Hey guys, dunno if anyone has ever experienced this before, but under hard acceleration (mainly WOT) i get a very nasty hesitation, like the car is fighting to get through the RPM's. There are no misfires recorded, no knock recorded, no check engine lights. Dunno what this could possibly be. It has brand new VVT solenoids, and it getting the timing chain replaced in the spring because its a bit loose even with the new tensioner, i dont feel comfortable with the way it is so Im doing the balance shaft chain and the timing chain.

Cant tell if this is an issue with possibly the cam phasers not actuating, the timing chain being stretched, or the throttle body not staying open completely.

 

Get a log of it. The hesitation is probably from it being an auto, drive by wire and slow car. Log cam positions in HPT and see if they're following what your telling them, but I doubt it is a mechanical problem. There is no point in doing anything with the balance shaft chain, just do the CED deluxe timing kit and be done.

 

Not sure what you mean by the hesitation being from it being auto, drive by wire, and a slow car, but the CED deluxe timing kit is way overpriced, i got the entire timing kit and the balance shaft kit for less then half of that, the question is should i replace the cam phasers or not.

 

is the car tuned??

 

Yeah Trevor he toones it.

Lol

 

ok then a log would help out alot.

and wats ur sparkplug gap?

 

Ill double check the datalog on the cam position sensors.

 

Took some logs of both cam position sensors, desired angles, and cam errors. Seeing peaks of up to 13 on both sides depending on where its at in the RPM's, averaging between 1-3 on the cam error reports. Question is though is there a threshold for this to trigger a DTC. Dont have a service manual to look this info up. If there needs to be a number of cam errors reported within a certain number of seconds etc.

 

I know you guys are talking about fancy stuff in here, but when have you done the plugs last? or the fuel filter?

 

Plugs and fuel filter were done 4 months ago. Gapped to stock.

 

The actuators are fine

 

good job, most don't do the fuel filter, seem to forget about the maintenance stuff sometimes.

Have you cleaned the TB, and MAF?

 

Yep, all of that and more was done as soon as I bought the car over the summer. MAF doesnt seem to have any issues during datalogging that would suggest a problem there. I came to find out 2 months after I bought the car that the head gasket had been replaced just before I bought it at elkin chevrolet, when I popped the valve cover off a month later to inspect the timing chain job, I found the tensioner had been replaced but the chain was still very loose. The inside of the valve cover had about an inch of sludge stuck to it, but the head itself was relatively clean. Which had me concerned that the cam actuators would be effected by the sludging, given how GM vane style actuators for VVT work. Just dont know if they can be disassembled for inspection and cleaning or not, or if they have to be replaced.

 

The actuator solenoids have a filter on them so if you pull them out just wipe them off.

 

Both of them were replaced a couple months ago, when I bought the car it had both codes for both intake and exhaust. Filters were relatively clean on the old ones though so I suppose thats a good sign.

 

Mines having rough acceleration too. I have replaced spark plugs, cam solenoids, fuel filter, new throttle body, k&n intake, used sea foam to clean her. No codes, no misfires, no history... MAF? Anyone know if maf can cause rpm surges? or lurching?