Poor Acceleration and Smelling Gas

[ZX-Smoov]

HI everyone,
I've been peeking around the forum for about 3 weeks and I'm a 2-week owner of a 92 NA 2+2 (Ya me!).
I'm experiencing poor acceleration and vibration around 60mph and above. Is there a visible inspection to confirm a driveshaft problem? I plan to do some of the other tests for fuel and air pressure.
Gas milage is terrible (less than 30 miles on a half tank) and there's a smell of gasoline. HELP!!

Work done so far:
Cleaned K&N Air Filter
New NGK's 6-11b
New fuel filter
New shocks

Need to check the CAS and timing. I'm not sure if #6 coil is good or bad.
Building up the nerve to pull my plenum and check injectors.
Any thoughts or ideas?
You guys have offered some awesome advice- Great reading!!

[emiliog2276]

HI everyone,
I've been peeking around the forum for about 3 weeks and I'm a 2-week owner of a 92 NA 2+2 (Ya me!).
I'm experiencing poor acceleration and vibration around 60mph and above. Is there a visible inspection to confirm a driveshaft problem? I plan to do some of the other tests for fuel and air pressure.
Gas milage is terrible (less than 30 miles on a half tank) and there's a smell of gasoline. HELP!!

Work done so far:
Cleaned K&N Air Filter
New NGK's 6-11b
New fuel filter
New shocks

Need to check the CAS and timing. I'm not sure if #6 coil is good or bad.
Building up the nerve to pull my plenum and check injectors.
Any thoughts or ideas?


You guys have offered some awesome advice- Great reading!!

Is there a noticable location where the vibration is coming from? Does the car seem to take off after 2500 rmp? Pull the connector from #6 coil while running any change ? Smell of gasoline i would start looking for a fuel leak especially at the mpg your are getting. See if you can take a peek (feel moisture) at the small piece of hose that connects the fuel rail underneath the plenum [_]. Any codes? Grab a multimeter and check those injectors.

[BlackWidowZ]

Tighten the fuel clamps check for leaks.

[youtube]http://www.youtube.com/watch?v=KGZjNv-zqSQ[/youtube]

[ZX-Smoov]

Great suggestions!
I just picked an ohm meter today. Should this do the trick for testing? Has anyone seen a centralized listing for "normal" ranges or readings for various areas of the vehicle? I recall a video that says the TPS should throw 45 on a meter, correct? A chart would be great.
Thanks for the video link on clamps. That's a powerful map to follow. I'm not driving the vehicle so I will be checking this weekend and share results.

As for the vibration, the feeling seems to be under the rear seats as if I'm dragging the back half of the car. At 2500rpm, it still fights for acceleration. I'm between 3500-4000rpm steady while it climbs to 40mph. The psi gauge shoots over to 120 and only lowers to center between 55-65mph (steady hwy driving).
Underneath, she is wet below the engine (wish it was a woman) so it may be oil. Gotta check.

Thanks again, and I will report my findings soon!

[ZX-Smoov]

RE: Vibration.
I only feel it when the car is in gear. At stop lights, I put it in park or neutral and the vibration disappears.

[ZX-Smoov]

Had the garage for a few hours Saturday and here's my update:
All 6 coil packs gave 1.0 on the multimeter
Pulling connector on #6- No change in engine RPM's
ECU- threw code 34: The Knock (detonation) Sensor
MAF is responding- car shuts down when pulled

Thanks for the video link on clamps!!! I made between 2-5 turns on most of them, except for those on fuel filter from my previous install.

Planning on ordering a knock sensor and sub harness for a relocation install on top of engine just in front of the firewall. Anyone have any positive or negative feedback on the proposed switch?

Also, anyone have a good explanation on pinched o-rings and where they are located? I don't know if this is a concern, but I'd like to learn more about the Z!

Thanks for the shared wisdom and professonalism on this forum!!

[nexus08]

Had the garage for a few hours Saturday and here's my update:
All 6 coil packs gave 1.0 on the multimeter
Pulling connector on #6- No change in engine RPM's
ECU- threw code 34: The Knock (detonation) Sensor
MAF is responding- car shuts down when pulled

Thanks for the video link on clamps!!! I made between 2-5 turns on most of them, except for those on fuel filter from my previous install.

Planning on ordering a knock sensor and sub harness for a relocation install on top of engine just in front of the firewall. Anyone have any positive or negative feedback on the proposed switch?

Also, anyone have a good explanation on pinched o-rings and where they are located? I don't know if this is a concern, but I'd like to learn more about the Z!

Thanks for the shared wisdom and professonalism on this forum!!

No change on #6 means it isn't firing. Could be bad spark, or bad fuel injector. Since you smell gas, maybe bad spark?

The bad knock sensor code means it isn't reading the sensor. Could just be a bad connection. Pull it, clean it, see if it helps.

