99svtvenom

Hey guys looking for a little help on a hard start problem with a PO340 code. I've researched the issue and have seen the "dreaded" po340 issues but don't think it is related too much to that as the car does not bog, stall, run rough or anything like that. The only issue is that sometimes you have to crank the car over 5 or 6 times before it will start up. It does not matter if it is cold or warm it always takes multiple attempts to start the car up. Once the car is started it runs perfectly fine with no hesitation, bogging, no rough idle or anything just the hard start. There is a code and it is reading po340 and the check VSC light is also on, but I'm not sure what is up with the VSC light or if it is related to the problem. If you guys could help me out and point me in the right direction I would really appreciate it!

99svtvenom

Bump for some help

billydpowe

iTrader: (1)

my VSC lite was the oil control valve (VVT) on the front of the left head. remove plug, 1 bolt and pull it out spray with carb cleaner, and in the chamber also, and replace, my light went off.
hope this helps???

99svtvenom

Awesome, I'll try that for the VSC and let you know if it works.

NisMax

Could you clarify which plug is the OCV specifically in the second picture? I see a black plug and a gray plug. Thanks in advance.

billydpowe

iTrader: (1)

Sure, it is the black plug, (2nd photo) unplug it, remove the little bolt, twist it back and forth while pulling it towards the center of the motor and it will come out. you will have to press some wires out of your way. and the other side is a lot harder because you have to remove more items,,, good luck

NisMax

^What do you mean the other side?

I wasn't able to get it out fully, as these pesky wires behind it got in the way. I suppose you had to remove a few different items.

Also, do you know where the coolant temp sensor is on these motors?

NisMax

I did clean the top of the OCV w/o removing the full unit. The car no longer makes less gurgling noises.

BNastee

Old thread revived.

My 99 is doing the dreaded VSC light and P0340. I've previously fixed my 2000 LS400 by cleaning the sensors as Billy suggested. That hasn't fixed my 99 yet. Admittedly the oil is pretty dark so I'll change that tonight and cross my fingers. Next step might be to consider the alternator. I know weird things happen when voltage is low and mine runs at 14.0 volts. My guess would be 14.6 is normal but I want to confirm.


Rich

BNastee

Update on the 99 LS400 with VSC light and P0340. I could have saved myself a bunch of trouble. The timing belt skipped a few teeth. That was the root of the problem.

I nearly caught it right away. The day it popped the code, I took off the cam covers and they were aligned. I didn't check the crankshaft alignment. Big mistake! Both cams were lined up so I went to checking other things.

- Voltage was under 14 volts, and low voltage does weird things, so a new alternator went on. Also swapped in a known good battery.
- New cam sensor even though the original one tested within spec.
- Ohmed out all the cam position sensor wiring.
- Cleaned the throttle body and air passages under the plate.
- Cleaned the oil control valves.
- Finally my son asked if I checked the timing belt. I had, but just the cams, so I lined up the cams again and the crankshaft was off!!! I loosened the tensioner and rotated the crank, making sure the cams didn't move. Started right up with no codes!

I'll order a new timing belt kit and install it ASAP.

Sherl

Did you replace the knock sensor for p0330 code?

BNastee

My knock sensor issue is on another 99. #Goldilocks. Did not replace because I think it's a symptom not the cause.

My timing belt woes were on my high mileage black 99 #Butter. It's in the capable hands of a teenage driver now :-(.