1jz doesnt boost past 0.7bar anymore

toyotahachiroku

New Member
May 8, 2007
23
0
0
vancouver
this is for a 1990 twin turbo r with a blitz ecu, an intake, no cat, egt temp sensor removed, cone filter intake, safc2, speed limiter delete.

few days ago, i had a idle hunting problem. oddly enough it seemed to have fixed itself somewhat after i cleaned the icv. the 1 way valve looks good as well as the gasket for it. car idles fine at 800rpm but i believe the icv is broken and it just happen to be stuck at a place where the car can idle. reached this conclusions because turning on the ac no longer bumps the idle up.

anyways, on with the current problem. while the icv was acting up, the car would drive fine after 2500rpms. it would full boost and not have any trouble doing it repeatedly.

however, right now, it seems to hit boost cut or something like that around 0.7 bar. in 1st and 2nd gear, it would hesitate slightly at around 0.7 then boost till 1. but in 3rd 4th and 5th, it would get to 0.7 and wouldnt go anymore. occasionally it would go to 1 but it takes a lot more effort and time to get there compared to before.

when it can get to 1, the car would boost to 0.7, hold at 0.7 for a few seconds, then continue boosting. snapping the throttle seem to help.

i've checked for leaks on around the intake manifold, i've checked for leaked around the turbos, i've checked for leaksing around the intercooler and piping. found nothing. i've tried doing runs with certain suspect sensors disconnected and certain hoses blocked off. didnt change anything. i've tried to pull code with t1 and e1 but doesnt seem to be working. i've even went and replaced all the hoses and hose clamps that didnt look so great and it didnt improve the situation either. i've considered the fact that it would be a tank of bad gas and the ecu is running the car in safe mode. so i've emptied the tank of gas and put in 94 with 2 bottles of octane boost. that didnt help either. i've also inspected the plugs and even swapped in a new set of bkr7e gapped at 0.030 and still no luck.

safc2 tells me the tps is good because it does register 0-100% with no flat spots in it. it also tells me the map sensor is good cuz it reads vacuum and pressure properly. it does however register some knock on it after driving high boost for a while. around 20 or so. but i doubt its accurate. i know what knocking feels like and it doesnt appear to be knocking. i've switched from the tuned file in the safc to a normal standard settings and the problem still exist.

i also suspect the blitz ecu because disconnecting the map sensor, icv, air temp sensor, turbo sensor, tps, coolant temp wont light the CEL up. i found that very odd.

im totally stumped! any help with figuring this out would be appreaciated. also, if you are in the vancouver area and have known good parts i can swap and test and possibly buy, have fsm for the 1jz, know of a local 1jz expert or have a scope i can use to back probe the sensors with let me know.