1990 300zx na Hesitation

[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!

[es.biggs]

The first page of the TSB I posted lists a few dates, the cars manufactured prior to those dates were affected. July 20, 1990 was the latest date on there, so your 1993 should be good unless some body swapped a bad left head onto your car. Good luck with you and your friend's problem...checking timing is a great, easy way to start eliminating possibilities!

-Biggs

[pMetal]

I was having the same hesitation/trouble getting from 1700-3000 rpm problem on my 93 N/A and am overjoyed to report that it is now fixed.

The car when I received it had been sitting without plates for over 4 years, so everything was suspect.

Here is what I did (in order) along the quest to fix this problem:
1. Replaced fuel filter: Didn't feel much difference, although maybe the car was able to rev up faster.
2. Replaced air filters, standard Fram type: Car was definitely happier and had more power (old filters were really dirty), but main issue was still not resolved.
3. Replaced throttle position sensor: I tried to clean the old one but it was destroyed in the process. There may have been a slight improvement in the main issue, but it may have been in my head.
4. Cleaned MAF sensor: I did this at the same time as the filter change so I can't say if I saw an improvement from this.
5. Replaced the 3 belts in front: I did this because the alternator belt broke. I don't know if this had any affect on the hesitation issue, however some unrelated other electrical problems which I was having resolved themselves following this. Maybe while the alternator belt was weak and failing, maybe the car wasn't generating enough electricity to support all of its needs, and therefore the car wasn't able to accelerate properly. The belt job was done by a mechanic (not me), so maybe the electrical problems were resolved because maybe he disconnected and reconnected a corroded connector in the process. Who knows... Could be. If this did help the hesitation issue, it was not the magic bullet yet.
6. Added more oil. I was not sure previously if I had enough oil in the car since the dipstick is hard to read (always comes out wet well beyond the H mark nomatter how little oil is in the car). I don't know if this had an effect because it was done at the same time as the next step.
7. Cleaned the throttle bodies. Bam! Suddenly the car was fast! Way way faster than before, and there was no more hesitation problem.

Now here's an interesting note on a mistake that I made while cleaning the throttle bodies, which may have actually helped things: I used a whole bottle of aerosol throttle body cleaner between the two throttle boddies, and apparently I didn't wait long enough for all the fluid to evaporate prior to putting the rubber hoses back on and trying to start the car. The car cranked and cranked and wouldn't start. At one point I got the car to kick on for a moment with me stepping on the gas. The exhaust gases smelled really strange (the smell of throttle body cleaner burning). I realized that the areas inside the plenum that must normally let air into the cylinders were probably flooded with throttle body cleaner. I was really concerned that I may have done some serious damage. I took the rubber hoses off again and there was lots of smoke (from the cleaner) coming out. I opened the throttles up and put a fan in front for 20 minutes or so to make sure it dried out properly. When I reconnected the hoses, the car started right up and from then on the car has been great.

Now here's what I'm wondering: Maybe by trying to start the engine while the plenum was flooded with throttle body cleaner, maybe the cleaner ended up getting sucked in through the air inlets (excuse me for not knowing proper terminology or for not being sure of what goes on in there) and ended up cleaning this normally inaccessible and uncleanable area. Maybe that's what made the difference.

And the difference is night and day. Not only is the hesitation problem gone, but the car is so much faster. Previously the car could not even make the tires squeal. Not even close. The car couldn't rev up and down fast. It was just damn slow previously. Now this thing feels like a sports car for real!

Thanks to everybody who has posted up on this issue on this board and elsewhere on the internet. Hopefully my results will help somebody else to fix their problems.

Perhaps some other people can chime in as to whether my mistake of trying to start the car while the plenum still had throttle body cleaner in it helped or not, and whether people should try to do it on purpose or if it is a really dangerous bad idea. I mean I suppose it could have caught on fire or caused an explosion if things went differently. I have no idea.

All I can say though is I am super happy with my Z which is now fast for the first time since I have owned it!

[Ace2cool]

FWIW, the car is supposed to be hard to start back up after a good TB cleaning. Mine took about 20 seconds to catch spark, then died. Started it again, and it slowly chugged back to life. Glad to hear you got your problem resolved, BTW.

[GerryO]

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

If I'm not mistaken, codes are stored until the steps are followed to clear them or after a fair number of engine restarts without them occurring. My ECU seemed to want to display only one at a time though, once not coughing a second code until I'd fixed the first.

[es.biggs]

Thanks for that post pMetal, good information! Glad your car is running right, feels good doesn't it?