300zxBoulderCO

Ok...mechanic just pulled the upper plenum today! He said there is a big hole (1/4 inch by 3 inches) in it by the number 3 tube on the drivers side. Any input on this? He said that someone put JB Weld in there to hold it up I guess! I just got the new injectors conversion kit and want to do all of this right the first time without patching anything up so I can get rollin again..the right way. My question is..how bad is this for the car by patching it up and is it recommended to just get a new upper plenum so I don't have to deal with this problem later? If so, where should I buy? New or used? I see a used one on Ebay for decently cheap but I'm tired of doing things cheap and getting burned later? All input appreciated..you guys are saving me a lot of time and money with all of your knowledge

ZLover4Life

Get a new upper plenum. WTF kind of mechanic recommends using JB Weld on a ****ing intake plenum? Does he work out of a garage attached to an alley in the slums of Denver?

I have an upper plenum I'd be willing to sell, by the way... if you're interested, let me know and I'll do some price searching.

300zxBoulderCO

It was the last mechanic that screwed up my injectors in the first place (by super gluing them) who I am assuming JB welded the damn plenum while he was at it. I'll buy another one that way I can get this done right..I think I'll go ahead and order the EGR bypass kit as well since I'll be waiting yet another week to get another plenum. What kinda price can you get me and where are you located?

300zxBoulderCO

My bad I can see Chicago..hope Cutler works out for you guys..hated him here in Denver.

300zxBoulderCO

I got an upper plenum for $60 and all new style injectors were installed. I'm being told my car is still hesitating a little So now I have replaced new injectors, spark plugs, fuel pump, fuel filter, air filters and its still not right! Mechanic pulled the codes again and it displayed fuel temperature sensor. Could this cause hesitation? I've read that this is the point of the sensor "The Nissan 300zx Fuel Rail Temperature Sensor monitors the temperature of the fuel and adjusts the fuel pressure for better performance and fuel economy." Can you clean this or how do you tell if it needs to be replaced? If not what else should I really be looking for to correct my problem. He was going to clean the MAF sensor as well to see if that makes any difference.

ZLover4Life

It's a temp sensor... cleaning it won't do anything (it's just a plug of metal whose resistance changes with temperature, thus allowing different voltages to transmit through it, signaling temperature).

Replace it.

300zxBoulderCO

I've ordered the fuel temp sensor. We took it out and it was cracked so makes sense I got the code for it from ecu..I'm not sure how this part plays a part in my hesitation problem though. I only appear to be having a hesitation at low gears and starting out. It feels like when I barely push on the gas for take off the rpm's go down a little bit first instead of going up right away and taking off. Once I hit 2nd or 3rd gear it feels like the car kicks in finally. I've got a good write up from twinturbo.net on things to check. Any suggestions here in order or importance to keep checking stuff?

# Clean the TPS (Throttle Position Sensor)
# Clean the air filter - I've got new air filters
# Clean the injectors - Newly installed new style injectors and connectors
# Change the spark plugs - tested and good
# Change the fuel filter - new fuel filter
# Clean the Crank Angle Sensor (CAS) connector
# Clean the Throttle Bodies
# Clean the detonation sensor connector
# Clean the Mass Airflow Sensor (MAS) connector - was next in the list
# Induce turbulence in the air intake
# Clean the coolant temperature connector
# Change/add coolant
# Clean intake valves
# Do you have an updated Power Transistor?
# Is it a 1990 model?

300zxBoulderCO

Ok I picked up the car from mechanic today as I found another mechanic nearby who has actually owned a few Z's before so I guess I'll give him a shot. Since my last post this is what has been done:

# Clean the TPS (Throttle Position Sensor) - cleaned
# Clean the air filter - I've got new air filters
# Clean the injectors - Newly installed new style injectors and connectors
# Change the spark plugs - tested and good
# Change the fuel filter - new fuel filter
# Clean the Crank Angle Sensor (CAS) connector - cleaned
# Clean the Throttle Bodies - cleaned
# Clean the detonation sensor connector
# Clean the Mass Airflow Sensor (MAS) connector - cleaned
# Induce turbulence in the air intake
# Clean the coolant temperature connector - cleaned
# Change/add coolant - yes
# Clean intake valves
# Do you have an updated Power Transistor? - ?????
# Is it a 1990 model? - yes it is

I guess I'm moving on to someone with more Z experience as its clear you need someone who has this knowledge to work on these cars. I've learned a lot through research trying to get this car right but its not there yet. Its still hesitating at start. It sputters off until I get well into second gear..from there I can feel the power and feels normal.

My mechanic did notice some wires spliced together in the ecu harness..I'm not sure what this is or if it was even done right. It looks like a skinnier white and purple wire going to one thicker white wire. Suggestions on this? What else is there to check after my list of performed tasks?

http://s105.photobucket.com/albums/m...t=300ZXecu.jpg

Here is some throttle plates taken from my upper plenum if anyone is interested:

http://s105.photobucket.com/albums/m...ttlePlates.jpg

Here is old fuel rail and old injectors before new style was replaced:

http://s105.photobucket.com/albums/m...ZXfuelRail.jpg

300zxBoulderCO

Anyone...input?

