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Occasional Engine Stutter - '77 280Z

Old 06-01-2015, 09:39 PM
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Occasional Engine Stutter - '77 280Z

Hello again!

I thought I would start another thread about my '77 280Z and it's engine issues. A little background on me:

I have done minor repairs such as replacing brakes, tuning an old carburetor, and even pulling a few pistons from an old '55 Plymouth. But I am pretty ignorant when it comes to the inner workings of a car, for the most part, though I am willing to learn.

Now, a little about what's going on with the Z and what's been done thus far:

When I first got the car a few months back, the car would not run at all. I could get it to start some of the time, but could not keep it running. It would sputter and spurt and then die. Even when it seemed it was somewhat running, applying the gas would cause it to just quit.

The car was then worked on by a mechanic and he did much to the vehicle for me - went through and replaced all the fuel lines, installed a new fuel pump and filter, replaced the injectors and pig tails, checked fuel pressure, etc. I had known this mechanic for some time and trusted him, but it turns out he is really good with newer cars (i.e. cars where a computer can tell you exactly what is wrong), but was frustrated with my Z and trying to get it to run smoothly. I got the car back from him mostly running, but it would stall ... a lot. In other words, I could drive the car and it would end up stalling at odd times. It was not heat related as the engine was sufficiently cooled by the radiator, etc., and maintained a good engine temp throughout. The car would purr along ... and then die. Sometimes it would die shortly after starting it and driving. Sometimes it would go for quite some time (15-20 minutes of constant driving) and then it would start to sputter and lose speed, going to a crawl and then shutting off.

When the car stalled out, turning the key would not get the engine to run. It would crank, sputter again, and the die. Sometimes it would just crank and do nothing more. If I let the car sit for a few minutes (literally a few minutes ... sometimes only 5) and crank it, the car would start up and drive as if nothing were ever wrong.

Since the mechanic did not want to deal with the car any more, I decided to see what ignorant me could do. I purchased and installed an inline fuel filter and installed it between the tank and the fuel pump. I thought that perhaps there was rust in the tank. At least with the clear plastic filter I could check it and see what was going on. The filter seemed to help and the car did not stall for a few days, but then it started to stall again. Looking at the filter there was water in the gas and very little rust at all. I used a bottle of HEET and this seemed to help, but not completely. The car would sputter from time to time, but not always stall out. I fueled up and tried a second round of HEET and the car was running awesomely after this ... for the most part.

The car no longer stalls and shuts down. But there are a few times where it starts to stutter. Most of the time it does not lose speed, but just sort of stutters. You can hear that the engine is not running as smoothly and you can feel it as you are driving. This has happened both when I am driving in the city (i.e. 35 MPH) and on the highway (65 MPH). Tonight, however, as I was driving on the highway, it started to stutter and lose speed. It did not die out (dropped from about 60 MPH to about 50 MPH and would not go any faster) and after about 30 seconds of driving that way it righted itself and purred along just fine all the way home.

I need to check the filter to see what's going on, but it's dark right now. I'll do this in the morning. But since this is on my mind, I wanted to share what I am currently experiencing to see if anyone thinks they have an idea what is going on.

Could something like the ECU or Ignition Control Module be failing or starting to fail (and, if so, could either of these have this kind of effect)? If this were happening to your Z, what would you check first?

Please keep in mind that I am fairly dumb about this stuff, though learning. Please spell out things like "AFM" as "Air Flow Module" since I will most likely not know what you are talking about. When I first saw ECU, ICM, and the like, I had to do a search to find out what they were and hope that I was finding the right thing.

Thanks again for any help and your patience. I truly appreciate it.
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Old 06-01-2015, 10:46 PM
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I would lean towards it being more to do with fuel than electrical issue (ignition module). It is a distinct difference between engine having a hard time when its not firing due to electrical issue, and fuel issue. I just went through similar thing with my Z, it would be gutless at about 3k rpm, and would not pull a hill. Pulled over, changed fuel filter (where you have yours, between fuel pump and tank), and she came alive again.

Check your spark plugs, see what color they are. It seems like you are starving for fuel, I would change the pre pump filter, and engine bay filter as well and try again. It doesn't take much crap to plug up the pre fuel pump filter, and starve the engine.
My best opinion.
Good luck.

And there is no such thing as being dumb when you want to learn!!

Last edited by Skully; 06-01-2015 at 10:48 PM.
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