Hi guys, I am hoping someone here can shed some light on my 5.3 build running issues.

I have built a 5.3 from the block up using flat top pistons, a mild cam and LS6 intake and injectors. Still using the 5.3 throttle body that I polished.

I have built the engine on a stand and sent the PCM off to LSX Power Tuning in Texas with a complete list of all the mods and specs on my build. (below)

Gen 3, 2003 New old stock 5.3 LS iron block, deburred.
Gen 3, Stock crank, balanced and polished with Speed Pro main bearings.
Gen 4, Connecting rods with ARP rod bolts and Speed Pro bearings, balanced with crank.
Gen 4, Speed Pro 4.8 LS flat top pistons with Speed Pro rings and floating wrist pins. (10.2:1 CR)
Trick Flow camshaft P/N 30602001 and ARP cam sprocket bolts.
Trick Flow double row roller adjustable timing chain and billet gears with Trick Flow chain dampener.
Melling standard volume and pressure oil pump.
Trick flow LS7 hydraulic roller lifters
Reconditioned 862 cylinder heads, Ported and polished with three angle valve job, 2” Manley LS1 SS Intake valves, 1.55” Manley LS1 SS Exhaust valves and Trick Flow double valve springs.
GM MLS head Gaskets and new TTY Mahle head bolts.
Texas Speed & Performance chromoly pushrods, 0.080 wall thickness, 7.400” Intake, 7.350” Exhaust.
Stock 1.7 ratio rocker arms with Straub trunnions and bronze bushings.
LS6 intake and fuel injectors. Fuel Injectors reconditioned and flow tested by Witchunter Performance in WA.
LS1 balancer, water pump tensioner and accessories. 187 degree thermostat.

The problem I am having is that the engine will start but rev high. After a few seconds the idle starts to come down but if I give the engine a rev it will rev but then immediately die. I can keep it running if I play with the throttle after the rev but inevitably it will die. It does restart immediately but idles high for the first few seconds then works its way down to an idle of about 750 RPM as it warms up.

I have added a link to the youtube video I made yesterday of the issue.

About half way through I notice a leak at the cylinder head that I thought was oil, turns out it can’t be oil as there4 is no pressurized oil in the heads and is most likely coolant from the steam vent line that has a slight leak. I will fix that in the next day or two and confirm.

What do you guys think? Should I contact LSX Power Tuning and ask them about the tune? Almost everything on this engine is new including IACV and I used AC Delco or Delphi sensors exclusively.

BTW this engine is going in a 2003 BMW 330Ci

Any help, direction or ideas would be appreciated.

 

Extra thoughts: My code scanner was working but every time the engine was re started the scanner turned off. Yesterday I downloaded the Torque app and will use that to collect data next start, after I put the steam the back on (fixed the leak) and put a crush washer under the block plug. Turns out the block plug was seeping oil and the steam line was leaking coolant down the side of the head to drip of the corner of the head gasket (see end of video)

 

That is one cool engine run stand! Do you have a way to see your IAC (Idle Air Control) steps or counts when its warm idling?

 

Unfortunately I don't see that the Torque app gives me the option to data log the IACV. My IACV is brand new however.

 

I dont think anything is wrong with the iac but depending on what the steps/counts are the throttle body idle screw may need to be adjusted.

 

You know you might be onto something there, I had the throttle body apart when I ported and polished it but don't remember how I set up the idle screw.
Any secrets to setting it?

 

The real secret is a scanner like HP Tuners, which allows you to see the counts. You set the counts, on HOT coolant temps to something between 20-50 with the engine at 230* coolant temp, again, read in the scanner. The scanner can disable the fans to allow this, since they are PCM controlled. When it's set right your counts should hover around 40-80 with fans on and ECT of 180, or normal temps. This method works pretty well to allow the IAC to open to up to the max value of 310 on cold mornings and so forth. Normally, it shouldn't get this high if set and tuned right because once the IAC hits one of the limits, either full closed or full open, the PCM loses control of adaptive idle airflow, and then must use spark to compensate. It's best to give it as much control as possible and tune it as such, using both air and spark to control the idle. It's also one of the hardest things to get right.

If you have a friend with HPT or EFI live, scanning is completely free and can allow you to adjust the IAC down where it needs to be (using the throttle blade, opening reduces counts). Then it's just a matter of getting your adaptives right, idle spark, base running airflow, VE, MAF, and the IAC itself. IAC Effective Area changes will also change the "desired airflow" so the RAF table will need to be revisited a few times while adjusting it in the tune. Any actual changes to the tune will require credits. HPT would cost 2 credits.

No one really likes idle tuning I think (especially cold start idle tuning), because it can be pretty tricky to get everything to play nice with a nice cold engine and nice cold weather involved. Adds a lot of factors to the tune that aren't normally present at operating temps, where practically every other type of tuning is done. Also considering, you can only check your idle adjustments once a day with a truly cold engine, maybe twice if its a cold day.

 

I second this, VERY cool engine run stand. Wish I would have thought to do something like that. Would of made cam changes and all kinds of tuning a bit easier than having to tear it down in the car.

 

Chopper, thanks very much for that information on tuning the idle, sounds pretty complicated for someone without any tuning experience like me.

I wish I knew someone local to the Cincinnati area who could come out and plug into HP Tuners for me. Any idea how I could find someone like this, I would be happy to pay for their time.

I looked at the throttle body idle screw as I was leaving for work this morning and it looked like it was probably not too far off, but I'm sure a little bit of adjustment could make a big difference in engine idle. My visual guess is the idle screw was sticking out about 1/16".

Thanks for your comments on the test stand. Its really just a standard engine stand that I made a pair of legs for that attach to the engine mount locations on the block. I used a super cheap pair of block style engine mounts between the block and legs for cushion. I bought a used Camaro rad and fans off craigslist and made a simple shelf style holder for them.