ZLover4Life

... when you put the new style injectors in, did you use a newer lower plenum or 300Degree rails? (Apologies if you've answered this, but I was on my way to bed and the thought that the injectors may not be installed right came to mind.)

300zxBoulderCO

To be honest with you I'm not really sure. Just used the new style conversion kit from Bernie and purchased a new upper plenum.

I finally took it in to certified mechanics and they spend some time tracking down the "intermittent spark". They traced it to some bad wiring butt connectors coming from the ECU which was giving me bad grounding issues. They also said the PTU was bad and was causing the rest of the issues. They quoted me $150 dollars to order the part and install (I know its easy to install). Does anyone know of a better place to get one with cheaper cost?

hoov100

I've got a couple good PTU's for $40 each, I'll sell both for $70 shipped.

300zxBoulderCO

New Style PTU? Why so cheap and why would I need two? I need to let them know asap as I gave him the go ahead to order but they may be able to cancel. Let me know.

hoov100

New style, I have a box of them and get them for free and you never know, a spare PTU comes in handy from time to time. That and you really can't beet the price.

300zxBoulderCO

Dang a little too late..I'm paying the extra I guess. At least I'm getting a warranty from them on the part so that's a good thing. I'll wait to see if this solves my car issues!

300zxBoulderCO

Installed a new PTU..still intermittent spark. I was now told they pulled the coil on plug boots and there were cracks in 5 of them. New ones will be installed today and I'll give everyone an update whether or not this fixes my problem.

I tried doing some research on this and couldn't find much. Could people chime in with a little more input and how important this is?? Here is what I found:

There is no distributor cap on a 300zx. There is no distributor either.. It has coil over plug. Meaning individual coils for each spark plug.

300zx has individual coil packs so there is no distributor, just a Cam timing sensor, coil packs (1 per cylinder), and a power transistor. I'm having a very similar problem and it's either the cam timing sensor or the power transistor

N/A for this application as the z has no distributor. It uses a cas(crank angle sensor) for timing measurement and a ptu (power transistor unit) to tell each coil to fire. From your description it sounds like a fuel problem, were it a spark problem I would check the connections at the ptu and cas. They are both located on the front of the engine on the front cover over the cylinder head. Cas is is drivers side, ptu passenger side. More likely the problem is the fuel pump control module. This is located behind the seats under the panel and is connected to the wiring for the fuel pump. It is possible to bypass the fpcm for testing purposes.

ZLover4Life

Uh, yeah... the 300ZX doesn't have a distributor (duh)... the CAS and PTU basically take its place. This is how coil-on-plug ignition systems work. (When there is a coil per cylinder, there is a CAS and PTU [often having different names depending on company] that tell each coil when to spark; when there's one coil feeding all cylinders, there's a distributor, sending spark to each cylinder.) What more info do you want?

And an intermittent spark, in my experience, is not likely a fuel delivery problem. Could be a fuel pressure problem, perhaps, though... have your fuel system pressure tested.

300zxBoulderCO

Yeah that makes sense just needed a little extra assurance as to how the whole system works. Would tiny hairline cracks in the COP boots cause this type of misfiring I have been experiencing in this whole thread? Could this cause the PTU to go out (this is what the mechanics are telling me as to why the PTU could have gone out)?

hoov100

The "mechanic" is just trying to up your bill so he can make more money off of you at this point. and no, little hairline cracks won't cause the coil to randomly misfire. I would highly suggest you take the z home, buy a cheap digital multimeter to test the coilpacks and injectors and buy a cheap mechanical oil pressure gauge to check your fuel pressure.

I would be more interested at this point if it was my car to find out if it's just one cylinder or multiple cylinders randomly not firing.

ZLover4Life

+1

A bad coil will never damage the PTU. And a bad coil boot won't cause misfiring. This is why we don't recommend taking these cars (or really any cars) to mechanics... they're interested in lining their pockets, especially when handling these cars. Furthermore, most mechanics (and I emphasize MOST) are not qualified to work on a 300ZX.

300zxBoulderCO

Ok got the car back..runs much better. Only a slight misfire now occasionally and only happens when driving so its really hard to pinpoint what cylinder its coming from.

