New Engine Very low on power

[70TWO NOVA]

Ok guys, looking for a little guidance. I rebuilt a 5.3 lm7 with all stock bottom end, new bearings throughout. New 4.8l pistons, ls6 cam, intake, tb and injectors. I fired the car for the first time the other day and drove it for the first time today. The problem is, it is extremely low on power and has virtually no throttle response. Engine rpm barely increases even at 3/4 throttle or more. Iam stumped here. Any ideas as to why it would seem to be so low on power? When the car is in park or neutral it will rev up fine though the RPM range and sounds to be fairly healthy.....

any insight or help is greatly appreciated.

[Denvervet]

Fuel pressure &timing come to mind first. Throttle cable? Got lots to check. If this is efi can you datalog and watch parameters?

[Todd in Vancouver]

Sounds like its in "limp mode". Have you scanned it yet?

[70TWO NOVA]

i havent check fuel pressure yet, ill def be doing that soon, i did find out that the trans fluid was low. could tht cause the sluggish feel of the engine? I havent scanned it as I dont have a scan tool. It has a factory "base" tune that a local tuner flashed for me

[Nessumsar]

It would be worth your time to pick up a $15 bluetooth OBDII reader and use some sort of Android/IOS device to see all of the parameters of your engine.

[70TWO NOVA]

where could I get one? I always thought those were expensive

[Nessumsar]

Try Amazon or www.newegg.com. Search for "Bluetooth ODBII Dongle". I know Newegg had one for $12, but it had some mixed reviews.

You'll need the dongle and an app for your device; such as "Torque" for Android, or Fuel (?) for IOS.

[howehot]

When I first fired my LS1 it was super lean. Turned out I failed to ground the fuel pump. Check all your grounds, engine to body, body to chassis, chassis to engine.

[70TWO NOVA]

ok, thanks for all the help guys, ill keep all this in mind when troubleshooting

[Todd in Vancouver]

Also please keep us posted as we can help you dig a little further if needed

[70TWO NOVA]

well I checked a few things the other night, I couldnt find any obvious issues (no vacuum leaks etc), cylinder 7 is definintely missing though. The ignition system checked out, also used a noid light to assure the injector circuit for that cylinder was working. Im starting to think maybe its a bad injector?? Also the transmission was really low. I guess I didnt put enough fluid in when I initially filled it. It took a good 2.5 quarts. I guess that would explain it not wanting to go anywhere when I tried to accelerate. But I still dont get why the engine didnt want to rev under load...

[KnightMare]

my Avalanche did that to me a few years ago. Those engine have like a safety feature to reduce power to not damage the engine. I believe the dealer had to replace my PCM after they spent a week replacing stuff and was still getting the same result. It can be a wide range of things triggering the PCM. I'd double check all you sensors and connections, get a scanner

[70TWO NOVA]

A little update, I think I narrowed it down to the trans being in "limp mode". All the research I did points to this. The engine seems to being running fine but the trans is stuck in third gear (will go into 2nd if done manually) I do have reverse though. So I did a little testing and made sure there is 12v going to the trans and that the VSS is operating (I even swapped it out with a new VSS, no change) From here Im not sure what to do. How do I clear the PCM from limp mode? What else would cause this? Anything else I should check? Any additional help is greatly appreciated.

[70TWO NOVA]

Ok, so I scanned the PCM and got the following codes;
P0300--Random Misfire(which I know cyl 7 is missing)
P0351--Ignition Coil "A" Primary/Secondary Circuit (which doesn't make sense cause its cyl 7 missing, not cyl 1)
P0740--TCC Circuit
P0753--Shift Solenoid "A" Electrical
P0758--Shift Solenoid "B" Electrical

So Im thinking the reason Im getting all 3 of the transmission related codes at once is because there is an issue with the wiring or connector going to it. It just seems unlikely that all 3 of these things would go wrong with the trans at the same time. Am I wrong for thinking that?? Any Ideas?

[70TWO NOVA]

This may be a stupid question, but does the trans/pcm need an electrical input from the shifter to know what gear its been placed into? I only ask becuase Iam using the factory 1980 camaro shifter setup. There is no PNP switch or anything, just the shifter cable. I just know the 4th gen camaros had an electical switch mounted on the shifter itself and I want to make sure this isnt why Im having this problem.

[70TWO NOVA]

Well I figured it out finally, the company I bought the harness from screwed up and put the wires in wrong in the main trans connector. Luckily I had a factory harness to compare to. The wires were put in 180 degrees backwards in the connector. I had to removed them all, turn the connector 180 and reinstall them. Everything seems to work fine now. I haven't gotten into 3rd or 4th gear yet but it seems to be shifting perfectly fine. Now all I have to do is figure this misfire out....

[SickSpeedMonte]

Doesn't a random misfire mean that multiple cylinders are missing? When I had a bad coil, the OBD told me which cylinder it was. Then I switched the coil to another hole and got the random misfire code for a day or so, and then it switched to just the new cylinder.

