How reliable are these cars and what should I look for in buying a used 90+? They have been around for 8 years now, and there are still plenty of models that were built in 1989 in circulation. I've seen plenty of examples of 1989 built cars with serial numbers in the low thousands still running well - with their interior showing signs of wear, but no rust on the body.

Time has shown that the engine itself is generally very reliable, with turbo seal and bearing failure being one of the more costly items requiring attention later in engine life. Faulty components aside, the engine needs almost no adjustment. Self adjusting hydraulic valve lifters means nothing to do there. Platinum tipped spark plugs need changing only at 60,000 mile intervals. Once ignition timing is set, it can't vary unless the crank angle sensor goes faulty.

Some weak points have surfaced over the years, but nothing that can't be fixed with a bit of spare cash and TLC. The important thing about buying a used Z is to start with a non accident car. This will involve a reasonably thorough examination of the chassis, and checking that all plastic guards under the front of the car are still in place and undamaged.

A lot of small refinements have been made over the years which impact on reliability. For example, electric seat switches were changed in 1990 because the previous ones were prone to jamming and breaking, the oil feed pipe to the turbo was changed to one with a ceramic wrap to reduce pipe clogging in 1993. So generally , the later the model, the better the long term reliability. You may want to avoid the 1996 model if you plan to upgrade the engine computer. At the time of writing, computer upgrades to not appear to be available for this model.

One problem that Nissan have never addressed is the problem of preventing stones, plastic bags, straw, and all sorts of debris from entering the radiator and intercooler inlets. When I purchased my 300ZX's, the first thing I did was buy some black anodised aluminium fly screen, 1mm mesh size, (only a couple of US dollars), and install this in all front air vents.

If your prospective Z is past about 50,000 miles, watch out for these weaknesses, and factor the cost of repairs in the purchase price: Warped front rotors (shimmering of steering wheel under braking), slipping clutch, grinding noise in 4th & 5th gear due to worn synchros, leaking brake master cylinder, rusted auxiliary induction valves (makes a gurgling sound when the car is idling), blue smoke from the exhaust under hard acceleration caused by worn turbo seals, turbo whine indicating worn turbo bearing, vibration at 25 & 50 mph due to worn propeller shaft centre bearing, clunking noise when going over bumps from front suspension due to multi link wear, damage to intercoolers and radiator due to stones entering intakes, water leaking through targa top due to perished rubber.

If just over 60,000 miles you'll want confirmation that this major service interval has been done correctly

Another weakness is the failure of the ignition power transistor unit (made by Mitsubishi, Nissan part # 22020 58522 TSR IGN Unit / Mitsubishi 5126 0701. In you are in the US this is a recall item. In most other countries it is not, and you have to pay for it yourself if it fails out of the car warranty period.

Here are some comments by other owners (prices in $ US):

Dan Banks, Dbanks4708@aol.com 1977: [edited]

I bought my 1990 300ZXTT in September, 1990 which now has 96,500miles. My car remains almost completely stock and is the only Z-Car I've owned.

I have virtually all my maintenance done at Nissan dealers and prefer smaller dealers.

In my case, I had found out only about the camshaft end seals and had nothing else replaced at 60,000 miles. About 30,000 miles after the 60,000 mile major maintenance was performed a squeal developed from the front lower center of the engine after it warmed up and I suspected the water pump. The water pumps are not expected to go 120,000 miles. If one seizes up on you it is conceivable that it could throw off metal slivers that you don't want in your coolant system/radiator. The camshaft belt tensioner is another component that wears out and starts to make "bad bearing" noises.

For peace of mind, I simply had all the above components removed and replaced all over again half way to the 120,000 mile interval, re-paying the previous labor. Nissan's cost on the above named components is $450 and they will want 8 to 9 hours of labor. The only thing fancy I did was to replace the lower rubber radiator hose, which is a 2 1/2 foot long tube, with the Stillen aluminium lower hose designed expressly for the Twin Turbo. (See their new catalogue). Even though the original ran the 90,000 miles and emerged in good shape, I figured the aluminium hose would be a good replacement. It costs about $110 compared to the rubber hose which is around $40.

The bearings in the factory turbochargers can leak anywhere between 60,000 and 80,000 miles. For me the symptom was that after letting my car sit for a week, upon start up and after about 3 minutes, a cloud of blue oil smoke would emerge from both exhaust pipes for about 1 minute or so. No more oil smoke after warming up on the first start, no apparent oil consumption overall. The symptom would reappear only after the car sat again for a week. Test for this condition by applying full throttle to bring the boost up to maximum in 2nd gear. If you see the smoke and the car has high miles, suspect the seals. Opinions vary on how long one should run a turbo car with such a problem. In my case, my car was purchased with Nissan's then "Gold Plan" warranty which was 100,000 miles and 72 months and covered the turbos. At 82,000 miles and 70 months into my warranty, a small Nissan dealer who had never done the job before pulled the engine and removed and replaced the turbos for a single $25 deductible. That was 13,500 miles ago and the oil smoke problem has not re-appeared. It took the shop 4 men and 22 hours of labor to do the job. The company that holds the Gold Plan warranties allows only 11 hours of labor to be paid to Nissan while Nissan's service schedule book allows billing a customer 15.7 hours to remove and replace the turbos. The parts package of both turbos with all new oil lines, studs, nuts, etc. ( a total of 35 parts for each side) costs $2400. Figure on another 15.7 hours of labor at whatever rate your dealer charges. People who own upgraded performance Twin Turbos indicate that the replacement is relatively a straight forward affair but time consuming and best done with the engine out of the car. Nobody seems avers to having a Nissan service department do it if you haven't bought performance turbos from an established shop.

