Built LS1 won't idle.
 

Looking for suggestions as to what may be wrong with my car. Mods are as follows:
Fast 102 Intake, 102 TB.
SLP Lid
42 LB injectors
PRC 227 Heads
MS3 Cam
TSP Longtubes
TSP True duals

Freshly rebuilt engine, won't idle right. Runs fine when on the throttle, constantly dies at idle. Have had multiple tunes, have checked for vacuum leaks 3 times. The only code it is throwing is P0102, have tried two different MAFs, neither one changed anything. Has anyone had a similar issue?

There's a forum for tune/diagnostics...

Probably needs more finetuning of the idle parameters. Those are big changes you made with the 102 intake manifold/TB and the big ass cam and heads you put on there.

Driving is easy to get down compared to idle as you usually run alot more rpm there.

Are you sure that the idle control valve is working, or that it is seeing manifold vacuum?

Yes, everything is working, have had 5 re tunes, going on 6 today. All fuses are good, all sensors are good, plugs, wires are good, all new vacuum hoses, have checked every possible leak 3x, the only thing that isn't right is the code, and the fuel trims are showing 0.

Thank you for your concern, however I did post there and got 0 responses.

if you give it throttle can you get it to run at 800-900rpm? what's the lowest RPM can you get it to run at?

There are at least a dozen things that could cause this.

Have you upgraded fuel system other than injectors?
Does it idle after warmed up?
MAF code, have you tried unplugging the MAF to run SD?
Are you 100% sure all connectors are plugged into the right sensor?

Fuel system was cleaned and it has fast raids
The car hasn't ran long enough to get warmed up.
The MAF is going to get unplugged today if this tune doesn't work.
500% sure, everything has been checked 5000000 times.

The lowest the car will idle is about 1000-1100. The car wouldn't idle at all until the 5th tune. The 5th tune allowed it do idle if the throttle was held at 1000-1100, then the plugs got fouled 30 seconds in and it started backfiring and running like shit.

It's also an automatic with a 3700 stall.

Well, tune #6 was a bust, however tune #7 the car finally idles, tries to die after you rev it, but it finally idles on its own. Apparently it was just the tune. One more tune and it should finally be done after 2 months...Thanks to those who actually had some useful input.

Verify the MAP and Oil Pressure connectors aren't backwards. Same exact connectors in the same section of harness.

If that doesn't do the trick unplug the MAF. Code will still be there but if it idles then your problem is likely a pinched MAF wire in the harness or grounding problem.

Has anybody tried cleaning the MAF sensor? You said 2 sensors have the same problem but if both have been cleaned with water they are both trash.


Tune/Diagnostics won't come into play until the car can idle on its own.

It idles now with the most recent tune, we'll see if the next tune fixes the stumble. One MAF was the original that worked prior to rebuild and was not cleaned. The other was off an LS1 camaro, and it was cleaned (with MAF cleaner of course).

Post the tune. I'll take a look.

Idle is actually pretty easy with a big cam once you know how to do it. It took me forever to get it right initially when I was learning to tune. But then I swapped my injectors and started with a brand new base tune, and had the car idling in under 5 mins. It's all based on what the car wants. Once you get the injector data right, it's air and spark. You set air first via the VE table. Lean it out and listen for the lean/stumble. No wideband needed.

Then play with timing until you get the kPa to drop.

That's a good solid base tune for the idle at that point.

Just watch your IAC counts. Try to get them around 50-80 hot. If not, open up the set screw on the TB.

Then let it cool off and run the base airflow config (Russ K has a good one) and get your RAF set.

Once RAF is good, the VE is dialed in (400-800-1200 cells), and timing is pretty good (that cam will probably like 28 degrees or more - mine actually loves 32); then it should hold a pretty solid idle. Just make sure you're in SD mode to play with the VE table. Let me know if that's not something you know how to get to.

Built LS1 won't idle.
 

There's your clue, too much fuel... this can be due to too much air in VE table, or too much fuel in OLFA table, or injectors undermodeled (so they spray too much)... I take it engine has not achieved closed loop.

Since you see P0102 you are running from VE table.

Also need to do RAF tuning as said... and probably look at TC/TF.

Cracker and Follower would be something I'd leave until after VE is set.

In the OLFA I'd set it to 1 across the board. PE I'd set to 1 in the cells below 1200. Don't have any additional fueling. Get it set to Stoich at idle. Actually, that cam will want to be leaner than stoich. .95-.97 lambda or so (15.1-15.5:1 AFR) which can be achieved with the VE table.

If it took 6 trips to a tuner to get it to idle I'd find another tuner. He should have at least had it running before you left the first time.

It's getting tuned via email. The closest actual tuner to me is about 4-5 hours east. The only issue the car has now is when you rev it it tries to die when it comes back to idle. Also the 02s are barely moving and there still are no fuel trims. Currently running 02s off a 2003 Z06. Going to swap them out with stock and see what happens.

I have tuners close by but one of the best investments I made 10 years ago when my car was stock was getting HP Tuners, a LC-1 wideband controller and spending a little time to learn the basics of tuning. Nothing replaces logging real time AFR and being able to tweak things like idle especially after a cam.