Well the car was running fine at the beginning of the autox I just got back from. After shutting it off after my 5th run, I started it up again and the AFL% on the SAFC II read 100%. Drivability is good when in vacuum and light thottle, however very rough bucking when going into boost (harder throttle). Also there is a very strong 3k hesitation which was not there before. When revving in neutral it can rev past 3k (with a little hesitation) however, when in gear its like hitting a wall at 3k with the car bucking and backfiring. Also Idle is good and smooth. I was hoping someone could tell me a few places to start trouble shooting?? I am really worried about this =(

Background info on car:
- N/A + turbo with stock N/A sensors and all (NOT TII swap)
- MSD 6a ignition boxes (leading coils)
- Apexi SAFC II
thats pretty much all thats engine relevant =(

 

Boost sensor?
TPS??
Secondary injectors/connectors???

 

the pressure sensor might be a good possibility because it runs like crap when in boost and I thought the secondaries kicked in at 3800 rpm?

 

It should run like crap in boost- the n/a sensor wasn't designed to sense any positive boost...You might have "blown it"- can you pull codes?

Secondaries are easy enough to troubleshoot, either per Haynes/ FSM (their testing steps never seem to work for me), or by attaching your meter pos lead to the ECU pins for the injectors (neg lead to ground), then going for a spin...

 

On a SAFC, does the AF1 not represent the vane position in the AFM/?????? I don't have an answer why it's at 100 percent since I've never seen more than approx 93 percent on one. Maybe that wire is *open*???? Or the flap/vane is stuck open (ain't likely at all). I go for the wire being open ....some place.

 

thanks for advice guys, I'll head out in a few to check it out. Does the SAFC read read the afl% based on increased voltage? (IE 5V=100% and 0V=0%)?

 

update: Tested the AFM and it looks like the resistances are about to spec, but the AFL% on the SAFC still reads 100% Could anyone tell me how to test the pressure sensor? Thanks in advance

 

Are you using the stock boost/ pressure sensor? I'm confused...

 

yeah I'm using a stock s4 N/A pressure sensor, I dont think it even see's boost, I think it stops reading at 0psi doesnt it?

 

I don't know when it hits it's limit (atmospheric I've heard), but I know you should be using a boost sensor/ ECU (or SAFC) combination that can interpret your positive boost pressures....

 

Yeah I was thinking about that however, I didnt think the stock N/A ECU was compatible with a turbo pressure sensor

 

I'm almost positive the AF1 reading is a product of the afm and nothing else. To the best of my memory, the voltage to the ECU starts out high, then as the vane is pulled back under high throttle, the voltage goes down.

What I'd do is monitor the SENSOR READINGS while pushing the vane back from its resting spot. The voltage should change as you push on the vane. IF it does not...then there is a break or some other disfunction in the wiring to the SAFC. I doubt its the afm itself. Most likely the wiring from the SAFC to the ECU wiring.

Check the yellow and the white wires on the SAFC.

If that does not produce results....put a meter on the afm output wire and see what you read when shoving the flap/vane in and out on the afm.

Or try this: with the key to ON and the car not running, the SENSOR CHECK should show approx 4 volts. Then start the engine. The reading should now show approx 2.5 to 3.5 volts.

 

I just went out to the car at midnight with a cold car. The voltage for the afm when looking at SENSOR VOLTAGE, shows 3.9 volts with the key to ON. At idle its like 2.3 volts. Don't hold me to the 2.3. The car is cold. When hot the reading a bit less, I think. Like 2.1 or so. Usually on the MONITOR the voltage reads something like .4 percent when at idle. I've never seen 100 percent at full throttle OR when pushing the vane all the way aft by hand. Only seen maybe 93percent with the vane all the way aft.

 

HAILERS: Thanks alot for the indeph explanation! (and sorry for all the trouble lol, I know how much of a pain it is to be doin car stuff that late) I'll try it and hopefully its a simple short.

 

A little correction on the figures from last night.

Key to ON, engine not running, the percent is .4 percent.(Monitor)

Car idling....the percent is approx 1 (one) percent. (Monitor)

The voltage with the key to ON, engine off, is 3.9 volts(Snsr voltage in ETC)

Warm engine idling is approx 2.7 volts. (Snsr voltage in ETC)

 

alright, the culprit so far has been a broken connection (I dont know how) at where the ecu meets the safc. So now i see .04 AFL% with car off (thanks ALOT hailers). Tommorrow gotta replace the coil pack and see if I can get her fired up and see if she runs, thanks alot again for your help guys!