1990 300zx na Hesitation

[jsd300zx90]

??????

..Can't wait to hear back from you!

[es.biggs]

Didn't get them yet, I have been crazy busy with work and school. I'm going to the Nissan dealership tomorrow probably and if they are cheap enough there I will buy them and if not, I'll wait for them to come in off the internet.

I'll be sure to post the results tho ASAP!

[zxFarside]

Didn't get them yet, I have been crazy busy with work and school. I'm going to the Nissan dealership tomorrow probably and if they are cheap enough there I will buy them and if not, I'll wait for them to come in off the internet.

I'll be sure to post the results tho ASAP!

You can get them from Z1 and you should get them in a day if your order them in the morning.

[es.biggs]

Just won an auction at ebay...

I get 9 new NGK PFR6B-11 spark plugs for just under $30

Gotta love that! Can't wait for them to come in

[zxFarside]

I hope that clears up the problem.

[mada300zx]

If that does clear up the problem. I would still clean up some of the plugs on the car.... dam i miss that thing!

[es.biggs]

Today was topless weather! haha this car is fun as hell man.

whatd you end up buying?

[es.biggs]

Just installed the new plugs...NGK PFR6B-11

There is no question the car runs a lot better now; smoother idle, better throttle response, and it seems to have gained a good bit of power back with the right plugs.

But unfortunately, the original problem is still a problem...so basically here is a recap of the big problem with the car:

At certain rpms below 3,000 the car seems to hesitate and it shakes pretty hard. It happens at about 1800, 2400, and 2700-2900. Those are just ballpark numbers to give you an idea. Once the tach passes 3000 the car takes off and feels healthy. You can physically FEEL the difference as 3000 rpm is passed, while keeping the throttle at the same level. This "hesitation" only occurs while the engine is under load. Revs in neutral are very smooth. There is an occasional backfire both during acceleration and in neutral. Sounds like it comes from the catalytic converter. When the car is cold, it accelerates smoothly at all rpms (I have never driven it past 4000 while cold though.) As the car gets warmer, the hesitation problem becomes much more apparent.

It almost seems like a predetonation/spark knock problem.

I took the car to Nissan today and spoke to a guy in the service department. I showed him a copy of the TSB regarding the early Z32s with heads that were machined wrong. After looking at my VIN, he told me that my car does fall under the early number of cars that were produced with that problem, according to the TSB. He said because of how old the car is he can't look back that far and see if the repair (new head, camshaft, CAS) was actually made back then, but he did mention that if this car was affected by the TSB then the previous owner would have had the repair done because it would have been noticed within a year of buying the car new.

I really don't know if I can believe whether or not the guy knows what he is talking about though. He seemed like he just wanted to get me out of the way so he could go make some money ripping off of some of the women in the waiting room. I hate dealerships, and I'm not going to work at one when I graduate.

My next step is going to be to check/adjust timing to 15 degrees before TDC. I might pull the CAS off and look at the teeth on it and see if they are chewed up.

Oh well. I'll keep this thread updated until the problem is solved.

[zxFarside]

Dealers are not the way to go.

There is a Nissan/Infinity shop on 74, Its past the super walmart on the right side. I personally have never been but I have been referred to them several times by a few people. It may be worth a shot to check them out to see if they can help you.

just found the site. http://www.nisstech.com/

[mada300zx]

I would definitely check the CAS before you do anything else. I read a forum that a guy cleaned his CAS and his problem instantly went away. Too bad it wasn't as simple as spark plugs huh? Anyway goodluck with it man. I'm buying a 2005 Acura TL on Friday. I have been driving my girlfriends busted ford focus all week. FML

[zxFarside]

I'm gonna replace my o2 sensors. I dont think mine have EVER been changed, and coming up to 160k I think its time.

[es.biggs]

I have heard of that NissTech place. They seem really legit...I might run up there to get some opinions. Either way I'm going to do the work myself. I don't have the money to pay anybody hundreds of dollars in labor, you know? I just need to borrow one of my friends garage space haha. My world would be complete with a garage at my house.

