JDM swap fd3s drives poorly when cold, great when warm.
08-17-14, 09:27 AM
#1
JDM swap fd3s drives poorly when cold, great when warm.
Hello all,
As the title suggests I am having a problem. I recently purchased my car ( a 94 fd3s )
Engine has about 500 miles on the full rebuild. Apexi FMIC, street port, non sequential twins, magnaflow exhaust, wideband, STOCK ecu.
I am staying out of boost for the most part during the engine break in, premixing my fuel, and at 1000 miles I plan on changing all fluids and going with a power fc to tune. BUT before I do....
The car drives great WHEN WARM. Has the very common 3k hesitation which doesn't overly bother me and has the*also common problem with key ignition (takes a couple tries to get starter to click). WHEN WARM the air fuel ratios look good under acceleration and idle, and the idle is rock solid. Now*onto the problem: when the car is cold, idle is extremely jumpy from 1k to 1500 rpms, the air fuel ratio is LEAN at idle and under load, and the car bucks/jerks/cuts extremely hard when accelerating if you attempt too much throttle, if taken easy shifting before 3k and slow steady acceleration it won't do it. Now once the engine warms up all of these issues goes away. Holds boost perfectly and pulls like a freight train.
I am brand new to rotaries and I've owned this car about 2 weeks. Spoke to the shop who did the rebuild in depth and had Cam at Pettit do an inspection. His opinion is that we won't be able to know what causes this until I get the PFC and see what's actually occuring. He mentioned that the engine sounded great and this issue was NOT fuel cut running LEAN, which was my fear with the street port on a stock ecu (he drove it). I'm hoping that the gurus here can chime in as to why in the heck does the car drive so great when WARM, yet so bad when cold.
Many thanks in advanced!!
As the title suggests I am having a problem. I recently purchased my car ( a 94 fd3s )
Engine has about 500 miles on the full rebuild. Apexi FMIC, street port, non sequential twins, magnaflow exhaust, wideband, STOCK ecu.
I am staying out of boost for the most part during the engine break in, premixing my fuel, and at 1000 miles I plan on changing all fluids and going with a power fc to tune. BUT before I do....
The car drives great WHEN WARM. Has the very common 3k hesitation which doesn't overly bother me and has the*also common problem with key ignition (takes a couple tries to get starter to click). WHEN WARM the air fuel ratios look good under acceleration and idle, and the idle is rock solid. Now*onto the problem: when the car is cold, idle is extremely jumpy from 1k to 1500 rpms, the air fuel ratio is LEAN at idle and under load, and the car bucks/jerks/cuts extremely hard when accelerating if you attempt too much throttle, if taken easy shifting before 3k and slow steady acceleration it won't do it. Now once the engine warms up all of these issues goes away. Holds boost perfectly and pulls like a freight train.
I am brand new to rotaries and I've owned this car about 2 weeks. Spoke to the shop who did the rebuild in depth and had Cam at Pettit do an inspection. His opinion is that we won't be able to know what causes this until I get the PFC and see what's actually occuring. He mentioned that the engine sounded great and this issue was NOT fuel cut running LEAN, which was my fear with the street port on a stock ecu (he drove it). I'm hoping that the gurus here can chime in as to why in the heck does the car drive so great when WARM, yet so bad when cold.
Many thanks in advanced!!
08-18-14, 05:15 AM
#2
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I'm not an FD guy but I have seen that the fuel system comes with a Fuel temp sensor.
This thing I have read creates havoc.
As I said,not familiar with the car but Hey!..it's a guess..
Sarge may wanna jump in on this..
Sarge??...where are ya?
This thing I have read creates havoc.
As I said,not familiar with the car but Hey!..it's a guess..
Sarge may wanna jump in on this..
Sarge??...where are ya?
08-18-14, 10:19 AM
#3
Yes, please
Please do chime in! Very curious as to why this is happening! Thanks for the reply
No problem.
I first looked at your location and I thought it said TUMERIC..
I thought HMMM?..home of the Spice Girls???
(consider this a bump so Jim can see the thread..lol!)
No problem.
I first looked at your location and I thought it said TUMERIC..
I thought HMMM?..home of the Spice Girls???
(consider this a bump so Jim can see the thread..lol!)
Last edited by misterstyx69; 08-19-14 at 08:29 AM.
08-21-14, 07:58 AM
#6
Haven't ever dealt with the problems exactly as you describe.
