car dies under boost
 

got a 93 singal turbo supra when it starts building boost ( which is about 4000) it just dies! i have no idea what it is.. really need some help from the supra gurus

What is your air:fuel ratio when it dies?

Please tell us more about your car (i.e. list all modifications):

the a/r's stay around 12.9 before it dies, its a singal turbo 50mm waste gate stock computer 750cc injectors 255 walbro adjustable FPR and cam gears with the exhaust cam retarded 4 degrees, the guy thinks a AEM will slove his problems but i cant give him a clear answer about, another thing that strikes me as off the maf is on the intake side inline with the intercooler pipes :confused: crazy! its also missing most of its sensors that where on the intake

Which guy? The owner? Is he paying you to work on his Supra?

I agree the maf configuration needs to be changed back to oem - this is a strong suspect as the first troubleshooting step to take. Although an AEM might fix the problem, that's like fixing a cut in your finger by replacing your arm with a robotic prosthetic. A whole AEM setup is $2500+, and this could likely be fixed with a few hours (or less) of troubleshooting with the existing setup.

yes the owner he's my best bud no money just help him out mybe i'll get a 6-pack of budlight lol it looks like a DSM setup with the maf like a blowthru he wants the AEM pretty bad i agreed that the AEM would give him a boost of performance! i hooked up the computer to the car and it pulled 5 codes fuel pump relay, coolant temp sensor, TPS sensor, and turbo boost pressure sensor *2

Actually, the AEM might not give him a great boost of performance. What size of turbo is it?

The coolant temp sensor problem needs to be fixed; it's even needed with the AEM.

Either the Throttle Position Sensor and the Turbo Pressor Sensor could be a part of the stalling problem, so they should be corrected as well.

Troubleshooting steps for these sensors are all in the TSRM (Toyota Supra Repair Manual). If your buddy doesn't already have one for his Supra, he needs to get one.

i've tested the coolant temp sensor & replaced it, and adjusted the TPS only showing 78% of throttle open got it back to 100% the turbo pressure sensor was the one's on the intake and they are gone now :werd:

sorry i didnt answer this earlyer he said its a 70mm?

Cool thx.

Please keep us updated with your troubleshooting steps. If anything's going on that I can help with I'll be sure to respond.

well i spoke with him and he's pretty much made his mind up i think he wants a AEM before he marry's his old lady lol

made some head way on the car this weekend, spoke with dusty at MVP ( awesome guy!) a and we both seem to think its the a mass air flow sensor issue luckly for my bro i have a car just like his :bigthumb: so i will swap mine over to his and give it a try

I'm glad Dusty agrees with me:
Please say 'hi' to him for me, next time you talk. :)

P.S. The current post-turbo MAF configuration could be the very reason that MAF got ruined (if that's the problem)... excess heat or oil from the turbos could easily mess up the sensor. Please keep that in mind before you swap yours into a questionable configuration...

agreed i dont want to screw up my maf sensor..he's order a AEM today so we might not ever know what was wrong with it

ok i need somone to explan! i pulled the car out today hosed off all the dirt hit the engine with some grease lighting and chagned the oil..then took it down the road the car spooled up but didnt die, side note i had the fuel preassure WAY to high, turn it down a bit took it back out and it ran GREAT!! like a monster :dunno: so whats the deal went from being unable to boost to a friggin rocket??

If your fuel pressure was "WAY too high", how was the a:f ratio "around 12.9 before it dies"? Something doesn't add up.

i had adjusted on it before today, when the car was brought in i think it was set at 25 pounds and i had turned it up to 35 so i went up 10 pounds from, but after i readjusted it it stayed right at 13.1 under full boost

well it's not the mass air flow sensor :wtc: back to square one. this car is driving me crazy :nuts: i have no other idea what it could be i've changed or adjusted every sensor that it was pulling codes for.

Did you put the MAF back to the oem configuration (pre-smic/fmic)?

yes sir its back to the oe location

Does it still die at 4000 rpm?

yes still dies at 4k but if you shift the car your self and let it get past 4k the go to WOT then she will pull hard under boost but still dies very shortly after that :werd:

One possibility is (believe it or not) the solder leads on your oem odometer! They may need to be re-flowed. Either that or just bridge the speed sensor inpuy & output from the odo cluster harness plug. In short, if the solder leads are cracked, the oem ecu doesn't get a speed sensor signal from the transmission, which causes an artificial rev limit....usually at about 5k... This isn't a for-sure diagnosis, just one possibility...

hmmm i'll have to check in on this.


side note could you please tell me where the a/c amplifier is the one in my car died.

As far as I know, the air conditioning system does not have an amplifier.
http://www.mkiv.com/specifications/ncf/ncf93/ncf235.jpg
http://www.mkiv.com/specifications/ncf/ncf93/ncf236.jpg

toyota calls it a a/c amplifier and holy crap batman it's expensive! (748 bucks) damn and i was looking to buy a singal turbo kit from sound performance :mad:. thanks pwpanas for the info also..

lol Supras do that to people..

lol no doubt my supra is like my women on the side lol :naughty:

sorry its been so long since i've posted been working on the bike taking care of kids the whole nine yards. but we did figure out the problem! ready for it....the rings on number six & one are shot and it has a blown head gasket major bummer! enjoy some photos one of my sons were out there to help but wasnt tall enough to reach the tranny bolts hahaha so he just ate a few shop rags

wouldnt allow me no more than five :dunno:

Thanks for posting back. Why were the bad rings limiting your rpm? Was it smoking at all (via the exhaust)? Are you sure this is the (only) problem?

no your right the bad ring was'nt limiting the rpms we did find a BROKE rear cam sensor and i mean bad broke like it was two piece's mybe this was the cause

Strange - that should have been throwing an ecu code...

well get this after i preassure tested it & compression tested it put it all back together to put i back on the trailer to take it vback to my house she fired up ran like shit but no check engine light!??

Sorry, I mean there should have been an ecu code *before* you fixed the cam timing sensor...

no no we havent fixed it yet

So let me get this straight: Your rear cam sensor is broken in two pieces, and you have no check-engine light??? Are you still running the oem ecu, or have you switched to the AEM?

still running the stock ECU man this car has got the bugs or somthin, as of right now the block being bored .20 over the roating assemble is getting balanced (wisco pistons eagle rods AC bearings) so if i see a sensor that even looks like it might be messed up then ill replace it this thing has been broke to long!

I don't know if I'm not getting the complete story here or what, but the approach to finding the problem doesn't make a lot of sense. From your description it seems like the answer to an rpm limit problem was to bore the block and rebuild the bottom end. In truth, even a piston with a very low compression/leakdown won't limit your rpm. What were the compression/leakdown numbers before you all decided to tear down the shortblock? And again, was the ecu showing any codes?

At the very least, I'd ask that you don't tell anyone that we said you should rebuild the engine because of an rpm problem - because we didn't! :) Thanks in advance...

Dude I am telling you the whole story. The only reason we pulled the motor because of was wore out but for all we know it still has the rpm limiting problem

How do you know it was worn out? Was a leakdown test done? Again, was it smoking (whitish-blue) from the exhaust?