Mada, I would stay away from the pepboys you had that tune-up done at. 5 out of the 6 coilpack connectors were cracked, broken, and damaged in some way. They stay on well enough to run but it definitely isn't as secure as you would want them to be you know? AND they put the wrong spark plugs in, and they were all gapped pretty badly. One was about .045 and another was .035, etc.

[zxFarside]

I would love a garage or a carport. When I put my driveshaft in I was on my patio covered in the last snow we got in the freezing cold lol

[mada300zx]

Mada, I would stay away from the pepboys you had that tune-up done at. 5 out of the 6 coilpack connectors were cracked, broken, and damaged in some way. They stay on well enough to run but it definitely isn't as secure as you would want them to be you know? AND they put the wrong spark plugs in, and they were all gapped pretty badly. One was about .045 and another was .035, etc.

Well the spark plugs that I bought, it was actually more my fault because I should have known what my car is suppose to have lol. But I guess there computers are off if they say that they worked for my car. I don't doubt there installation was bad, not for one second. They are good at installing parts on 1995 ford rangers, not any kind of semi-difficult import.

[es.biggs]

I just got a timing light and adjusted my CAS. Timing was no doubt my problem. When I checked it initially, it was at about 3 or 4 degrees BTDC. I adjusted it in increments until it was at 15. Now it is adjusted so far counterclockwise that it can't be moved any more in that direction.

The car runs beautifully right now, like it is supposed to. No hesitation, no backfires. Only problem is the idle is a little high ~900. But I am worried that the previous owners never had the recalled cylinder head replaced. Why else would CAS be so far out of adjustment? I am hoping the timing stays at 15 degrees BTDC, because if it doesn't, I'm guessing I'll need the new head.

Is it possible to remove the CAS and turn it a little, then attach it back onto the camshaft if I need to further adjust it at some point in the future?

Here is a picture of my CAS right now, and you can see how much I had to adjust it by the two black marks

I was also wondering if you guys think my valves or anything else internally could have been damaged because the timing was so far off. I don't hear any ticks, and the engine is smooth as butter now, but I'm kinda wondering a little about that.

If you guys have any opinions or input, please let me know! Anyhow, whatever happens, I am loving this car to death. I don't care if it's N/A it beats the hell out of my old Accord I used to have! Even if it is a cop magnet

[mada300zx]

very good to hear man! Have fun!

[zxFarside]

That's fantastic. If the car is running good I wouldn't worry about anything till it happens lol

[es.biggs]

Hell yeah! Feels good fellas. Just drove the car home and man what a difference this car is a blast now. I thought it was great when it ran OUT of time, it's freaking awesome now.

Thanks Adam. I'm glad you didn't give me the car and just say eff that guy it's his problem now lol.

I appreciate everybody's help hopefully I won't have to post any more problems in this thread.

[mada300zx]

No problem man! I'm glad everything got figured out. Keep me updated if you do anything crazy to the car like a TT conversion or something. Have fun and like I said when I sold you the car, DON'T GET TOO MANY SPEEDING TICKETS LOL!

[mn300zx]

Fu**ing Right!! I knew a thread like this existed, I have a '90 n/a and NO ONE knew what the problem was!! i went to the 3 dealerships in the Minneapolis area to no avail. I will check my plugs when I get my paycheck and check my CAS. I've been searching for the thread since I got the car last july!!

Thanks everyone!!

[es.biggs]

I wouldn't trust a dealership with my car, unless you know somebody there knows this car well. It's kinda quirky haha

Good luck with your problem though let us know what you find out!

PS - I haven't checked my timing in a few weeks, but so far it's running great still!

[cjrboy14]

Does anyone get a check engine light that comes on and off? Never stays on but usually occurs during or right before the hesitation? Mine does it sometimes.

[es.biggs]

Maybe it's a misfire code

Never happened to me

[cjrboy14]

no clue usually by the time i stop somewhere or get home the code disappears so im not able to even pull it from the ecu...

