Drilling throttle blades?

[Nikkormat]

Now that the weathers hotter I've been having more problems with the cherokee dying at idle. Put it in gear, it bogs, and the IAC can't recover.

What's the solution to this? It wouldn't stay idling up on guanella yesterday but after removing a cap from a 3/16" vacuum port it would.

Does it just need more air? Does one accomplish this by drilling small holes in the throttle blades?

Before you ask, yes the IAC is set up properly. And it's 350 throttle body on a 401.

What do you experts say?

[Tatsadasayago]

Sounds to me like your O2 sensor is reading/sending bad info to the ECU.
Where did you place the sensor and is it an EGO or HEGO, Narrow or wideband?

I would never recommend drilling holes in the throttle plates...A forever fix for a temporary problem that will come back to bite you.

[Stuka]

It means your AFR is wrong. Do NOT fix this by drilling a whole in the throttle plate.

Like Tats said, you need to figure out what is going on. Either you are getting some wrong readings, or the readings are right, but the ECU is putting too much fuel in.

[Tatsadasayago]

Another possible issue is the camshaft profile. If it has more lift and duration than the GM 350 the ECU was programmed for you could have a situation where it is seeing erroneous feedback from the sensors.
Out of normal duration and overlap tends to confuse an ECU...
We assume your EFI is going into closed loop after the engine is at operating temp. If not, this would explain things.
I would wager USN Bill might have something to say about this.

[Nikkormat]

It only does it in open loop. The IAC is howling away so I suspect it just can't open any further. Closed loop it idles fine. If I open the throttle blades any further it won't hold a low idle. Any higher than I've got it and it will idle up to 1200. I don't think there is any more adjustment room in my TPS without really starting to modify it.

The throttle plates/blades are replaceable.

[FSJ Guy]

Your base idle speed is NOT set correctly if it's dying in idle. Base idle (with IAC closed and unplugged) should be about 50 rpm or so LOWER than your desired idle speed. You may need to wallow out the holes in your TPS to get your closed throttle TPS voltage to 0.54 volts.

Open up your closed throttle position via the torx screw on the right hand side of the throttle body and re-adjust your TPS. Then check your base idle speed with the IAC driven closed and disconnected. Repeat this until you get the desired base idle speed. Reconnect everything and see how it runs.

As mentioned by others, DO NOT DRILL HOLES in your throttle blades!!!!!

[Nikkormat]

First, there is an issue with my bin file. It thinks the throttle is closed at .37 volts. This issue was previously unresolvable. Bill pretty much told me to start over with a stock 350 bin and tune from there. That wasn't an option. the idle is set to a little over 600 rpm with the IAC driven closed. I can not set it any higher without idling up the motor to 1200 rpm with the IAC connected or without limiting the amount of throttle opening with the TPS moved further back. I spent hours agonizing over this and no one seemed to know what the problem was.

I tired importing my fuel and timing tables into a bin that didn't have the TPS voltage issue but never finished the process and I had to return the tuner to Blake.

The TPS issue first occurred the second time Blake and I were tuning it. We thought we couldn't get the IAC relearn to stick (as the TPS voltage was correct but it was idling up to 1200) but later discovered that the computer thought the throttle was 7% open at .54 volts. At .37 volts it is zero percent open.

I've tried four different ECU's, checked every wire of the harness, and no, the AC trigger is not activated.

So what I need is a way to temporarily add more bypass air flow. I don't have the time or money to invest in a tuner setup right now. And yes, throttle blades are replaceable.

If I can't just fix it as it is now I'll take the dang thing off and put the carburetor back on. I spent all this money on fuel injection to stop my vapor lock issue and it still vapor locks.

[Nikkormat]

I think my base idle must be lower than I remember, IAC counts wouldn't be 80-110 to bring it up 150 rpm.

[AwesomeJ10]

I Know everyone is saying to NOT drill the throttle plates, but I think you should.

