300zxBoulderCO

Ok I have been having issues of sputtering and power loss for about a year now and am ready to start tackling the issues for my 1990 Z n/a. I started off by getting brand new injectors before winter and that did not appear to solve my problem.

My symptoms are:

1. sputtering at low gears and starting off..I really have to give it some gas and clutch to get a good start. When I first push on the gas my rpms go down a little before eventually going up to get the car going. Continues to sputter 1st and 2nd gear and doesn't seem normal until I am on the highway in 4th or 5th gear.

2. the car idles fine at about 700 rpm...I usually start the car in the morning..if I leave it running about 10 minutes I notice that the rpms start to fluctuate --> low to a little higher to low to a little higher.

I figured I would stop dealing with local mechanics that don't know much about Z's and take it into the dealer to at least get a good diagnostic. They told me 120 dollars so I said fine. I took it in and they said they needed to keep it a few days that there were too much things to check and were going to charge me 360 to do this. He said he hooked it up to the computer and that produced nothing. So I took the car back not really wanting to pay that much just to see whats going on. He did tell me that my fuel pump was bad that it was leaking and making noise which I can see and hear and told me to start there.

I figured I would start by replacing the fuel pump with a local mechanic so I don't get screwed by the dealer and maybe taking it back to the dealer to continue testing? What type of fuel pump should I get as he said he would not get a generic one only factory? Any other advice or ideas? Thanks!

NismoPick

He hooked it up to the computer?

How about just checking the ecu codes yourself? Have you done that yet? Have you checked the fuel pump / fuel pressure yourself?

300zxBoulderCO

By hooking up to computer I mean he checked the ECU codes..nothing. I have not checked the fuel pump or pressure all I know is that it makes some pretty good noise. How do I test these?

ZLover4Life

TT or NA?

1) Get an OEM pump. Your "mechanic" is a f*cking fool to suggest otherwise.

2) Test your injectors (multimeter, set to read ohms, across the leads on the injector... should be 10-14 ohms, it's possible that any early-style injectors can be problematic).

KasbeKZ

did you order your new injectors for a '90 model?

check fuel pressure.

start the car and perform the "pinch test" while cold. just pinch the line that goes to the middle of the balance tube, the black tube that bridges from one side of the engine to the other at the rear of the intake.

if i understood you correctly, it sounds like your cold idle is at 700, meaning, it doesn't rise when you start it. so i'm curious to see if your idle control valves are providing the extra air that is required at start up.

a pretty generic response to any problems pertaining to idle or poor run quality, for me anyway, is to clean the three idle control connectors on the rear of the plenum. IACV and IAA connectors. just google those parts to find pictures. un clip them, clean them, tighten them, and put them back.

also, i don't understand how a bad fuel pump would leak.. call me what you will, but the fuel pump is inside the gas tank. if it's leaking out side of the gas tank, that's just loose hoses. the noise, i don't know what to tell you. but do check fuel pressure before you order a new pump.

300zxBoulderCO

Before I replaced the fuel pump I took off the fuel filter and it was leaking a bunch of black stuff so I decided to replace that since it was cheap. I also changed both air filters as those were really dirty as well as those were cheap...still no change in the performance of the Z. I then replaced the fuel pump with a factory OEM pump (was kind of a hassle to get the hoses on and off). Anyone have an easy way of doing this? I pretty much has to play with the hoses little by little with a needle nose to get them off/on. Still no change in performance.

I know ZLover is gonna get pissed at me for doing all this without rechecking my injectors (I had them all replaced before last winter) but I am no mechanic and do not have the knowledge for this. I took it to my other local mechanic and this is what he came up with:

1. He said that all of the pigtails/injector plugs were missing and that the guy that did my injectors superglued them..wtf. What could this do for the performance? Where would be a good place to buy all 6 injector plugs cheap? Also he said two of the injectors were misfiring..again where would be a good place to replace the two?

2. He said I had 5 NGK spark plugs and 1 auto light spark plug. He suggested to get another NGK plug. Suggestions on this? Arn't these cheap anyway? Just do all 6 opposed to just the 1 new one?

3. He said I had a fuel line leak that was happening sometimes that he noticed. He suggested to cut the metal line off and replace with a rubber hose? Does this sound right? What could this do for the performance?

Again thanks for all the suggestions I really appreciate it!

