CT5-V engine surge / "porpoising"

[GTANotch88]

Yea, my 5bw was built like 6 weeks ago, so who knows when itll show up.

 

[burn813]

I’ll give a full report probably over the weekend.

I am waiting with baited breath

 

[jkg]

So, i dropped off my car for a service appt on tuesday morning. the dealership was very nice and gave me a loaner. they didnt do anything to the car until wednesday because their top technician was working on a corvette. took just a couple hours for them to replace the camshaft position actuator solenoid. then they drove the car for about 7 miles to test it. i picked it up wednesday night. drove it a few times since then. sometimes i think the engine oscillation is better, but other times i definitely still see it. it's a little hard to tell, because a performance engine might sometimes run a little rough, but i'm not sure how rough is normal.

i'll see over the next few days as I drive it some more. My snow tires also have a slight vibration, so it sometimes is hard to tell. the big question will be if the car does one of the dramatic "porpoising" that makes it impossible to drive for 15 seconds. it has done this about once every 2 weeks for the past few months, so have to wait and see. But i definitely still see oscillation in the tach needle when i hold the engine at about 1500rpm in neutral, especially when engine not fully warmed up

 

[jkg]

Here is a video of the oscillation when it is mild. in the video, i raise the engine from idle to part throttle and can see in the second half of the video, how the rpms are oscillating or surging despite careful constant throttle while in neutral. i doubt this is normal for this LT4 engine

 

[burn813]

Here is a video of the oscillation when it is mild. in the video, i raise the engine from idle to part throttle and can see in the second half of the video, how the rpms are oscillating or surging despite careful constant throttle while in neutral. i doubt this is normal for this LT4 engine

This is after the "fix"?

 

[jkg]

Yes after service visit.

 

[jkg]

I wonder if anyone else's car does this- with engine temp less than 150, hold part throttle while in neutral not moving, at around 1500 rpm. does the tach needle hold steady throttle, or does the engine surge up and down like seen in my video here and previous?

 

[jkg]

Here is another video. Ignore the news radio. Watch the second half to see the surging back and forth of 50-100 rpm or so

 

[burn813]

I wonder if anyone else's car does this- with engine temp less than 150, hold part throttle while in neutral not moving, at around 1500 rpm. does the tach needle hold steady throttle, or does the engine surge up and down like seen in my video here and previous?

When I have it out again, I will try the same thing that you are doing... Is it at any temp below 150 or is it "close to" 150?

 

[jkg]

Seems to be less prominent once engine temp (water not oil) is over 170. Seems to do it from cold start up through 155 plus

 

[burn813]

I do not see the exact same thing. I did this last night without recording it before it was up to operating temperature and it seemed to be ok... Like I said, my case seems a little odd... it happened in the same place (location) a couple of times but outside of that it has seemed to be ok.

 

[jkg]

Thanks for checking. Sounds good for you but maybe not for me. On the other hand, may be the problem we’re both having with engine surging while driving is nothing to do with the Oscillation I’m seeing in a neutral

 

[jwolf99]

I tried this on mine this morning (A10 while in neutral, from cold start up and right thru 150 F coolant) and did not have any fluctuation similar to yours.

 

[jkg]

Here’s another video that shows the surging increases over a few seconds while I hold the throttle constant in neutral

 

[jkg]

Keeping all my friends here in the loop - I heard back from some higher-ups in-the-know at Cadillac (thanks to my cadillac friends for being so accessible!), and they report the surging i am showing in the recent videos while in neutral not moving is normal behavior for this engine. I'll keep an eye out for the original problem that brought this, which is serious surging/porpoising while under power in motion. i havent seen it yet since my service visit, but it has only been a few days. If the problem is gone, then i will be one happy customer. (although i find the ride of this Blackwing a little rougher than my 13 V, the increased engine power and improved exhaust sound makes this 5BW the best car i have ever driven). If the problem recurs, then I will be sad...but bigger things to worry about in the big picture.

 

[jkg]

i hope I am not bringing myself bad luck by speaking too soon, but i have had the car back after the service visit for more than 2 weeks - have driven the car many times and no recurrence of the surging while under power. so, even though the engine surges while revving in neutral, perhaps the actual problem is resolved? it was fairly infrequent enough that i won't feel totally "cured" until another couple months passes by

 

[travysh]

Any idea what they did?

I haven't managed to get a video of it yet, but I can mostly reproduce it.
If I'm cruising along at 40 MPH in 4th gear with very light throttle right as the car is starting to come up to temperature, it will buck/surge pretty bad for like 10-15 seconds. If I give it a few revs / heavy throttle it'll be fine, but it's super annoying when it happens.

I'd like to get a video of it and then I'll schedule something with the dealership, but knowing what was done to yours might help them.

 

[jkg]

I listed the replaced part under post 43 above. Camshaft actuator that does the variable valve timing thing

 

[travysh]

I listed the replaced part under post 43 above. Camshaft actuator that does the variable valve timing thing

Gotcha, I thought that didn't actually resolve it, and you had to go back

 

[jkg]

No just one visit so far. Hopefully this will solve the problem.