car-start up stumble, PFC D-Jetro, experts come help me!

[jspaeth]

I had my car tuned about 6 months ago by Jeff Evans in PA....for those that don't know, he is like a Honda tuning god and just a great tuner in general.

Went from a stock SR and T25 and ECU and added on PFC D-Jetro, GT2871R, and Tomei 740cc injectors.


Here's the problem:

-The car runs PEFECTLY after I have driven it for about 10 minutes.

-For the first 10 minutes or so, trying to go from idle to low RPM, if I touch the gas, the revs drop STRAIGHT down, and I have to keep feathering the gas to get them to come back up, and once they are up and I have my foot on the gas steady, it is fine....so ONLY when I first touch the gas a bit

- My first instinct was that this was an air/fuel issue, possibly associated with the water temp, since it only happens when I first start the car.

- However, I have performed a few "experiments" to check this.

- For example....if I drive the car for 2 hours, so that everything gets good and hot........then, I come outside after letting it sit for another 3 hours or so (so that the water temp is back down to where it was when I first started the car), the problem is NOT there, even though the water temp is still very low.

- I have tried drastically lowering the water temp injection values in the PFC, and this doesn't help....

They WERE:

80C -- 1.00
50C -- 1.07
30C -- 1.14
10C -- 1.25


I made it:

80C -- 1.00
50C -- 1.04
30C -- 1.08
10C -- 1.15



This stumbling and dying upon initial throttle coming up from idle SEEMS of course to be related to the fact that the car is cold....like i said, it only happens within the first 10 minutes.....HOWEVER, my experiences show me that it is NOT due to the fuel maps because A) Making changes to the low RPM values and water temp. corrections didn't do shit, and B) The experience I've had where if I drive the car to warm the WHOLE thing up good, and then drive it 2 hours later (when the water temp has come down) and do NOT have this problem.

Any ideas?

The bad news is that Evans Tuning is like an hour from me, so the problem WON'T show up when I am there (unless I drive up there the night before and sleep in my car!).

It's not a MAJOR problem, just an annoyance, since a good deal of my driving is short driving that only lasts a few minutes from when I start the car.

Thanks fellas.

[jspaeth]

bump plz thx

[jspaeth]

Final bump........can someone that has seen this before chime in please?

[born2boost]

no vac leaks? Idle air control valve ok?

[jspaeth]

Yeah I believe so, because like i said, it goes awaw after the first 10 mintues or so....

[born2boost]

Id try cleaning your iac valve. whats your idle at?

[jspaeth]

Okay I will try that out. Thanks

[RACETUNE]

I had my car tuned about 6 months ago by Jeff Evans in PA....for those that don't know, he is like a Honda tuning god and just a great tuner in general.

Went from a stock SR and T25 and ECU and added on PFC D-Jetro, GT2871R, and Tomei 740cc injectors.


Here's the problem:

-The car runs PEFECTLY after I have driven it for about 10 minutes.

-For the first 10 minutes or so, trying to go from idle to low RPM, if I touch the gas, the revs drop STRAIGHT down, and I have to keep feathering the gas to get them to come back up, and once they are up and I have my foot on the gas steady, it is fine....so ONLY when I first touch the gas a bit

- My first instinct was that this was an air/fuel issue, possibly associated with the water temp, since it only happens when I first start the car.

- However, I have performed a few "experiments" to check this.

- For example....if I drive the car for 2 hours, so that everything gets good and hot........then, I come outside after letting it sit for another 3 hours or so (so that the water temp is back down to where it was when I first started the car), the problem is NOT there, even though the water temp is still very low.

- I have tried drastically lowering the water temp injection values in the PFC, and this doesn't help....

They WERE:

80C -- 1.00
50C -- 1.07
30C -- 1.14
10C -- 1.25


I made it:

80C -- 1.00
50C -- 1.04
30C -- 1.08
10C -- 1.15



This stumbling and dying upon initial throttle coming up from idle SEEMS of course to be related to the fact that the car is cold....like i said, it only happens within the first 10 minutes.....HOWEVER, my experiences show me that it is NOT due to the fuel maps because A) Making changes to the low RPM values and water temp. corrections didn't do shit, and B) The experience I've had where if I drive the car to warm the WHOLE thing up good, and then drive it 2 hours later (when the water temp has come down) and do NOT have this problem.

Any ideas?

The bad news is that Evans Tuning is like an hour from me, so the problem WON'T show up when I am there (unless I drive up there the night before and sleep in my car!).

It's not a MAJOR problem, just an annoyance, since a good deal of my driving is short driving that only lasts a few minutes from when I start the car.

Thanks fellas.

It sounds to me that you are on the right track due to it from the warm up and you are adjusting the temp correction. But you have more than one adjustment off, if the injector valve/time is off that can also cause but that will need your car retuned again.

-Frank

[jspaeth]

I didn't think there was a timing correction for water temp....I will have to look at that too....


But now I am thinking maybe it could be IACV related, especially since it dies on decel.......again, ONLY in the first 10 minutes..

[P_TAN]

The post is kinda old just want to know if you've corrected the problem?

[steve shadows]

I didn't think there was a timing correction for water temp....I will have to look at that too....



There is...



make sure your idle timing is not too advanced, this can cause rich conditions as well.

[Z U L8R]

i've seen a similar problem when the customer had his intake air temp sensor in the intercooler pipe and not tapped in the intake manifold after the throttle body.

just throwing that out there.

gl,
Dave