thunderstruck507

iTrader: (18)

I'm getting desperate now. I'm sick of my car running like **** (well down on power...it runs fine). I am to the point I'm debating pulling everything off to look at the cam and make sure its right.

But at the same time I really don't know if it even could be. The car is down on power for sure, but the weird thing is extremely rarely it seems to run better (like 3-5 times since the engine was installed nearly a year ago). The transmission acts like trash and short shifts most of the time, but once in a blue moon the car feels amazing and the transmission firms up and starts shifting where it should. This made me think MAF sensor problem....but a borrowed one from a friend did no better.

Put in 3 different tunes with no results. No codes, my sensor readings look normal best I can tell, plugs/wires are perfect, no knock retard, good timing, good pcm grounds...

I am just at a loss. I'm frustrated to the point I hate my car.

On the dyno it made 325rwhp with cutouts open (so please don't point fingers at the exhaust) with the ls1 intake. Now I am trapping 86-87 in the 1/8th and getting outrun by bolt on cars. I estimate my rwhp to be around 340-350 max right now.

I really think the issue is something electrical but I'm out of things I can check and getting desperate.

On the dyno my power peaked and fell off at 5600rpm, everyone told me it was the ls1 intakes fault so I got rid of it, I can tell I have more power up top for sure but I've been reading and searching on here the last 2 hours and several people say the cam being off a tooth would cause the early peak and drop off instead of peaking later and riding out some.

The drivetrain is a little louder than I expected it to be but I'm not used to ls1s so I don't know how normal some noise is for a cammed car. It got a lot louder when I put the fast intake on.

I almost want to just run the thing off a cliff.

thunderstruck507

iTrader: (18)

things I've changed/checked:

maf sensor
map sensor
tps sensor
all pcm grounds good
plugs
wires
coil packs
o2 sensors fluctuate normally
vss sensor reads correct
voltage is 13 running
cylinder balance test didn't show a weak cylinder
26 degrees timing WOT
knock sensors replaced during intake swap, no knock retard
no vacuum leaks or leak symptoms at idle
no misfires according to scans or noticeable to me

I am out of ideas...I might have even missed listing something else I tried

thunderstruck507

iTrader: (18)

compression check results:

1, 3, 5 are all 200, 7 is 205

2, 4 are 190+, 6,8 are 200

Onemeanbird

How are the crank and cam signals?

thunderstruck507

iTrader: (18)

no codes for them, I can check them tomorrow

what range should they be in? I'm really leaning to this being some kinda of electrical issue, most likely MAF related

bjamick

iTrader: (31)

Did you degree your cam when you installed it?

thunderstruck507

iTrader: (18)

it was installed dot to dot, everything looked perfect

bjamick

iTrader: (31)

Then it's very possible that the cam might be off from comp. Some have seen where it was off 6*. So that could be it, but if your trapping 87 in the 1/8 that's really not to bad if your 60' blows *****.

01ssreda4

iTrader: (96)

i have to admit though, lots of cams are dogs down low without a converter. Do you think thats making the car feel slow driving around??

Arc00TA

iTrader: (17)

You said you checked the TPS sensor, did you check to see what % it is at when you put the pedal to the floor? When I looked at my tune from bone stock my PCM was reading WOT as 94%.

thunderstruck507

iTrader: (18)

100%, but what's odd is that it reads 100% at 4.14volts all the way up to 4.5volts (I can get that voltage by pressing harder

I am really leaning toward it being some kind of electrical thing still, every once in a blue moon the car will come alive...this includes firmer shifts and proper wot shift points. 99.8% of the time the pcm short shifts by several hundred rpm to as much as 500rpm for no apparent reason.

Not only is the trap low but a friend's bolt on trans am missed third and still beat me by a car in a roll race from 50-120 while he weighed more than me.

I know the stall sucks but something else is amiss I'm pretty sure.

Arc00TA

iTrader: (17)

Yeah, I would agree with you on the intermittent electrical gremlins. That sounds really strange. You seem to have checked everything I can think of off the top of my head. Is it a built transmission? I can't think of much else that could be checked.

thunderstruck507

iTrader: (18)

stock transmission with a trans go kit

whenever its running better and the trans is working right its something you can even hear in the idle...it sounds a lot meaner like a cammed ls1 should, very aggressive idle with lots of the pop one would expect from a higher compression engine

i checked my pcm ground but just realized i don't have a ground from the engine to the chassis, just the negative battery terminal is grounded to the block and has a small lead going to the fender

is a engine to chassis ground necessary?

98RedBird

iTrader: (77)

The way that's grounded sounds correct to me. The only chassis grounds that I recall are on the front radiator support both (L) and (R) sides, the (L) and (R) fender humps and the drivers side frame rail. There's also the grounds on the (L) and (R) sides of the engine block. Then you've got the grounds on the rear of the drivers side head. I would check there if you haven't already. Mine came loose on my last build and was doing a lot of what you're talking about. It grounds the injectors/coilpacks and I'm not sure what else, so you would expect to see performance issues.

Arc00TA

iTrader: (17)

YES it is. Like 98redbird said you need all the grounds on the stock LS1 wiring harness to be hooked up for it to work correctly. I would check the ones on the side of the block and the back of the heads first.

thunderstruck507

iTrader: (18)

I think I communicated incorrectly there...I have 3 grounds on the rear driver's head. I just checked them yesterday, the bolt was a little loose so I cleaned everything with a wire brush and tightened it back down.

I meant I didn't know if there needs to be a wire going from the block to the car body/frame also.

I'm starting to wonder if there might be an issue in the harness or pcm itself.

Arc00TA

iTrader: (17)

Yes, there are two grounds going from the sides of the block near the bottom to the frame. Since the PCM is grounded to the block, the block needs to be grounded to the chassis.

thunderstruck507

iTrader: (18)

I'll go ahead and add one then, can't hurt. Technically I would think it would ground with the battery terminal which is also grounded to the body, but like I said...can't hurt.

The reason I though of it is I had a weird problem where the battery cable turned out where its bolted to the head a couple weeks ago because the bolt loosened up...and there was an arc jumping from the cable to the header flange during starting. Seemed weird to me, but I just cleaned the terminal end, turned it back down where it only touched the head and retightened it.

5.3LJimmy

iTrader: (10)

This sounds exactly like my brothers car. It was an auto but has been swapped to a six speed. It is sluggish 98% of the time and used to short shift when it had the auto, the other 2% it runs just as you would expect from a cammed LS1. His car will occasionally sound like it's on a 2 step while accelerating at part throttle, but this is very rare and only last a few seconds. I have swapped every sensor, the wire harness, and the PCM with known good parts from my car and it does the same thing. Fuel pressure is rock steady at 58 PSI under all driving conditions(I drove the car for a week with the pressure gauge attached).

When he first got the car it was very strong but spun a rod bearing within the first 500 miles. The guy he bought the engine from was kind enough to rebuild it free of charge. Every internal engine component is original with the exception of the crank and one connecting rod, which were taken from a 5.3 engine the seller had for parts. Compression is great along with all sensor signals and outputs. My next step is going to be to pull the engine to inspect the reluctor wheel on the crank. I pray that I find a damaged tooth on it because if that's not the problem I have no idea where to go from there.

I am not attempting to hijack your thread, just sharing my experience with what sounds like a very similar problem in the hopes that one of us will find the culprit. Good luck with yours and if I find anything I'll be sure to post it here.

Onemeanbird

Im not sure what the exact spec on the cam or crank sensor is but best way to check it is to watch it as live data on a scan tool. Sounds more like your having ground problems to me though.