You are having similar issues that my 401 TBI had - it wasn't getting enough air (I think) that I could not get the IAC dialed in. So I think you should take the TBI off, drill it out, re-install and repeat the ISP's.

Are we still having that meet n greet next weekend? I have another TBI unit that you could try as well (or at least swap it out if you end up drilling the hole too much).

[AwesomeJ10]

Another option you/we could try is going with 7427. I have not messed with the 7427 that I have cause my Honcho is now a trailer queen and as a result, I've lost interest in it.

[FSJ Guy]

You'd have to rework your harness for the 7427 ECM. Different plugs.

Nikkormat, you're using the 12277747 ECM, correct? PM me your bin file AND your XDF file and I can take a look.

In the meantime, you can run a "compare" check on your current bin vs. a stock 350 bin. That will tell you all the things you've changed. Maybe there's something that got adjusted and you forgot about it. I run a log sheet of all my changes and results so if I screw something up, I have a fighting chance of knowing what I did wrong.

Once you change the base idle setting by adjusting your throttle blades, the TPS MUST be re-adjusted to show the ECM that it is in the closed throttle position. Without seeing anything else, and from what you've said about it going up to 1200 rpm, that seems to be the root issue and switching ECMs will not change things. Let's get that sorted out and go from there.

[Nikkormat]

Ethan I would really appreciate that. I know I've got my bin but I don't know if I've got Blake's XDF file. My XDF is missing some parameters that his has.

Right now the throttle blades are open as far as I can open them without losing 4 volts at wot. I could adjust the TPS and the idle screw to allow more airflow but I would loose 4 volts at wot.

I'm all for fixing it right but I need something in the meantime as the Jeep is my only reliable vehicle and I'm really tired of looking like an idiot as my IAC howels away and my Jeep stalls.

[AwesomeJ10]

I thought you had grabbed my XDF? I will see if I can find it and post it on here. I think I may also have your bin

[Nikkormat]

I think I did. I'm going to have to charge the tuning laptop and see.

[AwesomeJ10]

XDF http://blakeoffroad.com/vps/YaBB.pl?act ... V5_9_3.xdf

only bin I have for Gabe 3/13/16 http://blakeoffroad.com/vps/YaBB.pl?act ... bes401.bin

[Nikkormat]

Gabe's Bins.zip

OK, 401 incorrect idle is the last bin Blake and I burned and has the issue.
HonchoRich is known correct idle voltage.

I can't remember where I got my XDF from, Moates forums or something.

[AwesomeJ10]

well I'm not messing with any tuning, so if you want the moates back, I will give it to you in exchange for those front springs

[FSJ Guy]

Alright. I'll take a look at it over the weekend.

[babywag]

From your description is just sounds like your fuel table is way off...Creating a vacuum leak to change AF ratio enough to quit stalling.
The IAC should have more than enough capacity to adjust for idle.
If tuning isn't an option try dropping fuel pressure 1psi and see if it improves. You should easily be able to make your FP regulator adjustable if you haven't already.

Far as the TPS, just adjust it for ~.54v don't worry about losing voltage on WOT end.
The ECM stores the lowest TPS voltage setting, every time it compares with last measurement, so if you're see .37 it isn't a .bin problem.
It's a sloppy throttle shaft, or an adjustment issue.

Without a log really hard to see what's going on.
You want ~10-40 IAC counts @ warm idle.

Once the fuel table is tuned you also should be able to run/drive/idle/etc. in open loop with no issues, even unplugged O2 sensor.
It's a good test of your tune to unplug the o2 sensor, and see how it runs.

[Bill usn-1]

If your not going to set it up correctly then you should go back to a carb.

Listen to Babywag. He has good basic TBI knowledge and won't steer you wrong.
DO NOT make modifications to overcome an improper installation.

Vapor lock is a specific condition caused by the boiling of fuel building pressure that over rides the pumps output pressure.

A stalling warm engine is not vapor lock if it restarts.