Warm startup idle 'hunting'

[TwIzTeD_3kGt]

Ever since I installed my PTE 550cc injectors, on warm start-ups the engine will hunt for idle for a few seconds then smooth out. Has never done this from a cold start. There are no other idle or drivability problems.

Is there a setting I should have changed related to this?

[Greg E]

How old is your throttle body?

[TwIzTeD_3kGt]

Original throttle body.

Actually it only does it on the first start after it's sat a while, an hour or so. Makes me think it might be a leaky injector.

[Greg E]

You can try tweaking the ISC tables that fall under the operation conditions you're experiencing this issue.

[kywhitelightning]

Three questions with that:
Did you disconnect the battery when you swapped injectors?

How long have the injectors been in there?

What are the low fuel trims?

I have always found that hunting idle problems go away with time at idle. If I don't allow it to warm up at idle right after hooking up the battery, it will hunt for a while. The last time it was hunting, after the battery was pulled, I started the car and drove with 0 learn time and it would hunt for about a week and a half. It eventually stopped hunting and settled down but it is quite embarassing driving it around like that.

Jeff

[TwIzTeD_3kGt]

Three questions with that:
Did you disconnect the battery when you swapped injectors?

How long have the injectors been in there?

What are the low fuel trims?

I have always found that hunting idle problems go away with time at idle. If I don't allow it to warm up at idle right after hooking up the battery, it will hunt for a while. The last time it was hunting, after the battery was pulled, I started the car and drove with 0 learn time and it would hunt for about a week and a half. It eventually stopped hunting and settled down but it is quite embarassing driving it around like that.

Jeff

Injectors have been in there for quite some time, 3-4 months now. I don't remember it doing this when I first installed them, and I can't say my idle has ever hunted before, even after a battery disconnect. It only does it for a few seconds IF the engine has been run and then left to sit for a while. If I were to shut it off and start it back up within 15 minutes, no idle hunting. Let it sit longer and it'll probably do it.

Seems to be getting worse over time, as it will sometimes stall out now. Giving it gas prevents any of this from happening. I'll have to break out the laptop and see what the IAC is doing...

[kywhitelightning]

I'll have to break out the laptop and see what the IAC is doing...

Agreed. Also watch what the timing and o2's are doing.

Jeff

[Greg E]

I just had a customer go back and forth with me about his car running perfectly for weeks but then suddenly develop an issue while driving down the road. He instated the issue was with chrome while I insisted his car developed an intake leak.

Guess who was right?

If your car was perfect before and gradually developed an issue, that's a sign that you have a mechanical issue that has come up. Bet you a taco it's an intake leak. ;)

[TwIzTeD_3kGt]

I just had a customer go back and forth with me about his car running perfectly for weeks but then suddenly develop an issue while driving down the road. He instated the issue was with chrome while I insisted his car developed an intake leak.

Guess who was right?

If your car was perfect before and gradually developed an issue, that's a sign that you have a mechanical issue that has come up. Bet you a taco it's an intake leak. ;)

Pressure test is on the to-do list for this coming week, last one was done about a month ago. Although, fuel trims are right where I left them when I first re-tuned it almost 2 months ago (Low -7/7, Mid -3/4, Hi 0), so there shouldn't be any significant leaks.

Could just be my injectors are crappy PTE's that sat on a shelf for 3 years before going in. Just the other day I read a post by one member saying how having his injectors cleaned fixed his idle hunting issue. I also suspect injectors because the problem isn't immediately repeatable. Won't hunt at all if I shut it off and start it back up, meaning the problem somehow cleared itself out (leaky injector while fuel pressure bleeds down). Would also explain why it doesn't do it on a cold engine since a cold engine requires more fuel anyway.

In the meantime, I bumped the ISC cranking steps above 100*F up 5%, still stalled out from a 125*F coolant temp start.

Also, I found I can't really log anything relating to this problem since it's gone by the time I can connect.

[Greg E]

You can log the ECU without the engine running. Just turn the ignition on, connect evoscan then turn the key.

[TwIzTeD_3kGt]

You can log the ECU without the engine running. Just turn the ignition on, connect evoscan then turn the key.

I thought I tried that, and it disconnected during cranking. I'll try again.

[Greg E]

Ah maybe your battery loses too much voltage and it disconnects.

[TwIzTeD_3kGt]

Tried again and got some data to look at. Looks like the IAC is doing what it should. Starts off at 80 step during cranking, then incrementally drops to it's learned idle value.

As far as the 'warm startup after sitting idle hunting', after the first upward rev of startup, the AFR dives way rich almost stalling the engine, then the IAC opens to compensate, AFR goes back up, IAC drops back down to where it's wanted, AFR dives RICH again, etc. until it evens out. In my mind, it's showing rich because there's fuel sitting in the cylinders. I'll pull the rail and see if any of them leak under pressure while closed. Any thoughts?

[Greg E]

Back off the warm up fuel enrichment and post start enrichment a bit.