warrenss

when i had my 346 tuned with my heads @cam it ran perfect and made 430 rwhp.so i built my 383 and went with bigger cam and the car would still crank and idle perfect with the same tune.but i had it tuned far the 383 trying to get all the power i could out of it .it made good power it made 490 rwhp but when i got back home and started it up the hot starts suck!it will idle at 500 rpm far aminute then it will idle up at normal rpm .so i took the car back to the tuner and he said the pcm is giving the car 20 to 30% more fuel at idle so he said replace the o2 sensors and i did with no luck checked far vacume leaks and exhaust leaks but the car still try to add more fuel at idle he said that there was something else is wrong not the tune. but it never did it untill he tuned far the new moter .the only thing i know he did was take out some timing far the raised compression but he said that has nothing to do with the problem does any body have any idea what problem might be . by the the way cold starts r fine but the hot starts r driving me crazy please help

pekkaz

If the problem is during initial open loop then crank and main VE tables may be too high around idle area.. typical for large cams. Added fuel during closed loop could be a sensor problem but it does not match well with good cold - bad hot start.

94SS

Are you still running a MAF?

98A4LS1

iTrader: (1)

Base RAF values may need adjustments.

dynocar

Make sure that your fuel system holds some fuel pressure for at least 20 minutes after turning your engine off when at operating temp? Some defective fuel pumps or regulators leak down fuel pressure too soon thus the fuel will boil in the hot fuel rails. This will cause a hard start and/or will idle too lean for several minutes until all of the fuel vapor caused from boiling in the rail and lines are purged out.

SMOKINV8

iTrader: (6)

You can't be serious...

warrenss

i still have maf.the cam is not to big it is 237-242 on113 lsa 603-609 lift

warrenss

thanks far any help

hellbents10

iTrader: (10)

Cranking VE and start up fuel multiplier vs. coolant temp.

warrenss

is any one around mississippi that could try to fix my car far me? i have no tuning tools .and if i did i would not know how to use them lol

white2001s10

iTrader: (4)

I would think it was start-up enrichment, after-start enrichment, and the after-start decay tables that would need adjustment.

RedHardSupra

iTrader: (1)

RAF seems to be the usual suspect here, since it's temp dependent. can you verify if it happens in open or closed loop?

white2001s10

iTrader: (4)

or slightly enlarge the hole in the TB blade for the larger cube/cam motor.

94SS

Deleting the MAF cured it for me.

RedHardSupra

iTrader: (1)

you know, MAF isn't the source of all evil, it's just a measuring device afterall. does you having a thermometer screw up the weather?
granted, it's a device that's in a way of airflow, but considering all the other bottlenecks it isn't so bad. now reversion is a proper thing to complain about.

Bink

^^^^ well said.

My vote is Cranking VE. I had a similar problem. My idle VE% was/is about 25% and stock VE%, at the same RPM/kPa values, was/is around 65% - big difference.
I rescaled the Cranking VE to reflect the new VE table. Helped a lot with the hot starts.

dynocar

Yes, I was very serious, again, fuel at no pressure in a very hot fuel rail can easily boil and engines do not start and idle well when injectors inject only fuel vapor, that too can be serious, especially when mis-diagnosed.

warrenss

is their a downfall to not having a maf? will it make it drink more gas?more info please

warrenss

we turned the o2s off and still had the same problem .so we turned them back on

silverTA2002

iTrader: (1)

The only downfalls I've read about are things like....

The need to retune when weather/conditions are different.

A loss of a low octane spark table (safety measure).

That's about it.

Tuned right, they both seem to make the same power, but tuning for a MAF is more difficult than just deleting it. (so I've found)