car goes crazy once warm WTF?

[jtt220]

When I drive my 95 240sx (sr20det swap, stock MAF, turbo, FMIC, piston type BOV non-circulating, JWT ecu) when the engine is cold, it runs great. After the engine gets up to operating temperature it bucks, smokes, and generally runs like shit. Exspecially when trying to hold thottle part open for extended periods (over 5 seconds). Anybody have any idea what is going on?!?
:wtf:

[Ghettokracker71]

dammmmmmmN! hope you can get it fixed soon!

[jtt220]

nobody has ever experienced this?

[zero.counter]

First I must ask, did you upgrade the radiator? Have you cleaned the MAF, throttle plate, and checked hoses (air relevant)for any leaks. I would recommend checking the AIT sensor but you have an SR. The thermostat and water temp sensor for inaccurate readings. Alot of this (electronic problems) can be diagnosed with a multi-meter whichh has proven to be very useful.

Then check fuel pressure, injectors, ignition spark...

[jtt220]

I should have been more specific.... I have checked the obvious things that I could think of; vacuum lines, intercooler and piping for leaks, cleaned the MAF, checked spark, timing, changed fuel filter, and checked fuel pressure.
I can try ohming out the thermostat and water temp sensor, but do you know what the range I should be looking for is? Also, when I rehooked my MAF up after taking it out to do some cleaning up of the wiring harness, I accidently switched the signal wire with the power wire. It started and I drove it about 30-40ft with black smoke blowing out the tailpipe before I realized what I had done (duh!). Judgeing by the soot in the tailpipe I can only assume the tops of my pistons have some oil deposits on them. Maybe this would cause a problem with combustion? But then why would it only be when it is warm? And why only at steady or slightly off throttle?

[Ghettokracker71]

I should have been more specific.... I have checked the obvious things that I could think of; vacuum lines, intercooler and piping for leaks, cleaned the MAF, checked spark, timing, changed fuel filter, and checked fuel pressure.
I can try ohming out the thermostat and water temp sensor, but do you know what the range I should be looking for is? Also, when I rehooked my MAF up after taking it out to do some cleaning up of the wiring harness, I accidently switched the signal wire with the power wire. It started and I drove it about 30-40ft with black smoke blowing out the tailpipe before I realized what I had done (duh!). Judgeing by the soot in the tailpipe I can only assume the tops of my pistons have some oil deposits on them. Maybe this would cause a problem with combustion? But then why would it only be when it is warm? And why only at steady or slightly off throttle?
Do SR's have a TPS?

[jtt220]

Yes sr's have a throttle position sensor, do you think my problem could be related to it?

[Ghettokracker71]

Yes sr's have a throttle position sensor, do you think my problem could be related to it?
Sounds to me like it could be a TPS.....you should proble check it

[jtt220]

Where is it? And do you have a recommended way to check if it is functioning properly? Where can I get I get a new one? Sorry for all the questions!

[Var]

You can check the tps with a multimeter. with the key on, engine off, the tps should read about .5 volts with no throttle and about 4.5 volts at WOT.

you can also check for bad spots in the tps


you need a digital oscilliscope to check it. hook it up to the tps, turn the key on, fully depress and let go of the throttle over a period of 1-2 seconds. look at the line on the screen. it should go up and down smoothly. if there is any fuzz in the line(which should show on the incline and decline at identical places) the tps has a bad spot

i dont think the tps is causing this, but it's not impossible

[jtt220]

Do you have a theory(S) of wwht the problem could be? Thanks for the info, I will check it out within the next few days. By the way (me swollowing my pride) where the hell is the damn TPS?

[Ghettokracker71]

Do you have a theory(S) of wwht the problem could be? Thanks for the info, I will check it out within the next few days. By the way (me swollowing my pride) where the hell is the damn TPS?
sorry don't know on an SR myself either....I use KA "power" :).....and everybody had to learn sometime

[91rusty240sx]

how about your o2 sensors? they couldve taken a dump cause your o2 sensors start working once your car is properly warmed up. everything else relys on it to decide if it should run rich or lean.

if you had an oscilliscope, you could check the o2 sensor. the voltage running from it should be high and low, high and low. it should not be high or low, because that means that its constantly running rich or lean.

[Ghettokracker71]

how about your o2 sensors? they couldve taken a dump cause your o2 sensors start working once your car is properly warmed up. everything else relys on it to decide if it should run rich or lean.

if you had an oscilliscope, you could check the o2 sensor. the voltage running from it should be high and low, high and low. it should not be high or low, because that means that its constantly running rich or lean.
good idea:)...I'll second that idea hah hah

[jtt220]

hmmmm....I'll see if i can get ahold of an oscilliscope. I think my neibor is a electronics tech, I'll knock on his door and let ya know....

[black s13]

the TPS is on the throttle body, oppostie the throttle "pulley" or whatever its called. its a little black box with a plug on it.