my car stutters when i hit the gas hard from a stop once it gets to about 4000rpms it takes off better i have changed air filter gas filter spark plugs and i put lucas fuel injector cleaner hope someone can help me thanks

 

Sounds like possibly a bad injector (low resistance = too much fuel => runs better at higher RPM)... test the resistance across the leads of your injectors, it should read 10-14 ohms.

After you've done that, we'll discuss other possibilities (a few sensors that could cause that, but injectors are a common issue and can cause this, so no point in checking other things until we rule those out).

 

Thanks ill try to get it done today and ill let u kno once again thanks

 

I was at da shop today and they plug the computer thing on my car and 2 codes came up one was a oxigen sensor is bad and a engine temperature sensor os something like that is also bad they tell me the reason why the cardrives that way is because of the oxigen sensor you guys think thats true? How hard is it to change the o2 sensor hope u can help me thanks

 

ya that kind of sounds right. my 85 300zx is doin the same thing because the guy i bought it from took the o2 sensors and the cat. out. they are not that hard to change

 

Ok cool thanks

 

You know I've been having the same problem for a while now. I replaced everything (CHTS, Air Filters) and most recently replaced both Oxygen Sensors with Bosch 13091's (great price at advance auto! Well compared to dealer prices) and i STILL have the hesitation at take off.

I hooked up my OBD cable and found that my timing goes WAAAYYY too advanced on initial accelaration. Could have been an error in the reading but it even went into the negative!

Now, this is after I meticulously checked the timing several times. Both with the OBD cable and a timing light.

Under no load the timing is perfect. Once you get on the road and floor it, it takes a LOOOOnnng time to get up in the RPM's. So this afternoon I'm going to check my CAS and injectors.

Not sure what else to check though.

 

Changing them isnt hard. Get the oxygen sensor tool and you can swap them out in 20 minutes!

The passenger side one is very easy. The drivers side put up a little fight though.

 

I doubt it's going to resolve your issues, to be honest, but if the sensors are bad, they do need to be replaced.

 

Ok today we found out the one of the cyliders was not working it was getting spark but the injector conection was really old and the metal turn green kinda like when the battery terminals are dirty so we replace the conector and the cars idles better and takes off better but it still stutters maybe after the injector was not working for who knows how long it got dirty so i put a injector cleaner in the thank and im waiting to see if it gets better what do you guys think it could be some one told me maybe the piston does not have any compresion if so how can i check hope ome one can hell me thanks

 

Hello run-on sentence. So you didn't test the injectors like I told you to in my first response? Let me say it again, then. CHECK YOUR INJECTORS. If cylinders aren't firing, they are the MOST likely culprit. (Damn I'm tired of repeating myself when people don't take my advice the first time - I'd bet your car would be running nice and smoothly if you had tested the injectors like I recommended.)

By the way... good job consulting us on the fuel injector cleaner. I'd have told you not to use it because it probably contains alcohol - the source of bad injectors on 300ZX's.

Searching can answer the rest of your questions... compression testing is an elementary and well documented vehicle diagnosis technique.

 

I try to tell the mechanic to test them but they only plug the computer to it and said in is the o2 sensor and i when to another shop and the guy put a long screw driver on top of the injectors to listen to one at a time and he only said that he would clean my injectors for 800 i thing he was just trying to get money out of me sowy about my typing i have a touch screen phone and is just faster to type non stop

 

Which is why my advice was never "take it to a mechanic." The average mechanic will not know how to diagnose these cars, and the ECU codes clearly didn't cut it. They also won't know that the early 300ZX's have a constant voltage applied to all six injectors even when the car is off, and they won't know that a constant voltage applied to a coil submersed in alcohol is more likely to oxidize and cause injector failure. But people like me who have worked on 300ZX's for nearly a decade will know that.

Get a multimeter (<$15 at Sears).
Pull connectors off injectors.
Set multimeter to read ohms (range that includes 10-14 ohms).
Touch tips of multimeter to each lead on the injector.
If not between 10 and 14 ohms, the injector is bad.
Count how many are bad.
Call local Nissan dealer or reputable vendor who sells OEM injectors.
Order 6 injectors if 3 or more are bad, else order as many as needed.

Then tell us where you are so we can tell you where to get them replaced without being raped.

 

Ok guys i just came back from my friends house were we tested the injectors and compression compression is good 5 injectors tested in the range off 10 to 14 ohms the other one said 130 or something ariund there but here is the funny thing when i got in the car this morning it ran just fine i feel it should b faster but no stutter it even idles better how could that happen

 

Nandocruz, Welcome to ZDriver!

Please use proper punctuation (periods, commas, capital letters at the beginning of sentences) so we can clearly understand what you are trying to say.

itsverydifficulttodecipherwhatsomeoneistryingtosay whentheydontuseanypunctuation

Thanks!

 

So I'm a little surprised that nobody has mentioned checking for vacuum leaks. Mine's a TT, so maybe its more sensitive to vacuum leaks, but tightening all of my vacuum connections made a huge difference for me. In the process I found that a couple of the hose clamps were basically stripped, so they weren't doing any good at all. For $2.50 I replaced two clamps. At the same time I bought MAF sensor cleaner ($7) and sprayed it down. Now the car doesn't studder and the idle is not erratic. $10 well invested. If your injectors are good, this is where I'd look next.

 

now that u mention it there is a hose that is unpluged and i dont know were it goes....also there are a few hoses that are in place but have no clamps....

 

The injector is the larger problem than vacuum leaks, which is why I said to start there. Vacuum leaks can cause small issues (hesitation, low power, etc), but nothing to the magnitude of stuttering.

Replace your bad injector and see how much of your problem that solves. And of course, if you have visible vacuum leaks, figure out how to fix them... the system after the MAF should be air-tight.

High ohms means it's not firing enough - that cylinder isn't getting the fuel it needs. (Low ohms means it's firing too much, causing a rich condition).

 

Ok now... how hard would it be to replace the injector.... also the car smells alot like gas when it idles and after i drive it

 

You probably also have a fuel leak under the plenum... if it smells strongly like fuel, I'd stop driving it until it's fixed (yes, fuel leaks have led to fires in 300ZXs - so much so that every winter on twinturbo.net they affix a banner to the top of the forum that says "tis the season for fuel leaks" and has a link to a writeup for locating which hoses need their clamps tightened).

Since you're going to be replacing fuel hoses anyway (or at the least, tightening hose clamps), in attempt to remedy the leak, you're going to have to pull the plenum... and if it's never been done before, it's a VERY difficult task (it's probably going to take you the better part of a day). The bright side is, while you have it off, you can do the coolant line bypass and possibly eliminate the EGR valve, making future pulls MUCH easier.

Where are you located? Perhaps I know of local people who'd be willing to help you out...

 

Im in in alexandria VA .........the smell of gas comes from the exhaust..... the fumes smell like gas

 

You're in extreme luck... Bernie is also in Alexandria.

Email berniebilski@***.net. Tell him you need an injector replaced and describe the issues you're having. He's likely going to charge you (it'll be less than a dealership or any other shop), but I personally guarantee his work (he's one of the only people I go to for answers of my own). If I was in the area and there was something I couldn't do to my own car, he's the person I'd talk to about it.

 

i might have to go on a trip up to meet bernie one of these days.

so it's alcohol in the fuel causing the oxidation? i thought you said a while back it was the ethanol. probably just my bad memory though. or is ethanol just a type of alcohol? i'm not a chemist...

 

...

Yep.

 

I just email him thanks everyone thanks zlover4life u been so much help