When I come to a junction I slow down and if it is clear I pull away. when I put my foot on the throttle not having come to a complete standstill the revs drop and for a couple of seconds nothing happens then the engine revs pick up and it pulls away. It's a nightmare if you try to pull out with an oncoming car in the wet cos when it does pick up the back end flies out.

I have cleaned the IAA valve, throttle bodies and replaced the TPS. I currently have the idle turned up to 1500rpm to stop the hesitation.

Anyone got any ideas

 

Stu, here's some information I borrowed from another site :-)

 

Why does my Z32 hesitate sometimes?

 

This is long and semi-complicated. Here are things to consider in a general order of increasing unlikeliness:

 

Clean the TPS (Throttle Position Sensor)

Clean the air filter

Clean the injectors

Change the spark plugs

Change the 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

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?

 

Clean the TPS (Throttle Position Sensor)

The TPS is located on the driver's side of the engine. Look at the throttle body, it's the big box with the huge rubber intake hose going into it. The TPS is the small black plastic box on the side of the throttle body with wires coming out of it. The connector is held on by a little wire spring/clip. Use a small screwdriver or something to pop it off. Be very careful when doing this; don't lose it, it WILL go flying if you're not careful!

 

 

 

When removed, it might have green corrosion on the electrical connectors. Go to Radio Shack and buy connector/contact cleaner, or just use some ultrafine grit sandpaper, just get rid of that corrosion! Make those connectors shine and then reinstall the TPS. Corroded TPS connections are some of the most common causes of hesitation.

 

Time required: approximately 15-20 minutes.

 

 

Clean the air filter

This procedure is illustrated on www.ttzd.com.

 

Time required: 10 minutes for stock airbox; 1 or 2 hours to clean the K&N and let it dry.

 

 

Clean the injectors

Many people will come out and say the injectors should only be cleaned professionally by removing them. Nissan also says this. However, for the DIY'er, purchase a bottle of Chevron Techroline or some Red Line injector cleaner and run it through according to directions.

 

 

Change the spark plugs

This procedure is illustrated on www.ttzd.com.

 

It may be a good idea to at least PULL your plugs to inspect them, since as they age they will take on characteristics that vary based on the health of the engine.

 

The following is from the NGK homepage:

 

Reading spark plugs can be a valuable tuning aid. By examining the Insulator firing nose color, an experienced engine tuner can determine much about the engine's overall operating condition.

 

In general, a light tan/gray color tells you that the spark plug is at the optimum temperature and that the engine is in good operating condition.

 

Dark coloring, such as heavy black wet or dry deposits usually indicate a fouling problem. Heavy, dry deposits can indicate an overly rich condition, too cold a heat range spark plug, possible vacuum leak, low compression, overly retarded timing, or too large a plug gap.

 

If the deposits are wet, it can be an indication of a breached head gasket, oil control from rings or valvetrain problems, or an extremely rich condition, depending on what liquid is present at the firing tip.

 

One must also look for signs of detonation, such as silver specs, black specs, or melting or breakage at the firing tip.

 

Signs of fouling or excessive heat must be traced quickly to prevent further deterioration of performance and to prevent possible engine damage.

 

 

Here are some ideas for what you might see:

 

 

Thanks to CarloZ for the link info.

 

 

Change the fuel filter

This procedure is illustrated on www.ttzd.com.

 

If the filter was getting full of debris, it could lead to fuel starvation; but it would probably manifest itself in the higher RPM ranges where the engine requires more fuel.

 

Time required: 10-15 minutes.

 

 

Clean the Crank Angle Sensor (CAS) connector

This is nearly identical in procedure to cleaning the TPS. Except the CAS is in a different place. Stand by the nosepiece between the headlights. Look behind the radiator/fan, there are some hoses going into the middle of the engine. Those are for the water pump. To the right (driver's side) of those hoses is a round metal plate 3" to 4" across.

 

 

 

This is the CAS. There is a connector similar to the one on the TPS going into the CAS. Clean it. The procedure is the same, just a little more difficult to get to.

 

Time required: 20-25 minutes.

 

 

Clean the Throttle Bodies

This procedure is illustrated here

 

Time required: 20-25 minutes.

 

 

Clean the detonation sensor connector

This looks like any other electrical connector under the hood. It should be two or three inches directly behind the stripe on the throttle cable cover.

 

 

 

Disconnect and clean. Hopefully this will solve any problems as far as the connection is concerned, since to actually get to the detonation sensor, the plenum must be removed.

 

Time required: 5-10 minutes.

 

 

Clean the Mass Airflow Sensor (MAS) connector

Remove the nosepiece between the headlights again. The MAS is the little black box with wires coming out of it connected to the air intake. Be careful, this connector also has the spring clip like the TPS & CAS. Clean the connectors and reinstall.

 

Time required: 10-15 minutes.

 

 

Clean the coolant temperature sensor connector.

If the temperature gauge drops under acceleration or goes up and down erratically under acceleration, clean or replace the temp. sending unit. It is located on the top aluminum pipe in the front of the motor. It is the sensor to the right with only one wire coming out of it.

 

 

 

First remove the plug, press in the clip on the right side and pull, clean out the gunk in the plug. Next remove the sensor itself, 12mm deep socket or 12mm wrench. Clean the junk off of that too. Replace both the sensor and the wire. If it still fluctuates, replace the sensor for about $20.00.

 

Time required: 10-20 minutes.

