Bogging/missfire-built SR with D jettro

[brian3676]

I am working on a S13 with a S13 SR swap, motor if fully built, CP 8.5 pistons, eagle rods, full BC valve terrain with stg 2 cams, cosworth HG, HKS manifold, GT30 turbo, 740cc injectors, stock intake manifold. Its running on a apexi PFC D-jettro (MAP based so no MAF). Anyway it had many problems that i worked out, now the last one i can not get, It idals perfect, if you give it gas (in nutural or under load) it boggs and will almost die then all of a sudden it will rev up to redline. Only in nutural though will it go to redline after bogging. Its like the MAF is bad or a IC pipe poped off kinda missfire/bog. I have checked the following so far and they all tested perfect according to FSM specs and testing procedures.

-All 4 coil packs
-CTS
-TPS
-CAS
-All grounds are good
-Altinator is putting out fill power
-All plugs are good and gaped perfectly
-NO boost leaks (pressure tested whole IC set up)

The car sat for months due to other problems, finally got it started, fuel pump craped out on (low pressure) replaced the fuel pump now i have full pressure(walbro 255)

During this time the car was attempted to be fixed by others so battery was pulled replaced proble 10 times tried to start with no power bla bla bla, SO long story short im down to 2 options unless someone has some other advice

Its A) lost its tune with all the messing around with the car from other people so i just need to re tune it or B) the MAP sensor went bad. Im good with SR's, just unfamiliar with the D-Jettro.......

Advice?

[jspaeth]

Im working on a S13 with a S13 SR swap, motor if fully built, CP 8.5 pistons, eagle rods, full BC valve terrain with stg 2 cams, cosworth HG, HKS manifold, GT30 turbo, 740cc injectors, stock intake manifold. Its running on a apexi PFC D-jettro (MAP based so no MAF). Anyway it had many problems that i worked out, now the last one i can not get, It idals perfect, if you give it gas (in nutural or under load) it boggs and will almost die then all of a sudden it will rev up to redline. Only in nutural though will it go to redline after bogging. Its like the MAF is bad or a IC pipe poped off kinda missfire/bog. I have checked the following so far and they all tested perfect according to FSM specs and testing procedures.

-All 4 coil packs
-CTS
-TPS
-CAS
-All grounds are good
-Altinator is putting out fill power
-All plugs are good and gaped perfectly
-NO boost leaks (pressure tested whole IC set up)

The car sat for months due to other problems, finally got it started, fuel pump craped out on (low pressure) replaced the fuel pump now i have full pressure(walbro 255)

During this time the car was attempted to be fixed by others so battery was pulled replaced proble 10 times tried to start with no power bla bla bla, SO long story short im down to 2 options unless someone has some other advice

Its A) lost its tune with all the messing around with the car from other people so i just need to re tune it or B) the MAP sensor went bad

Advice?

I have a similar problem and have had it for the past 2 years, when I switched over 2 D-Jetro PFC and 740 cc injectors.

For the first 5-10 minutes of driving the car, the car doesn' respond to throttle...well it does, but there is a delay.

If you blip the throttle, it tries to die then revs up too high.

At first thought it may be a water temp issue or poor vaporization of fuel at cold engine temps.

However, the problem persists for a few minutes AFTER the water temp has hit 80-85C.

Thus, the problem is NOT associated with water temp/fuel trims.


After discussion with my tuner, the only conclusion we can get to is that the injectors are not responding to input correctly when they are cold (physically not warmed up).

I can come up with the following scenario:

For some reason, the injectors, when cool/cold behave in a laggy way....first, the engine heats up to operating temperature....however, it takes sometime for this heat to make it's way through the aluminum manifold and heat up the injectors.

Once the injectors start to "warm up", they behave fine.



Like I said, I've had this problem for 2 years, and no one can figure it out.


Also, when it IS doing this behavior.....when I FIRST step on the gas, it tries to die, then revs up.....if I keep my foot in the gas, I can hold steady revs wherever I want to.



ALSO.......another possible cause is a slightly sticky IACV that isn't responding correctly.....when you give it gas, the IACV should close......perhaps when the car is still warming up (again, this may take longer than the time for the water temp to get up to 80C), the IACV is not opening/closing fast enough to respond to throttle inputs, causing the car to run super-lean upon throttle tip in and want to die.


......again these are just theories, but on my car, the key issue is that the problem STILL persists for few minutes after the water temp has reached 80C-85C.


justin

[brian3676]

But your saying that after it worms up and the heat makes its way to the injectors and worms your injectors up it runs fine? Because it seems we have exactly the same problem/ symptoms

[jspaeth]

Yes.

I believe it is either injectors or IACV.

But NOT due to a tuning/fuel trim/timing issue.


Again, the reason I say this, is that the problem IS present for some period of time when the water temp hits operating temperature 80-85C.

However, it then goes away a few minutes later.

Only possible explanation for that is something is physically sticky or not responding correctly, but then responding correctly when it is getting warmer.

Only 2 things I can think of are IACV and injectors.


I think IACV is more likely the culprit......however, I did NOT have this problem before swapping in the injectors/PFC, so perhaps it is the injectors......hmmmmm?



As you can imagine, driving the car around town/local/stop and go is a BITCH when the car is first started, especially since I have a 6-puck haha

[brian3676]

If anyone was intrested turns out it lost its tune we got a new map runs perfect

[steve shadows]

Haha, well I guess I did call it correctly in a way!

let me know if you'd like me to put together a timing map for ya anyways. Maybe you can compare yours to mine and see if it sparks some imagination

cheers

[brian3676]

Haha, well I guess I did call it correctly in a way!

let me know if you'd like me to put together a timing map for ya anyways. Maybe you can compare yours to mine and see if it sparks some imagination

cheers


If you wanna send it to me to compare ours that would be cool i bet there not too different though considering there just base maps. Anyway thanks for the help!

Brian