"Started with scanning ECU for proper data and codes that may have been stored. 42 fuel temp code stored. Traced circuit to open wire in engine compartment. Sensor is missing (I already knew this as I took it out to get a new one). Upon viewing ecu data we found that some of the parameters (voltages and valves) were moving all over the place, so we pulled the ecu down and found that many wires to the ecu hard been cut and poorly spliced. Moving the wires they came apart so we soldered the connections and did a pinout test on all ecu wiring insuring that all connectors and valves were proper. However even after soldering we found that the valves for the crank cam sensor would blink out using a lab scope. We removed the wiring to the sensor and found heavy corrosion on all the pins, so we took the connector apart and sensor to clean (this acts like a insulator to voltage) recrimpped the connection and the valves were now stable. We then moved to the IAC valve. We found that the connection to the valve was off and once we found it the connection was destroyed with corrosion, so we replaced the connection. Next we noticed that the off idle switch valve was not normal and once again found heavy corrosion so we cleaned it. The next thing to test was spart output to plugs. All 6 coils tested extremely weak. This was traced to the power transistor and once again we found the terminals corroded. We cleaned and retested. The spark was still weak so we replaced it. Then we found the reason for the transistor failing..all the coils were cracked allowing the coil to wonk at maximum capacity at all times. We replaced all the coil boots. Next we replaced all 6 spark plugs. Repaired all the vacuum leaks that were present. However there are many vacuum lines that are plugged (a golf tee and a screw on a few of them). We also found that the main ecu ground wires had small amount of voltages on them 1.16 to 1.35v. Cleaned all ground wires and remounted them now at .020 volts.

Coil output at start was 4Kv.
After replacement 22Kv.

Check performance of MAF sensor and all other sensors. (ME: I would really like to know what other sensors were tested).

Any sensor that has this type of corrosion should be replaced because its also on the inside of the sensor (I think he is talking about the CAS sensor).

Also while setting the crank cam sensor we found that the proper timing could not be set. This is probably due to a timing belt that is not correctly timed. Need to pull cover for inspection.

Then ran a resistance test on all injectors. All 6 were from 10.9 to 10.8 ohms. Next ran a balance test on all injectors. They were well within 1 lbs of fuel pressure drop.

Fuel pressure was at 52 psi with no air in fuel stream and volume was ok.

All 6 coils measured .8 ohms on primary side.

Compression on 6 cylinders.
1. 138
2. 135
3. 140
4. 135
5. 130
6. 138

Throttle plates were way out of sync. They had 1/4" of movement before other side started to open.

----------------

This is the writeup of the mechanic. Any input would be appreciated. It looks like he is leaning towards replaced the CAS and checking to see if timing is ok. Its 90% of the way there and says needs few more hours to diagnos. What do you guys think about all of this?

hoov100

Aren't N/A's supposed to pump in the 180's dry?

300zxBoulderCO

Ok bare with me..I'm still at it on this Z and am almost there. With the last slight misfire the shop wanted to take a look at the timing belt next. They pulled the cover and told me the belt is wore and looks like "alligator skin". They quoted me 600 dollars for parts which included (I'm on my way to the shop to look at it now to see what they are talking about and get a full list of parts they told me because I don't remember off the top of my head from our conversation): water pump, belt tensioner..ugghh I'll repost with the exact list when I get back. They also quoted me 5 hours of labor of $500...so $1300 for everything. They said they won't touch the engine any further until all of this is done in fear of blowing up the engine..which makes sense to me. My question is about the parts and labor quotes they are giving me..does this sound right?

I've done some research on other posts related to timing belts and it appears there are a few different kits. ZLover said the AMS kit is ****..and recommended the unorthodox pulley set which includes from research: Description: Unorthodox Racing pulley for the 1990-1996 300ZX Twin Turbo/Non Turbo. UR pulleys will add 22-24HP for a Twin Turbo, and 16-18HP for a non turbo. These are by far the best bang for the buck. The complete 4 piece pulley set comes with Crank, Alternator, Water Pump, and Power Steering Pulley. All pulleys come with Genuine Gates Belts(which are shorter, and are not stock sized belts).

Forgive me if I am asking a stupid question..but how does all of this tie into the timing belt replacement? Does this kit include everything I need...like the actual timing belt? Tensioner? Where should I really be buying this kit from? Are there additional parts I will need to purchase as well for this job? This kit is right around $400 so its much less than the quote I'm getting from the shop. I'm just worried they will say they won't warranty the parts because they didn't come from them.

Please any help is appreciated everyone has been really helpful..I'm almost there. I'd like to get this done right and not the cheap with with cheap parts so I don't have to do it a second time.

300zxBoulderCO

Ok just got back from the shop and here is the rundown. I saw the belt and it was majorly cracked the whole way around so I guess I've been lucky it hasn't broken on me..

All OEM Parts - $707.53
Timing Belt Kit (TB 251 K1) $311.20
T-Belt Tension Assembly Inc. Hydraulic Adjuster (13070-45v04) $196.00
Water Pump (B1010-22P27) $140.62
Antifree (Clear Choice) $19.98

Labor - $509.77
WATER PUMP - remove and replace $425.14
(Additional Time) - Where Air Cond interferes add $19.77
(Combination) TIMING BELT - Remove & Replace $49.44
Environmental Charge (wtf is this???) 15.42

With this being said...is this correct? There is nothing here about the alternator or power steering like kits online include? What are the drawbacks by purchasing these kits vs the stock OEM parts listed above? Even with all of this they can't guarantee that this will fix my problem

hoov100

Go with the courtesyparts.com kit, it includes everything and are all nissan parts.