Im having an issue with my ls1. I have no power at all when I give it partial throttle, its surging, bogging and takes forever to go up to 3k rpm. I have an awesome idle @ 700-800rpm, Today I unplugged all the ignition coils one by one and something weird happened. On cylinders 2-3-5-8 unplugging the coils when the engine is running doesnt change the idle at all. Like the it doesnt care if they are plugged in or not.

I have a spark at the end of the wires tho... maybe a weak spark but its sparking. wtf is up with this, Im at loss.

Everything is new on the car. New plugs 41-985 gapped @ 0.40, new wires, new racetronix fuel pump (Im receiving 60+ psi at the rail), new fuel filter.

Anyone has an idea of whats going on here?

 

Sounds like you either have a harness issue or a crank or cam position sensor could be gone. I'd veryify the Grounds on that banks ign coils
first. Heck add some ground neatly from engine to chassi, engine to body, body to chassis etc. You simply cannot have too many grounds this will
only help and never hurt so start there.

Failing that I'd look into the wiring harness and verify it's correctly
routed as there's no sense buying new sensors you may not need. Not too difficult to verify the wiring either you just need to find the pins at the PCM that the problematic bank uses then do a continuity test with meter fro
the PCM pin end to the harness plug pin for each of them and this will tell
you if they are wired correctly.

Failing that I think it could be the crank pos sensor

 

Thanks for the reply cam.

I tested and ruled out the ignition coils wiring. I rechecked every wires / continuity goin to the pcm. All the coils are firing (header pipes are hot).

Wouldnt a faulty CPS cause a bad idle or difficutly to start? isnt there a way to test a Crank sensor with a multimeter?

All the installed grounds on the car are 0 gauge, Ill add another coming from the battery to the engine.

 

Mm ok. Three things. First start it up and tap the injectors lightly and repeatedly on the sides and see if that wakes them up. It's not uncommon for them to lightly sieze in closed position after sitting idle for long time frames. Second are you certain the tune in the PCM is stock oem and correct for your engine/trans? Third do you have a functioning iat sensor? Can you log any of your particulars via hptuners etc?

 

Ok, Ill go tap the injectors this afternoon to see if Im getting any change.

I bought the pcm from Jesse @ waitforme performance. I told him to put in a stock 02 F-body T56 tune (I cant rule the pcm out yet because I dont know if its the sensors or the pcm acting funny). I cant be 100% sure it is in fact programmed the way I told him to. I guess I can just take his word for it.

As far as the IAT goes, I dont know if its functionning proprely... I would need a data scanning tool to see sensors reaction in real time. Do you think a bad IAT could make the engine run so poorly? I believe just unplugging it sets the default Temp to -39 Celcius (not sure what it is in Farenheit) and makes the engine runs richer, altho I might be wrong, its been a while since auto school

 

I just went to the garage and took a second to test the IAT's resistance. Its supposed to be between 1500 and 2000 ohms and Im reading infinite resistance. Looks like its trashed.

 

I've had iat, maf, and o2 sensors cause all sorts of mysterious head scratching problems. Nowadays I just go through a process of elimination by unplugging them one at a time and testing it usually points out the faulty unit. Tune wise it sounds to me as if your good to go as well. As for testing the CPS I do not know how to do this off the sop of my head but I'm sure a quick search will net some answers.

Regardless the iat has a huge impact on how well these things run so fusing that toast is a good sign. Plus they're cheap around fifteen bucks from the stealership

 

Ok. little update. My IAT was good in fact. I took the time to re-check the resistance and it tests ok. I tried unplugging it while the engine is running and it dies right away, or idles VERY rough. So this is ruled out.

I then tapped on each injectors, theyre all clicking and the wiring is ok. All of the headers tubes are hot so as far as the functionnality goes, they work. Now, are they clogged or dirty? maybe but I think that would cause me idle problems too right?

I took the CPS from my dad's truck and its doing the same thing. I used mine on his truck and it runs flawlessly.

New things I noticed today is that if I unplug the knock sensor, TPS or IAC while the engine is running, its not even noticing it. I mean, the MIL is on but idle wise, it keeps on going smooth like nothing happened.

I thought that unplugging the TPS would have caused the engine to die instantly since Im supposely using a Speed Density tune. I would try it with my dad's truck but since its DBW Id rather not mess with it.

 

hmm thy plot thickens. Well as you can see the iat has a major impact on how well it runs but this isn't the trouble it seems. Crank pos sensor is out so maybe cam sensor? Before you go through the effort of swapping that though I would verify some simpler things which in my experience usuaally are the root cause of these types or gremilns.

Did you change your fuel filter? When you swapped pumps are you absolutely certain you have the hoses clamped on properly inside the tank? If not you can bleed off pressure very quickly as engine demand goes up. I've witnessed this first hand on another build where the high volume aftermarket pump was too strong for the stock aligator clamps and was squirting fuel out like mad passed them. Of course this was all happening inside the tank so the only way to Brody it was to hook up an exernal fuel pressure gauge and mount it in the hood and go for a drive and watch what happened to the pressure as they drive. Thought the new pump was gone ( racetronics too oddly enough ) but tested the entire pick up assembly on the bench and voilà the fuel was squirting out all
over. A few stainless fuel hose clamps later and they were good to go.

As for the sd tune I do know they are typically more challenging to dial in than a maf tune so other than that I don't know what else to tell you about your tune.

Considering the iac? Should still run fine off idle which is where your problems lie so I wouldn't be thinking anything wrong here. Tps? While this does affect how well it runs the tps really only comes into play for enrichment purposes through the pe tables iirc. Again I don't really know about the sd tune so it's possible that the tps is causing problems but it doesn't feel right to me as the cause for your woes. Knock sensors are reactive though and will not affect anything other than pulling timing if they sense knock. Plus it's not very common for these to fail and you have two.

