Chiropaul

iTrader: (2)

So my car runs great with the LSx swap. It is 99% there but the only thing that keeps bugging the hell out of me is the engine will die if I go from 30+ mph and come to a stop quickly. Like exiting freeway and coming to a complete stop. If I stab the gas real quick I can save it from dying.

Originally I didn't have a vss hooked up so I assumed it had something to do with that. But now I have a vss hooked up and it works fine. Would the brake switch signal wire cause this issue?? Or the vacuum assisted brakes??

This is literally the only thing wrong with this car and its kind of embarrassing to have it die with five cars behind you at a stop sign. Any suggestions??

erickcastillo95

iTrader: (1)

check the iac sensor it controls the idle speed and it can cause a car to die like that

i r teh noobz

iTrader: (4)

Hook up the brake switch and see if it persists. I've been told that its pretty important to the PCM.

Sticking IAC could cause this as well.

Auto or manual?

bczee

iTrader: (12)

Do you have the VSS connected ?

Chiropaul

iTrader: (2)

Vss is connected. Put in a brand new iac a few weeks ago because it was idling like Crap. Turns out my coolant temp sensor was reading -38.5* so motor was d dumping way to much fuel.

With the iac disconnected it doesn't die it just idles a little high.

bczee

iTrader: (12)

Sound like your narrowing it down..

406chvycamaro

iTrader: (7)

Let me know what you find to be the problem. Mine Is doing the same thing. Thanks

99MUSTANG5.3L

I would say if it's an auto car not having the brake switch signal hooked up is the problem. Remember when hooking this up that the ECU sends a ground signal.

Chiropaul

iTrader: (2)

Will do. I'm going to mess with it tomorrow.

Yes it is an auto car. Going to look and see if I have a poor or incorrect connection at the brake switch

homemade87

If none of the above pans out, I had a truck that did the same thing. Turned out to be the fuel tank. I had no baffle in the tank and the fuel was running away from the pickup under quick stops and it would stall. I had to run above a 1/4 tank to get it not to do it. If you fill your tank full and it goes away thats your problem. It's just a thought.

lynx853

iTrader: (8)

what are you running for a MAF? ported? stock? aftermarket? or dirty?

Unplug the maf, and retest.

If the issue goes away - there's your problem

406chvycamaro

iTrader: (7)

I don't understand. If it runs better with the maf unplugged then that's your problem?

Chiropaul

iTrader: (2)

I have a truck MAF with the screen removed. We cleaned the same time I change the IAC (2 weeks ago). But I will check that out and see if that is the issue.

Good question, I am running a fuel cell that has foam in the tank and it is sumped. I try to keep it at least over 1/4 to 1/2 tank. I do have the fuel and return line both going into the sumped part of the tank and have been planning to run the return into the top of the tank just to prevent any turbulence in the sump. Looks like I need to go ahead and take care of that this weekend too.


THANKS for all the replies. I'm going to attack all the suggestions from you guys this weekend and try and figure this thing out once and for all.

i r teh noobz

iTrader: (4)

Sometimes the MAF can send bad data without failing an OBD test. Unplugging it forces the PCM to default to the MAP sensor data.

Old Geezer

iTrader: (3)

You don't list any mods to the engine. Should it be modified, such as a cam, injs, etc, it may be that the throttle follower, or the MAF tables need to be adjusted.
Maf isn't in backwards, is it?
How close to the MAF is the air cleaner?
Air cleaner directly in the fan wash?

Chiropaul

iTrader: (2)

Mods should be in my sig. But motor is an LS1 with LS6 intake MS4 cam, ported TB, 36lb injector, mid length hedman headers, texas speed tune.

The maf is in correctly with the airflow arrow pointing toward the intake. I do have a relatively short intake due to space issues in the engine bay.

pdsq98gt

Is the tune a custom tune where you brought the vehicle to them and they actually tuned it in person? Or is it just a canned tune? Sounds like you need a better tune.

Chiropaul

iTrader: (2)

I agree on better tune. Need to get the car dosh to Fresno (1hr away) for a real tune. This was based on all the mods I had on the car figured it was their cam and injectors in the motor so it would at least get me Rollin.

406chvycamaro

iTrader: (7)

Any luck finding the problem this weekend?

Chiropaul

iTrader: (2)

So I am pretty sure the issue is with the fuel tank when it is low. I filled up the tank and drove it and slowed down very quickly and it didn't die on me. I am still not sure if the brake switch is working or not. My buddy and I are going to test that out tonight.

One other potential issue is my IAT's have been way high. It has been anywhere from 40-56*F here during the day (today 56*) and after about 8 minutes of driving my IAT's were 96*F. Part of the issue is my air cleaner/intake is very short and it is getting very warm as the engine compartment heats up.

Do you think this could have any bearing on my issue?? I'm going to figure out a way to route a cold air intake no matter what. How far from the TB should the MAF be?? THANKS

The attached picture shows current location of the intake. My battery is on front drivers side and I have a coolant overflow tank in the recess on the front passenger side so I need to decide which to relocate to clear a path for a CAI