408ws6ta

First off. I'm new to the Fbody world so any help would be greatly appreciated. I come from turbo rx7 and turbo sc300 imports and know a lot about cars and performance setups... but these problems are new to me. I have yet to mess with OBDII cars.

The Setup:
2000 ws6 t/a M6 with 69k miles
Iron block 408 -243 heads, ls6 intake, lid, k&n filter, pace setter LT, TSP TD...
I don't know compression or what cam but it has a pretty beast lope at idle.
No EGR, AIR, or cats.
It pulls 13-15 inches of vacuum at idle cold.
The temp points directly at 210 when warm.

Pic of the internals:



Problems:

Hesitation
It idles at 850-1000 depending on how warm it is.
It hesitates in neutral if you jab the throttle and let off.
It hesitates, pops and backfires if you try to run it through a gear anything over 50% throttle.

Oil Pressure
The oil pressure is 30-35 cold idle and 15-22 hot idle. Cruising at 1500 rpm its around 30-35 at running temp. It has gone in the red and caused a CG light at 800rpm idle before.
I have not changed the oil yet because I don't know what weight to use. I read that stroker motors need 10w-40 so I got some... but didn't want to change it until I was sure. Any ideas?

CEL codes
p0171, p0174, p1133 -These are lean and o2 sensor codes.
I cleaned the MAF using spray from advanced auto today and got a new fuel filter. (not installed yet)

I plan to change the plugs when I figure out which ones I should put in it.

I will buy new O2 sensors asap. I read the corvette ones have better heating elements in them....

I will check fuel pressure asap.



What should I check? New oil pump? Tune? Fuel pump?

Thanks,

408ws6ta

UPDATE:

Today I changed oil and filter to 10w-40 and it pressure is 40 cold start and 18-20 hot idle. :/

It is still throwing lean codes and popping/hesitating when you try to rev it.

Spraying carb cleaner to check for vac leaks found nothing. :/

I recorded the data from the sensors using Torque app on my Droid.
(all readings were taken at idle after idling the car for 30min to warm it up)

Fuel Pressure: ~59-62psi
Temp: 88c
RPM: 940
Oil Pressure: 18psi on factory gauge
Bank1 Correction: ~19.5-26%
Bank2 Correction: ~19.5-26%
O2 Bank1 Sensor1: ~0.83-0.02v
O2 Bank1 Sensor2: .44v solid
O2 Bank2 Sensor1: ~0.82-0.01
O2 Bank2 Sensor2: .44v solid
Mass Air Rate: 9.85-10.18gs
TPS: .39%
Timing Advance: 20.5 - 23
Volts: 13.9v
AIT: 32c
Intake mani pressure: 55kpa
Vac: -6.72psi


Any ideas what to do now?

DrkPhx

iTrader: (15)

Is this a new motor? I would try a 20w-50 dino oil. Low oil pressure could be pinched o-ring in the oil pump or bearing clearance issues. Hard to say over the internet. Doesn't sound like the car has been tuned, or just barely. The symptoms you listed are the result of running too lean. Who tuned it and do you have access to tuning software? If not, I strongly recommend it for your set up. Do you have the cam specs?

408ws6ta

I dont have the cam specs. I dont have much info on the motor because the guy I got it from scored it cheap from a repo auction. It was listed as a normal ls1. The Iron block was a dead give away. (this is they story I was given anyway)

A guy at work remembered seeing the car at a small dealer 2 years ago. I called them and he remembered the car. It is indeed a 408. He didnt know who built the motor or what is in it for sure. The block has 6.0 stamped on it and the pic of the inside shows aftermarket crank, rods, and pistons. It also shows the block is clearance for the stroke.

The AIR, EGR, and rear O2s have been tuned out but it might have been a mail order tune or something.

I plan to get the car tuned soon but I want it to be ready first so they dont just turn me away or charge me an arm and a leg trouble shooting for days. The closest tuner is 3 hours away from me in Charlotte NC. I want to get the car good for the 3 hour trip there so I dont mess it up on the way.

I didnt want to put in 20w-50 because I read it is way too thick and wont protect at start up. It really seems there is a pinched o-ring or a weak pump. Either way, if I open it up to check.... Ill replace the pump with a melling high volume.

Thanks for the input. I will keep this thread updated as I trouble shoot.