I did search the 3rd Gen. section and found this that comes close....
https://www.rx7club.com/3rd-generati...n-warm-898451/
The other dynamic is the fact that in your title you indicate it's a 'JDM' swap, but no details. If you have a JDM engine, you may/probably have a JDM ECU and harness, which means you won't get the typical Check Engine Lights that you would with a North American OBD I. I would suggest looking at things like the Intake Air Thermosensor, which normally would throw a code #11 on North American cars with a stock ECU. It's relatively inexpensive but a bit of a pain to access under the upper intake manifold.
You don't get a CEL with a PFC either, but on the Sensor Check screen a bad one will be shaded, which is probably why Pettit suggested it.
If you haven't yet, get a copy of the Factory Service Manual (FSM) here: 1993 Mazda RX-7 Factory Service Manual
If the IAT sensor doesn't help, I would try looking through some of the trouble-shooting in the fuel system section....or get that PFC.
I did search the 3rd Gen. section and found this that comes close....
https://www.rx7club.com/3rd-generati...n-warm-898451/
The other dynamic is the fact that in your title you indicate it's a 'JDM' swap, but no details. If you have a JDM engine, you may/probably have a JDM ECU and harness, which means you won't get the typical Check Engine Lights that you would with a North American OBD I. I would suggest looking at things like the Intake Air Thermosensor, which normally would throw a code #11 on North American cars with a stock ECU. It's relatively inexpensive but a bit of a pain to access under the upper intake manifold.
You don't get a CEL with a PFC either, but on the Sensor Check screen a bad one will be shaded, which is probably why Pettit suggested it.
If you haven't yet, get a copy of the Factory Service Manual (FSM) here: 1993 Mazda RX-7 Factory Service Manual
If the IAT sensor doesn't help, I would try looking through some of the trouble-shooting in the fuel system section....or get that PFC.
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09-24-14, 12:17 PM
#8
Ok , the question is do you have a wide band ?
It COULD be a sensor like the water temp sensor going bad , OR the fuel temp sensor being swapped , BUT your engine would of blown by now since the fans wouldnt of turned on .
Now what has changed , lets look at this scientifically , You are using a a stock ECU , on a ported motor , by porting the motor you make more air flow into the motor .
, Now a colder motor needs more fuel , then a hotter motor ( this was why mazda made hte FD run as hot as it does and why many OEM manufactures make their car runs on the limit of heat now ) So if you compound the fact that more air is flowing into the motor , But the ECU is still thinking its the OEM ports so its not compensating with more fuel .
when hot since the motor is warm , and needs less fuel maybe the fuel given by the ECU is just enough to keep it from breaking up .
It COULD be a sensor like the water temp sensor going bad , OR the fuel temp sensor being swapped , BUT your engine would of blown by now since the fans wouldnt of turned on .
Now what has changed , lets look at this scientifically , You are using a a stock ECU , on a ported motor , by porting the motor you make more air flow into the motor .
, Now a colder motor needs more fuel , then a hotter motor ( this was why mazda made hte FD run as hot as it does and why many OEM manufactures make their car runs on the limit of heat now ) So if you compound the fact that more air is flowing into the motor , But the ECU is still thinking its the OEM ports so its not compensating with more fuel .
when hot since the motor is warm , and needs less fuel maybe the fuel given by the ECU is just enough to keep it from breaking up .
09-24-14, 03:13 PM
#10
My vote is for water temp sensor. Easiest thing to do is plug the PFC in, it "pings" (for lack of better term) all of the sensors and will highlight any problematic ones. Thats how I found out my IAT sensor was fucky
09-24-14, 03:34 PM
#11
https://www.rx7club.com/3rd-generati.../#post11393062
09-26-14, 10:40 PM
#13
A JDM harness won't work in a USDM car without a decent amount of modification. I suggest throwing a power fc in there and seeing how it runs. Maybe someone local can lend you one? You can also check the sensors like others suggested through its sensor/switch check menu. Also check if you didn't mix up the coolant temp and fuel temp connectors. They look the same. You're going to need a power fc to safely run those mods anyway.
09-26-14, 11:14 PM
#14
I had that same problem with my Fd, that was because I installed the power fc and I was running it lean for it to pass emissions but after the emissions I set it to the stock setting and it idles good when cold. U should try getting a power fc maybe that would solve your problem.
09-29-14, 09:04 AM
#17
Good luck , there are alot of choices for EMS depending on what you want to do with the car .
Look into some and see what may work best for you .
Also good luck if you need some help or something I'm pretty close by so feel free to msg me and I will gladly help how ever I can !
Look into some and see what may work best for you .
Also good luck if you need some help or something I'm pretty close by so feel free to msg me and I will gladly help how ever I can !
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