1fastls1ss

iTrader: (7)

I have stock LS1 engine with stock 241 heads not ported/milled with PAC 1518 springs, stock rockers, TSP 7.4 push rods, and a TSP 233/239 cam on a 112 lsa. I installed the cam dot to dot (checked it 10x), re-installed the heads with GM MLS gaskets, all torqued to spec, and a LS6 intake and stock 98 injectors. Here is my problem...the engine will fire and run with your foot on the gas, BUT when you let off the gas the engine idles for a few seconds then there is a loud POP/backfire from the exhaust and we shut it down. There are no engine codes, I have spark, and coils are working, ruled out the MAF, and all sensor appear to be working when hooked up to the computer.

I've looked up the issue and can't pin this one down. Anyone ever had this issue? or any suggestions? The car has been at a LSx local shop right now and we are kinda stumped at this point.

allan808

iTrader: (3)

It needs a tune!

1fastls1ss

iTrader: (7)

It has a tune on it already for the mods, yet it will not idle on its own and the backfire is LOUD! The shop that it is at is well known on here, and they kinda feel it may be the cam, but it runs with no backfires/knocking with your foot on the gas.

badazz81z28

iTrader: (6)

You had a tune done with the new cam installed??

Dot to Dot does NOT necessarily mean the cam is installed correctly, that's why there are degree wheels out there. You need to check it correctly. The back fire could be timing or a lean condition.

As for it not idling, probably a lack of air to stay running and that's in the tune.

Shiftslow

iTrader: (9)

Get it tuned mine did the same thing.

1fastls1ss

iTrader: (7)

How loud was the POP on yours? Mine sounds like a shot gun in a metal barrel. The shop said it's not a tuning issue, and are pointing at the cam as the problem. I didn't think the cam is the issue, if it runs above 1,000rpm it will not back fire, but let it idle and backfires. There is a basic tune on it that I am told should allow the car to at least idle properly without the backfire.

87silverbullet

iTrader: (11)

Sounds like you need to find a new shop

redtan

iTrader: (5)

Clearly it doesn't have a correct one, as the car will not idle. It's either a half assed job or the tuner has no clue what they are doing.

A shop that cannot tune that cam and blames IT for how poor the car runs is a very very shitty tuner. Either they don't have the skill or don't feel like putting in the work required to make such a cam run.

Either way, I would take it to an actual capable tuner and watch your car idle and drive almost as well as stock. That cam isn't that big that it cannot be tuned. People have much bigger cams in their cars and theirs idles and drives.

sscamaroburn02

iTrader: (14)

I have same cam and my car idled bad after install. Had lmr work out the tune and runs like a champ! I suggest get a new shop imo

1fastls1ss

iTrader: (7)

I'm hoping that's all it needs is a tune. I have been working on cars for over 12 years and have had this one for over 10. I strongly feel that it is nothing mechanical/electrical or it would throw a code or not even start. I put the cam in the car when it was the stock short block with the stock cam, I put it TDC, the cam gear dot was at 6 o'clock and the crank dot was at 12, pulled the stock gear then cam, put in the new one in, EXACTLY as the stock cam came out, and the cam gear lined up perfectly with the crank. All this with a new LS2 timing chain, so I know if the cam is ground correctly then all is good.

Would an improper tune really make the car backfire so loud at idle? I'm very frustrated at this point as to the time I have put into the motor build and money spent into having someone swap out motors (if I had a lift I'd do it myself).

sscamaroburn02

iTrader: (14)

Get a proper tune and report back.

Streetlegal?

iTrader: (25)

Improper tune will make a difference on the idle. What is your idle set at? You could have it set too low for the cam. I know with mine I had to turn the idle up to 950 instead of 825, but I had a larger cam than you did.

Have you checked your spark plugs to see if they are clean and good? You may have spark but you could've killed them.

Personally I would go to another shop or find someone around that has HP tuners. I know it's a simple question but did they open the small hole in the throttle blade up at all? You're IAC could be bad and the hole could be too small so the engine can't get enough air. Just a thought.

thunderstruck507

iTrader: (18)

check plugs, wires, and coils

1fastls1ss

iTrader: (7)

Checked it out today, turned out to be the coil packs, the shop put on a set of coils from another car and she is running PERFECT! Thanks to all that replied, it is a huge relief. I am going to check the coil wiring, because i think the wire harness was flipped resulting in the firing order to be reversed on one side. If that is the case that may have been an error on my part not theirs.

thunderstruck507

iTrader: (18)

I had a set do the same thing when I was first getting my swap done. Chased my tail for a week before I borrowed an extra set to try and it fired right up

flattusmaximus78

iTrader: (1)

Love threads that end like this. Good job OP, hope you get to enjoy it!

1fastls1ss

iTrader: (7)

Can't wait to get it back. The cam sounds SICK, and the dyno yielded 374hp and 361 torq. If I had the extra money I would have bought some ported heads, but the car is only driven about 1,500 miles a year and I do not race it. After owning it for over 12 years I have come to just enjoy having the car instead of beating the crap out of it. Don't get me wrong their will be the occasional itch in my right foot, but I'm gonna love the choppy cam notes from the exhaust.