Motor
Rebuild S5 T2 motor,with perfect cond housings,very nice cond plates,atkins apex seals.oem apex seals springs,FD corner seals,solid corner seals,oem side seals springs and atkins side seals.
Problem
The motor starts very easy when cold and it idles at 750 RPM but when my thermostat opens and my aftermarket guage reads around 185 to 190(almost quarter of the stock temp guage)the cars stumbles misfire and dies,i looked at my narrow band o2 sensor while this was happening and it goes crazy,It jumps from reach to lean until the motor dies and then is very hard to start.This engine only has around 50 miles on it and it was driven on NA form and never been overheated,any inputs?thanks Joey

 

My first guess would be that either the engine temperature sensor is broken, disconnected, or has a weak connection.

I don't know how to check the ECU codes on the S5, but check the codes, see what it thinks is wrong. That's the first place to start.

-=Russ=-

 

its a s5 motor on a s4 chasis,harness was replaced but i will check my conections and the temp sensor,thanks Joey

 

Please clarify your comment above....it idles at 750 while cold or fully warmed up? What happens if you give it a little throttle when it wants to die? Can you raise the idle a little bit and see how she runs?

 

Hm...

The S5 has a "check engine" light that illuminates if it's unhappy with things.

The S4 doesn't - it just uses default values.

Are you using the S4 or the S5 ECU? If you have the S5 ECU in an S4 chassis, you most likely don't have the check engine light. You may need to rig a test LED or something to pull the codes.

I'm willing to bet finding a way to pull the ECU codes will give you at least some clue as to where to start.

-=Russ=-

 

okay im running full S4 turbo sensors,it idles cold at 750,when the motor reaches the 185-190 mark the idle starts bouncing and the AFR guage goes crazy,I also noticed that when the motor hit the 3500,3800 RPMs it feels like im hitting a wall,it loses power also when this happen my boost guage its around the 0 vac line.

 

Should be idling around from 1,500 right at startup, down to 1200-1300 soon, and then gradually down to 750 when warm. I'm lost as far as the other problems are concerned.

 

Maybe the primary & secondary injector plugs got swapped?

 

rent an obd 1 reader from autozone...should help you out...and its free.

 

no ACV thats why it idles at 750,i taught that if the injectors were plug in wrong the car wouldnt start at all cause no fuel its getting injected to the motor.

 

i know a guy out here by me that did the same swap s5 to s4 if i remember right it was a sensor or some wires ill check to make sure

 

Wierd that once your Thermostat opens,that you encounter a Problem..Perhaps the ECU is going into Limp Mode?..Is thsi an S5 Block with s4 Operating Stuff on top?and s4 ecu?..checked your Cat?..are the injectors hooked up correctly?..(just throwing Random questions at you to Feel what you have)

 

Its a S5 block,the swap was done 2 years ago and the car ran fine until the motor took a dump a couple of months ago.(fuel pump took a crap one night and it destroy the rear rotor and housing).All the electronics were pulled of a 10A donor car,i just installed a another emissions harness and it didnt help i also order a OEM coolant temp sensor to replace mine and see what happens,Thanks for the help guys Joey