The pinched O-rings would be the ones that seal the fuel injector. I think I read there was a way to test for this without pulling them... maybe someone else can chime in.

[nexus08]

Oh, and the MAF maybe working but dirty... I cleaned mine (CRC MAF Cleaner) and it made a big difference in performance.

[Ziggy1621]

Welcome to Nico! Post up some pics of that baby!

Driveshafts normally shake somewhere around 2500rmp-ish when the carrier bearing is going out. Have you had the tires balanced to make sure also?

If you're going to have to replace he knock sensor, then you will want to save up. You have to pull the upper plenum which means pulling the timing. So depending on how long ago the timing was done, you may have to do that while its apart... it will save you cash doing it all at the same time.

As far as the pinched oring, I'm not aware of any way to tell without pulling them. When its been pinched from my experiences, it causes hydrolock. I would ohm out the injector on #6 and make sure you have spark.

Start by going through this post, its a Must read when you own a Z: everything-you-need-to-know-about-the-z32-t508376.html

keep us updated!

[ZX-Smoov]

Hi everyone,
I am baffled by the lack of response of the number 6 because the plugs have been replaced and I did get a reading on that injector.
I'm thinking that this problem may be a wire or possibly the coil pack.
Before bolting them down, I will switch positions and see if its the pack. If its not, then maybe its a wire.

Condition:
I pulled the connectors on all six injectors and everything was GREEN!!
I cleaned the mess out of them because I was not getting a reading on a few.
The corrosion was a mess and the wire casings are brittle.

After cleaning here are the numbers for the injectors:
1- ~14
3- ~25.9
5- ~15.4

2- ~12.8
4- ~10.4
6- ~12
Any feedback on "normal range"?

Regarding code 34 Det/knock sensor:
I did a relocation on top of the plenum just in front of the firewall, so I will check for a cleared code when everything is reconnected.

I still need to reinstall the coil packs and balance tube.
Sealing and wrapping some tubes and hoses that were cracked then connect the battery and test drive.

I will get the tires balanced before exploring a driveshaft switch.

[nissanfreak12]

1,2,4,6 are all within range. 3,5 are out. Range is between 10-14, if you replace 2, it is best to do all 6. get the new style, you will not regret it.

If #6 is not firing, pull the plug What does it look like? Is it wet? Very possible the injector could be stuck open or an oring just bad.

[ZX-Smoov]

Reconnected everything and went for a test drive of about 15 miles. What a difference it makes when hoses are sealed, clamps are tightened, and connections are cleaned!!
No smell of gas.
This means a lot since my 8 yr old boy wants to ride in the Z ("Dad, this is small enough for me to drive").
I remember the previous owner telling me he put on a new CAS, so now that I have new plugs and cleaned connectors, I will study the process for adjusting the CAS and/or TPS. I can't believe that any attention would have been given to setting the CAS if the other aspects of the engine were so poorly disrgarded.
Shifting from 3rd to 4th felt hesitant during a punch on the accelerator and RPM's were at 5K (its an automatic) so I need to confirm the fluid level for the transmission.
I will also check for any codes.

Question:
Does anybody know what it takes to recalibrate the ECU to compensate for the upgraded airfilter and modified exhaust?

These mods were done before I bought the car and both are designed to increase airlfow and horsepower, but I understand the ECU should be recalibrated.

Thanks again for the suggestions.
I know they will help me and others stopping by!

[RubyRed300ZX]

No need to recalibrate the ECU for a modified air filter as it (the air filter) is upstream of the MAF (mass airflow sensor). Same for the exhaust system (it's all downstream from the last sensor, O2).

[ZX-Smoov]

Thanks RubyRed!!
I just read that injectors should ohm out between 10-14 so my 3/5 both should be replaced. I think I'm going to dremel the plenum to get them out. I will report on the progress.

[Ziggy1621]

You are going to put the knock sensor back right

[ZX-Smoov]

Ordered two injectors but received only one. I dremeled the plenum and it saved a ton of time! Replaced the #3 injector and when the new one arrives, I will replace #5.

With the new injector and hoses clamped, code 34 is no more.
ECU throws a CODE 53.
Is this an O2 sensor or something else?

From reading other posts about "safe mode," I'm trying to determine if this may be my problem for low-end power or a transmission issue. The transmission jerks going into 2nd and is stubborn to shift gears. Fluid is light and full.
I will take it in to be evaluated by a mechanic.
Updates to come.

[ZX-Smoov]

Hi Gang,
I am concluding that my problem also has much to do with my transmission. I put in a bottle of transmission treatment and it ran much smoother. The next day I found a small puddle of transmission fluid in the driveway the car ran rough again.

