2G Randomly dying on deceleration

[MikeyTsi]

Car - 1995 Talon TSi AWD (has my '97 drivetrain in it)
mostly stock, unstock stuff is hard pipes, Hallman MBC, mechanical boost gauge, high output alternator (we ran an additional power wire so we wouldn't have to mess with the stock wiring)

I've got an issue that's starting to get progressively worse where it appears the car is randomly dying when not on throttle (engine braking or sitting at idle). Had it happen a few times when on the freeway, at that point pressing on the throttle got it going again. Had a few issues where it would die at a stoplight, first time it took a few tries to get it going again (it would immediately start then immediately die). A few days ago it died while driving and took a good 5 seconds for it to start up again under "bump starting" (it was already moving). Tonight it took a good minute or so to get it to start (using the key since I was stopped). It also died a second time on the freeway, but kicked back on immediately when I pressed the throttle.
No engine codes. I've recently installed Torque Pro, but it looks like the links for the 2G apks aren't valid (the one I found doesn't appear to have any 4G63 options), and it looks like my ancient BT OBDII module is too old anyway

When I was messing with it last weekend it would pretty reliably die at idle but would immediately start up again. Wiggling cables and connectors didn't seem to change behavior

Other issues I'm seeing (which may or may not be related):
- If I drive somewhere and get out for like 10-15 minutes the car has trouble maintaining idle on its own unless I put the throttle in it a bit; it'll start up then rpm drops immediately and it struggles or dies. Once it's going though it's fine (I'm assuming I need to re-do base idle adjustment)
- If I drive somewhere and am out of the car for like 2-3 hours, Upon restart I've been pretty regularly getting something that seems like light vapor lock. Not sure what that issue is.

Any thoughts on what might be causing this?

 

[chrysler kid]

The easiest to start with is to make sure your ground connections are good, the main one is from a bolt on the top of the bell housing by the starter that runs to the negative terminal, and the wire from the negative terminal to the chassis. The factory ground cable from the negative post to the firewall is very weak and the eyelet on the firewall can have a bad connection.

The other thing I can think of would be the fuel pressure regulator vacuum hose may have slipped off, double check the vacuum hose nipple that goes to the fuel pressure regulator.

Do you have any check engine light codes? The other items to check would be related to vacuum leaks around the intake manifold or the biss screw adjustment

 

[steve]

Does this car also have the ACT flywheel? (Need a new profile for this car)
What ISC/IAC and have you checked the coil resistances on it?

 

[MikeyTsi]

Does this car also have the ACT flywheel? (Need a new profile for this car)
What ISC/IAC and have you checked the coil resistances on it?

Yeah, it's got an ACT and a 2600.
The IAC is stock.

The easiest to start with is to make sure your ground connections are good, the main one is from a bolt on the top of the bell housing by the starter that runs to the negative terminal, and the wire from the negative terminal to the chassis. The factory ground cable from the negative post to the firewall is very weak and the eyelet on the firewall can have a bad connection.

The other thing I can think of would be the fuel pressure regulator vacuum hose may have slipped off, double check the vacuum hose nipple that goes to the fuel pressure regulator.

Do you have any check engine light codes? The other items to check would be related to vacuum leaks around the intake manifold or the biss screw adjustment

Both the starter and chassis grounds are new (well, made and installed a year ago when I was finishing swapping the engine in to the roller)

 

[MikeyTsi]

Noticed it's dropping tach signal when it dies as well. Assuming it gets home in the morning I don't have to drive it for a week so I can hopefully spend some time on further diagnostics on the weekend.

 

[MikeyTsi]

Well, it's almost certainly "not" the PTU (because the connector locking tab is broken, and that's almost certainly the problem)

 

[MikeyTsi]

Okay, dug in to this rather a bit more.
I've tried 4 different PTUs now, none of them has resolved the issue. I've been zip tieing them to the connector to eliminate any potential issues with the connector.
I've noticed that this is really only happening when the engine gets to operating temperature, I'm suspecting that when it's trying to move to closed loop is when this issue is occurring. I'm assuming it's something that's dumping fuel/spark and the reason it's dropping tach is because something is killing signal to the PTU so it's not firing or functioning. Does anyone have any thoughts on what could cause the system to kill spark and fuel when switching to closed loop that wouldn't throw a code?

 

[pauleyman]

Torque pro should work.
Main clue seems to be tach dropping out. You could have issues in the harness at ptu. Datalog would help if you can get torque pro to work

 

[MikeyTsi]

Yeah, I've got torque pro installed, but I'm having a hard time finding the 4g63 extensions for it (I see them referenced online and in the app, but it throws an error when trying to get to them), and it looks like my bluetooth elm adapter is so old torque pro won't talk to it so I need to order a newer one.

 

[pauleyman]

Yeah, I've got torque pro installed, but I'm having a hard time finding the 4g63 extensions for it (I see them referenced online and in the app, but it throws an error when trying to get to them), and it looks like my bluetooth elm adapter is so old torque pro won't talk to it so I need to order a newer one.

Its been awhile but I dont remember specific 4g63 setup. I also had problems with cheap elm adapters. Gotta do a little research.

 

[MikeyTsi]

In theory there's an "EX" plug-in that should have some specific monitors and there looks to be a MUT plug-in (which i could really use to try to figure out what srs code is throwing)