Surging and bucking at idle while in gear

[Clark111t]

I have a 2013 chevrolet equinox 2.4l ecotec vvt. I just rebuilt the engine with new rings, pistons, bearings, cams, rockers, lifters, valves and timing. I have also replaced almost all of the sensors, as well as the cat. New fuel injectors, high pressure fuel pump, fuel pump in the tank. New coils and spark plugs.
It runs smooth on the road or at idle while in nutral, but at idle in gear it surges and bucks. There are no codes. It is so frustrating. I need help to figure this out.

 

[Dragonary]

I have that on occasion. Make sure your oil is at the right level and you are using the right stuff. Other than that you could try a new throttle body (or used one on eBay which is what I did). Something else you could try is disconnecting the MAF sensor and driving it and see if it changes the issue. Then try the MAP sensor. You may have a vacuum leak too.

 

[Clark111t]

I tried a new throttle body and MAF sensor. Neither were the problem. I just ordered new cam phasers because they are the only thing left that retard or advance the timing other than the ICU.

 

[Dragonary]

I read something about the EVAP system that can cause problems. You might be able to disconnect and block it off to rule it out. since it's in gear at idle, I would suspect something more like that or a vacuum leak.

 

[corvairbob]

i'm dragonary on the vacuum leaks. sometimes you get this and no codes. one more thing what is the idle speed? if the gas peddle and TB are not in sync that can caused that issue. lets see if other chime in to confirm that but on my girls 2013 after a completed rebuild i had that issue and the gas and TB just could ot get back into sync. i had to do a TB relearn but i forget how i did that now. but there are YT showing that procedure. good luck and keep us posted

 

[Clark111t]

I've tried everything to figure this out. The engine has been rebuilt with new rings, bearings, pistons, timing, both fuel pumps, vvt solenoids, both fuel pressure sensors, fuel injectors, plugs, coils, cam phasers and both 02 sensors. It has random multiple misfire at idle and bucks and jerks when in gear at idle. When given a little throttle it smooths out. If I unplug both vvt solenoids it runs and idles good but throw codes for the vvt solenoidsand also 02 sensors for running rich. I'm at a total loss and need some help to figure it out.

 

[corvairbob]

almost sounds like the TB may need to be cleaned. if you did that then the gas pedal sensor's are failing.

so try this check to make sure it is not in eco mode. and try it with the a/c on so the ecu will give it a bit more gas. that is what i had my girl do and her car ran a lot better.

one thing i did before i had her make sure the eco mode was off and then she found that when it was in a/c mode it ran a lot better and idled smooth, was i wrapped the gas pedal with electrical tape stop to force the gas pedal to be depressed just a bit. i tried to add a screw but there was not enough room to add one so i put a shim there, i think for testing i did electrical tape. so give that try and see if one of these works.

another thing i was going to do was build a tB plate stop to hold the TB plate open kind of like the old school TB plate idle adjusting screws, but the girl said having the eco mode off and the a/c on made the engine run a bit faster and smooth. good luck

 

[Taabalb]

Hello new here but 30 yr. veteran mechanic, I have the exact same problem, surging at stop sign. I have been fighting this over a year, I have replaced everything except the ECM. and when i say everything i do mean everything. Except for internal in engine. car runs rich and gases up the oil. leakdown test is good so its static compression.

So if anybody has fixed this issues any help would be greatly appreciated.