98Z28CobraKiller

iTrader: (17)

I just got done swapping in a 402 LS2 into my 98 Z28 M6 stock tune.

https://ls1tech.com/forums/generation-iv-internal-engine/433240-started-install-my-ls2-402-slp-w-pics.html

Now, I fire it up and it wont idle. Lots of popping and stuff at start up. Good oil pressure. Once I get out of the sub 1500 rpm range and hold it around 2000 rpm for like 2 min, it will let me settle it back down to about 1500 before it starts to fall apart.

Is this a tuning problem? I am ordering HPTuners right now. Will HPtuner tell me if I am dropping a cylinder ?

dragonZ28

iTrader: (32)

What kind of fuel system do you have?

Have you made any tuning changes to the stock program?

98Z28CobraKiller

iTrader: (17)

No changes to programming but I removed the EGR and Air and also the rear O2 sensors but touched nothing in the computer. I was under the impression that removing these items w/o deleting them in the PCM would only through codes but not hurt driveability. Is this correct? Oh and Stock fuel system.

GuitsBoy

iTrader: (4)

Well, really, what do you expect? You cant run stock tuning and expect your 402 to purr like a kitten. Between the added cubes and the big cam and high flowing heads, youre moving a ton more air than a stock motor, but since youre still running stock programming, youre not adding any additional gas to support the extra air. I would suggest getting some help with the tuning from somebody who's done a few big cube motors before. Tuning a 402 is not something the first timer will likely master straight away.

98Z28CobraKiller

iTrader: (17)

Not really looking to master it, just looking to learn on the job. I am a computer tech by trade and am very handy with both computers and cars. I just haven't gotten into tuning cars before. I learn fast. My question is about the removal of all of the stuff w/o deleting it in the tune. Is that making it worse, or is it just throwing codes that trip the SES light.

GuitsBoy

iTrader: (4)

I dont mean to be an ******* or anything, but the simple fact that you ran an engine without first have a base tune for it is evidence that you would do well with some guidance. Tuning a 402 is really not for the faint of heart, and I certainly wouldnt attempt it as your first try. Its challenge enough trying to get a stock cubed motor dialed in. I fear you may be a few levels over your head, no matter how fast you learn. An improperly tuned motor could easily lay waste to your brand new engine. But in the end, its your money if youre willing to gamble with it.

A solid ses light because of removing emission devices wont harm the engine. But a blinking light means misfire and this could be potentially damaging.

dragonZ28

iTrader: (32)

Here's what you need to do, in this order:

1 - Get a RaceTronix fuel kit. It's inexpensive, and it works great.
2 - Get some new injectors. Try a 40#+
3 - Install them
4 - Have the car towed to a reputable tuner knowledgeable in LS1 cars, or have an experienced friend do the job.

DO NOT under any circumstances fire that engine up again until it is ready to be tuned. I promise it's hurting your engine running on a stock tune and stock fuel system. You're going to need more fuel even at idle. A tune can make your stock injectors work at that RPM, but it can't make them work at WOT higher RPMs. You'll need a set of bigger injectors. Do this right - you have too much money invested in the project.

AVB

iTrader: (9)

W/ stock injectors and no changes to the tune you need to stop tryin to run it.

This is a new motor yes? One that needs to be broken in? You don't want it idling without a load or set up too rich (it's most likely lean) cause it'll never break in that way. If you want this motor to run properly, get it broken in (which means on a tune from someone who knows what they're doing). Some tuners will get you a base tune knowing they will get to doing the optimum tune afterwards.

DrkPhx

iTrader: (15)

It won't idle until properly tuned, so I would not run the engine until you have at least a base tune. I ordered a base mail order tune from Don at DEZ Racing (Slowhawk here) so when I started mine I could run it. The tune was way rich, so I had a friend with EFILive Flashscan rescale the injectors. The popping could be the cam sensor not hooked up right. You also need to run a diagnostic like Autotap to check the vitals. Patience.

98Z28CobraKiller

iTrader: (17)

OK. I wont do anything else until I can get it tuned.

98Z28CobraKiller

iTrader: (17)

I did get Autotap hooked up and got a bunch of codes. Here is the list. Tell me if anything looks wierd considering there is no tune in the car yet and some things like the rear O2's, the AIR and EGR will need to be deleted. I am concerned mostly about the CMP code listed below.

P0405 EGR Low Volt
P0153 HO2S Slow Response Bank2 Sensor1
P0343 CMP Sensor High Voltage
P0500 Vehicle Speed Sensor Circuit
P1133 HO2S Insufficient Switching Bank1 Sensor1

The one that stands out to me the most is the CMP (Cam Position Sensor). Is this going to be resolved once I get the tune in and delete the other codes that need deleting or is there a connection/sensor/whatever problem that I should try to address now?

GuitsBoy

iTrader: (4)

Yes, the CMP sensor is the most serious of the bunch by far. Three possibilities for having a high signal error are:

1. The cam sensor wiring has been pinched and the wires are conducting from one to another (shorted out).

2. The cam bolts have loosened or the cam was incorrectly installed, or possibly the cam was manufactured incorectly, and now the reluctor groove is out of alignment with the cam pos sensor.

3. Youve got a small piece of magnetic metal stufk to the end of the cam pos sensor.

DrkPhx

iTrader: (15)

This is for a LS2 based 402. The cam sensor is located in the front cover and picks up the signal from the LS2 timing chain sprocket. It's more than likely a a result of crossed cam sensor wires.

98Z - I would recommend buying an aftermarket cam sensor conversion harness (Katech sells them) instead of cutting and splicing. Much easier and it's configured to swap the wires. This will eliminate any false or inaccurate readings. The cam sensor circuit is ultra sensitive to voltage and sometimes even the wrong gauge wire can cause fluctuations. I went through this aggravation and was happy to get rid of it. Hope this helps.

98Z28CobraKiller

iTrader: (17)

I am using an extension from SPDC. Hmmmmmmm.

GuitsBoy

iTrader: (4)

DOH!!! I knew that... No, really! I did! I swear! I just... uhh... forgot.... or something.

DrkPhx

iTrader: (15)

Well that eliminates that problem because I believe Katech makes the harnesses for SDPC. Are you also getting DTC PO341 CMP Sensor Performance? Did you fix the oil leak yet?

DrkPhx

iTrader: (15)

LOL.

98Z28CobraKiller

iTrader: (17)

Nope. The codes listed are the only ones that I am getting. Oil leak not fixed but I also haven't driven the car yet. It is still up off the ground.

I suppose that the harness could have been made wrong. What if I switched the outside pins? Could I make it worse? A buddy suggested that I test the harness with an ohm meter but getting that f#$ker out is going to be a real pain in the ***.

hpcubed

It should run fine without the cam sensor. That only assists for quicker startups.

If you are running the maf, the computer knows how much air is coming in. Doesn't matter if its a 402, timing calculations will be off a little. Bottom line is if you open the throttle stop a little, it should idle at 1K pretty decent.

DrkPhx

iTrader: (15)

If the wired are crossed, it will cause a backfire and pop condition similar to mismatched plug wires on a SBC.