300zgearhead

Valves? My 90 na had the same issue with power loss. It turned out that only about 4 valves were good.

300zxBoulderCO

So I'm no mechanic..what do you mean by the 4 valves? Are they called something specific so I can do the research and relay the information back to my mechanic? Thanks!

SpeciallySpiked

Each cylinder has a set of valves that open/close for air/fuel/exhaust to go in and out of your engine. He's saying that out of all of his valves, only 4 of them were good. That's a pretty bad thing but can be fixed fairly easily.



Not saying your car has 4 valves per cylinder (I don't know honestly, they change from car to car. Mine has 2...) but that picture helps describe what I was saying

300zxBoulderCO

Ok, so my 1990 Z N/A has 6 cylinders (2 valves per cylinder). How can you test the valves and when you say can be fixed fairly easily..saying I have some bad valves what would be the procedure to fix? I'm sure my mechanic would understand this more than I just trying to get a little knowledge under my belt. I'm a software developer no mechanic and like learning new things Thanks!

ZLover4Life

OK, so your 1990 NA Z has DOHC, which means you have 4 valves per cylinder. Replacing valves is NOT an easy task to undergo, so don't bother with it until you have no other options. Testing them is easy for your mechanic, though... tell him you want to check the internals with compression and leakdown tests.

Supergluing electrical connections is retarded. You can get the connectors from a guy on TwinTurbo.NET - go to their classifieds and email a guy named Bernie. It could very well be the cause of your misfire.

NGK plugs are about $10 a piece, but you definitely need NGK and not any other brand. Get NGK PFR6G-11 plugs. Replace all if you can, but you could probably get away with just replacing the one.

If you're referring to the metal fuel hardlines on the engine, many people have replaced those with hoses. It won't impact performance at all, just might make the engine bay look a little more out of order because you have hoses strewn all over the place.

Don't worry about engine internals (valves) until you do the basic stuff, first (unless your compression and leakdown test results come back bad).

SpeciallySpiked

Sorry, did not mean they change from individual car to car. I meant my '83 280ZX has 2 per cylinder; your 300ZX would be different. Just informing you about valves. Listen to ZLover4Life's advice, he knows what he's talking about.

300zxBoulderCO

All compression and leakdown tests came back good. He said I needed all connectors and pigtails which I am going to order from Bernie for $55 dollars. He said I needed two injectors replaced. He said they all ohmed out correctly but two of the injectors were not spraying fuel..can I get some input on this? I got a quote from Bernie and he said $135 per injector..is this a good deal?

I talked to mechanic and he said the metal line leak was by my left rear tire not on the engine. Does anyone know what he is referring to?

I'm getting ready to order parts tonight so input appreciated!

300zxBoulderCO

I was just looking at Bernies site. If I'm going to pay $135 X2 and $55 for the injector connectors = $325 is it really worth it paying this amount instead of $525 for all 6 injectors and the whole kit? I mean what do I do with the other 4 good injectors that I already have? Thanks for input in advance.


TwinTurbo or Non-Turbo New Style Injector Drop-In Conversion Kit

This kit is for 90-94 TwinTurbo OR 90-93 non-turbo 300zx which have the older pintle (square connector) injectors that are prone to accelerated failure from today's ethanol fuel blends. This is a 100% drop in conversion to new style injectors. Injectors are sonic cleaned and tested - all are in spec @ 10.9 ohms and click test as well.

Includes:
Pair of assembled & ready to install fuel rails featuring:

6x cleaned low mileage new style injectors in factory specs
6x new upper isolators
6x new lower isolators
6x new upper & lower orings
6x new style injector caps
6x Deatschwerks P1 to P2 adapters
6x new style injector connectors
1x plenum gasket
1ft Nissan fuel line (not pictured)

90-93 Non Turbo
$525 shipped (2-3 Day Priority Mail) in the USA

ZLover4Life

I think you might need to take your car to someone other than this "mechanic." While it is possible for a fuel injector to be clogged, it only really happens if your fuel filter is shot, and I've never heard of a confirmed case of it on a Z32. If all injectors ohmed within spec, I believe they are all fine. Furthermore, I'd like to see how he came to the conclusion that they're not spraying...

It's your money, so I can't tell you what to do... but I can say that it is not a bad idea to convert to the new style injectors (if you have old style injectors at current). What year is your car? (This info should ALWAYS be included in the first of any technical post you make, by the way.)