 

Bob:300zx.org

 

 

Induce turbulence in the air intake

Sometimes airflow around the POP charger will be so smooth the MAS has trouble registering the correct amount of air, and as a result gives strange readings to the ECU! Strange but true... To solve this, place two 3" long strips of duct tape along the bottom of the POP charger. This forces the air to flow into the intake and around the MAS in a different manner; and should eliminate the problem.

 

Time required: 5-10 minutes

 

Jim Bullitt

 

 

Change/add coolant

Loosen the petcock on the bottom of the radiator & remove the radiator cap and secondary screw on the top of the radiator. This will drain a lot of the fluid out. Then run the engine for 15 seconds to flush coolant out of the heads, etc... Don't run the engine too long without coolant or it'll overheat! Close the petcock, then add coolant. This can be a bottle of Red Line Water Wetter and distilled/filtered water (not tap water) if in a warm climate, OR a mixture of water/antifreeze/Water Wetter (according to directions on the antifreeze) if in a climate where it gets cold. Even in the warmer areas, a little antifreeze is probably a good idea. According to the owner's manual, the cooling system capacity is 9 quarts. Fill the radiator, and the resovoir up to the "HIGH" mark on the resovoir dipstick. Then with the radiator cap still off, run the car for 30 seconds. The level will go down as the heads and tubing are re-filled with coolant. Add more coolant to the radiator. Make sure the resovoir is still at HIGH. Run the engine for another minute or two, make sure the radiator is still full and put on the cap.

 

The next couple of days, check the level to make sure it's still satisfactory and there are no leaks.

 

Time required: 20-30 minutes.

 

 

Clean intake valves and manifold

This is a slightly controversial procedure. Basically, expose the intake and run the throttle up to about 2500RPMs. Put something on the gas pedal to hold the engine there. Next, VERY slowly pour water into the intake. Like, a tablespoon every ten seconds or so. In fact, use a tablespoon to keep from pouring TOO much and hydrolocking the engine (water doesn't like to compress!).

 

The idea here is a continuous misting of the inside of the intake manifold will break loose small carbon deposits and free up airflow. While doing this expect steam out of the exhaust (in small amounts) and perhaps some smoke if its freeing up a lot of fouling. Keep this up for 10-20 minutes, then drive the car afterwards to make sure everything's OK.

 

Chris(Miami)

 

 

Do you have an updated Power Transistor?

There was a recall on power transistors a few years back. Seems the old ones can quit working properly after a while. To find out, simply call or visit the local dealer. Have them look up your VIN and see if the recall replacement has been performed. If it hasn't, now might be an excellent time to get it done.

 

 

 

 

Is it a 1990 model?

The driver's side head was machined wrong and the result is a problem with the crank angle sensor to exhaust cam splined joint. They will wear themselves out and the car will develop a hesitation that will continue to get worse. There are some Band-Aid fixes like only replacing the CAS ($350) or the cam and sensor ($2100) but the real fix is to replace the heads. Check with the dealer about a TSB Nissan has issued on this problem to see if your car is affected. I believe all 90 models are.

 

Bruce S

 

If for some reason all of this doesn't help, try the even MORE extensive Hesitation FAQ by Andy Woo and Steve Chong at www.zhome.com!!

 

Researched and compiled by JaimeZX.

 

Hope this helps

 

Steve

 

 

 

Thanks but I have been through that with a previous fault.

I must have the most unreliable Nissan on the planet it's broken down on me over 10 times!!!!

 

If I were you I'd find a reasonable person to run the Nissan Console on your car to diag all the voltages etc, in the garage and during the problem.

 

 

 

 

Stu,

 

Like Jez said you need to get a consult test done. I had the same problems until yesterday when I had the PCV valves and O2 sensors replaced. Mine happened all the time when the engine was cold. The springs in the PCV valves are known to become weak and they move about especially when braking to a stop hence the revs dropping and almost stalling.

Not expensive to replace.

 

Andy

 

I had exactly the same problem. After advice from the forum. I cleaned the throttle bodies (couldnt belive how much shit came out) and the TPS connection. Transfromed the performance....no hesitation at all. The car will need a good blast afterwards..

 

Hope this helps

 

Stu,

has anyone messed with the throttle body synchronization?

 

I would first try to look for air leaks by "pumping up" the engine.

You have to block the intake at the filter and apply pressurized air

to the intake system. Listen for leaks.

It's a great method, cause you're checking all the hoses at once!

Do it on a warm engine, cause the hoses are softer then.

 

Next I would check/set the TB-synchronization.

The butterfly valve should close just past a little hole on the bottom of the TB.

(Props to Henri for the pic!)

 

Check that both valves close equally with respect to that hole.

Secure the spring-loaded pin under the adjustment plate (on the left TB linkage) by sticking a wire through a hole in it.

Loosen the adjustment screw .

Now screw it in so that it rests on the adjustment plate without moving it.

Actually the manual states that it should move a fraction of a millimeter

but to see that you would need a special gauge mounted there.

Lock the locking nut and remove the wire from the pin.

 

You may have to try it a couple of times before it's perfect.

Good luck!

Maciej

 

 

Thanks Macie I will check it on the weekend.

 

 

Checked the throttle bodies and they are aligned and clean.

Cleaned the IAA valves again and suprise suprise it still tries to stall when I stop.

The best bit was my dad who reckons the knocking is my big end bearings going.

What a nightmare!!