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Can't wait for Spring!
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Discussion Starter #1
alright... so i'm shooting some footage for a video i'm planning on doing featuring my car. I'm crusing about 55mph on the highway and i'm video taping the boost gauge. So i step on it, its boostin about 6psi then STOP!! All of a sudden, the car jolts, felt like what others have described as fuel cut... But i'm an NA, no fuel cut for me. So, i'm a little freaked. I richen up the a/f's on my safc cause my first assumption was detonation. So i try boosting again, i get to 2 psi and it stops again and jerks. So i pull up to a stop sign and its idling bad, real jumpy. I put it in first and try to go and the engine dies. So i'm thinking bhg or vapor lock. So, i start it up and it gets going, i get to town and fill up with new 93 octane gas. I then let it idle for a while, its still kinda rough, so i rev it to 2k and hold it. It stays but about every 5 seconds it dips about 300 rpm and makes a wierd "ching" noise. It moves fine now, but still idles a little rough. There are no other strong indicators to a bhg. no smoke, no dirty coolant, temp gauge is fine, oil pressure fine, egt's fine. there was a small amount of gurgling under the dash, but i just pulled the engine, i don't expect the cooling system to be rid of all air.

For those that don't know, i'm driving a 86.5 na, with a turbo on it. SAFC, EGT, 440 injectors, 93 pump gas from mobil. I pulled codes and it gave me either an 11 ( bad ground) or a 1. I did notice that i got shocked by the afm when i touched it...

please help, i appreciate it. --jon
 

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Could be an AFM problem...but honestly it kinda sounds like an exhaust issue..Any other problems with it..and more description you can give as to what you have done or have figured out not to be a problem..
 

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Can't wait for Spring!
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Discussion Starter #3
i thought i heard awhile back that some dude was having problems and he got shocked by his AFM, so he grounded it and it resolved evrything. I think i'm going to try grounding the AFM and see if that helps. This is wierd cause it was working perfectly fine and now it jolts under boost and idles wierd.

I talked to Dr.j and he asked me some questions but we didn't really get anywhere. My EGT was 1000F which is what i normally run at highway speeds (1000-1200) oh and the EGT probe is behind the turbo. My oil pressure was a hair under 40 in/lb2, the temp gauge never rose at all, it stayed one line under halfway the entire time. My vacuum gauge is reading normally -16 during idle, and -20 during hard decelleration. My SAFC is tuned correctly, its never had any issues before.

I checked the coolant, the level is fine and its clear/green. There is no smoke coming out of the exhaust and the manifold, turbo, elbow, DP, and cat back are all snug and not leaking. My TPS is working fine, and my fuses are all fine.
did i miss anything?
 

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Can't wait for Spring!
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2,364 Posts
Discussion Starter #5
i put a groundstrip on the AFM and that helped with the bad idle, but it still doesn't hold an RPM, specifically 2000-2500 very well. It'll hold it, then rev down 300 rpm, then rev back up, and during this it'll make a strange noise. Like the engine is hiccuping. lol. So, i starting playing around with the SAFC, and i noticed a direct correlation between the hiccups and the tuning. The Richer i set the SAFC , the less freguent and less dramatic the hiccups occur. i played around with the SAFC on the low settings and pretty much eliminated these hiccups.

These are my settings right now...
#RPM (SAFC CORRECTION)
low throttle
1000 to 6500 ( 0%)
High Throttle
1000(0%)
1500(+3%)
2000(+5%)
2500(+5%)
3000 to 6500 (+7%)

Keep in mind these are with 440 injectors.
 

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Member Bushwood CC
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357 Posts
I just had to replace the electronics in a 90T that I did a HG job on. Car ran fine until idle, the it would die. I tried everything to get ti running right, checked the codes and AFM kept coming back, code 31 or 34, can't remember. Anyway, put different electronics in the AFM and now the car runs like a dream.

I never got shocked though.