If I were you, and I had the funds to convert to the new-style injectors, I'd do it. If money was tight, I'd first replace the injector connectors (or, if possible, just repair the connections on the ones you already have)... I wouldn't be surprised if that remedied the issue for now. (I say "for now," because the old-style injectors are prone to failure, so it'll likely not be long before you end up having to replace some of them anyway.)

300zxBoulderCO

Sorry I will post in the first line for now on..I did however post a few posts up that it is a 1990 N/A. The price difference between the two injectors and connectors to the all six injectors kit is only a diff of $200 so I just figured it was a no brainer if money is not very tight. I did post above that I replaced the fuel filter, fuel pump and air filters myself.

Do you know what he is talking about in regards to the fuel leak in the metal line by the back left rear tire? Could this also be part of my problem?

ZLover4Life

Well if you're not getting adequate fuel pressure (which can be caused by a fuel leak), it can cause misfiring. You need to find out why it's leaking (if it is really leaking)... because metal fuel lines don't just leak for no reason.

And yeah, if you currently have the old style injectors, it is not a bad idea to switch to the new style. Also, do the switch-power rewire (search twinturbo.net auto-FAQ for the writeups).

300zxBoulderCO

He said it was twisted somehow..just wasn't sure what fuel lines would be back there..?

ZLover4Life

Well the fuel lines run from the tank, which is directly behind the seats on the 2+0 (under the hatch floor on the 2+2), down to the driver's side of the chassis, up to the engine bay...

I think you need to have this mechanic show you what he's talking about... there is no reason that those metal lines would be subjected to any twisting force.

300zxBoulderCO

I've ordered the TwinTurbo or Non-Turbo New Style Injector Drop-In Conversion Kit from Bernie and should have sometime next week. I'm going to have my mechanic do this..is there any tips I could pass along for this procedure? Anything else I could check or have done while he's in there?

ZLover4Life

Since the plenum has to come off, you might consider the EGR elimination and throttle body coolant hose bypass. Even if he has to leave the EGR valve in there (it's a bitch to get to), it'll make future plenum pulls considerably easier.

http://300degree.com/hard_parts/egrkit/

300zxBoulderCO

Thx ZLover..I've done some research on this and saw some postings from you regarding this that were very helpful:

To understand where the problem can come from, one must first understand the job of the EGR valve. What it does is basically feeds exhaust gasses into the intake tract in order to keep combustion temperatures down. By diluting the air, there is less of a burn and thus temps drop a bit. (For the record, there has been insufficient evidence to suggest that the amount that an EGR valve drops temperature is even helpful.) The EGR solenoid (one of the solenoids in the cluster on the rear passenger's side of the bay) allows vacuum to open the valve during constant RPM's under 3000, so basically it helps only while you're cruising around.

A well-functioning EGR valve will never do any harm, the problem comes with they either become clogged with carbon (on most cars, it's considered a regular maintenance item for this reason) or are improperly installed (which is too easy to do, given the mess of vacuum lines). In either case, the EGR valve could be open at all times. If you were to run full throttle, the extremely hot exhaust gasses that exit the engine could then be routed via open EGR valve back into the engine, causing catastrophic damage.

The general consensus of safety vs. benefits is that the risk of a malfunctioning EGR system is FAR greater than the benefits of a properly functioning one. Thus, most people (including myself) remove them.

My question is: how would this effect emission testing?

ZLover4Life

I have never heard of a Z32 failing a sniffer test without an EGR valve (search twinturbo.net for testimony about passing with it, because there are many people who have posted that they passed just fine). You will, however, fail a visual inspection if that's required and the guy knows what to look for (and that's a big if on the Z32, given that you can't see the EGR valve without some serious effort). You could always leave the valve itself (and cut-off piping) in to fool them, though.

KasbeKZ

i've had trouble finding, on this topic, what else is involved in the delete. i've got all the pipes cut now, and the plenum and manifold plugged, but i still have vacum lines to worry about. am i correct in saying that the part with the 3 vacuum lines and the 2 wired plug going to it on the passenger's side plenum brace is the EGR solenoid? what do i do with all that stuff?

SpeciallySpiked

In Colorado they don't have the visual test. Too bad you don't have it registered in the springs (like I do) - you don't need to pass emissions, only Diesels!