Afraid to drive my Z now... Please help

[HeatRaveR]

I'm afraid to drive my beloved Z and I'm hoping you guys can help me. First, the basics, it's a '82 280ZX Turbo. While it has many aftermarket upgrades, I haven't done anything that majorly changes the functioning of the engine other than the JWT ECU conversion. It has run great for the past 6 years and traveled thousands of miles across the country without missing a beat. Forgive me if the description is a bit long but I'm hoping the details help diagnose it.

 

This last winter, I had taken it in for a smog check, and following advice I gleaned from multiple sources, I added 2 gallons of E85 (in addition to the 91 octane that I usually fill the 21 gallon tank with) to help it pass. It passed (barely), and I parked it in the garage over the winter connected to battery charger. When I next drove it after a 3-month hiatus, it ran fine; I took it on the freeway, boosted it up, etc. I drove about 25 miles with no problem. Then when I got into town again and was pulling away from a stoplight, suddenly the car started sputtering and lurching as the engine seemed to want to die. I'd never experienced this in all my years with the car. I pulled over and quickly turned the engine off. I waited a moment and tried restarting the engine. The car shook a lot, and I could barely get it moving forward enough to get it safely into a parking lot. I checked under the hood to see if there was anything obviously wrong, but everything looked normal. My fuel pressure and voltage readings were nominal. After a few minutes I tried starting it again, and it was suddenly working fine again. I cautiously drove slowly around the parking lot and it seemed fine. I made my way back to the freeway without issue, but when I started to accelerate onto the freeway it suddenly started dying again.

 

At that point, I called for a tow truck. When they unloaded my Z back at my house, I started the engine to pull the car into the garage, and once again, it ran fine (or at least long enough to get back in the garage). Recently, I've been test driving my Z around my neighborhod for a few miles and it seems to run alright. Though, I could swear it feels slightly shakier at idle, and a little down on the pickup when accelerating from a stop . I'm sure we can all agree that intermittent problems are just THE worst to try and figure out! So does anyone have any ideas of what the issue might be or what I could check that would cause such a problem? It sucks being too scare to take the poor Z out anymore!

 

I considered that it might be the gas from having sat there, but 3 months doesn't seem long enough for it to have gone bad. And if it was the gas, I would imagine it would run badly all the time and not like this.

[djwarner]

The real problem with E85 is ethanol's propensity to absorb water. From what you described you started out with about 10% ethanol and then boosted it up to about 18% when you added the E85. If you are in an area that cools down to the dew point each night, you may have just created a water magnet.

 

Heat is transferred in three different ways: Conduction, convection, and radiation. Ignoring radiation for the moment, your gas tank will cool down to the outside temperature by convection and conduction. Literally energetic molecules in your gas tank will transfer energy to the air or anything it touches that is cooler. Once the temperatures equalizes, the energy transfers stop.

 

Radiation is a different animal. When you look at a light bulb, it glows orange/yellow as energetic photons are emitted from the surface of the filament. As temperature increases, the color changes more towards blue and then ultraviolet. As a body cools, the color turns to orange, red and then infrared. So even though you can't see a glow at room temperature, metal parts are still radiating energy in the infrared spectrum. As the radiation continues, additional heat is lost and the temperature of the gas tank falls below the outside air temperature. If the air has cooled to the dew point, dew will form on the metal surface. As it beads and runs into the gas, the ethanol mixes the water into the solution. Depending on how much water you have, the concentration being sucked up by the fuel pump might be quite strong.

 

Water in gas doesn't burn very well - as your car has been telling you.

 

The best way to remedy the problem would be to pull the bad gas out and put good gas in. This might be difficult to do. They sell additives for this to help mix and suspend the water so you can burn it out. This might be your short term solution.

Edited April 9, 2013 by djwarner

[daddydonuts]

Sounds like fuel, maybe filters are clogged... this happened to me on another vehicle with same symptoms...replaced filters and ran fine

[djwarner]

BTW one of the functions of the fuel filter is to separate water and trap it in the filter. The original Datsun filters were clear plastic and you could observe the water trapped there. SOP was to disconnect the filter, blow in the reverse direction to expel the water and reconnect.

