Backfire, Bogging at 4-5 psi
 

This FD runs ok, until it gets to about 4-5 PSI of boost and it just stutters, and all the power goes. I checked for boost leaks, and nothing obvious. I was researching the archives, and found some people with a similar problem. Someone suggested the Boost sensor. Where is this located?

Thanks

Boost sensor is the black plastic sensor attached to your firewall, right by your throttle body.

I would look into ignition to check for your problem.

The car has some cheap AFR gauge, the needle is constantly pegged on the rich side. Whenever the engine cuts out, it kind of feels like it is running too rich, so I made sure I dont have any major boost leaks. during the boost leak test, the BOV closer to the firewall started to leak pretty bad around 5 PSI, but unfortunately that wasn't the problem.

do you get a "check engine" light? If so, get the code. Believe it or not, it might be the thermo sensor on the back of the water neck. If I remember correctly, it is a green plastic plug. Mine did the same thing as you described.

there is no check engine light on, but then, i first need to check whether it works, it's a friends car. I had a similar problem on an eclipse turbo before, where the thermo sensor caused it to run very poor.

thanks for you input!

Sounds like a secondary injector issue. Im assuming you guys have already changed the spark plugs to a new set as step 1?

Haven't done that yet. I just got all the DTCs from the ECU, and there's a bunch of them. I have codes:

5 Knock Sensor
9 Thermo Sensor
11 Intake Air Temp sensor
16 EGR Switch
17 Feedback System
30 Split Air Bypass Solenoid Valve
33 Port Air Bypass Solenoid Valve
39 Relief 2 Solenoid Valve
51 Fuel Pump Relay

That's a bunch a codes. I guess i'll just go one by one, unless someone has some suggestions.

Check the primary coil.

The spark plugs were recently changed, and I checked the thermo sensor, it checked out fine although there is a code for it. all of the sensor harness looks really bad, cut, spliced, and briddle in a lot of places. In my opinion the best thing for this motor would be a new harness along with a few new sensors.

thanks for the input guys, i'll let you know once I figure out what the exact problem was.

It in limp mode, code 5 will put you in limp mode all day every day as well as possibly the fuel pump relay but I cant recall. Everyone makes all these wild suggestions and you will be running around chasing your tail, replace hte knock sensor and you should be good to go.

Also, is the car converted to non-sequential and does it have resistors in the harness. You are pulling some weird codes that arent common on the fd.

I don't know about the resistors in the harness, but i believe it is still in the sequential setup. I thought of something like a limp mode, so I erased all the codes, and after doing so, before starting the car, I only get codes 30, 33, and 39 for the bypass solenoids.

I started the car, and got a low coolant light, turns out one of the briddle hoses started leaking after r&r of the temp sensor, so i replaced it, and after doing this, i turned the car on, and the tach didn't work anymore, i checked if there were any wires that might have gotten disconected or so, but didn't find anything. the car seems to run good now, no bogging anymore and at 6 psi or so because i hooked up the wastegate actuators straight to vacuum for minimum boost.
thanks for the input djseven, i think your absolutely right, but does anyone have any idea what the problem with the tach could be now. it seemed to work just fine before. this car is really giving me a headache.

The tach started working again without doing anything, I assume it may just be some poor connection, as there seem to be many in that harness. the car runs fine after redoing one of the wires of the thermosensor, and some of the other wires, and clearing the codes. the knock sensor code is back though, so i'm afraid that that might make it go back into limp mode eventually. i'll just see whether there is some problem with the connection to the knock sensor before replacing it.

thanks for the help guys!