Running rough on the highway

Clint623 · October 28, 2018

I have an issue with my 2014 and it idles fine but when I get it on the highway at cruising speeds it seems like it has a random miss. Just a small bump on acceleration is all I feel. I changed out the spark plugs and wires and also checked ignition with my in line spark tester and all is normal. So, I went to the corner store and threw some stp engine cleaner ( they didn’t have seafoam) in the gas tank and filled it with premium. I ran it hard for about 20 miles and it’s still doing it..

Can I add Seafoam to the STP? And also put it in the intake? Is there a hose off the master cylinder to pour it into for the injectors or do I have to spray it into the throttle body? It only has about 85k miles on it.

Sent from my iPhone using Tapatalk

1SLOW1500 · October 28, 2018

best is to have the engine running in park and get spray can seafoam and slip the red hose under a loosened up clamp after the maf have one person bring the idle up a little and spray. You can also add to oil run truck and do a oil change. If I had to guess with no thrown codes I say oil build up in intake and heads or injector issues. But it is hard to say.

Ludasmith · October 29, 2018

My truck has a random miss from like 50-72 mph. I thought it was transmission related, like the torque converter locking and unlocking. I can watch the tach dance up and down about 200 RPMs total.

Ludasmith · October 29, 2018

Alright, I noticed this morning mine is only doing it in V4 mode. I can watch it clear up as it switches back to V8.

Clint623 · October 29, 2018

I put some seafoam in the intake and let it sit for 15 minutes and when I got it on the road I only got one good puff of white smoke and that was it. Three cans of seafoam in the tank and a half a tank a gas later it’s still acting up but not as bad but still noticeable.

Sent from my iPhone using Tapatalk

Clint623 · October 30, 2018

Anyone have any advice?

Sent from my iPhone using Tapatalk

Dr Awesome · October 30, 2018

Usually if it is a common issue it will be fixed with carbon cleaning (GDI intake cleaner or actual carbon cleaning), plugs, coils/wires, and/or some seafoam in the crankcase for a couple hundred miles and an oil change. I used the seafoam GDI cleaner sprayed into the intake and followed the directions and it worked very well on my wife's equinox. I would do it every 15-20k, just to keep on top of it, if you want to curb buildup that requires real carbon cleaning. Anyway, if it's not one of those, it could be tuned out since they tend to increase idle and shift points to keep it running smoother.

Clint623 · November 1, 2018

Transmission ended up going out completely, no grip at all and it just sat there and rev’d up. Warranty went out 3 months ago[emoji30], so now it’s at a shop.

Sent from my iPhone using Tapatalk