[nexus08]

Hi Gang,
I am concluding that my problem also has much to do with my transmission. I put in a bottle of transmission treatment and it ran much smoother. The next day I found a small puddle of transmission fluid in the driveway the car ran rough again.

Uh oh... don't know if that is a big or small issue. Others might be able to chime in. I recently read somewhere where there is a way to get the car to give you codes on the auto transmission too that is different than the ECU. I haven't done it but here is the link -

http://www.twinturbo.net/nissan/300zx/t ... odiag.html

[DCaff300ZX]

I believe that the FSM covers that:
http://300zx-twinturbo.com/cgi-bin/manual.cgi

[ZX-Smoov]

It's been quite a while since my last post. The weather has been crappy and cold (-12F) so I haven't yet replaced the #6 injector. Happy to report that the interior trim in the rear looks better now that I've re-wrapped the pieces with new leather.
My faulty glovebox is now closing solid. I pulled that puppy out and fixed the latch mechanism.
I had the cherry bomb exhausts removed and replaced with quieter mufflers.
New rectangular tips were ordered and I will put them on when the weather breaks.
The rear hatch shocks had gone soft, so I installed new ones.
New battery- I thought I needed to replace my dash bulbs but the original battery was on its last leg.
I learned the hard way when it refused to turn over after two jumps.

After a week in the transmission shop they charged me ZERO dollars. Driveline Performance Transmission in Hazel Park, MI.
Honest group of guys. They came highly reccomended and have been in business over 30 years.
They did source an O2 sensor code- passenger side. It gets tackled when I do the #6 injector this spring.

Once the snow is cleared from the roads, I'm going to the Nissan dealership for a full diagnostic.
Yeah, yeah , I know, but I'm only getting just so much info from my datascan readings. I'm using the free version of ECUTalk and the software that came with the scan unit.--- Any suggestions for locatiing cost-effective (free) software upgrades?

Gotta get some acceleration. Not cool to be in a Z and Ford Fiestas are taking me off the line.

[ZX-Smoov]

Hello Everyone,
It's been months and much work. Here is what's been done:
Vacuum hoses replaced
Clamps tightened
Upper Plenum pulled
Injectors replaved- all 6 at the same time (270cc)
Injector Clips replaced
EGR Pipes cleaned- leading into upper plenum
Sub Harness replaced
Replaced mufflers
Replaced Fuel Filter
Replaced Plugs- 6 NGK's
Sprayed MAF Senor
Replaced Battery

Acceleration remains poor. There is a dropin RPMs when 2-6 coil pack plugs are pulled, but no change when #1 is pulled. I switched #1 and #3 coil packs and still no drop in RPM's when the @1 coil plug is pulled.
I switched #3 and #1 coils back and pulled the coil pack itself from #1 and could hear and see spark (arc) but no change in RPM.
I pulled the injector clip and still no change on #1 cylinder.
Any suggestions?

[ZX-Smoov]

Also want to mention that when the plug on the coil pack is pulled (#1), there is no arc or spark, no clicking sound.
I have not checked timimg, nor have I checked compression. You may recall from a previous post that #6 was not responding, but now #1 cylinder does not respond when the connector is pulled from the coil pack.

[Ziggy1621]

Did you put new injectors in or used? If used, ohm that injector. You can also do the 'click test' with a screwdriver. While the car is running, you put the tip of the screwdriver on the injector and the other end up to your ear to listen for clicking.

You said you put a new sub harness. Which harness are you referring to?

Check for corrosion or broken wires on the coil connector for the #1 cylinder. Pull the coil pack and plug. Have a buddy turn the engine over while you ground the tip of the plug to see if you have spark.

If that fails, do a compression or leak down test

[ThisIsSparTTa]

Let's take a step back. If you're not getting spark on #1, then start there. Are you sure you're getting spark on other cylinders (ie: you're performing the spark test correctly)? I had to learn that the engine needs to be running to test for spark...and also to be careful where and how you're holding it .

We went around and around on this stuff on my friends car. Start with the PTU test posted in this forum. From there I would inspect the PTU subharness as it will often corrode and cause problems. Many people cut that subharness out and solder it straight as its not necessary. Then I'd check continuity from PTU to Coil Pack Connector, then Continuity from ECU to PTU. Even if all of that checks out, you could still have an issue in one of your wires as you can still have continuity if just 1 strand is connected. That's what ended up happening with my friend's car, we tested EVERYTHING. Finally he took it to the local Z shop and they figure out the wire from PTU to the coil pack was bad, and I guess bypassed it.

[ZX-Smoov]

Did you put new injectors in or used? If used, ohm that injector. You can also do the 'click test' with a screwdriver. While the car is running, you put the tip of the screwdriver on the injector and the other end up to your ear to listen for clicking.

You said you put a new sub harness. Which harness are you referring to?