I checks my tps cables and the connectors had green dried up caked on crap on it so im wondering if that is the prob. I drove it today and no hesitation...yet. My car doesn't do it often so I will have to wait and drive it for a week.

The same goes for the ptu harness connectors. All had the green poweder crap caked on the metal connectors. Is there a cleaner for this? I went at it with a blade and a tooth brush.
Modified by cjrboy14 at 11:29 PM 3/26/2010

[es.biggs]

you could also try cleaning it with a fingernail file then spraying it with electric parts cleaner (found at autozone) and the using some dielectric grease to protect it from corrosion in the future

[es.biggs]

It's coming back. I checked the timing two weeks ago, it was at like 13-14, now its at 11-12.

1000-3000 RPMs = sput sput sputt3000+ RPMs = HOLY VTEC BATMAN and the car takes off like it should

Maybe the spark is advanced more and more as the RPMs increase, which negates the retarded timing that is killing me in the lower RPMS.

Either way, I can slowly feel the hesitation sneaking back up on me, and I can't turn my CAS counterclockwise any more. I'm like 90% sure the thing is all chewed up on the inside

This s***tyness kind of makes me want to........

[zxFarside]

My car runs great in warm weather so I'm not having any issues atm.

[es.biggs]

I wanted to update this thread...since it seems to have a few people following...I made a copy of the TSB that pertains to the problem with my car. I will post that in here later.

My car has been running worse and worse, especially in the lower rpm range (again.) I can feel it getting progressively worse with time. Now my ignition timing is back to about 11 degrees before top dead center. Because I can't adjust the CAS any further to fix the timing, I decided to pull it off and inspect everything. I looked at the index pegs; they are little half moon shaped roads that connect the spinning camshaft to the stationary CAS, causing the CAS to spin with the camshaft.

The index peg on the CAS was worn down, it looked as if it was slowly ground down on one side, causing it to change the shape, and preventing it from "meshing" with the camshaft, therefore it throws off the timing.

I'm pretty sure this verifies that I do have one of the early, badly machined left heads. Which is BS...its not my fault Nissan epically failed at this. Anyways, I have 2 options now...replace the CAS with another good one and see how long it stays in time, if at all, or (hopefully not) R&R the head. I checked out the flat rate labor time for a head job...17.5 hours. Ouch.

Here's a link to another thread I made, which includes pics of the index pegs on the cam and CAS.http://zclub.nicoclub.com/zerothread/488085

Also, here's a copy of that TSB about the heads that were machined wrong:

[es.biggs]

I bought a pair of 91 TT heads today for $150. Owner blew a head gasket and swapped in a whole new JDM engine into his Z. Hopefully no cracks from the heat...I checked with the straight edge as well they don't seem warped at all.

They fit as a direct bolt on, and they have better flow than the NA heads. Similar to a port I guess. I'm getting them pressure tested whenever I get a chance to, not in any rush though I have a lot of saving to do before I install them.

Anyways, I have my 60k kit, my new heads, now I need to save for my gasket kit, EGR delete kit, and whatever else I might want to do while I have my engine bay all ripped apart.

Suggestions, tips, thoughts???

-Ethan

[E_Cruz1989]

I bought a pair of 91 TT heads today for $150. Owner blew a head gasket and swapped in a whole new JDM engine into his Z. Hopefully no cracks from the heat...I checked with the straight edge as well they don't seem warped at all.

They fit as a direct bolt on, and they have better flow than the NA heads. Similar to a port I guess. I'm getting them pressure tested whenever I get a chance to, not in any rush though I have a lot of saving to do before I install them.

Anyways, I have my 60k kit, my new heads, now I need to save for my gasket kit, EGR delete kit, and whatever else I might want to do while I have my engine bay all ripped apart.

Suggestions, tips, thoughts???

-Ethan

Hey, just a quick question, does that TSB only pertain to the 1990 series? Mines a 1993 and I don't really want to have the problem the 1990s do, but I'm going to inform my friend who has a 90 auto about this TSB. And I'm also going to check my CAS and see if I can smooth out my ride some more, so thanks for having this trouble! JK!