z31 bogs down when sitting at stop - Nissan : Datsun ZCar forum :Nissan Z Forum: 240Z to 370Z
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post #1 of 12 (permalink) Old 12-19-2016, 05:05 PM Thread Starter
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z31 bogs down when sitting at stop

Hello everyone,

My Z has been acting up recently and I was hoping someone could help me out. First off, its a 1987 300zx Turbo, Automatic, 118,000 miles, fresh timing belt as of 3k miles ago, no mods other than a cone air filter. I know it has an exhaust leak on the manifold that has gotten worse since I purchased the car. It ticks now at the manifold on cylinder one. It has a slightly rough idle when in neutral which fluctuates the RPM's slightly. But, when I sit at a stop when the car is in drive, it'll idle really rough and if I sit long enough, when I accelerate it'll bog down and kind of jolt forward intermittently. It smells of gas when this happens too and my foot is halfway to the floor when I do this. No matter the throttle position it will do this. Then, after a bit of stumbling, it will return to normal and drive fine again. The RPM's become pretty low when I sit at a light too, around 500-650. I ran codes off of the ECU and the only codes it pulled was a lean fuel mixture and "check idle switch circuit". I checked the fuel pump a month or so ago when I had a distributor issue (the rotor bolt fell out) and it was working great. I guess it could've stopped now but I'm not sure since it runs fine any other time. If I idle at neutral, it won't run rough, but sometimes if I sit at a stop in neutral and put it into drive when I go, it still has the jolt-y acceleration problem. This started a couple days ago and has shown none of these signs before. I will include that my transmission is due for a fluid flush and change as it isn't acting the best all of the time so I'm having that done soon. Not sure if that's a culprit but I'll include it anyway. Is this an exhaust leak problem? It's on the passenger side so it's not the turbo side. This is my first car and I've been put into a situation where I'm forced to work on this myself as before it was a 2 person project. If this has been answered elsewhere please let me know, I've looked everywhere, FSM, forums, Hayne's etc and none have had anything as specific as this. I was quoted at 850 dollars to have new gaskets put on due to labor costs. I can't afford that so if it is an exhaust leak I will attempt to do the one side that's leaking myself. I'm at a loss and any info will help.

Thank you for looking,
-Jake

"It's like a tractor beam of hotness" -Ricky Bobby
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post #2 of 12 (permalink) Old 12-19-2016, 07:13 PM
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sounds like a fuel starvation problem to me...


have you done the basic tune-up checks? spark plugs, wires, and fuel filter? how about the electrical connections... have they been cleaned?
if you already know how to run the codes via the ECU by the factory service manual, then you are well on your way to being able to troubleshoot and work minor mechanical issues yourself.
its possible your MAF could be outta whack, but unlikely. electrical.... the Z31 acts weird sometimes if it has electrical issues. trust me, they do. make sure your battery and alternator are good and everything is tight.


stick with the basics first. if you have an exhaust leak at the right side exhaust, no need to go into the engine, but some things up top will have to come off in order to get to it and replace the gasket, if that is where the leak is. find a competent mechanic, preferably one who has some Z experience.


Bonny

All the Gods, all the Heavens, all the Hells, are within you. - Joseph Campbell -

Pooja II ~ 1984 300ZXT 50th AE ~ 2018 - 2019
Pooja ~ 1987 300ZX 2+2 NA2T ~ 2012 - 2018
Suzanna ~ 1983 280ZX Coupe ~ 2010 - 2019
Alana ~ 1976 280z Coupe NA2T ~ 2008 - 2019
Dianna ~ 1980 280ZX Slick Top ~ 2001 - 2007
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post #3 of 12 (permalink) Old 12-19-2016, 08:19 PM Thread Starter
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Yep. Cap, rotor, wires, plugs, fuel filter etc, all replaced October of last year. I replaced the fuel filter again yesterday in case that was the culprit and there was no difference. Whenever i find a connector that's odd looking I'll clean it. AAC, FPR, etc, things like that I run across while doing other maintenance. I don't have much mechanical experience, especially at my age, but doing the timing belt, water pump, power steering pump replacement ad the like by myself, I've come to know my car fairly well. And reading up on any information I can. Took forever to save for this car and I like learning about it so hands on doesn't faze me. MAF shouldn't be messed up, I had an ex mechanic friend of mine check it out a while back for a different reason. Alternator is brand new too, of October last year as well. Battery is a brand new Red Top Optima as of 3 months ago. If you think it's a fuel issue, why would it run fine while moving or short stops but cause a problem when sitting for lengths of time? FPR? Injectors? I know the gasket needs replacing but if I were to get it fixed and it doesn't solve the problem then I'm no better off. Maybe I can see if they will only replace the non-turbo side. It smelled heavily of gas when it happened though, wouldn't that indicate a rich fuel mixture? Thank you for the insight, it's much appreciated.

