Question : Serious Idle Issue

[asylummotorsports]

OK here's the issue.

3500, 3t40

At normal driving the car runs just fine.

However as soon as the throttle is close (take your foot off the peddle or back off quickly) the tach bounces around like crazy, the engine start backfiring and missing, and all hell breaks loose. It is actually quite scary!

And this can happen at the very slightest of negative throttle movement.

If I shove it into neutral and rev it up a bit, actually quite a bit at times, it will settle down and I can bring it slowly down to idle.

NO CODES!

Already completely replaced the ECU with a known good one. New MAP sensor.

Fuel pressure is 48/58.

Car ran 14.18 @ 99 mph last night so that seems just fine. Consistent as hell, won $200.

Drove it home 90 minutes all Hwy, runs fine unless you back off.

I just can't back off in a hurry.

If I slow down and keep throttle pressure (two feet) it will sometimes come down slowly.

IAC has been suggested, so has TPS, but I'm really not about to start swapping out a bunch of parts without some imput.

O2 is disconnected and running a wideband. A/F is dead on. NO EGR.

THANX!

[SappySE107]

Did it ever decel normal?

[asylummotorsports]

Oh hell ya. This is a new problem in the last couple of weeks.

Car has been running for almost three years.

New TCE 65mm TB, IAC and TPS this past spring and all was good.

[SappySE107]

Does the scan show anything? You can check TPS easily with that.

[asylummotorsports]

Rodney had it on his laptop last week (Tuner Pro) and it showed O2 so he snipped that and hooked up the wideband, then it said MAP so I bought one.

Then it threw an EGR code of just a second (32, two flashes) and the car doesn't even have an EGR and the program is deleted in the ECU!! WTF? That lead to the ECU swap to a known good one.

And there was some noticeable corrosion on the yellow connector. Cleaned that up and applied Dilectric grease on the plug before installing the new ECU.

But nothing strange about TPS, in fact it showed perfect or the other suggested IAC motor and still NO CODES.

FRUSTRATING to say the least.

[robertisaar]

don't suppose anyone played with the throttle follower tables?

[pocket-rocket]

Why not try tossing a NB in since it's been known that WB don't play 100% well with our ECMs (even with the simulated NB output)?

[Superdave]

you can't delete the EGR from the tune, you can only set it's enable temp higher than the coolant will ever get.


have him post up a datalog

[IsaacHayes]

CPS? ICM? Coils? Have the last 2 tested...

And I hope they are not some cheap Autozone $11 PoS that will fail in less than a year. Borg Warner unit at least.

[SappySE107]

yes, we need a datalog so we can see what is going on. Your TPS can be shot and still read 0 and 99, just not in between all the time. I am sure we can tell by the O2 simulation from the WB if that is working as well, and the same with the IAC.

[robertisaar]

you can't delete the EGR from the tune, you can only set it's enable temp higher than the coolant will ever get.


have him post up a datalog

if you want to get real fancy, you can change a few lines of the algorithm and completely remove it....

but setting the enable temp to the max is MUCH easier...

[Superdave]

yah, i doubt anyone would go that far.. lol

[asylummotorsports]

Thanx for all the suggestions!

It's just frustrating as hell when the car isn't right, although it ran 14.18 "on the brakes" and won $200 for the day.

How many of you can say that on a bad day?? LOL! Experience pays off.

Rodney will get it figured out. It's just that like most everyone else, he has to work for a living, and has other things in his life that are WAY more important than my damn car.

Like his 3500 turbo/intercooled Beretta.

As it is, he does more than I deserve.

I was just throwing it out for opinions.

Rodney makes this car what it is, and there isn't a better/quicker automatic Beretta anywhere.

As I suggested, just frustrated and looking for opinions.

There are three people I trust with this car.

Rodney for the tune.

Bill Clark for the trans and front end, and ME to make the right decisions.

I just get frustrated and that is sometimes not fair to the people who actually know what they are doing, and I don't!

Did I mention I WON the Bracket Class on Sunday and $200 in a hurt car?

[ForcedFirebird]

Don't need decel to race though, do ya?

[SappySE107]

You don't need rodney to post a datalog do you?