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RX-7 2nd Gen Specific (1986-92) RX-7 1986-92 Discussion including performance modifications and technical support sections.


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Old 07-09-2010, 09:37 PM   #1
NoDOHC
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Default Problem Caused by running E85 - now what is it?

Short story, I ran a tank of E85 through the car and shortly afterward, I lost an injector on the rear rotor. I replaced the injector and all was fine for a while, now the car is exibiting other strange symptoms.

Please try to ignore the fact that I am using a Haltech E6X for fuel and ignition. This ECU has over 30,000 miles on it with no trouble. The issue is intermittent, so I doubt that it is ECU-related.

Symptoms:
Car starts great cold, won't even try to fire warm. Before this problem arose, it started hard cold and perfectly warm. Compression is good, spark is good, I haven't had any time to look at the fuel system, but I am pretty sure that the problem is there.
Car will not run at partial throttle below 3,000 rpm and stutters really bad at WOT. (This happens warm or cold) My wideband is reading dashes, but this is expected as the car is misfiring.
Car will not run at WOT past about 4,000 RPM cold, but can get to 8,000 RPM warm. Once again the wideband is pegged lean. It is making like 50 Hp.
Car will not even try to idle.
Here is the interresting thing:
Sometimes the car idles perfectly and runs fine for a little while.
If I shut the car off while idling perfectly, it will restart just fine.
Other times it will quit completely, even from high revs and will not even try to restart. Waiting about 15 minutes seems to make this ok. 15 minutes is not enough time for the engine to cool off, so I doubt that the problem is a hot engine/cold engine thing.
Driving it tonight, I got it to kick in hard at about 7,000 RPM and then it cruised for several miles normally under partial throttle at about 2200 rpm, then it quit. I got it going again by flooring it, but it would barely run the rest of the way home.

Interestingly, the starting cold but not warm indicates that the car is getting too much fuel, but the plugs are never even wet after trying to get the car to start when warm. Even when not misfiring, the wideband never really gets out of max lean except on throttle transitions where I might see 16:1 AFR

Anyway, I hesitate to hastily categorize this, I am mostly looking for logical suggestions as to where on the fuel system to start. When I get time I intend to put a fuel pressure gauge on it. At this point I am looking for ideas, because the intermittent nature of the problem has me baffled.

Let me reitterate, I did connect a compression gauge (piston engine style) when it wouldn't start. No bounces below 60 psi on either rotor. I also had spark while cranking when it wouldn't start.

I may end up replacing the entire fuel system anyway, so this might not be an issue.






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Old 07-09-2010, 09:44 PM   #2
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one big misconception with E85 is that it ruins your fuel system... Actually it does the complete opposite. It cleans everything out. So if your using the old fuel lines, filter, tank, ect. It will pick up everything (sometimes turning it to sludge) and pack it into the injectors.

Also, you should NEVER use a paper element filter. Always use a steel (or other metals) fuel filter.

The air fuel ratios you should be looking for are far different than pump gas. Or any type of "gas" really. So you need to learn what afr's your supposed to be looking for.

You need to re-tune the entire MAP. You cannot just put some E85 in the car and expect it to run with a "gas" map...



So basically, clean out your fuel system VERY thoroughly, or replace everything. Then re-tune the car. I doubt you have an actual problem...
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Old 07-09-2010, 09:56 PM   #3
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I should have explained that, I did retune the car for E85, I ran it for a while, then switched back to pump gas. I have my pump gas tune back in the ECU and the same pump gas I always run in the tank. Even the injector failure occured after runnging E85, not while it was in the tank.

I am not too worried about this, as it made me stop driving that car and actually start thinking about tearing it apart to do upgrades again. I was enjoying driving it too much to want to tear it up.
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Old 07-09-2010, 11:25 PM   #4
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Quote:
Originally Posted by sen2two View Post
one big misconception with E85 is that it ruins your fuel system... Actually it does the complete opposite. It cleans everything out. So if your using the old fuel lines, filter, tank, ect. It will pick up everything (sometimes turning it to sludge) and pack it into the injectors.

Also, you should NEVER use a paper element filter. Always use a steel (or other metals) fuel filter.

The air fuel ratios you should be looking for are far different than pump gas. Or any type of "gas" really. So you need to learn what afr's your supposed to be looking for.

You need to re-tune the entire MAP. You cannot just put some E85 in the car and expect it to run with a "gas" map...



So basically, clean out your fuel system VERY thoroughly, or replace everything. Then re-tune the car. I doubt you have an actual problem...
So E85 cleans out your fuel system but after running e85 you need to thoroughly clean out the fuel system? So which is it?

In my experience, ethanol in any content absorbs moisture, clogs filters, kills pumps, and breaks up any crude, junk, whatever in the tank.......... and if it sits it likes to corrode becuase ot has a tendancy to absorb and suspend moisture.
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Old 07-10-2010, 12:24 AM   #5
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I get on average an E-Mail a week from people who have had nothing but troubles running Ethanol at 85%.

It's rubbish, I'd never run the crap in any car unless it was someone I hated and wanted them to have non stop problems
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Old 09-23-2010, 10:46 PM   #6
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Back from the dead... It turns out that it was a combination of the fuel pressure regulator and another leaking injector. Since I already had the car in the garage (quite an undertaking since it refused to do anything but idle for the entire event), I went ahead and built another engine for in it (higher compression rotors) and replaced everything on the fuel system. The fuel pressure was starting at about 35 psi (running) and then it would intermittently drop out. It was completely random, I figured that it was the fuel pump, but pinching the return line with a pair of vise-grip pliers got the fuel pressure right up to where it should be (thus implicating the fuel pressure regulator).

I think that my very old fuel filter gave up the ghost from the E85 and the debris that it had caught over the last ??? years all got through and ruined my first injector and later the fuel pressure regulator. It turns out that I had a second leaking injector too, which explains the conflicting symptoms.

The FPR and all 4 injectors were replaced and no more problems!
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Old 10-03-2010, 02:29 PM   #7
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E85 and rotarys is not the best idea as far as i have heard from some rotary "experts" here in Norway. Tends to cause more wear in the engine, since it washes away the oil film in the housing, hence more friction between apex and housing.
Again not my words, just what i've heard from people who have rebuilt many rotarys, and have seen the difference in wear between running e85 and regular gas.
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