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post #4 of 12 (permalink) Old 12-20-2016, 01:12 AM
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all that idle stuff hanging off the left side of the plenum gets gunked up and gives you weird problems. throw it away. fab a plate out of 1/4 inch aluminum to cover up the hole in the plenum. three z's all ran nicer without that stuff. or try to clean it up and see if that helps. exaust leak.. unlikely your problem

86T, 350 Nismo 08 (#1415) gone but fondly remembered 81T, 83T, 83, 85T, 86T, 96TT
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post #5 of 12 (permalink) Old 12-20-2016, 02:57 AM Thread Starter
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With the exhaust leak though, the 02 sensor is behind it, wouldn't that cause incorrect readings? And by left side do you mean facing the engine or sitting in the car? Just wanna make sure, what exactly should I remove? Thanks for the help!
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post #6 of 12 (permalink) Old 12-20-2016, 10:04 AM
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no. what planet are you from a car only has one left side. why they talk about right hand drive and left hand drive.

86T, 350 Nismo 08 (#1415) gone but fondly remembered 81T, 83T, 83, 85T, 86T, 96TT
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post #7 of 12 (permalink) Old 12-20-2016, 10:41 AM
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left side, meaning the car's left as you are sitting in the cockpit looking forward. think of it this way, the turbo is located on the left side of the engine and your battery is on the right side of the engine bay. you can also simply say, driver's or passenger's side.


have you checked out www.xenonzcar.com
read up on the Z31 section. it has a lot of info regarding all of your questions, including the one about removing the idle controls on the left side. I have thought about doing this on my own car. I did remove the AIV system and the car seems to be running normal. your O2 sensor is probably okay. do you have a sensor light illuminating on your instrument panel? it is designed to come on after 30,000 miles for servicing, and then it comes on again after 60,000, and then after that it doesn't come on again.... at least that's what I gathered from the owners manual. you can manually reset it to get it to turn off. your ECU should also tell you if the sensor is bad if you ran the codes. you should check the fuel pressure regulator for problems. read up on that site I listed. you will find it handy.


Bon

All the Gods, all the Heavens, all the Hells, are within you. - Joseph Campbell -

Pooja II ~ 1984 300ZXT 50th AE ~ 2018 - 2019
Pooja ~ 1987 300ZX 2+2 NA2T ~ 2012 - 2018
Suzanna ~ 1983 280ZX Coupe ~ 2010 - 2019
Alana ~ 1976 280z Coupe NA2T ~ 2008 - 2019
Dianna ~ 1980 280ZX Slick Top ~ 2001 - 2007
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post #8 of 12 (permalink) Old 12-20-2016, 11:34 AM
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Originally Posted by rogerz View Post
all that idle stuff hanging off the left side of the plenum gets gunked up and gives you weird problems. throw it away. fab a plate out of 1/4 inch aluminum to cover up the hole in the plenum. three z's all ran nicer without that stuff. or try to clean it up and see if that helps. exaust leak.. unlikely your problem

^ That is most likely your answer. I had the same problem for a couple of years. Tried several different things. Cleaning that stuff up did the trick.

1986ZXT GLL: 56k NA motor and trans with Turbo goodies added. K & N, CM 3" turbo back, Turbosmart MBC @ 9 psi, fmic (old guy kept the A/C), Dual Fans, Maxima Alternator, ASCO plenum, Eibach/KYB, Champion 3 row
2013 Ford Taurus SHO Performance Package
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post #9 of 12 (permalink) Old 12-20-2016, 02:59 PM Thread Starter
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Yes that's what I meant. I've heard people say left side from both perspectives. I will take a look at the idle components. The IAC and the AAC could be the issue it sounds like. I'll keey you updated. Thank you all for the input.

"It's like a tractor beam of hotness" -Ricky Bobby
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post #10 of 12 (permalink) Old 12-20-2016, 08:19 PM Thread Starter
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Update: That seemed to be the culprit. I removed the AAC and FICD from the intake, took off the brass piece, out fell what I assume is the sensor, one side was shaped like a cone and the other a small cylinder with grooves in between. The cylinder side which entered the opening where air flow comes through was very gummed up. Gave everything but the brass piece a nice bath and reattached it. Changed the tubes that go from the valve cover to behind the MAF and the one that went from the AAC to the intake pipng while I was at it. I decided to keep it on since I don't fully have the means to make a block off plate and when the engine was running and I disconnected the AAC (by accident, I need new connectors) the engine sputtered and died. Sat in it in front of my house in drive with the break on to reenact it's problems and it lagged to go very briefly a couple times then smoothed out. Idles a bit nicer now too. Thank you guys so much for the help. One step closer to getting this thing to the way I want it.

Eventually I would like to gut the extra plenum I have from my parts car, I've read up on it but I had a quick question about the bolts that hold it down. If I were to completely gut the inside and have cylinders welded in where the bolts would go and then a plate welded on top would the bolts be too long? I've heard about plenum spacers, If the bolts are too long, would they work with the spacer, or would I have to get new ones all together? Just planning out how I would go about doing this when I have the cash.

Thank you all again, couldn't have done it without you.

"It's like a tractor beam of hotness" -Ricky Bobby
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