CODE !@#!$$%%!

[SupraBo]

:1zhelp:

Ok guys I am stumped here. I just put the new motor in the car and have been driving her around. Besides some little oil leaks and some other odds and ends she is running pretty good.

The car sat for some time, I got a new gas tank, fuel pump and new fuel filter.

Well heres the problem, I got a code 25

I looked it up and pretty much if its under the hood it could be the issue.
Here are some of the symptoms

It’s a little smoky. I was told that JDM motors have chemicals put into the motor for shipping purposes also I put oil in each cylinder. The motor has 200 miles on it so I doubt that’s the issue anymore
Under full throttle there are no issues, it’s all at idle. When I let off the motor drops to less then 700 rpms if not completely dies. Idle when cold is anything but.

Also it pulsates idling, the check engine light comes on when idling. Driving around it goes away.

I would like to say to JetJock that I read a lot of your posts. You have a lot of useful information and I thank you for sharing that.

I probably left something out so let me know,

 

[SupraBo]

oh yeah, i have a welbro 255, would the j-tube have anything to do with this? it isn't blocked off

 

[jetjock]

Since you asked nicely

Code 25 is because the O2 sensor stopped cross counting and stayed hard over for several seconds. Fuel pressure could indeed be one of many causes. What is Vf at idle? Not sure what you mean by the J tube being "blocked off". Did you leave it as is when you installed the pump?

 

[SupraBo]

JetJock,
in this link it says the J tube will produce to much vacuum for FPR. with aftermarket fuel pump, its in the stock configuration right now

I do apologize for the next question. But im not sure what VF means, im assuming it means fuel to air ratio.

How would I test this?

http://www.supramania.com/forums/showthread.php?t=34548

 

[jetjock]

Well, the mighty shaeff's words in the first paragraph of that link stand on their own merit. What part of "it's essential to bypass or drill out the stock j-tube" didn't you understand? You can't install a high flow pump without opening up the J tube or the pressure in the fuel system will be too high. Remove the restriction.

Vf is the signal that tells you what the ECU is doing to correct for a mixture imbalance. Connect a voltmeter to terminal Vf (in the diagnostic block under your hood) and battery negative to read it.

 

[mhopemk3]

FYI SupraBo, Idle should be around 650.. Mine idles around there with no problems..

 

[ForcedTorque]

It's also much easier to bypass the J-tube than drill it once the engine is in the car...

The symptoms also could be a bad/misaligned TPS sensor. You can find all kinds of info regarding how to check/fix that if you search or look at the TSRM.

Cut him some slack on the search thing. The guy has 9 posts, and already knows that Jetjock is one of the more knowlegable guys here. He's obviously done Some searching.

Why don't we all just buy a TSRM, read it, and become mechanics. Who needs this site for discussion anyway. Everything I know about my Supra, or any other mechanics, I have learned either here, or on my own while parting one of these cars. I was like the OP in that I had no idea about Vf, and I know have an answer. I couldn't have found the 2 letter thing in a search if I would have gone looking.

 

[SupraBo]

Well thanks forced torque :icon_surp

I consider myself car savvy but when it comes to these cars, I’ll be the first person to say I’m not an expert.


But listen to this… I bypass the J-tube, much MUCH better. The only thing is I went for a spin and wow, much more power.

I turn around to head back home and nothing… it was running like my mass air flow sensor was disconnected or there was an intercooling pipe came undone. I was kinda pissed but I thought it was something simple.

So I pop the hood and nothing. Everything is intact. I limped her back home and starting playing with connections and nothing seemed to change. I ran the diagnostics and it threw a Code 51… by the way let me tell you that obd1 sucks

I figured it was the TPS, so I replaced it with another one I had laying around. And nothing still the same
It wont rev over 2000 rpm, If I put the pedal all the way done it wont go over 1000rpms

When I look at my boost controller while doing this the manifold pressure wont go positive

 

[JesseH]

Well thanks forced torque :icon_surp

I consider myself car savvy but when it comes to these cars, I’ll be the first person to say I’m not an expert.


But listen to this… I bypass the J-tube, much MUCH better. The only thing is I went for a spin and wow, much more power.

I turn around to head back home and nothing… it was running like my mass air flow sensor was disconnected or there was an intercooling pipe came undone. I was kinda pissed but I thought it was something simple.

So I pop the hood and nothing. Everything is intact. I limped her back home and starting playing with connections and nothing seemed to change. I ran the diagnostics and it threw a Code 51… by the way let me tell you that obd1 sucks

I figured it was the TPS, so I replaced it with another one I had laying around. And nothing still the same
It wont rev over 2000 rpm, If I put the pedal all the way done it wont go over 1000rpms

When I look at my boost controller while doing this the manifold pressure
wont go positive

are you sure you calibrated the TPS right? also you might want to check your ISC (idle speed control valve) If it gets really gunked up or stops working it can have a major effect too.

 

[SupraBo]

well the car was working. i mean i did some full speed runs and then nothing.

 

[Nick M]

51 doen't mean change your TPS. In fact, no code means change a part. It means the circuit is outside of its parameters.

