i had just picked up a 93 sc300 with a 70 trim turbo on about 10 lbs of boost and seems to be miss firing. i want to change plugs and wires but would like to get suggestions on what kind to buy because i always seem to buy sets that dont work best on car. and also any other advice on my miss firing problem would be great. thanks

 

Do you know if they or you changed out the HG before boosting?

 

yeah he put on a thicker HG i know for sure

 

Your prolly having a fuel prob. Do you know if your fuel pump can handle what your doing? Next inline is your fuel filter, how old is it? Next is your fuel pressure, is it set correctly? Then theres your injectors...are they big enough?

Im assuming you have a NA-T, Im not sure if you have to run colder plugs or not on this motor if you turbo it.

If your running a T70 or any turbo on a stock NA ECU alone, your gonna have probs no matter what.

 

OEM wires and NGK3330 plugs

Jonny

 

A T70? Like an ebay/xspower "T70", which really isn't a T70 at all? It won't be causing your misfiring, but anyone who puts on that turbo is likely to have messed up a lot of other stuff.

Is it "misfiring" under boost or just idling? Have a wideband?

Ian

 

naw its not an ebay turbo..it miss fires all the time pretty much..i got no wideband yet.

 

SC300Boost,
Immediately stop driving this car around mis-firing an untuned single turbo ! It is in serious danger of major damage. You've been very lucky, but god help you if you put your foot in it and stay in it, like bang, smoke and $$$.

Your car must have as a minimum a piggy back fuel computer like the $300 Apexi Neo and immediately put this car on a dyno and have it tuned. Get a handle on this or your engine bites the dust.

 

Under what conditions it misfires? Turbo brand or types (Ebay or not) won't cause misfiring. The timing may be off. Fuel could be a problem, but it's not likely to cause misfiring. It could cause fuel problem such as too lean (can cause misfiring, but more likely is pre-ignition). This is dangerous. Or too rich. Stock sparkplugs are hot and that's serious. The cheap NGK V-power will work wonderful. I'm using them for $2/each. Any Platinum type is hot and bad for FI engine. The auto part store might not know which plug is hot or cold. The cold plug has lower number. Check here: http://www.ngksparkplugs.com/tech_su...x.asp?mode=nml.

If you tend to run low boost up to 8-9 psi (max), you must have these components to be safe.
1) Hi-flow hi-pressure fuel pump such as Walbro (cheap & required for any setup)
2) A FMU with a fixed ratio of 12:1. The Vortech is best, but other brand can be used.

For more than 9 psi, I actually recommend 8 psi for the above setup, you'll need to replace 6 bigger fuel injectors. The cheap deal is to look for TT Supra injectors that have 440 cc/min. Then you must have a piggy back fuel controller such as the APEXI, Greddy...etc, and a proper tuning.

Other route is to run extra injectors with the injector controller.

Another cheap route is run (6) 295 cc/min injectors (yellow) or 315 cc/min injectors (light green) from older 7MGE Supra. You still need to run the FMU to raise up the fuel pressure, and the Walbro. The car ECU will learn to adjust at idle with bigger injectors fine. The 315 cc injectors might start the engine a little bit harder but they're still ok and allow you to be in the safer range than the 295 cc injectors. This setup up doesn't require any tuning and you'll be able to boost up to 10 psi safely.

You must have a wideband A/F gauge to monitor your A/F condition. The best deal is AEM. Don't use the cheap gauge. Second importance is a boost gauge. Without tuning and no idea of what the previous owner did, you're in the hot zone...Good luck.

P.S. I'm not trying to sell the injectors but I have 6 extra Supra 315 cc injectors. Just in case you're interested, I'll let them go for $50 cheap.

 

First things first, we need to know EXACTLY what has been done to the car. You havent provided us with enough info to determine the cause. FIRST, what ecu are you running? Do you still have the stock NA ECU? If so do you have any management at all? All these other things like plugs, injectors, can be a factor yes. But we need to know what exactly you are working with before we can really begin to help you, otherwise you will get nowhere fast. If you don't know, then you need to find out, in the meantime I would suggest not driving this car at all if you can help it. If you don't know how to look for something, or what something is, just ask, or take pictures, and it gives us something to work with. Good luck

Jon

 

When I was NA-t a few years back, I would get misfiring a lot due to lose intercooler piping (check to see if the clamps are tight right around the throttle body area). Especially if you're using regular clamps, I suggest you switch to t-bolt clamps. Also, reusing existing gaskets may cause exhaust leak, and that may be a problem too. For the plugs, I'd use NGK3330. Use NGK wires also, not that there's much of a difference though. You can get away with Supra ma70 NGK wires. They should fit, and blue looks good under the hood. Your tuning may also be off, depending on when the previous owner did his last tuning. It's really hard to take over someone else's turbocharged vehicle, because you know nothing about it. Start off with the minor stuff first, and work your way up. When you do the plugs, you might as well replace the throttle body gasket. NA-t's are known to burn up plugs quite often. Get the gasket from Toyota. Let me guess, you don't have much experience with Turbo; do yaa?

 

what are your symptoms when you say "miss firing"?

 

well i def. not driving it for right now being in this condition...tomorrow i am getting new plugs, wires, gona check exactly what fuel pump i have it in because the guy i just bought it from didnt know much bout this car anyway..i am taking my car to sound performance in chicago i am thinking in like 2 weeks i know it is untuned for this size turbo. thanks for all the info and just found out the guy has a wrong downpipe for my turbo because there is only one bolt holding it to turbo because it had a completely different flange so that was scaring me a little bit need to fix that and try a tune

 

Sounds like a good idea. That, a wideband, and an EGT would be a great start.

Ian

 

After you fix the bug, dyno it and show us some numbers...