So far I've replaced the plugs, dizzy, cap and rotor, plug wires, plugs, alternator, and it still hesitates when I give it throttle, especially between 40-60 mph. It also smells like gas in the cab, not really in the engine bay or outside the car. Misses a little bit during idling, but nothing major, advancing and retarding the dizzy doesn't seem to affect the idle as much as it should....read similar posts that talked about dirty MAF sensors so I'm going to clean that out and replace the O2 sensor next. Seems like a common problem with different fixes. If anyone can help I'd be SUPER appreciative.

 

Have you checked the ecu codes?

 

Yep it's reading 31 (A/C) which I've removed, and 23 which, depending on where you look i.e. on the ECU vs the manual, is two different things, on the ECU itself it says Idle switch. In the manual it says throttle control something or other.

So far just to "process of elimination" things I've replaced the MAF, and the TPS. No change. I WILL be getting this sorted out so any help I can get I'll totall reciprocate here on the forum as well as here in Portland where most my friends also have Z cars. It's a common problem with a dozen solutions from what I can tell. Ugh.

 

getting rid of that junk on the driver side of the plenum is nice (idle air junk). if you smell gas you have a leak or running extremely rich. just unplug the O2 sensor and see if there is a difference. the chts will give you problems but usually shows up when cold or hot not all the time. did you set the tps when you replaced it. it is just a switch and needs to open at the right point. have you checked your fuel pressure another often overlooked diagnostic value. bring it up to seattle for go kart night. we'll (zccw) sort it out for you.

 

We did set the TPS, we even adjusted it just to check it and then put it back. I'll try unplugging the O2 sensor tonight. Replacing the MAF, and TPS did nothing at all. I did get a printout and what we were calling the idle air control is called the Idle-up Solenoid valve (VG30E engine) on the printout. I need to fix or replace whatever's making it throw code 23. That's the only one I'm getting besides 31 which is the AC and I removed the AC so that makes sense. I would love to come to Seattle but I live in Portland and currently the Z wouldn't make it.

 

don't put a lot of faith in the ecu codes. My experience with 3 z31 seldom any help.

 

So we got the idle-up solenoid/air idle control valve replaced, along with all the old hoses, a few of which had leaks, and while we were doing it we noticed a pretty bad leak in the fuel line so we fixed that and guess what?!?!

...no change.

How the hell fixing a tear in the fuel line makes no difference is beyond me but I'd REALLY appreciate some help on this!!!

Here's the list...
REPLACED PARTS

Alternator
distributor
idle-up solenoid/air idle control valve
plugs, wires, cap, rotor (on the new dizzy even)
alternator
all new belts
cylinder head temp sensor (which fixed a code)
Fuel temp sensor
Mass Air Flow sensor and line

Next step is a fuel pump I guess? Starting to become a money pit and it's irritating that so many people seemed to have the same problem but never came back to the forum with the solution. EVEN IF YOU SOLD THE CAR AND GAVE UP LET PEOPLE KNOW!!!!


ALSO seems like it's getting worse despite all the new parts and work I'm putting in. I've been told not to put faith in the codes, but I was able to get rid of one the proper way and I'd feel a lot better if someone could at LEAST tell me accurately what code #23 is for!

 

For starters, automotive diagnostics doesn't begin with "throwing new parts at it until it runs good".

Did you read the spark plugs before replacing them? Since replacing them?
Before replacing the fuel pump, have you checked the fuel pressure?
Have you checked all sensor and ecu connections to make sure they are free of corrosion?
Are your battery terminals and cables tight and free of corrosion?
Have you tested your alternator output to make sure it's at ~14.7v?
(Electrical problems will cause sensor problems)
Did your car have the fuel injector recall done?
Have you downloaded the free FSM from XenonZ31 Reference ?
And lastly, from your PM you said you are "well financed". Instead of replacing all the parts of the car, it would be much more worth your time and money to just take the car to a reputable Euro or Import shop and have them diagnose it for you.

 

By "well financed" I didn't mean I wanted to drop 3-400 on a diagnostics trip haha, I just mean If I need to get a part it won't be months before I'm back on here with results. I'm about to go check the timing for the 3rd time, check the fuel pressure, the connections are all clean and clear, battery cables are good, I do have the FSM, but haven't had the injector recall done or looked into it. I'm still trying to figure out how the leak we found in the gas line and fixing it made NO difference, I mean it was dripping. Also I only started by replacing the parts that I could tell from visual inspection and testing needed it as far as "throwing parts at it" goes...it needed em. Still waiting to hear your view on what the code #23 means. I've replaced the TPS and the idle air control/idle up solenoid both. If that's not what #23 refers to I don't know what it means.