[70TWO NOVA]

yeah, Im gettin a random misfire code and a code for cylinder 1 missing. Not sure what the deal is since I know that its #7 missing. (cold header after startup) I switched the coil and plug wire to another cylinder to check so maybe thats why its saying "random misfire"? Im hoping the dude who built the harness didnt screw up the wires to the coils. I dont want to have to check all the pins at the PCM

[70TWO NOVA]

So far I have; verified good fuel pressure 58-60 psi, checked the plug wires and coil. Swapped the coil/plug wire and the misfire didnt follow the coil. I used a noid light to check the inctor circuits, removed the coil sub-harness and checked all the wires for continuity/resisance, pulled the valve cover and made sure the valves were opening properly, removed the plugs (#7 is clean and shows good continuity and isnt broken internally) I fired up the engine for a few seconds and touched each header and found that cylinder 7 is the only cold one. So far everything I have looked at checks out fine. The only things I havent done is verified good coil driver circuit for cylinder 7 or checked for a physical clog in the injector. Any other ideas??

[eroc022]

sounds like a bad #7 coil...... switch it with another cylinder and verify that the new cylinder is misfiring....

[70TWO NOVA]

I was starting to think it was the coil too. Now the miss is jumping around from cylinder to cylinder on the left bank. First it was 7, then 1 and now 5. I dont know what to do. Im pulling my hair out over this

[Denvervet]

Does that #7 plug look different than other plugs. Almost sounds like stray voltage from some bad wire...or poor grounding. Done basic cylinder testing on 7 like compression and or leak down just to rule some deeper things out?

[Todd in Vancouver]

I can not say this enough and make sure all your grounds are clean and tight. The last "ghost" I chased was due to poor grounds and lack of ground straps. Check and clean all grounds and make sure you have really good ground straps from the engine to the chassis as well as all battery to chassis straps. Also that the ECM is grounded to the battery and not just under the dash.

Sorry if this is a repeat and you've already done it but I'm not kidding when I say I've seen guys spend days, as in 8-10 hours per day chasing crazy diagnostic problems to end up finding a bad ground. Just try and explain to a customer that I've spent 20-30 hours shop time at $100+/hr and ended up cleaning a bad ground to fix the problem. :hammer:

Also, if all else fails don't discount a bad ECM because they do die.

[70TWO NOVA]

I can not say this enough and make sure all your grounds are clean and tight. The last "ghost" I chased was due to poor grounds and lack of ground straps. Check and clean all grounds and make sure you have really good ground straps from the engine to the chassis as well as all battery to chassis straps. Also that the ECM is grounded to the battery and not just under the dash.

Sorry if this is a repeat and you've already done it but I'm not kidding when I say I've seen guys spend days, as in 8-10 hours per day chasing crazy diagnostic problems to end up finding a bad ground. Just try and explain to a customer that I've spent 20-30 hours shop time at $100+/hr and ended up cleaning a bad ground to fix the problem. :hammer:

Also, if all else fails don't discount a bad ECM because they do die.
thanks for the help guys, Ill definitely check the grounds and everything tomorrow after work. Im seriously pulling my hair out over this. I even routed new dedicated wires from the PCM to the coil connector just to rule out the possiblity of a bad wire in the new harness. To no avail of course....

[70TWO NOVA]

Well after scratching my head over this for a while I finally figured it out I think. Since I pretty much ruled out an ignition problem I pulled the fuel rail and injectors last night. I found a few little pieces of what seemed to be silicone sealer (the orange stuff) in the inlet side of a few injectors. I cleaned them out, but the real issue was that the #5 injector wouldnt "click" at all when I applied power to it. I checked all 8 and that was the only one that didnt work. This makes perfect sense since #5 was the cylinder throwing the code (P0305). I ordered a new injector from Rock Auto last night. Hopefully it will come by Friday so I can verify that was the issue all along.

[70TWO NOVA]

We figured it out. Since the ignition system seemed to check out fine, I focused my attention to the fuel system. I had good fuel pressure to the rail so I decided to pull the injectors. All 8 of them ohmed out fine, and all the driver circuits in the harness worked fine with a noid light. I pulled all the injectors individually and put power to them using a connector from and old LS harness. With 12v to each only one didnt "click". #5 which happened to be the cylinder with the consistant miss and code. I went ahead and ordered a remanufactured injector from Rock Auto (bad idea). Got it, installed it, and got a huge plume of blue smoke out the drivers side exhaust. Turns out the "new" reman injector was stick open and gas washing the cylinder. Long story short I got a GM injector from a local dealer and $140 later she runs like a champ. No miss, no smoke and ready for its final tune and dyno run on Saturday. Ill post up some dyno numbers then. Thanks again guys for all the ideas, support and for sticking with me on this.

[Denvervet]

That's awesome. Great to hear another Gremlin defeated. We've all had some to chase and it's such a relief when we finally win.

[Todd in Vancouver]

Great news and looking forward to some Dyno numbers and a smoky burnout pics or video

[70TWO NOVA]

Great news and looking forward to some Dyno numbers and a smoky burnout pics or video

I will definitely post up some dyno videos tomorrow.

[70TWO NOVA]

I will definitely post up some dyno videos tomorrow.
Unfortunatley we didnt get to tune and dyno the car this weekend. The tuner wanted us to fix a few things before he worked on the car. I.e. rerout the PCV system, install a longer intake tube to stabilize MAF readings and install a new coolant crossover hose. Hopefully we will have it done in a couple weeks