Watch out for the front wheel bearings. I have replaced mine twice. If they go, get them fixed immediately. If the wheel goes out of round on its bearings it will hit the ABS sensor, immediately garbage it (2 times for me) and that sensor is a $900 part in itself.

Virtually all the above maintenance was, for me, covered under my warranty. Wheel bearings, 4 sets of brake rotors (I had one of the early I-warp-right-now equipped brake rotor versions of the car), the air conditioning compressor, 2 ABS sensors, and the turbochargers. Probably all added up, the warranty coverage over the past 6 years came to at least 50% of the original purchase price of the car ($31,500 plus $1000 for the warranty).

Joe C. Parish, jparrish@ssl.umd.edu, IZCC #131:

I'm at 122,000 miles on my '91 TT. The 60,000 to 120,000 mile interval was unremarkable. I did replace the clutch at 92,000 miles, the exhaust at 110,000 miles, and of course went through a couple or three sets of tires. I did the timing belt (along with the tensioner, and water pump) at 115,000 miles because it was starting to get loud. No evidence of turbo problems. I think my precats are clogged, as power is down somewhat over when new; I may have them drilled out if other work is going on in the vicinity. I plan to keep the car until 150,000 miles. No major advice other than to run synthetic oil at 3K change interval, follow the factory recommended maintenance schedule, fix small problems before they become big problems, and take care of the turbos. Insurance is $950/yr for 33 year old single male w/ clean record in Northern Virginia.

Rob Rothberg, rothberg@portkar.com:

I think I have the highest mileage Z. 90zxtt, S/N 337, built July '89,122,000 miles so far.

The engine still sounds fine and runs strong, I'm getting puffs of white smoke from the right exhaust though. Might be bad, might not. I guess we'll find out. I've gone through all the usual problems, brake master/slave cylinder back around 95,000, warped rotors (3 sets before I replaced them with Skylines), short clutch life (replaced with Jim Wolf Technology type). Shocks are going again, precats are melted, other than that, all is A-OK, nothing serious seems to be going on.

Alan Waterman, AWaterman@symantec.com:

In my original search for a TT, I came across several for sale that had high mileage. One had 168K miles on it. The owner claimed he'd never had any problems. Maybe he said that because he was trying to sell it. Another had over 300K miles on it. The owner claimed the same. They were both '90's. Both cars were high freeway mileage cars, so that doesn't really say how a TT with similar miles will hold up when it has that mileage in 10 years due to city driving.

Eric Schauble, schauble@leland.stanford.edu:

I have a 1990 2+2 non turbo which just turned 90K. I have taken very good care of the car and it is well-maintained. I run my car hard; local autocross events and track events. I have had no problems with my car and it is running strong. Just had a compression test done, results were great. I am confident that I will get at least 150K out of my engine as long as I don't slack on the maintenance.

Donn Vickrey, vickrey@cts.com:

Ed Peterson, from the San Diego Z club, has 4th. gen. ZX no. 1001. It was produced during the early "soft valve" period (See below). However, I know he has well over 100,000 miles on the original engine. It seems to me that he has somewhere in the neighbourhood of 150,000 miles. I think that, with the exception of the few early production cars that actually experienced problems with the softer valves, most non turbos will last a long, long time.

The twin turbos will be harder to assess since a very high percentage of TT owners run non stock boost levels (perhaps as high as 25%). Those that do not maintain their high boost cars properly, or those who flog them regularly, will undoubtedly find that the engines do not last over 100K. Another variable that will cause problems in assessing longevity is botched turbo replacements. One friend with a turbo supra lost his engine when a mechanic somehow lost a screw when installing a replacement turbo. Guess where it ended up!!! A friend on the Z list also lost his engine after a botched turbo job. Another friend blew his plenum up after accidentally turning the nitrous on when the engine was turned off. He turned the engine on, and boom! Those that buy used twin turbos, with performance enhancements, have no idea what the previous owner did to the car. Did they crank the boost up to 15 psi, load up on gas in Tijuana, and drive 150 MPH to Vegas??? Who knows... All I know is that these types of problems will not affect the non turbos and will bias estimates of ZXTT reliability downward.