 

Code 23 is the TPS. TPS = Throttle Position Sensor ( z31.com | Repairs | Throttle Position Sensor & repairs:codes [Z31.com] )

It's an idle switch via throttle position... this should not be complicated.

BUT, did you set the TPS with an ohm meter? You can't (shouldn't) just slap it on.

Eh? More like $50-$200 for a diagnostic. And if you find an Independent Euro or Nissan mechanic, they may help you out on the cheap (if you are NICE to them).

Z31 Injector Service Campaign Information

No difference in the smell of fuel, or no difference in the way the engine runs? It wouldn't make the engine run any differently unless it was hemorrhaging fuel.

 

Sometimes it can just be the ecu if all else fails. I had to do it a couple times.

 

Awesome. In the morning I'm checking the timing, and I'll take an ohmeter to the TPS, I've sent a request to find out if the injectors have been updated and will call in the morning too, the smell of fuel is gone but it doesn't run any better. Worse if anything.

Would it throw the code if the TPS was set incorrectly or only if it wasn't working at all?
The wire harness/plug for the TPS is HAGGARD. I'm replacing it as well.

Also...
"Thank you for contacting Nissan North America, Inc. and allowing us the opportunity to assist you.

A review of our records indicates that the above-referenced vehicle is not currently involved in any recalls or service campaigns."

...is what I got from Nissan.

 

if the recall was done you should find a yellow wire that splits out to all three injectors on one side.

 

Wow, few more sensors and you have a new car.

to me it looks like you need either better fuel, plugs or pull the sock out of your air intake piping.

Seriously though from your posts you are getting frustrated, get another set of eyes on it. even the best mechanics make mistakes and you may have missed something simple, good luck...we got a 3 day weekend coming up, hopefully you get this one taken care of,

Shogunb

 

1.) Ok. Checked the timing. The top two pulleys are perfectly on when the bottom pulley (the engine) is at TDC but the marks where the bottom one should be when it's at TDC are nowhere near right....but no idea what to do about this.

2.) I replaced the coil with one I knew was good just to check....no difference.
3.) Found two almost disconnected wires, one going to an injector, the other going to a sensor on the engine block, fixed them, noticed the O2 sensor was unhooked, connected it....no difference.
4.) On the way back from the shop tonight the car really had trouble running, i.e. is getting worse. It gradually bogged down so bad the car wouldn't even move, but if I shut it of and turn it back on it goes about two blocks before it "peters out" again. I was able to get home like this but there's no way I can get it to a shop for diagnostics at this point. I got offered $1600 for it for parts today and if I can't get this straightened out, I'll probably take it. I AM frustrated. My mechanic buddy who's been helping me on this (also has a 300zx) said his had the same mystery problem and it was fixed by replacing the injectors.... but without being sure, that is one hell of an undertaking. Especially when most the Z's issues are so similar regardless of what ends up being wrong.

If anyone has any suggestions at this point, maybe a way to test the injectors that'd be great. I checked the PDF of the Service Manual but I can't find anything helpful. Seriously about out of patience with this. I've never had such a hard time just diagnosing a problem so I can take care of it. I'm completely over playing detective on this one but I love my Z so I'm torn.

PS It's not just sensors..it's the alternator, distributor, coil, FPR, MAF, plugs, wires, belts...everything top to bottom short of the injectors. I don't mind throwing a little money at replacing the stuff...all of it was old and beat up anyway, but if there's no light at the end of the tunnel then there's no point.

 

Swapping the ECU this morning, just to see if that makes any difference. The Z is now stuck under my carport, I'm out of ideas and I need to get to work. Ideas? I really have a hard time believing that we can't get this ironed out on a Z car forum.........

 

Did you ever do this? Reading the spark plug tips is THE #1 EASIEST AND FASTEST way to find out what's going on with the engine... you are wasting your time if you don't start at the basics.

eh? You checked the timing pulleys... what about the ignition timing?????????

Ya know... with a timing light..........

 

Thanks for the help. Yes we checked the spark plug tips I'm sorry I forgot to mention that. They looked exactly like they should after about a week of minimal usage. Nothing out of the ordinary, also no gas/oil in the shaft. The ignition timing is right on when we check it with a light....it definitely SOUNDS like it's missing...but everything aside from that bottom pulleys marks being off are showing no problem. Ugh.

