Gradual Hesitation From Cold to Hot

[87supramario]

Start up is clean, just until the coolent meter starts to take liftoff, and the hesitation progresses from random spirts to very often, impossible to build boost. After the swap I did manage to have 4-5 good runs, until hesitation started to progress and went through 2 MAP sensors & 3 sets of coils that where all used in known working order.

Could a temp sensor cause this issue?

Stock ECU.
TT fuel pump with 12v.
Stock fuel system.
Stock boost.
No wideband yet.

I've already missed this season's first Supra meet which is this evening.

 

[hvyman]

Have you checked for codes?

 

[87supramario]

code 21 only, because o2 is not hooked up. I am working on converting my mustang 4 wire threaded o2 to replace factory o2.

 

[87supramario]

code 52 was also found after doing a oil change earlier this week. Was a ripped wire from rear knock sensor which was repaired today. I also made a extension from the existing o2 sensor harness to my rear chinaman Y-pipe runner and converted a threaded mustang o2 we had around the house with no positive results. The damn Y-pipe has a temp bung in the front runner and threaded o2 in the rear (perfect for wideband) so I wa never able to simply bolt up my o2 but I am suspecting the bolt on flange is under the surface.



Meanwhile there is a 1JZ VVT-i swapped MK2 in town and he was asking me for coils, because he had the same problem. Turns out he just solved his issue after discovering the flexible fuel line on top of the fuel pump was loose enough to drop fuel back in to the tank instead of sending it to the fuel rail. Since I don't have my wideband set up just yet and I don't have a FPR, I am ordering a new OEM replacement fuel filter and dropping the tank to double check the TT pump and mounts. 12v mod using factory relay has been done since the swap.

AEM 2 in 1 wideband & boost gauge to be the only aftermarket gauge in car.

 

[Getsideways86.5]

Following this. I just put a 3400 stall in my 1j mk3. Also did 3inch stainless turbos back. Now I get a hesitation until engine is warm.. it's also running lean as can be. Adding my trd afpr next week. Hopefully that's all that's wrong..

 

[87supramario]

I've solved the last bug. The major problem was a spark plug that was split pretty much down the middle. Other plugs had loose hats and gaps ranging from .028 - .045.

Connecting a Mustang threaded o2 sensor where I was wishing to install my wideband made a huge difference, then changed what looks like the original fuel filter made a bit of a difference, and finally changing the plugs and gapping them to .034 (stock boost) took the cake.

This looks like it is about 30 years old, considering I have car #818.

Following this. I just put a 3400 stall in my 1j mk3. Also did 3inch stainless turbos back. Now I get a hesitation until engine is warm.. it's also running lean as can be. Adding my trd afpr next week. Hopefully that's all that's wrong..

The thought process is that the ECU automatically calculates injection for cold start, then it switches to relying on the MAP, TPS, coolent Temp, and o2 sensor to determine air/fuel when the coolent gauge rises. If your issue does not relate to any sensors to blame, it may be the ECU itself, unless lack of fuel because there is no sensor that determines that. Twice people have told me to drop the tank and inspect the feedline that runs between the hardline and the fuel pump, because if they are too short they tend to pop off because the hardline is not flared. But once you hook up a FPR and gauge you will be able to spot that if it were to be an issue. Other than that I would try and borrow a known working MAP and ECU and see how that turns out.

 

[87supramario]

Found the answer two weeks ago. It was a split spark plug.

After installing new plugs before the engine was installed I never thought to check. But each plug was also out of gap range, between .028 - .045+. Car runs great!