Occassional Stuttering Engine - '77 280Z

[SilverSurfer]

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.

[siteunseen]

I'd put a fuel gauge on a length of hose and zip-tie it to the driver's side windshield wiper blade so you can watch it while you're driving, sounds like fuel problems to me.

 

[siteunseen]

Does your fuel pressure regulator have a good vacuum hose attached?  You could get a loaner vacuum gauge from an auto parts store and see how strong your vacuum is too.

 

[FastWoman]

Maybe you still have some water in the system?

[Patcon]

I agree with FastWoman. How many tanks of fuel have you run through it? It may still be water and bad gas. Keep running fuel through it. Sites suggestion is also good if it keeps doing it. Verify your fuel pressure is consistent.

[SilverSurfer]

Thanks everyone! I appreciate the help (and the photo, too, siteunseen).

@Patcon - I've only run it through approximately 1 tank of gas. I normally fill up at about a half tank. I've not wanted to take it on a long trip due to the stalling at odd times and I've been quite busy, so I don't get to drive it as much as I like. I plan to rectify that, though.

@Fastwoman - Yes, I was thinking that there still might be some water there and perhaps a few pieces of rust particles. There are a few laying at the bottom of the inline fuel filter.

@siteunseen - The mechanic had tested the pressure on the fuel line and said it was good. But I may test this if it keeps sputtering after a few more tanks of gas.

 

I was taking the car out this morning and it sputtered and died. I was at a stop light when it started to sputter. I managed to get it (barely) through the light, going no more than a few miles an hour, sputtering all the way, before the Z died. I tried to start it right away and it coughed and died immediately. I waited about 30 seconds, tried again, and it sputtered, but would not ultimately fire. After waiting about 2 minutes, I turned the key. The engine sputtered once, then revved wonderfully. The car has been driving perfectly ever since. I was taking the car in to get new tie rods and a front end alignment. I told the mechanic about the stalling. The tried to get it to stall and it would not. I'll just have to keep an eye on this.

[Patcon]

On his 280z does the fuel get pumped back to the tank in a return line? I don't know the 280Z system. So if the pump picked up a big slug of water would it eventually get pushed out of the fuel rail and back to the tank? Then the car would fire up. I would run the tank down as low as possible then fill it up. If you run it down low the fuel doesn't just get diluted with new fuel 50%/50% like fueling at half a tank more like 90%/10% or more.

[siteunseen]

Here's a good read with plenty of great pictures on our fuel tanks.  It got me to drop my tank and seal it with Red-Kote tank liner.  I was seeing small rust particles in my clear filter too.  I started worrying they could clog up the injectors, probably for no reason but it took that part out of the equation. 

 

http://atlanticz.ca/zclub/techtips/fuel/gastank/index.htm

[Zed Head]

 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.

 

I'm in the water-in-gas crowd.  If you're seeing water in the filter, then there's water in the tank.  You need to drain all of your fuel, flush the lines, dry the tank out, replace the filter, refill, then add HEET or some other drying agent to disperse the remainder of the water.  HEET is not going to fix that much water, if you're seeing it in the filter.  Plus, the water will soak the paper of the filter, and it will swell and cause a flow restriction.

 

But, are you sure you're seeing water?  The filter can get an air bubble and still function just fine.

Edited June 3, 2015 by Zed Head

[SilverSurfer]

 

But, are you sure you're seeing water?  The filter can get an air bubble and still function just fine.

 

I am not sure I am seeing water in the filter. I thought I was. I was at an Autozone and a mechanic was there. I asked him to take a look and he agreed that it was water.

[Patcon]

Then work on the premise that you have a water problem until proven otherwise.