Check for corrosion or broken wires on the coil connector for the #1 cylinder. Pull the coil pack and plug. Have a buddy turn the engine over while you ground the tip of the plug to see if you have spark.

If that fails, do a compression or leak down test

Hi Ziggy,
Thanks for your help. The injectors are remanufactured and came with a spec sheet for them. I Ohm'd it and got 11.8. I did hear clicking using a long socket wrench arm. will re-do using a screwdriver.

The sub harness is for the PTU. The 7-pin connector coming from the PTU to the CAS had a frayed white wire and the other 6 were exposed as if they had been hacked by the cooling fan. I jiggled the old harness and the engine perked up, so I ordered the replacement PTU harness.

No visible corrosion on coil pack connector.
How do I ground the tip of the plug? I'm not familiar with this.
I did have the car running and pulled the coil pack away from the spark plug. I did not get shocked, but I could hear the clicking become louder and I did see it spark at one point before lifting the pack too far out.

I need to rent a compression tool and read up on the procedure before attempting.
I've not heard of a leak down test before. Can you explain what it is, how it works, and what I should do?

I appreciate your wisdom!

[ZX-Smoov]

Let's take a step back. If you're not getting spark on #1, then start there. Are you sure you're getting spark on other cylinders (ie: you're performing the spark test correctly)? I had to learn that the engine needs to be running to test for spark...and also to be careful where and how you're holding it .

We went around and around on this stuff on my friends car. Start with the PTU test posted in this forum. From there I would inspect the PTU subharness as it will often corrode and cause problems. Many people cut that subharness out and solder it straight as its not necessary. Then I'd check continuity from PTU to Coil Pack Connector, then Continuity from ECU to PTU. Even if all of that checks out, you could still have an issue in one of your wires as you can still have continuity if just 1 strand is connected. That's what ended up happening with my friend's car, we tested EVERYTHING. Finally he took it to the local Z shop and they figure out the wire from PTU to the coil pack was bad, and I guess bypassed it.

Hey ThisIsSparTTa!
Thanks for replying on my other post as well as this one.
The other coils are responding when the coil connectors are pulled (RPM drops then increases when connector wires are replaced).
Engine was running and I did not get shocked this time (This Time).
I will search for How To Test The PTU on this forum. I can say that my PTU sub harness was a mess. I still question the wiring on this car. Its a very brittle harness throughout.
Regarding One-Strand Continuity, the white wire on the 7-pin connector coming from the PTU that locks into the side leading to the CAS (white wire) looked like it was connected only by the plastic casing that surrounds the wire (or missing wire in my case). I suspect the side leading to the CAS may be faulty in my case as well.
Is re-wiring the car harder than pulling the upper plenum? I swear I looked in the abyss during my pull!!
I need to wrap my brain around continuity testing the wires and learn what settings to use on my meter.
I need multimeter reading for dummies.
I do not wires from the PTU to the coil packs. I thought the coils led to the ECU. (keep in mind I'm replying to you at 3:30am so im not looking under the hood at the moment) I will go back and trace where the wires are going so I can better respond to you.

Thanks for sharing your friend's story and your insight!!

[ZX-Smoov]

On 5-10-14, I did a compression test on the cylinders and none of the plugs appeared wet, but there was build up of grime at the base of the threads where the compression ring of the spark plugs seat. Here are my numbers. They seem to be within range, but the variance is beyond the 14psi from one cyclinder to another:
#1- 160 #2- 145
#3- 158 #4- 145
#5- 170 #6- 140

These numbers were taken after applying 2/3 bottle of Rislone High Mileage Compression Repair. It did seem to smooth out the engine just a bit and the actual feel on the road is smoother (it doesn't feel like I'm driving over gravel as bad as prior to this application).

Anyone experience such a variance in numbers?
Any suggestions to rectify the low compression?

Thanks for your help.

[ThisIsSparTTa]

Replace your drivers side O2 sensor. Looks like its causing it to run lean, hence the whole bank is going low. I used the Bosch one over the "OEM", which are basically the same thing. Low compression is what it is. Can't do much until you're ready to do a rebuild.

[ZX-Smoov]

Rebuild as in "Rebuild The Engine?" I ask the question as if somehow the reply will be to do a simple oil check. I'm at a point in my life where I want to conquer the challenges in front of me. Soooo... with that being said, has anyone done their own rebuild and what does it take? I saw a video of someone who took their engine apart without puling it from the engine bay, but it seems like more work ultimately.
Any resources to help me learn how to get it done would be greatly appreciated.
As always, thanks for your wisdom!!

[Ziggy1621]

Those compression numbers are pretty off. Did you start on the Passenger side?

Spartta, can you elaborate on how a bad O2 sensor would change compression numbers? I'm only asking because I've never heard that before.It will cause a bank to run lean, but I've never heard it changing the dry compression numbers.