5.7 EFI stalls when warm and shifting into gear

[khe]

Does the Rinda allow you to see real time injector PWM? As the RPMs drop, ECM should be calling for more fuel as well as more air.

There is an injector pulse width in the engine data parameters. I'll check it out this afternoon.

 

[khe]

Just read through the broad strokes on this thread and you've done a lot of proper troubleshooting and there's some really good info provided here (thanks, muc)

I get you're ready to hang it up but being a new/reman long block its wise to ensure the valves are adjusted properly and at this point a compression test on a warm engine is in order.

Can't recall seeing any WOT performance numbers posted here but I wouldn't rule out engine mechanical yet. I've had more than one reman block delivered that has not been properly set up for install.

If all checks out mechanically I'd try base timing at 10 btdc and verify the advance isn't higher than 32 total

The wonky iac behavior is concerning but the numbers you've posted show it is indeed operating, keep in mind the ecm tells it to behave accordingly based on inputs received from other sensors. A mechanically unsound engine will create sensor readings that while not necessarily out of spec but just enough to cause issues with no active faults.

The base timing specification for my engine is 8° BTDC. The engine performs fine at cruising speed and any RPM above idle. I need to study the theory of operation section in the manual in order to determine what to look for next.

Scrolling through the engine data, the water temp sensor appears to be functioning correctly as the "coolant temp" is around 160°.

 

[khe]

Does the Rinda allow you to see real time injector PWM? As the RPMs drop, ECM should be calling for more fuel as well as more air.

When the RPMs begin to drop, the ECM is giving the engine additional fuel as the injector pulse width increases.

 

[khe]

I am out of ideas on if and where the engine might be drawing in unmetered air. It is not at the intake to heads, throttle body to intake manifold or the MAP sensor. The IAC counts are still zero at idle once the engine warms up. I plan to check the bushings on the throttle plate shaft but can't get past the idea the old engine did not have the issue before the head gasket went bad.

I am wondering is a smoke test into the throttle body would reveal anything? Adapt a smoke machine to the throttle body with the flame arrester removed and the shifter in the WOT position and look for any smoke leakage.

I checked the TPS voltage and it was 0.49VDC and the throttle percentage was 0.3% at idle (engine off). The ECT sensor reads very close to the ambient temperature of the engine with the engine cold.

Is there a vacuum port on the throttle body that I could hook up a vacuum gage? Would that provide any clues?

 

[alldodge]

Don't think smoke will work

Zero counts on IAC leans me to a vacuum leak. Don't know of a port to check on the motor

If MAP is off, this will mess up the IAC and fuel metering

 

[Scott06]

Would also think if IAC is closed it’s getting air elsewhere. Have you tried spraying carb cleaner or starting fluid around the gaskets on intake and throttle body ?

 

[nola mike]

Have you verified that the throttle plate is closing completely?

 

[khe]

Don't think smoke will work

Zero counts on IAC leans me to a vacuum leak. Don't know of a port to check on the motor

If MAP is off, this will mess up the IAC and fuel metering

I have sprayed carb. cleaner all around the intake to head joints, front and rear of the manifold, throttle body to intake and it does not affect the idle. Where else would a vacuum leak occur? I realy thought I found it when I discovered the bad bushing adapter on the MAP sensor but that was not it.

I wondered about a vacuum port as there are two plugs on the front side of the TBI unit.

 

[alldodge]

It can leak from under the intake
I don't remember but did you try the plastic bag over the one hose and plugging the other as Muc mentioned in post 29?

If the 2 ports your referencing are items 1 and 2 they are fuel

Unless you have item 6 covering the vac port then there is none
https://www.mercruiserparts.com/bam/subassembly/31880/2338/130

 

[khe]

It can leak from under the intake
I don't remember but did you try the plastic bag over the one hose and plugging the other as Muc mentioned in post 29?

If the 2 ports your referencing are items 1 and 2 they are fuel

Unless you have item 6 covering the vac port then there is none
https://www.mercruiserparts.com/bam/subassembly/31880/2338/130

What would cause a leak under the intake? The gaskets shifting during installation? How would I determine if there is a leak under the intake? I would hate to go through the trouble of tearing it down just to find nothing wrong.

I did do the plastic bag trick Muc mentioned and it passed - see my #30 post.

I was referring to the two ports but need to check to see if I have the nipple with the #6 cover.

 

[Scott06]

What would cause a leak under the intake? The gaskets shifting during installation? How would I determine if there is a leak under the intake? I would hate to go through the trouble of tearing it down just to find nothing wrong.

I did do the plastic bag trick Muc mentioned and it passed - see my #30 post.

I was referring to the two ports but need to check to see if I have the nipple with the #6 cover.

if it leaks below intake I think you would get oil sucked into intake ports maybe see it on spark plugs.

 

[Oldmercman]

Have you sprayed carb cleaner after it's up to operating temps? Maybe you are sealed with a cold engine and it opens up/leaks when hot?