me at a red light, then realized it was happening whenever I was stopped in Drive. Any thoughts?

In November of 2021 I had all 8 plugs and wires replaced at the dealership and that solved the problem. At my next oil change, the guy showed me where the dealer service guy had left the wires and plugs in that space in the engine bay that looks like it's another spot for a battery. There were only 7 plugs, and I thought the last one was probably in a ditch somewhere.

Fast forward a year-and-a-half to this week and on Monday it had a hard start and a rough idle in Drive again, with no warning whatsoever for either problem. They both started at the same time. It wouldn't start later on Monday and I got it going with my jump box. I charged the battery that night (it would only go to about 70%) and I took it to the shop that I deal with the next day. By then it was throwing a code, which they said was P0300 (?) and then figured out it was supposedly a cylinder 7 misfire. They said I needed to see about changing the plugs but didn't have to do it now. I told him the plugs were replaced not too long ago at the dealer and he said I needed to take it back there and have them look at it and explain why it's doing this now, since they did the plugs and wires. I'm wondering now if the #7 plug didn't get replaced. The alternator was bad and the battery was bad also, so we replaced both. The battery was only a couple years old and hadn't had any trouble at all before Monday. They said the alternator may have damaged the battery or worn it out prematurely.

The idle is very rough, and I need to get something done about it ASAP. To complicate matters, I have a health condition that affects my spine and it's very difficult for me to sit around at a dealership or any other place that isn't my home or office, where I have special furniture to accommodate that. Even the Tahoe has a modified driver's seat, so it's the only car I can drive or ride in and be comfortable, so unfortunately this is a bigger deal to me than it might be for most people. I would really appreciate any info that anybody can provide.

What I'm wondering about is this:

Is it normal to have the rough idle and the electrical problems (alt & battery) at the same time, totally out of the blue like this?

Assuming that the plugs and wires are good, is there something other than a fouled plug or bad wire that can cause the rough idle in Drive (it's not as bad in N or P.) A vacuum leak, maybe, but does that explain the electrical issues?

 

[Geotrash]

Is it normal to have the rough idle and the electrical problems (alt & battery) at the same time, totally out of the blue like this?

Assuming that the plugs and wires are good, is there something other than a fouled plug or bad wire that can cause the rough idle in Drive (it's not as bad in N or P.) A vacuum leak, maybe, but does that explain the electrical issues?

A bad battery and/or weak alternator components can absolutely result in idle quality problems on these trucks. I had the alternator on my '07 fail in my driveway back in 2020 just as I was pulling in (thank god), and I could barely keep the thing running.

The code should tell you what cylinder is misfiring. P0300 is a general misfire code and could mean a misfire on multiple cylinders. To narrow it down to cylinder 7 from the codes alone would require a P0307 code.

And if the shop failed to replace a spark plug, it would have been #8, and not #7 because it's the hardest one to get to. It would be worth pulling the plugs for #7 & 8 at a minimum to look for condition, but a consistent misfire on the same cylinder can come from many things, including a plug wire pulled loose from the boot, a fuel injector connector that's not seated right, a stuck valve lifter, a plugged injector, a broken wire, etc.