New Owner - New Member - Stumped by Fuel cut and codes

[Jebadoo]

Hi guys, I'm new to the forum and very new to the Supra world. Just picked up a 1987 Turbo Targa 5 Speed a few days ago. Minor issues that I've been working on.

I've driven it for a few days now, running slightly rich. Decided to pull codes from the Diagnostic. I got these: Code 21, 42, 43, 51. Now I've developed a few cut though it was boosting fine for two days.


My BOV is vented to the atmosphere and my speedo doesn't work so I know that's why I'm getting the one code. As far as 21 I'm pretty sure that's why I'm running rich and I need a new 02.

However, would a combination of these codes cause the car to fuel cut under load say around 3 - 4k?

I'm trying to figure out what may be causing this as the car holds steady vacuum (25 mmHg at idle) and idles a little high (1000-1200 rpm)

Any information would be great. Thanks guys!

 

[radiod]

What boost pressure is it fuel cutting at? Have you checked for boost leaks with a DIY boost leak tester?

1000-1200rpm is fairly normal for warming up, what's the coolant temp getting to?

 

[Jebadoo]

Car was warmed up, I suspected that as well. As far as boost leaks, it was dark and my gauge currently is unlit ( previous owner rigged it together). I was pulling a consistent 6 psi. Entire system is hard piped minus the intake to turbo. I won't have a chance to check today due to my schedule but I don't understand why it would be fine two days in a row ( minus rich condition and stalling sometimes due to my terrible shifting) to boost cutting every time I get on it.

 

[D.J.T.]

for oxygen sensor buy it off of rockauto.com
It's OEM (denso) for way less than any local auto parts store.

Code 42... does the speedo cable send signal to the ECU? i doubt it? Waiting for someone to chime in.

 

[Jebadoo]

speedo cable turns speedo, VSS sensor is in the cluster, not worried about code 42 too too much. Mainly 51 and 21. 42 and 43 are stupid things That shouldn't cause the issue I think. 42 is speed sensor, 43 is starter signal(?)... . 21 is o2 sensor and 51 is some crazy grab bag that involves the TPS(?)

 

[suprasick]

[strike]Code 51 would be knock sensor. 9/10 times the knock sensor wiring is to blame. Search knock sensor and there is a rewire guide. (I used shielded cable from radioshack that worked great.) I would take care of this first as the engine will pull timing and run like crap.[/strike]

I apologize for the wrong info as this is the tech section, here are some threads to help you.

http://www.supramania.com/forums/archive/index.php/t-46793.html

http://www.supramania.com/forums/archive/index.php/t-101668.html

http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?S=FI&P=26

 

[Jebadoo]

I thought code 51 didn't involve the knock sensor? Thought it was just TPS, A/C, and Neutral Position?

 

[Jebadoo]

I guess what I'm trying to ask is would the code 51 and 21 cause the odd fuel cut? Or should I still try to trace down a boost leak or bad vacuum line?

 

[Turbo Habanero]

No they would not.

When you check codes make sure you have the a/c button off for starters.

And you more then likely caused a boost leak in the past couple days (it happens) start with a DIY boost leak tester and check all the intercooler pipes are connected good.

A boost leak would be the likely cause of fuel cut because at 6psi you are no where near fuel cut..

 

[Jebadoo]

Wouldn't surprise me, would the manual boost controller that's practically blown apart cause the issue? I'm guessing yes?

 

[Turbo Habanero]

Wouldn't surprise me, would the manual boost controller that's practically blown apart cause the issue? I'm guessing yes?

Yes as it would allow to much boost.

Fuel cut on stock AFM is about 11-13psi

 

[Jebadoo]

Well, its blown apart but still reads no more than 7 psi at the gauge. But I'm assuming that if its internally broke (which I assume it is) the boost would leak off through every orifice throughout the controller, correct?

 

[jetjock]

If it was really fuel cut they'd be a code. Since there isn't it's not.

 

[Turbo Habanero]

replace the boost controller with a small piece of hose.

And jet jock is right

The jerking your feeling is tour Tps more then likely

 

[jonahs_supra]

jetjock is right
when fuel cut happens the ecu sets a code

i would test your tps and afm
only reason i suggest testing afm is mine did the same thing and it was due to my afm being bad when the climate would change(intake temp sensor part of afm was bad)

 

[Jebadoo]

Fixed! Boost controller literally blew apart, back to running stock boost for now.

Going to order new o2 and speedometer cable tomorrow. Then I've got to figure out the wiring nightmare behind the cluster behind the cluster the previous owner created because I only have needles lit up.

Once I get a new controller, how much can I safely turn it up to? Also I've got to figure out why I have a clunk from the rear when I get on and off the throttle. Wont lie, this car is awesome, but rather muddled

 

[Turbo Habanero]

Safe boost on stock turbo is 10-12psi

 

[Jebadoo]

That sounds good. I mean I'm happy with the power it has now on around 6.5 psi. But after I felt the pull this thing had when the controller blew apart I don't know how long I'll be satisfied at stock boost.

Definitely got to figure out the issues with the clunk, drives me crazy. Almost sounds like the backlash noise in an old Ford truck, hoping its something stupid and simple and not the differential itself.

 

[Turbo Habanero]

That sounds good. I mean I'm happy with the power it has now on around 6.5 psi. But after I felt the pull this thing had when the controller blew apart I don't know how long I'll be satisfied at stock boost.

So did the Fuel cut/jerking go away once you fixed the boost controller ?

 

[Jebadoo]

Yea, the guy had it rigged up in a terrible spot and it was one of those junk built EBay specials. Didn't notice that it literally blew the entire center section apart until I found the controller buried underneath the intake.

Now it it running consistent boost, I'm going to need a new intake pipe due to the stock rubber one being ripped pretty good ( temporarily fixed with electrical tape) but like I said, I don't want to get too crazy with it until I get the snow tires off, fix the speedo and dash lights, then onto figuring out the clunk....