300zx tt hesitation / pulsating

[Dave-Z]

Hi guys, my name is Dave. So I have a problem, I have a 1990 Nissan 300zx TT and it has horrible hesitation(I dont know if i should call it hesitation, have you ever seen a kid puts a p0ker card on his bike to hit the spokes, well it feels like that) when the temp is over 90ish degrees outside. Ive noticed that the hesitation stops when i fuel up but as soon as I run my car in the heat for a while it starts hesitating again. Every time that i fuel up i hear a huge amount of air come out of my tank. The car runs great when its cold outside. Any Ideas? Thanks.

[Ace2cool]

Is there a sound that accompanies this hesitation? Also, I'm moving this to home (Z32 tech)

If it's accompanied by a sound, try to get a video of it, and we'll see what we can figure out. Sounds like you may have an injector on its way out. Have you pulled ECU codes yet?

[Dave-Z]

My check engine light didn't turn on, so when I hooked it up to a code reader nothing came up. Its not so much a sound but just a feel, and a huge lack of power. I've been letting the air out of the gas tank every time I turn off the car, and it seems to help or get rid of the "hesitation", sometimes I have to open the gas cap to let the air out, close the gas cap, turn on the car, open the gas cap (while the car is running), then close it again. 8 out of 10 times the "hesitation" goes away or gets better.

[t.mcginley.jr]

Sounds like something is causing pressure to build up and disrupting fuel flow. Could be a clogged/kinked vacuum line or the fuel dampener or fuel pressure regulator. Do you have a fuel/oil pressure gauge? If so check the fuel pressure coming out of the fuel filter at idle.

And what do you mean you hooked up a code reader? Like the Conzult program?

[Dave-Z]

I changed the fuel pressure regulator and damper a few months back and it didn't fix it, I also changed the spark plugs just in case it was a bad plug. I don't have a fuel/oil pressure gauge, but I'll definitely see if I can get one to check that pressure. I checked the obd1 codes and nothing came up, is there a different way to run ecu codes? I'll also check for a leak or a kink in the vacuum lines. By the way thank you guys very much for your reply, This problem has been such a big headache for me.

[Dave-Z]

Ok so I just checked the vacuum lines and I found two possible culprits , I wont have time until tomorrow to do it. I'll keep you guys posted. Thanks again.

[t.mcginley.jr]

Ok hopefully that's your issue

To check for codes on these cars you check at the ecu itself:

http://www.nicoclub.com/archives/nissan ... ostic.html

Fuel pressure at the filter should be around 43psi

By the way, have you changed your PCV valves and hoses recently? They can cause issues like loss of power/hesitation if not changed at regular intervals.

[Dave-Z]

I changed my pcv valves no more than 6 months ago, I thought that would have something to do with that, but it didn't fix it. Tomorrow is my day off of work so im going to try to change all vacuum lines tomorrow and check the pressure. I have a jwt ecu upgrade so im hoping that I can still check the codes the same way. Thanks for the help, I'll keep you posted.

[Dave-Z]

OK guys, so here is the update, I changed every vacuum line that was was even questionably kinked, but the hesitation/pulsation didn't stop. I ordered a pressure gauge to test the fuel but it wont be in for a while. Today I was driving for about 2 miles, i stopped at the store and turned the car off, came back out and turned the car back on, pulsation started again, but when i opened the gas tank this time there wasnt that much pressure in the tank(I didnt hear the woosh when i opened the gas tank) but it still ran horrible. Any other thoughts?