I suspected it would be doing some troubleshooting on this engine and I wanted to be able to do that and have it pretty close to perfect before I put it in the car.

Really nice thing about doing the swap on a BMW is that the whole front end comes off, so no lifting over the core support.

 

OK, I have a little more to go on here.

Last night I installed a new TPS and fired it up again. Started right away and idled pretty well after an initial high idle.

I did adjust the idle set screw on the TB out just a little to where the butterfly is just beginning to open.

I had Torque Pro hooked up for tach, temp and data logging.

Same problem exists as before, in that if I rev the engine it then wont hold idle and dies.

You will also notice the engine revs to around 2000 on start then slowly goes down to the 900's over 30 seconds or so.

Attached is the log file, please have a look at it and tell me what you think. The main issue I see is bank 1, LTFT at -15 and bank 2, LTFT at 25, how do these numbers help me diagnose my improperly running engine?

 

Normally with mismatched numbers like that, I would suspect an exhaust leak before the O2 sensor somewhere. Check the plugs on that side to check for fouling too, the side that is reading +25 that is, bank 2. Check the manifold gasket and anywhere else there might be air coming in. The PCM is dumping fuel on that side because it thinks it's lean, when the other side obviously disagrees. Either that or there is an actual fueling issue on your rail or injectors, but 99% of the time this is not the case. Check for a dead injector anyway, but I'll bet it's an exhaust leak. Technically a dead injector acts just like an exhaust leak too though lol.

 

The only way to know if the TB needs adjusting is logging the IAC counts, there is 99% chance there is nothing wrong with tps, iac, tb or anything like that. The TB either needs to be adjusted or the idle airflow in the tune. Your fuel trims should match from bank to bank, having that big of difference means there is something going on, exhaust leak, clogged injector, vacuum leak etc. Feel free to call us anytime and we will help figure it out.

 

Don't call me unless you want to pay the international fee for it lol. Plus LSX gets paid for this stuff... I accept beer. LOL.

 

Thanks guys, It doesn't sound or feel like I have any sort of exhaust leak.

I think my next step will pull the intake manifold and make sure I don't have an intake leak somewhere, possibly because of the RTV water dam I made in front of the knock sensors.

Question: The part on the back of the LS6 intake that the MAP sensor plugs into is kinda loose. Not terrible but it moves a little if you wiggle it. Looks like there is a rubber seal about 3" diameter that does not appear to be serviceable. Should I try and seal it better somehow?

After that I will pull the injectors and test them. They were rebuilt by Wichunter performance a couple of months ago, but I suppose its possible one or more got some **** in them from the fuel rail when engine was first started.

 

Turns out I had a leak around the IACV. I stuck a hose through a rubber glove with the glove around the TB. I blew in the hose and heard air coming out so I sprayed soapy water around the TB and low and behold bubbles from around the IACV. I pulled the IACV and found the o-ring crushed. I put on a new o-ring and carefully slid it into place and screwed it back in. I trued blowing in the hose and no more leak around the IACV. Actually no air coming out of anywhere around the intake.

But the same problem still exists. It fired up and idled OK ish up until closed loop but eventually stalls out. I can sort of keep it running f I fiddle with the throttle but its hard to keep it going and if I let off will die out and stall.

So passing the intake smoke test now, what do I look at next, injectors or coils? Injectors were rebuilt but coils are of unknown age and origin.

Trying to keep positive but I am starting to run out of ideas.

 

Check the flange gasket right before the O2 sensor. Also you can switch the O2 sensors from bank to bank and see if it fault follows to rule out the sensor. If the problem switches sides, it's just a bad O2 sensor. If not, then it might be a pin hole leak at the gasket or manifold area. Re-torque the exhaust as with most setups, heat will cause the headers/manifolds to lose torque. It's an old rule my dad taught me after install, and still do to this day, re torque it after first few heat cycles and again after about 50 miles. You'd be surprised how lose the bolts can get sometimes after getting hot.

Keep in mind, it doesn't take much air at all to cause a bad O2 reading. A pin hole is enough if it's anywhere before the sensor.

 

I am thinking how I could test for an exhaust leak using air pressure and soapy water.

Tonight I will try the hose in the rubber glove over the exhaust outlet and blow air in through the exhaust outlet while spraying soapy water around the exhaust gaskets pre O2 sensors. If that tests well I will swap sensors side to side and see if the LTFT moves with the sensors.

But here's the thing, wouldn't it idle properly when cold and only act up after the O2 sensors come on line?

Should I be focused on the bank that has positive or negative fuel trim? (Bank 1 Negative 15 LTFT, Bank 2 positive 25 LTFT.

Thanks again for your help Chopper.

 

Here is yesterdays data log after fixing the IACV o-ring leak.

 

I am guessing you have 2 separate issues, the big issue being the fuel trims being so far apart. I would resolve that first. The second issue is most likely a tuning issue, the idle airflow and/or startup airflow tables could need to be adjusted in person with data logging. With a mail order tune we build them based off experience from other vehicles with similar builds BUT that only gets you close and it may need to be dialed in more in person. The further from stock and more variables the less chance you have of a getting the base tune close for that setup if that makes sense. I would not worry about the startup or idle currently until the fuel trim issue is figured out.

 

Searching for others that have had high positive fuel trim on one bank and negative trim on other bank, led me to a post about a guy who did a LS swap and had his O2 sensors plugged into the wrong bank. So inputs from bank 1 were being read by the bank 2 O2 sensor and vice versa.

I will be looking at the wiring tonight, I could easily have plugged my O2 sensors into the wrong banks. Not sure this explains the cold start issues but if this is my fuel trim issue I will be stoked.