I do think that the twin turbo will be somewhat of a pain in the rear to own and maintain due to its complexity - that is if you cannot locate a good mechanic that is able to diagnose niggling little problems. That being said, for a quasi-exotic, it is actually very easy to live with - if you know what you are getting in to. I do think that the reliability and cost of ownership will compare very favourably with other "exotics" of the same period. For example, it will hold up far better than the RX-7 TT, Corvette, Porshe 911 Turbo, and all Ferraris (which, coincidentally, performed at about the same level in 1990). The car will probably be as reliable as the Supra, 3000 GT and NSX. However, it will be more difficult to maintain, and less reliable than a well maintained 240Z. Of course, it will stomp on the 240Z in every performance measure - so it is a pretty meaningless comparison. Kind of like ZXTT vs. Camry. What's the point.

Right now, my 1990 ZXTT has 70K miles on it, 60K miles with the chip and intake, 40K miles with the chip, intake and exhaust. It still seems to run about the same as it did when I bought it three years ago. Well, it's a little quicker due to some additional tuning...

Donn Vickrey, vickrey@cts.com (again):

Another thing for owners of all '90 Zs (zx or zxtt) to check is the engine number on your car. It is harder than hell to find but may be very important to your pocket book. Apparently, early production motors had softer valves and valve springs that can begin to work their way out (unscrew themselves from the head) at around 100,000 miles. It costs about $2,000 to fix! Engine numbers below approximately 620000 may have this problem. To find your engine number, get a flashlight and look on the passengers side (LHD) of the car up near the fire wall where the block meets the head. There should be a six digit number followed by a letter. For example, my engine number is 677038W. Don't panic though because the cut-off is below 620000 - I just don't know the exact number. FWIW, cars that were produced after 12/89 are unlikely to have the soft valves. But it is still a possibility. Also, the VIN# is not reliable for determining whether your car has the soft valves.

Porter Slagle, p.slagle@netstart.net 1997: (edited)

You should read the text that follows. Doing so, may save you from possible damage to your car's engine. This applies to Turbo and Non Turbo 300ZXs. Even if you aren't having problems right now, be knowledgeable of this in case your car fails in the future, you may need to know the symptoms.

My wife's 1990 300ZX (mileage, 66,000) failed while on a trip to Atlanta. The car became barely drivable because of a severe loss of power and had to be towed to a Nissan Dealer. The Atlanta dealer diagnosed the problem as a known manufacturing defect (more about the defect later). They temporarily "adjusted" the problem and indicated the car could be driven, but the problem was sure to occur again. The car was taken to a local Independent Nissan/Toyota Garage after my wife's safe return home. The independent garage gave us an identical diagnosis and produced Nissan Bulletin # NTB92014 dated 02/27/92. However, within days, the car suddenly failed again (with a stripped out cam shaft spline) and had to be towed to the local dealer. The local dealer diagnosis was identical to the other two garages, they said that they had seen this problem before and could not understand why it took so long to fail or to show itself.

Manufacturing defect: Holes in the Left Cylinder Head intended to house the camshaft bearings are machined slightly off center which causes failure of the Camshaft and Crank Angle Sensor. The remedial action is to replace the Left Cylinder Head, Camshaft, Crank Angle Sensor as well as other associated parts such as gaskets and bearings. The garages have indicated that the cylinder head must be replaced (with a cylinder head with properly machined journals) or the crank angle sensor and camshaft will prematurely fail again.

Failure symptoms: The previously referenced Nissan bulletin will describe the problem or symptom of customers complaining about spark knock/detonation. This detonation is caused by the Crank Angle Sensor jumping out of timing to an excessively advanced condition. Garages will tell you that the Sensor can also cause the timing to become excessively retarded causing and extreme loss of power which renders the car virtually undriveable, which is what my wife experienced on her Atlanta trip. Another symptom is the camshaft actually stripping where it drives the crank angle sensor which is what happened when the car went into total shutdown and had to be towed to the local Nissan dealer.

It is possible that you may be having the problem right now and don't realise that when it finally manifests itself that you are going to have to pay $4000 to $5000 to get your car fixed.

The service adviser has told me that it is entirely possible that even if the repairs are done, which effectively replaces the top of the left half of the engine, that the new components on that half of the engine will "out perform" the older components on the right half of the engine; causing an unacceptable imbalance (roughness). It has been suggested that I may just wish to replace the entire engine ($9,000) because an imbalance would not be known until the work was performed.

What to do: In all fairness to Nissan, I have to say that their bulletin says that it only affects a certain range of cars manufactured before July 20, 1990. However, their bulletin is dated 02/27/92. I don't know if I have all of their bulletins, nor do I necessarily know that all of the problems have been documented; this is why I suggested that 1990 - 1992 owners may be interested.

Based upon what I have been able to determine, some or all of the following parts are sometimes replaced:
1. The Left (drivers side) Cylinder Head and/or
2. The Left Overhead Cam Shaft and/or
3. The Valves and Pistons on the left bank and/or
4. The Crank Angle Sensor