Engine cuts-out above 2000 RPM - Codes 41 and 52

[jessemkiiis]

Hey guys I have a 1988 turbo 5spd supra, Ive been working on it for some time now, The problem im having is the car wont rev past 2000 rpm.
the car starts fine, idles like a dream ect..
I have two CEL's TPS and Knock sensor
Ive done some homework but as far as i can tell neither of these should cause limp mode.
What will constitute limp mode?
My turbo is a modified CT26 with 3" downpipe and exhaust
stock intercooler and piping. nothing major.
Walbro 255
It has a Turboxs boost controller but it is all the way down.
my timing may be off some but nothing drastic(Im waiting on my friend and his timing light)
This is the only thing stopping me from taking it to be tuned and driven
Any help will be greatly appreciated.

 

[steven89]

IIRC Code 52 [knock sensor] can cause limp mode. Also, is your TPS set right?

 

[jessemkiiis]

I did calibrate the tps but it was off my parts car, thats good news about the knock sensor though, I plan on purchasing a new Tps.
should I try the KS rewire befor replacing the sensors themselves?

 

[steven89]

Well first off id check and see if the knock sensors are even plugged in. I would also check on the condition of the wires for em.

So you calibrated the TPS with throttle closed and checked full open [resistance?] and etc?

 

[ben1984j]

IIRC Code 52 [knock sensor] can cause limp mode. Also, is your TPS set right?

Not "limp mode" like he's experiencing...Code 52 will only cause timing to be retarded, and fuel mixture enriched. The motor will still rev all the way to redline...

I did calibrate the tps but it was off my parts car, thats good news about the knock sensor though, I plan on purchasing a new Tps.
should I try the KS rewire befor replacing the sensors themselves?

You should definitely do the rewire first, it usually (not always) is enough to fix a code 52. If it doesn't fix it then one of your sensors is bad (or even not plugged in as steven89 said) but either way you need reliable wiring to them...


Your problem sounds very similar to AFM fail safe mode, where the car won't rev over 3000 rpms or so. None of your codes are AFM-related though, so you should check for an intake leak (i.e. cracked hoses). As I understand it, this will have the same effect as a malfunctioning AFM, since you'll be pulling in excessive (and unmetered) air. I remembered reading about someone with the same problem awhile ago, this was the thread:
http://www.supramania.com/forums/showthread.php?t=102096

 

[Kevin]

Your problem sounds very similar to AFM fail safe mode, where the car won't rev over 3000 rpms or so. None of your codes are AFM-related though, so you should check for an intake leak (i.e. cracked hoses). As I understand it, this will have the same effect as a malfunctioning AFM, since you'll be pulling in excessive (and unmetered) air. I remembered reading about someone with the same problem awhile ago, this was the thread:
http://www.supramania.com/forums/showthread.php?t=102096

i had the same problem (wouldnt drive past 3000rpm) it was an intake leak + boost leak which cause it, i replce my accordian hose (it was cracked) and the coupler between the 3000 pipe and the throttle body and that fixed it.

you should definetely rewire your KS, i recently did last month and it got rid of my code 52. Code 52 wouldnt cause your problem though. Shaeff here sells a great rewire kit if you are too lazy to put everything together etc. i bought it off him and it's real straight forward to do. took me 10 mins to do. he has detailed instructions.

 

[jessemkiiis]

My car dosent drive to 3k and stay there... WHen i drive it it will go to 2k maybe a little farther, but when i get there it cuts out. no sputter or strange noise. just like fuel cut, or i let off the gas.
now that i think about it, its like my wastegate dumps. the sudden deacceleration when you shift... thats what it feels like

 

[jessemkiiis]

Ok so i just went to make sure my wastegate wasnt opening prematurly, and its not...
One more thing when i start my car and it idles there are no CELS
as soon as i rev it far enough to make it cut out, pop! CEL

 

[Poodles]

Yep, it's what happens when you blow an IC pipe off, do a boost leak test, but only after fixing the other codes.

 

[jessemkiiis]

Ive checked all the clamps and it has a new accordian hose, could it be the stock intercooler? Im going to fix the other codes while I wait on an intercooler kit to come in.
My boost gague stopped working the other day.... one thing right after another

 

[Poodles]

If you blew a pipe off it would appear to not be working...

 

[jessemkiiis]

could a pre turbo leak cause the same problem? like one of the connections on the accordian hose?

 

[Poodles]

The ECU is telling you what's wrong by showing you the error codes...start there.

 

[Kevin]

could a pre turbo leak cause the same problem? like one of the connections on the accordian hose?

leak between turbo and afm (acordian hose) could cause it... actually ANY leak before the afm could cause it.. after the afm wouldnt affect it (the airfilter/ plastic thing)
i say check everything for cracks... a lot of the ic piping will look alright untill you squeeze it to find the leak/crack.. so you gotta take the clamps off and tate the ic hoses out and thoroughly inspect it.. escpecially the pipe connected to the turbo. both the accordian hose and the one ic pipe under are common places.. also check the coupler between the 3000 pipe and the throttle body.... its also a common place.

and take care of your codes...and dont forget to clear them everytime you do/fix something.

 

[jessemkiiis]

Ok so i chased all my intercooler piping removed and inspected. no boost leak....
the coupler between 3000 pipe ant tb is new i replaced it today, after i retightened all the clamps the car revs to around 3k now. I havent got to test drive it yet will do tomorrow.The only possible leak that I can think of would be the intercooler...
I have not fixed my codes yet but I have collected new knock sensors and wiring. No tps have to wait till payday for it. thanks for the help guys ill keep you posted

 

[jdub]

Would someone care to explain to me exactly what "Limp Mode" is and what it's symptoms are?

 

[Kevin]

it's called fail safe mode not limp mode

 

[jdub]

^^^ Exactly! "Limp Mode" is a BS term...it does not exist.
A mode that does not exist has no place in any Tech section discussion....period.

There is also a back-up function for ECU microprocessor failure...this is bad.

Do any of you guys have a clue as to what causes the TCCS to go into fail-safe mode and what the ECU does as a result for each?
Hint: There are 9 different sensor malfunctions that will result in fail-safe.

Jesse - Exactly which TPS code do you have.

 

[jessemkiiis]

My codes as of now are 41 tps, and 52 knock sensor. I've always called it limp mode didnt know the tech. version, srry thats why there was a ? in the title....

 

[jdub]

Well now you know. The term is bad because the ECU substitutes values based on what sensor has failed. In your case, both a code 52 and code 41 will cause the ECU to go into fail-safe. The knock sensor failure will set the max timing retard angle...the car will run like crap, but not cause the sputtering above 2000 RPM you describe. It will make the following worse.

Code 41 is way different than the usual code 51 most people associate when you say "a TPS code". This code concerns VTA (throttle position) and the ECU sets a fixed TB plate open angle when it goes into fail-safe. This can and will cause the problem you describe. Suggest you focus your efforts here.

Being more specific would have saved 10+ posts in this thread...might want to think about that in the future.
I changed the title to something a bit more useful