 

Daddydonuts may very well be correct. Once the holding limit of the filter is reached, almost pure water flows to the carbs. Now, as to how much water remains in the tank, that's another matter.

[Domzs]

Take a fuel sample to see and the Z fuel tank has a drain plug ( if you to drain it ) .

[aarang]

Sounds like the CAS in the dizzy could possibly be going out, or you are falling victim to corroded EFI connections. Had the same thing happen to me. Same symptoms.

[seattlejester]

If it sat for a while with E85 (which is acidic) it could have eaten away at the rubber a bit and clogged the filter. Best case replace filter, worst case may have to replace some lines and have the injectors cleaned. But that's just the internet talking

[Tennesseejed]

Whenever an engine runs well, then then runs crappy, and then miraculously runs well again, my thoughts go immediately to electrical issues. 

 

One thing that stands out in the OP is leaving the battery hooked up to a trickle charger all Winter. 

 

I'd start with load testing the battery, check for corroded terminals, perhaps condensation in the distributor cap, etc.   

[HeatRaveR]

Thanks for all the responses everyone.   Some additional maintenance info: the fuel filter (standard metal Datsun 280ZX filter that's the size of half a soda can) was replaced about 17k miles ago, and the distributor cap was replaced about 23k miles ago. I checked inside the cap and everything seemed normal as far as I could tell.

 

This weekend I'll try and get some of that water-removal additive and see if that addresses the most obvious change from before (the E85). It was my understanding that modern hoses are more resistant/immune to E85's acidness; my fuel hoses were replaced with new hoses when I upgraded my fuel pump and rail.

[djwarner]

Gas filters are cheap. Go ahead and change it since it hasn't been changed since your troubles began.

[Tony D]

Water removal additive is ALCOHOL...

 

First, drain your tank.

Second, refill with fresh gasoline.

Third, pour in your "dry gas" additive.

 

The problem with alcohol-based compounds s they suck up water. Gasoline rejects it. You put alcohol into gasoline to "soak up" any little bits of water in the tank. It then usually passes through the engine with semi-flammability, and no fanfare.

 

To add dry gas to E85, well..... Futility comes to mind in polite circles. If that E85 had condensation over the winter, your fuel is toast, and needs replacement!

[TimZ]

Water removal additive is ALCOHOL...

 

First, drain your tank.

Second, refill with fresh gasoline.

Third, pour in your "dry gas" additive.

 

The problem with alcohol-based compounds s they suck up water. Gasoline rejects it. You put alcohol into gasoline to "soak up" any little bits of water in the tank. It then usually passes through the engine with semi-flammability, and no fanfare.

 

To add dry gas to E85, well..... Futility comes to mind in polite circles. If that E85 had condensation over the winter, your fuel is toast, and needs replacement!

What Tony said.  For future reference, they do make a Sta-Bil product for ethanol now, btw. If you've already got water condensed into your fuel, I don't think that will help at this point, though.

 

Also, E85 is reactive with organic compounds, but is barely acidic at all - actually less acidic than water.  If you have brass or non-anodized aluminum in your fuel system or the original rubber hoses it can be a problem, but modern hoses can usually deal with it, especially if you only had ~18% ethanol content.  

 

Do you know how much gasoline was in the tank when you added the 2 gal of E85?

[phil280zxt]

I've never seen a drain on a 280zx gas tank.  You'll have to suction the fuel out of the tank via the filler hose or disconnect the fuel line, hook up your fuel pump to a constant battery source and pump it out.

[phil280zxt]

You might also want to clean the ECU plugs.  Reseat them ssveral times to clean off any corrosion.

[rayaapp2]

Sounds like the CAS in the dizzy could possibly be going out, or you are falling victim to corroded EFI connections. Had the same thing happen to me. Same symptoms.

 

Id put money on the CAS...

Been there, SAME EXACT failure pattern. Despite E85(which can be an issue having been thoroughly pointed out already).

 

Put a timing light on it when it starts to run bad, hold the rpms up and see what the timing is doing. Its gonna move around a bit with a rough run issue, but see if it jumps wildly. I lost one L28et to this issue. I ended up breaking lands and skirts in very short order at 18psi. Ive seen many other times as well.