HTH
 

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Jon if stock NA's run around 300 cc injectors and you are running 440's, I'm kind of suprised at you having to add fuel. Do stock NA's run lean from the factory? I would think even with the added boost you would still have to lean you system out somewhat being that you are running injectors that are close to 50% larger than stock and make no mention of an adjustable fuel psi regulator. If stock fuel psi specs are 33 to 37 psi idling this is alot of fuel your pushing through your NA-T. Have you checked the basics? What do your plugs look like? Do you have any vacuum leaks? 16 inches of vacuum at idle is alittle low. You should be at around 18 to 20 inches at around 650 rpm. Have you checked you entire intake system from the throttle body to the afm? You might also check all your grounds from the battery to the engine and the engine to the body as well as your ecu grounds. It would be a bad idea to add a few extra grounds from the battery to the shock tower, head, and intake manifold. If nothing more they have managed to pick up alittle power by doing so.
 

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i had the same problem for a week, LOL

after installing my BOV, i didnt tighten the IC piping connecting to my IC, i also hade a pin hole leak on the stock plastic IC, so it forced me to use an alluminum piece. yes it was a boost leak,

after 2 weeks it started all over again, this time after i installed the S-AFC. the wires to the AFM signal on the S-afc to the ECU had become loose ( duct tape, lol)
so i crimped them and problem went away. no signal was being sent to the ecu.

first check your mechanicals then your elctrical, who know your S-AFC may be acting up. easy way to find out is disconnect the S-AFC, ( i disconnected the power, and connected the AFM signals back together for the ECU. it should work.
 

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i thiught at idle you should have right about -20psi. at least my na-t always sits fronm -19.5 to -20.5 and on deceleration it hits about -24. Although i do think i hit fuel cut today(running gte electronics) it was quite scary. maybe you have a boost leak.
 

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Can't wait for Spring!
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Discussion Starter #13
X-Man
Sean, i did an entire intake system check. Nothing. Not a single problem. My low throttle settings were at like -27% at idle and between -20 to -16% through the rest of full throttle. Its just this wierd "hiccuping" goes away with more fuel. I don't get it. I'm up at college now but when i get back i'm going to check the intake again and check timing. The plugs, brand new, were just inspected and they had little wear. As much of a noble effort i am giving, i think this project is really giving me a headache. I did notice a wierd idle after i messed around with the bov, but its nice and snug now. when i first started the car it was idleing normally but the bov wasn't releasing boost. I need to spend more time on this.

mk3supraholic
Tell me about it. lol


As a general notation...
My spec stg2 clutch feels a lot different now, compared to 200 miles ago when it was still new. It engages a lot harsher now. When i first started driving it felt like the stock clutch i just took out, now i have to be careful cause i spun the tires just by gently releasing it...
 

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LEADED FUEL ONLY
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2,068 Posts
You absolutley 100% need to get a wideband on this thing. I bet you're running VERY rich. I've experienced very similar symptoms on my car.
 

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Jon I agree with Alan, you will be happier if you get a wideband and an adjustable fuel psi regulator on the car. Normally if you are having to add fuel where you didn't before it would sound like you are picking up air from somewhere leaning it out. What kind of shape is the rest of your ignition in? Your cap and rotor and your wires? Goog luck and call if you need too.
 

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Can't wait for Spring!
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Discussion Starter #16
thanks sean, the cap rotor and wires are new as of last year. I think i'm really going to start evaulating my options. I need to set myself some goals and determine what i want out of this car. If i want to keep this engine, i'll invest into some serious engine tuning devices, if i want a powerful 7m, then i'll probably get a jdm clip or a nice gte, if i just want a powerful mk3, then maybe a 1jz is in my future. The car isn't being run right now so there isn't a real urgency on this problem.

What is a good wideband brand?

Thanks for all your help guys.
 

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the DIY-units get the nod in the price category

AEM is a good compromise between price and ease of use

FJO is a very good unit with many options, but is probably one of the more costly ways
 

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Can't wait for Spring!
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Discussion Starter #19
sweet, thanks
 

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25psi = 14" brakes :)
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PLX all the way.
Less than 300.00 with the sensor, and they are accurate too.
 
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