Here's A Head Scratcher

[kevst185]

Hi everyone i have a problem with my st185 and could really use some help. first of all i'll tell you a about my motor and what was done before it all went wrong. My celica is a japanese import narrow body which i purchased about 6 months ago for a very reasonable price the car was completely standard except it had been lowered and fitted with some drug dealer wheels. Since then here are my mods to date.

. Boost gauge

. Turbo timer

. Gutted cat

. 3" blue flame exhaust

. Disabled tvsv

. Blitz dump valve

. Fuel cut defender

. boost controller (relief valve)

. ct20b turbo

. 1 grade colder plugs

. straight air intake from sealed cold air feed box

. front mount intercooler

. relocated Battery

Now then last month or so under heavy acceleration my ct26 turbo let go and i had to replace it, the company that sold me the recon turbo told me that he had taken it of an st185rc but after a bit of research i discovered it was actually of an st205, as this was even better i kept my mouth shut. Anyway the new turbo was working just fine and the car was quick boosting around 15 psi, however after my last 2 mods things have never been wright. After installing the new turbo i thought what better than a nice shiny front mount intercooler, wich offers lower intake temps, better air flow and looks mean. In order to do this i had to swap the Battery and intake so at the same time i fabricated a polished alluminium cold air box. At this point i should just appoligise if it seems like im rambling but i feel if i give as much info as possible fellow gt4 owners will be able to diagnose better without having to ask to many questions. So after the intercooler installation for some strange reason im not able to boost above 12 psi without hitting fuel cut, now i know there could be many reasons for this but i feel i have illiminated every one. My first thoughts turned to the fuel cut defender but after i checked everything was ok. my second thought was to check the turbo pressure sensor and as this was such a small component i thought what the hell i'll just replace it. That was untll toyota told me they wanted £230 for a replacement, before spending that kind of money i wanted to be sure that it was the problem so i cut the pim wire to the ecu. This is where it gets confusing. I was lead to belive that fuel cut was a failsafe for turbo malfunction and therfore was only intrudeced when the ecu experienced over boosting, this is why we fit fcd's to increase stock boost levels, so cutting the pim wire to the ecu should illiminate fuel cut alltogether. The ecu error codes displayed that there was a problem with the air flow meter, throttle position sensor, turbo pressure sensor and the turbo itself all these have been checked and no faults found. I need to know what other problems could cause fuel cut if any ie. running to rich/lean do to a larger turbo even though the car ran fine before the front mount intercooler........ im confused please help.

[GTForbes]

well you've certainly gave plenty of information, there are apparently 2 failsafes on the 185 for over boosting, No1 being the turbo pressure sensor, No2 being in the AFM.

start from scratch, re-connect the wire that you cut, clear the fault codes and take it a run to see what codes you re-turn with.

When i first upped my boost to a bar i just disconnected the turbo pressure sensor tube and blocked it off so not to loose boost, give that a try, this is only a temp measure.

there is a possibility that you've damaged your AFM during all the new installatios but check that the connections are properly inserted and there are no loose wires.

if you follow the link in my sig there is a great site for info on everything GT-Four related and IIRC has a how to on checking the throttle position sensor.

if you have found a broken part contact the boys at TCB (toyota celica breakers) as they'll supply you replacement parts (2nd hand) at competitive prices, failing that check e-bay for someone breaking a four.

let us know how you get on