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13b N/A Weird behaviour no idle/lumpy throttle?

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Old 06-01-16, 06:18 PM
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13b N/A Weird behaviour no idle/lumpy throttle?

Long story short, I've swapped an s4 13b into an FB Chassis. And now It won't idle, but I can hold the throttle down and it does this strange throbbing in the range of 1000-1500 unless my ear tach is off... No tach hooked up atm this is pretty apparent. I am not running any exhaust other than just the reactor atm, A stud broke in the outlet...

(There's a video link at the bottom)

I am currently using the stock n318 ECU and as far as I know I have everything needed to properly run the engine. All wires have continuity and all grounds are now sorted...

All parts and sensors have been checked and are in working order, or are new.

I have the following setup:

-S4 13b N/A
-Throttle body stripped only running a TPS
-Water Thermo sensor
-S4 MAP sensor (Boost?)
-S4 AFM
-S4 o2 sensor
-For some reason 2 of my injectors were low imp. so I had to add in-line resistors, the low imp. are now at about 12.5 ohms.. (Maybe still need to be around 14?)
-CAS
-Main relay
-Fuel pump - walbro 255lph - wired a switch to cut power to the pump
-4 new plugs
-Ignition wires are new
-Coils work and are firing

I may have forgotten something so I am gonna go take some detailed pictures of my setup so it's easier to explain.

also here's a video

Last edited by Jush; 06-01-16 at 06:25 PM. Reason: Forgot ecu #
Old 06-01-16, 07:09 PM
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I believe that might be a little too much pump for a 13b NA, I do you not believe a bigger pump is necessary, and once you quite it down more than likely you'll hear it running, the newer pumps from Walbro are much quieter, are you running a fuel pressure regulator or gauge? Does sound like vacuum as well have you check for vacuum leak?
Old 06-01-16, 09:18 PM
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Thanks for the reply,

I have checked, I have every port capped or sealed as well as all gaskets.

The fuel pump is something I never considered, I do not have an fpr..
Old 06-01-16, 09:26 PM
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You need to see actually what the idle speed is. At close to 1200 the timing advances. You could be suffering from the timing advancing to where it backs off and so on in a continuous cycle. Visuals don't help much when searching for vacuum leaks. Spraying w/carb cleaner etc would be more definitive.
Old 06-01-16, 11:20 PM
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and you need to get the proper ECU, the 318 is for a turbo engine and won't work right with 440 injectors, and the walbro is working the opposite angle. you got multiple issues fighting against you.
Old 06-02-16, 11:23 AM
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Thanks for the replies, also my ECU might be a 338, it is an NA computer, it's from an 88 vert so actually I've heard it can run boost too :P

The ECU IS an N/A Ecu I am sure of that I just forgot the number.

Also It will not hold an idle so I can't even get out and monitor anything.

Last edited by Jush; 06-02-16 at 11:25 AM. Reason: forgot
Old 06-02-16, 12:33 PM
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Did you retain the thermowax when you stripped the throttlebody? Do you have a temperature gauge so you can tell when the engine is warmed up? If you haven't warmed the engine up, it won't idle without the thermowax/fast idle cam. Also, does it still have a BAC? I experienced all sorts of weird idle/part throttle behaviors when my BAC failed. You really need gauges in the car to set things up correctly (I'm sure you know this.)

I would also recommend finishing the exhaust before continuing. Having the fumes coming straight out of the manifold makes it annoying to be working on it while it's running (when you get it to that point.)
Old 06-02-16, 01:47 PM
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Originally Posted by satch
You need to see actually what the idle speed is. At close to 1200 the timing advances. You could be suffering from the timing advancing to where it backs off and so on in a continuous cycle. Visuals don't help much when searching for vacuum leaks. Spraying w/carb cleaner etc would be more definitive.
that's what it sounds like , he may have leaks or the throttle body is adjusted improperly, as well as the tps
Old 06-03-16, 11:05 AM
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Thanks for the input everyone...

Looks like I went a little crazy on the emissions removal..
I am going to say my lack of having a thermowax is the issue here, beyond that is making adjustments and fine tuning.
Old 06-03-16, 06:56 PM
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Hi guys I have a 1989 Rx7 GTU and I've been having idle issues. It took apart the intake to inspect the throttle body. Are the plates supposed to be opened? Idk if this is normal or not. If anyone can let me know I will be very appreciative.

Thanks
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Old 06-03-16, 06:58 PM
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Originally Posted by Hygoog
Hi guys I have a 1989 Rx7 GTU and I've been having idle issues. It took apart the intake to inspect the throttle body. Are the plates supposed to be opened? Idk if this is normal or not. If anyone can let me know I will be very appreciative.

Thanks
yes, and make your own thread.
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