 

[SupraBo]

51 doen't mean change your TPS. In fact, no code means change a part. It means the circuit is outside of its parameters.

that helped thanks lol

i did it because it was just a step in trouble shooting. i wanted to bypass the throttle body coolant lines anyway

if i were to guess on the problem right now it would be the mass air flow sensor.

but the car idles fine (when hot)

im about to put an ls1 in my car. i think it would be easier in the long run

 

[Nick M]

Why do you think the coolant lines on the throttle body? It isn't there because it looks neat.

Why not just pick up a 98 Camaro Z28 if money is that easy? I am not against project swaps, especially with a good engine like that. I just don't get trying to put a round peg in the square hole.

 

[SupraBo]

trying to put a round peg in the square hole.

i like that :biglaugh:

it was more sarcasium, honestly it would be more time then money.


when you have money you dont have time. when you have time you dont have money. you rarely have both :bigun2:

im still learning about these cars. i can read something and pick it up pretty fast but im kinda looking for a quick check point to bypass me swaping parts

 

[jetjock]

There are no shortcuts. Read the TRSM and it'll all become clear. Fwiw the EFI system works pretty much the same as it does in any car, OBD-1 or not. The principles are the same even if the diags aren't.

One tip: Careful with codes because you don't know how old they might be. That doesn't apply to 51 though, it's a code that doesn't get stored in memory. It can only occur in real time.

 

[SupraBo]

Well I feel comfortable working on this car. I just like to ask questions, my car is obviously down right now and I can’t figure it out what’s wrong with it right away. That’s usually not the case.

I thought the turbo froze or something like that so I spun it with my figure and it turns fine.
Everything was intact with the car. I changed nothing.

I thought maybe I jumped teeth in the timing belt but again it idles fine.

It wont rev over 2000 rpms

I bypassed the TB because I burned my f’ing hand on it. I drive the car in Florida and I the last thing I need to do is heat incoming air.

 

[Nick M]

I bypassed the TB because I burned my f’ing hand on it. I drive the car in Florida and I the last thing I need to do is heat incoming air.

Did you know, many cars headed to warm climates do have different features, such as rear window defrost delete.

However, coolant line delete is not one of them. Reading on volatility is a good start. Liquids don't burn, vapors do. And you need to heat liquids to make them a vapor. Luckily, gasoline evaporates easily. But not easy enough. The coolant lines get the intake a little warmer when needed, and just as important, cooler when the engine is hot in summer. It keeps the incoming air somewhat constant in temperature in different seasons. Have you ever opened the hood on a hot summer day and felt the radiation? Coolant is a good heat sink. That is why it is used. It will aborb that engine heat, and radiate it into the air in front of the car with the downstream of air on the radiator.

 

[SupraBo]

im sorry i just dont agree with you.

why have an would i have an intercooler then.

The colder, denser air i have in my combustion chamber. the more power i will produce. thats the bottom line

Whether or not my car doesn't properly heats up, I really don’t care

The concept of heat transfer wouldn’t apply to my throttle body.

 

[SupraBo]

Wow, that's some tough love from a guy with 1,400 posts. I've only got 300 here because I've been the webmaster for Supras.com for about 10 years and helped troubleshoot hundreds of stock and modded cars over that time. I own and have read the TSRM, the electrical, auto tranny and other supplement books for both the 1987 & 1990 and Turbo & NA.

Engine pulsating at idle, car won't idle, car is fine once the throttle is opened a bit, no relevent codes and "I changed the TPS" is a pretty strong indicator that his IDL circuit is open (which means a mis-oriented TPS). 90% of people don't realize that it is important to get the TPS aligned right. Had his problems continued, I would suggest unbolting the ISC and leaving it plugged in. Attempt to start the car and the plunger should move from fully retracted outward. Turn the key off and the plunger should fully retract and you usually hear 3-4 clicks. If the plunger doesn't move, the ISC should be replaced. I have learned that if the plunger does move, it may still be weak and therfore bad.

Now he's saying the car won't rev over 2,000RPM. That is classic dead AFM. Usually someone tries cleaning it with carb spray prior to posting that question. Since his problem seems intermittent though, I'd suggest unplugging and reseating the connector 6-12 times to rub off corrosion.

The smoking was probably due to the "J" restriction driving up fuel pressure but JJ had already covered that.

I really didn't think I would get a rise out of someone on this forum, asking questions.

On this forum like 10% of the people know what there talking about. The other 90% have no freaking clue. And the 10% that knows anything just write the same thing over and over again.

I would think that a "classic problem" would be a sticky.

By the way I remember saying it was the AFM, I unplugged the thing and it ran the exact same. I would replace the TPS over again because it doesn’t throw a code anymore.

is there anyway i can fix my current AFM?

 

[Nick M]

The coolant lines are on naturally aspirated and turbocharged engines. Think about it.

The intercooler is there to reduce engine knock from too high of temperatures in the intake. If the coolant lines were a problem, the coolant lines would not be there.

So your throttle body is supernatural and does not have to abide by the laws of physics. How interesting.

*shoveling faster*

Anyway, it is your car, I just want you to understand the consequences. An airflow meter is repairable, but I would not bother. There is an LED inside, a photocoupler, and a mirror that vibrates in the airstream. They are delicate and precise. I don't know about changing them, I would get another meter, if I can verify it is bad.