idle/engine problems.

[entimage]

Bare with me please, Im still learning about cars.

Here is my problem, I bought a 1990 300zx N/A car to trinker with. I dont think the car is running on all 6 cylinders. I replaced the coil packs for cylinders 5 and 6, but they still dont seem to be working. Also, sometimes the car struggles to start. I have to help it by giving it some gas. As for the idling, it's not always rough. It normally has a hard time after driving it for about 20+ mins. Any help would be greatly appreciated.

Just ask if you would like to know anymore details.

[robomatic12]

Do a power balance test to start, this will help you figure out what cylinder is not firing. Pull the coilpack connectors one at a time and listen for an RPM drop. If pulling any connector does not drop the rpm it is not firing. Then we can further diagnose if it is a fuel or spark issue. OHM the injectors from the cylinders that are not firing, if you want to feel good you can OHM them all. Do a search if you want a guide on how to do these things. Post back with results

[entimage]

Well I pulled the coil pack connectors. Cylinders 5,6, and 4 had no affect on the rpm's. Ill have to buy some tools tomorrow so that I can do the power balance test and OHM the injectors.

[robomatic12]

What you did was essentially the power balance test, swap the coil packs over to see if the dead cylinder follows the coilpack. If not it is probably the injector or a PTU/wiring issue. Do you have the version 1 PTU or the recall PTU with the new subharness?

[entimage]

I bought a new coil pack to test on the dead cylinders. 5 and 6 still don't seem to be working but 4 is. As for the PTU, I'm not sure which one I have. I'll do some research and post back with an answer.

[robomatic12]

Ok so now we are just dealing with cylinders 5 and 6? Grab a multimeter and ohm the injectors, you will need to remove the connectors first.

The older PTU has a silver heatsink on the back and the newer one is just a black box with connectors on either side. The newer one also requires another harness to be plugged inbetween the old connector and the new PTU as the connectors were not the same type. Old style uses a metal clip, new style is plastic push clips.

[entimage]

Now We are only dealing with Cylinders 5 and 6. I checked the PTU and it looks like I have the old verison of the PTU. It has the silver heatsink on the back of it.

An addition that I left out of the original post. When Accelerating, The car makes a whistling sound until it's in 4th gear.

*Edit* I took the PTU off and cleaned it up real good and the other 2 cylinders started to work, but it still feels like its missing power. It is also still riching rich.

[robomatic12]

The whistling could be a vacuum leak which would explain the power loss. Check all the vacuum lines and intake hoses/clamps. See if you can hear the hiss in the engine bay.

These cars have a big problem with corrosion in the electrical connectors, ideally you should clean every connector under the hood and then protect them with some dielectric grease on the connector. Get rid of any green corrosion.

You should do a general tune up; spark plugs, fuel filter, air filter, fluid changes. Also not sure if you know or not but make sure you know when the timing belt was last replaced. They are due every 60k miles. If it fails the valves can contact the piston and costs lots of $$$.

[entimage]

Ok I checked to see if I could hear the hiss in the engine bay. I could, but barely. I can't tell were it is coming from. Any suggestions on how to pin point where it is coming from besides checking every vacuum line and intake hose?

[robomatic12]

If you grab a section of hose, doesnt matter what size perhaps a 3/8-1/2" hose and hold it to your ear and move around the engine bay. The hiss will be very prounounced through the hose.

Go around and tighten every hose clamp connection you see on the intake piping. With the hose check around the intake plenum where it connects to the intake manifold.

If I were you and you are keeping this car for a while I would invest in the series 2 ptu and subharness.

[entimage]

thanks for all of your help and advice. Ill get the new PTU and subharness and do the tune up and let you know how she's running afterwards.

I did the tune up and I am waiting for the new PTU to come in.

[Ace2cool]

The PTU was a recall item through Nissan. You could have just taken it to them and they would have converted it.

[robomatic12]

They are still doing the recall for free???

[Ace2cool]

They were like 2 years ago, AFAIK.

[robomatic12]

Good to know! Ive never heard of it up here, possibility that nissan canada wants nothing to do with it.