UPDATE - My buddy offered to sell me new injectors and put em in for $100 so I dropped the z off. Should be done tomorrow evening. I know that falls into the "throwing parts at it" category but like I said, I don't mind replacing things as long as the thing runs eventually and $100 was a screaming deal. He's also going to inspect the wiring while he's in there.

 

So we swapped injectors, redid the wiring harness, still didn't fix it. Threw in my buddies ECU just to cover all the bases and guess what?

....yeah it runs now. There's still an issue with the TPS but I think it's the connector and I'm replacing that tomorrow. It just doesn't run at 100%, but I'd say it's at 85%. Teeny tiny hesitation at low rpms but almost unnoticeable. Idles perfect runs nice and smooth. Taking it for an extended run tomorrow but drove it all evening before I came to post and it feels solid.

UPDATE!!!

Runs really smooth, no misfiring, feels weak though. I'm replacing the pigtail on the TPS sensor today other than that any ideas? Feels like I'm at about 75 percent of the available HP....

UPDATE!!!!

Replaced the TPS and it's pigtail and the Z is running SOOOOO much better. It IS still throwing code #23 and feels a tiny bit underpowered, but no missing, no stalling and the hesitation is super minimal. I'd still appreciate some advice if anyone is still following this thread, I feel like i've done a fairly good job of keeping everyone abreast on the topic, and coming back with results...it'd be nice if someone else would return the favor.

 

Good call. Flacster.

 

Anyone have any ideas or should I just find a forum that's actually proactive? This ones pretty much a wash. I gor more replies telling me what was wrong with my post than what was wrong with my Z car. Pathetic.

 

No one's got a gun to your head... There are a few other forums with more Z31 support, but if you are an *** there like you are here, you'll likely be banned before you know what hit you.

Instead of wasting your time and money, you could have just taken the car to a reputable shop and be driving happy by now...

 

So....again no help on my car, just on my posting techniques? It's called being pro active. My car is running FINE. I've been driving it over 100 per day since we fixed it. It was the ECU..as per my post. Now I'm trying to make it exceptional and also for the record, going through my process of elimination has helped multiple people here in McMinnville....and I also don't understand how just taking it to a tech is the right way to approach it on a forum about fixing your own car?!?! If we had tons of money no kiddin we'd just "take it in and get it fixed". Duh. If you want to condemn me for being pro active and helpful go right ahead, but my car got fixed, and WILL be awesome because I'm a beast at getting things done. My results speak for themselves. Now I'm working on getting my tach/speedo working after the digital to analog swap, so if anyone wants to help with that sans a grammer/forum lesson I'd REALLY appreciate it. I'm here to work on cars not semantics.

So aside from calling me "an ***" for trying to get things done in my lifetime......anything?

 

So just where does the pointer line up when at tdc? should be on the first line on the left, looking down on the pulley. That's when the cam sprockets should be on their marks too, if not,turn the crankshaft over one turn with a breaker bar and re check. When that is ok, set your timing with a light... 20 deg btdc, or 4th line from the left, at 700-800rpm. These settings make mine run great. Sometime the tps is shorted out inside and will make it run real bad. Adjust it to have continuity when throttle is closed and none when just off of idle. about 1/16 in. Toobad you had to replace all those parts, but the ecu is only the problem 25% of the time in my experience....My 6th Z car

 

Thanks!!! Just checked it to be sure. Aside from the bottom bottom pointer which is like 6-8 inches off the timing is still on the money it doesn't missfire or miss on idle either. I took the gas tank off last night and found that the clamps on both the intake and out were super loose. Put new ones on there and no more gas smell and 90% of the hesitation under acceleration is gone.

SUCCESS!!!!

The little tiny bit of lag that's left I'm attributing to the fact that it was converted from an auto to a 5 speed and the tps wiring and a couple other things are still kind of different. IE the tps is adjustable and I have it where it belongs/works and can totally tell the difference when I adjust it, that being said, it still throws the code for it and it doesn't use one of the pigtails (I'm told it was for telling the auto tranny when to downshift). So short of rewiring some pigtails/adding pins etc I think it's about where it should be...considering. And I'm SUPER happy with it. It's running great. Getting about 28+ MPG 0-60 and 60-100 are really good for what is basically a stock car. Considering starting a new thread to try and get my analog dash working but I don't want to get verbally smacked I really DO appreciate the help and like I maintained....I knew we would get her running!