FCD causing boost sensor error code and poor everything?
 

Hey everybody,

Well, got done stripping down the engine bay, cleaning electric connections, cleaning grounds, inspecting injectors, checking coils, checking for any type of vacuum leaks ect, to troubleshoot why my car runs like absolute crap.

It'll start fine, but when it starts to warm the shit hits the fan and it'll start to bog down (sounds like running on one rotor), maybe die. If it stops running, gotta wait 15 mins and start it up again. It's not flooding and I have great compression.

After trying everything, the car still runs like crap. Ran the ECU codes and got the boost sensor code. Hmmm, maybe it's the FCD. Removed the FCD, reset the CPU and no codes. Took it around the block a few times (carefully) and still no codes, and the car runs great!

Do FCD's crap out? Are they known for always giving trouble codes? The car is an '87 turbo swap conversion, RB FCD, RB downpipe/presilences, rat's nest and emmisions removed, walbro fuel pump, stock injectors and ignition. Thanks.

Get a new FCD? Any of ur friends have a TII?, If so,see if it works on theres, if it does then somethings wrong with your car.

A swap????????? And what ECU are you using and especially WHAT boost sensor are you using. Both should be turboII items. And the FCD should be one made for series four, not series five. There's a big difference.

It's a complete swap, so S4 T2 ECU, boost sensor, wiring harness, everything. And the FCD is for a S4.

Dump the FCD and get an Rtek.

Yeah, that's what I'll most likely do. Especially all the good stuff I've heard about them. About the same price as a new FCD too! I just wanted to find out if it could be anything other than the FCD. Thanks.

Well if u removed it and the problem went away most likely it was the fcd. Over time anything electrical will crap out. I mean just look at out horrible soldered ecu's.

Go write down ALL the numbers on your boost/pressure sensor and post them, please. And count the number of wires on your boost/pressure sensor and post them also.

Are you real sure the FCD was built for a series four and not a series five???? They are different for sure. One built for one series, won't work in the other series.

Boost sensor # is N318, four wire plug with one vacuum nipple, and FCD is RB #11570. Double checked on RB's website and this is the right FCD. Now I'm gonna serch and verify I got the right boost sensor. The FCD is around 6 months old.

I'll second that and if was going to buy a new fcd I would get the creeping death one for 1/2 the price of a RB.

Checking continuity across the wires of the FCD (from one connnector to the other, I figured they should all have continuity with some resistance since it 'conditions' the signal) I had 0 ohms for all wires except for the yellow/blue wire (upper right if looking at plug with the clicky thingy on the bottom) which was an open. I figured at least one of those would give a value of resistance if working properly to allow the signal from the boost sensor to change before it gets to the ECU.

I've said it once and I'll say it again. I ain't no electrician. I maybe talking crap, but is this a indication of a failed FCD?

Why spend so, so , so much money when you can build one for ten bucks?

The N318 is for a tubo alright.

About the best way I know of to see if the FCD is good, is to backprobe pin 2B on the ECU. Then with the key to ON read the voltage in dc volts. Then turn the key off and hookup the FCD in the circuit and read pin 2B again. It should read the same as without the FCD, around 2.3 to 2.7 volts dc. Use one of the hold down bolts/nuts for the ECU as a ground for the meter. Maybe attach a needle to the positive lead of the meter and shove it up the backside of pin 2B. It is a brown/red wire.