Bogging down???

Ohsnap06

You know how I roll
Apr 22, 2008
30
0
0
33
Cleveland,Tennessee
Man, where do I begin? Alright, so about a month ago my car would just bog down super bad at about 3500 RPM as soon as it built boost... My dad and I were convinced it was the Mass Air Flow sensor... So we cleaned it and for some reason that fixed it.. then it came back so we tried the same thing but it didn't help it at all.
Ever since I got the car it has been throwing the knock sensor code.
My dad is a mechanic and owns his own shop, but he knows more about doemestic cars than imports. He knows a guy that built up an MkIII Supra so, we figured we would take it to him.

The guy was convinced it was the knock sensors. He fixed them after about a week of me not having my car. I think all he did was rewire them with some pretty thick cable. I went and picked up the car and it was doing the exact same thing. It was terrible because you have to make sure you have about 30 seconds to get to the speed limit before you pull out in front of someone. As soon as the car would build up boost and would just bog down bad. The only thing was that it's only when driving and not sitting at an idle. The boost stayed up fine on the gauge and never went up and down or anything. So, I knew it wasn't the turbo.

So, my dad figured it was either air or fuel. The guy that fixed the knock sensors put a new AFM on it to see if it was that and it did nothing. So my dad and I decided to change the fuel pump for the second time in just about 4 months. We pulled the fuel tank and pulled out the pump and sock was full with rust and all kinds of other bull crap. The car had been sitting about a year prior to when we bought it so we figured that's what it was. So we changed the sock and it was all good. It's just that when it gets low on gas it runs like absolute crap.

The only thing is now it seems like unless I have a full tank of gas the car isn't running like it should. It used to build up boost quicker but I dunno. It may be just me. I was just wondering has anyone else had this problem?

Also I thought about cutting off the converter on the down pipe which would officially make my car illegal but Georgia and Tennessee don't have emissions test. I was thinking that would give me more power. I looking into getting a intake system too because from what I've read it helps a lot. If you have any suggestion for what I should save my money for let me know. Oh yeah, and the cutting the converter thing off would be free since my dad has a muffler and brake shop.

Thanks
 

7MGTEsup

Formerly 'Down but not out'
Jun 14, 2005
614
0
0
England
Sounds like you have a fuel pickup problem. A downpipe will make a fair bit of difference, that cat has seen 20 years service so will be fairly clogged and supplying your turbo with backpressure that it doesn't need or want. Get some 3" pipe and make your own exhaust let the engine breath.

Also worth looking into is the wiring for the pump is old and could have a high resistance causing voltage drop.
 

Ohsnap06

You know how I roll
Apr 22, 2008
30
0
0
33
Cleveland,Tennessee
Down but not out;999436 said:
Sounds like you have a fuel pickup problem. A downpipe will make a fair bit of difference, that cat has seen 20 years service so will be fairly clogged and supplying your turbo with backpressure that it doesn't need or want. Get some 3" pipe and make your own exhaust let the engine breath.

Also worth looking into is the wiring for the pump is old and could have a high resistance causing voltage drop.


Thanks man, I'll make sure and check that stuff out.
 

Supra87T

2-Tone BLUE
Feb 23, 2006
135
0
0
Cincinnati, OH
You may also want to check fuel pressure to make sure that the motor is getting enough fuel. The lines may be clogged. Have you change the fuel filter?
 

Ohsnap06

You know how I roll
Apr 22, 2008
30
0
0
33
Cleveland,Tennessee
Supra87T;999477 said:
You may also want to check fuel pressure to make sure that the motor is getting enough fuel. The lines may be clogged. Have you change the fuel filter?


Yeah, we changed that at the same time as the pump.
 

boosted88

New Member
Nov 27, 2007
47
0
0
36
wisconsin
Omg my car has benn doing this for the last 3 months and I keep getting that code 52. I have tried everything to fix it. So when you changed the fuel pump it fixed it? please let me know. Thanks.
 

jdub

Official SM Expert: Motor Oil, Lubricants & Fil
SM Expert
Feb 10, 2006
10,730
1
38
Valley of the Sun
I'll promise you changing the fuel pump did not fix a code 52. It's usually a wiring issue between the knock sensors and the ECU.
 

Poodles

I play with fire
Jul 22, 2006
16,757
0
0
42
Fort Worth, TX
If you're getting a code 52, the ECU is not able to detect knock, so as a precaution, it pulls timing...BADLY

Fix the knock sensor wiring and it will go away.
 

supra_89_vang

New Member
Dec 29, 2005
95
0
0
madison
What is the main reason why lots of people including my self have to rewire the knock sensor. Is the knock sensor wires not thickness for the ECU to read? When rewiring, do you have to completely rewire both knock sensor to the ECU? Also will code 52 clear it self when the problem is fixed or do I have to reset it by pulling the fuse?
Thanks
 

jdub

Official SM Expert: Motor Oil, Lubricants & Fil
SM Expert
Feb 10, 2006
10,730
1
38
Valley of the Sun
The wire is a shielded type...it deteriorates over time and the ground becomes a problem.

You have to rewire both sensors.

You will need to clear the ECU code after you fix it.

Shaeff sells a rewire kit for those that are a bit "wiring challenged" ;)