I'm leaning towards a fuel issue in my mind still. At least I'd like to ensure that the fuel system from top to bottom is perfect before it's ruled out. What injectors are you using and where did they come from?

 

Heres a little vid a made showing what Im talking about.

RPM gauge gauge cant pass 1k RPM, engine has awesome idle but no power/torque.
Great fuel pres.
No colored exhaust gases.
Voltage @ 14.5V

http://www.youtube.com/watch?v=_SPGCeqBVuM

 

sounds like it's not running on all 8 to me but it's tricky to say for sure i'm only checking this with my phone. Simple test

try squirting fresh fuel right into the throttle body and rev it up and see how she runs.

 

Im gonna go out and buy 0 gauge wire from the battery out back to the engine, maybe a stronger ground would help. I rechecked my fuel lines at the tank. Im using the LS1 tank and the Feed is clearly marked on the top of the pump assembly. Its also 3/8" in diameter and the return is 5/16. Fuel pres. climbs at 62-63 at the rail when Im playing with the throttle.

Heres a pic I made. Red lines are the grounds I already have, and the blue line is the line Ill add. thoughts?

Btw Cam, thanks a lot for figuring this out with me! Ill have to make a joy ride to Ontario soon

 

While grounds help, you dont have to add that many. Use a meter to check the resistance from the engine to chassis. If its more than a few ohms, add another ground, otherwise you're wasting cable

 

Ok the ground I added definately helped. Not my problem, but the fuel pump primes quicker and the gauges looks more accurate. Still the same problem tho. God Im getting pissed.

 

Pissed I can certainly understand. These things can be extremely frustrating indeed. Anyways just to absolutely define whther we are dealing with an electrical issue or a fuel issue please try this.

Take an empty 1 liter oil can and pour some fresh gas into it and clean out the oil residue ( shake it and pour it into something safe ) then take the oil can cap and drill a small 1/16" or less hole in the middle. Fill the 1 liter back up about 1/2 with fresh fuel. Take your air intake elbow off the throttle body and start the car. Taking your high tech 1 liter oil can gas squirter try squirting fuel straight into the throttle body and rev it up. If it wakes up and revs up quickly and sound powerful then we can say for certain your issues are simply fuel related. This wont hurt your engine so dont fear about that so long as the gas is clean and fresh you have nothing to lose.

If we can establish its fuel then we can go from there. Of course if the gas squirt does nothing then we can be sure its an electrical issue and move in that direction.

 

Absolutely true and I appreciate the less is more thinking but for the 1/4lb and $5.00 worth of wire this is something that has very few downsides and it can never hurt to have too many grounds it only helps. Besides that most swappers have plenty of scrap wire kicking around so its usually "free" anyways.

Also one has to consider corrosion over time. Over time the clean bond between the frame and chassis often can become compromised. By adding grounds its a simple, cheap, and safe way to start off with a good working electrical system and keeping it that way.

 

K, I just did the gas bottle trick and it did not changed a thing. Altho, its a cool tool to have under hand, who knows, it might get useful in a near future.

My dad came to my home today with his truck (2004 Silverado 5.3) I wanted to install my PCM in his truck but his has the blue and green connectors. So no match here. Not giving up, I busted out my multimeter and test light and started measuring wires @ the big ignition coils connector. All the measurements I made was the same thing on my car; pin 60-61 from C2, grounds, 12v feed etc.

I started the car again, took measurements again and again; Im still in the same position. If I unplug coil # 2 - 3 - 5 - 8 the engine doesnt even notice it. Plugs are blackish, a little wet nothing bad. So I started swaping the coils Im suspecting not to work with those I know work for sure.

I installed coil #1 connector on coil #2, took the plug wire that went to cylinder #2 and installed it on plug #1 and the coil works like a charm. I tested the others doing the same thing. So I guess thats ruling out bad coils or bad wiring (wiring that I checked like 10x). Which is leaving me with a bad PCM...

I guess that would explain the p1518 and p1514 Im getting and the fact that Im not getting any codes as far as misfires goes. Shouldnt I have DTCs for cylinder 2 - 3 - 5 - 8? The pcm has its grounds, ign + and 12v bat.

What do you guys think?

 

Well fuels out thats half the battle. Almost a shame really as i think that would be a much easier fix LOL.

Anyways It sure would be handy at this stage to have a second stock tuned PCM around that was the same year etc to plug in and try wouldnt it? Any friends or locals you could maybe borrow one from? I have no idea why only one bank would be affected by the cam sensor either after thinking about it. Something is awry with the tune or the PCM itself if the wiring is ok I just cant think of anything else that it could be that would affect your engine the way it does?

Weird situation is an understatement...

 

Sadly Im on my own as far as pcm goes. Ill contact Jesse @ waitforme to see what he has to say about that.

Ok so I just ohmed all the injectors, and they all are between 13-15 ohms. So I guess they are ok electrical wise. Might still be clogged... but 4 of them? I can feel them clicking when the engine is running. Im using a brand new vette filter, new hoses etc, I doubt they are clogged.

Finally, to add to my pcm theory, The cylinders that arent working (2,3,5,8) are all controlled next to each other by the PCM. Maybe that "zone" of the pcm is trashed.

 

With a name like Waitforme Performance, I think it's safe to say it's the PCM LOL

Sorry...not trying to be an *******....I just could not resist. Seriously though....sorry to hear about your problems. From everything else you've described, I honestly think that the PCM is highly suspect.

One other thing....vaccum leaks?? I've seen them do some strange things. Just a thought.