Intermittent Miss

[rrgabe23]

90N/A 103K miles
This started back in the summer. I had driven about 30 miles to an appointment. I came out at lunch started the car and it was missing. I drove about 5 miles and it quit. This happened a couple of more times so I changed the fuel filter and poured in some injector cleaner. The problem went until a week ago. I came out of work and it was missing. I checked to ensure all plugs were secure. I re-started the car and it was OK. It then did the same a third time. I left work to get a hair cut, came out afterwards and it was missing. The miss is on the drivers side bank. I took it to a mechanic and ask him to check it out. He has had it a week and found nothing. He said the compresssion is good, no codes on the ECU. He said he hooked the scope up and all looked good. I ask him to check the PTU connection as well as the injector and coil packs. I suspect it is a high resistance connection. He is suppose to do so today. In the mean time does anyone had a similar experience and if so what di you find? Many thanks for your suggestions.

[tnkrstoyco]

You are probably on the right track checking the connectors, corrosion is a problem. I've read that certain injector cleaners do more harm than good on the Z's injectors.
Was it damp outside at the time?

[rrgabe23]

Thanks for the response. No, it was not damp. The first time it happened was in July in North Carolina. The humidity was high and around 90F. In the past, it would always clear up after a short drive. This last time it has not.

[rrgabe23]

So everyone knows, it was the PTU. It finally would not start at all and settled on a code 21. Mine has the Hitachi unit. It lasted 16 years as far as I know. There was a TSB for the 1990 300ZX for this module. The Hitachi unit is replaced by a Mitsubishi unit. The bulletin number is NTB94117 issued in February of 1995. I already purchased one for around $500. I am going to try and get Nissan to cover it.

[bjz]

$500.. Wow you got ripped... Shouldn't be more than $200 for the ptu which includes the new ptu sub-harness.