Engine still running after being turned off
 

I have a 1990 FC that I picked up a while back and it's a decent car but I noticed that when I shut the car off, it continues to run for 3 -5 seconds and I'm afraid to get the emissions done because I don't want it to fail because of that. I would like to get the problem fixed right away but I'm wondering what the problem could be. Has anyone here experienced anything like this before? I don't smell any gas or anything like it's running rich. Thanks in advance for any help.

lol, does it have a turbo timer?

That would do the trick! lol

This is a guess but I bet your car is dieseling because you either have leaky injectors or your butterfly valve is not closing properly. As far as emissions, I have no idea whether it would pass or not. We don't have emissions in Michigan :)

Brian

Usually it's caused by voltage backfeeding from the alternator circuit. But if that was so it'd keep running until you stalled the engine with the clutch pedal/shift lever.

It could be a defective ignition switch or something else backfeeding into the ignition circuit. Maybe a aftermarket radio wired differently?

To answer all questions,

It's not a turbo. I can get the injectors checked out if that's the problem. can you tell me where the butterfly valve is so I can take a look at it?

that would be my guess. in my case, i had an auxilary electric fan that kept feeding back to the alternator and the engine would run until the fan stopped spinning.

m5runner, what non-stock electrical devices do you have?

be happy it runs.

^ +1 :crying:

Another thing it could be is that the MAIN RELAY is not relaxing when the key is put to OFF. Mabe it's taking several seconds before the internal contacts seperate killing the feed to the ignitors/coils/ECU.

That's going to be a bit of a difficult problem to figure out if you don't have a meter with long leads on it. Don't just change parts out. That's expensive.

The mech that put the motor in did the electric fan mod and that's it. I do understand what you are saying about the main relay though. The guy that put the motor in said he wants to look at it again to see what it is. I'm just trying to save myself the trip to his house, swapping cars, etc. I am happy it runs, trust me. I got the emissions done today and it was much better than my BMW in that fashion so I'm happy.

Hailers Beat me to it...wanted to add that you should check Where the electric fan was hooked to..As Hailers said maybe there is something Backfeeding to the ignition,and it could be just that.

I'll look at it when I wake up in the morning. Where would be an ideal place to connect it?

Electric fan instead of the stock mechanical fan is what I understand it to be. So I figure there has to be wires with connectors to that fan. I'd try disconnecting those wires temporarily and then start and then turn the engine off.

I'm assuming this running with the key to OFF, happens each and every time you do that, so if now the wires are taken off the fan, and the engine turns off like a normal engine, then there is the source of the problem. Not the FIX for the problem, but at least knowing what the source of the problem is.

It won't hurt to run the engine with no fan for this small period of time, just don't run the engne for a prolonged period of time like that.

Thinking a little more about that...................it may take more than just pulling the wires off the fan. A lot depends on how and where he is tapping into the harness to get power for the fan. I'd help more if you knew where he is getting the power for the fan/fan relay etc and disable that wire and then turn the engine on then off.

Much like the Turbo Timer idea mentioned in one of the first posts.

Good idea. I'll see how everything is connected, then follow with your suggestions. Thanks for the help so far

my car does this as well but im thinkin its cuz the previous owner wired the fuel pump to a seperate switch to turn on and off, it is wired completly seprate from the car and the car wont shut off unless if i turn the fuel pump off and wait a few seconds

It takes more than fuel to keep it running. Somewhere, somehow there is a circuit that is backfeeding electrical power to the coils and ECU. Evidently thru the *seperate switch* you mention.

Dieseling will keep a motor running for quite a few seconds, BUT the deiseling I've experienced has only been on piston engined cars, never a rotary. When it does that on a piston car it is not a common smooth idle. It's rough and bucking type idle and last usually for only a few to ten seconds (really *depends* on things).

Wish I could spell diesel/deisel (i before e except after c and a bunch of exceptions here and there).

This happend to me a few years ago while not knowing to much about which wire goes where in the harness, hooked the efan up to a plug near the engine fuse box. Well. The engine would stay running till the fan stopped spinning.

I had this problem once....turned out to be the alternator being bad. Get the alternator checked out....

Yes, I'm a female & I don't work on cars but have been around shops for years, did anyone consider pre-ignition?? check this out!!

http://en.wikipedia.org/wiki/Engine_...g#Pre-ignition

http://fc3spro.com/TECH/FAQ/deton.html

His engine would be shot if it was pre-ignition/detonation.

not necessarily if corrected before it gets to detonation. Timing, spark plugs etc.

my diesel rabbit did that once, it kind of scared me. i had to rip off the pcv hose because it was running on the engine oil. i don't suppose that really helped you though. Your car needs spark and fuel somehow to run, so check the wiring.

If he was turning off his car and it was working correctly, there wouldn't be any spark, thus timing would be irrelevant. There also wouldn't be any fuel pumping/injecting. :dunno:

"Pre-ignition and "dieseling" or "run on" are the same phenomenon, except in the latter case the engine continues to run after the ignition is shut off with a hot spot as an ignition source. Pre-ignition might cause rough running due to the advanced and erratic effective igniton timing and may cause noise if it leads to detonation. It may also cause "rumble" which is fast and premature but not detonating combustion."

Eh, I guess it's possible... I still don't see how it would do it without gas in the chamber... but what do I know.

It's also an N/A. I don't think I've ever heard of an N/A having that problem, but once again, what do I know.

My vote goes to listening to Hailers. He's never let me down.

I'm not saying that's what it is, I'm just saying it's a possibility! If you read what I linked it might enlighten you to how it could be possible. The only reason I mentioned it was because I had it in one of my old cars (piston) I know the disdain for piston engines so I researched it on rotarys and found the 2nd link. It's also one of the disclaimers on warranties for rebuilt rotary engines.

There would have to be power back feeding the electrical system or ECU or somthing to allow the injectors and coils to keep firing.

Rx7s can't really desiel since they are Fuel Injected. The injectors are supposed to be turned off and if they were firing, the ignition would have to be firing as well. Unless for some REAL bad reason your injectors leak so much even after they are off that enough fuel still gets into the chambers and is ignited by a surface hot enough. This would only cause it to run EXTREMELY rough, not smooth.

What RotaMan99 said... :p: I just don't see how fuel would be in the chamber if the car was really off. No fuel, no pre-ignition or detonation.

The wires on the alt are crossed and its feeding back.. Pure and simple. And FCs dont diesel....

haha hes got it easier than i do. at least his shuts off after a few seconds. i just dropped a new motor (86') into my 88' and after i turn the key off it keeps on going.......nice and strong..... no rough idle at all.
we're thinking its related to my ecu, so we're swapping the ecu from the 86' in tomorrow, hopefully this is the problem.

pretty crazy seeing your car running strong while you're holding the keys outside the car. gotta pull that alternator wire to make it stop.

Not really. It's like J-RAT mentioned above, the electrical system is backfeeding. Usually it's thru the alternator wires (small plug on the back of it) being crossed.

It is odd though. Same type engine? Like both non turbo or both are turbo? IF the problem continues after swapping the ECU's, then next time try to just pull the ENGINE fuse in the interior.

Did you change the EM harness on the engine? I'm asking, is it the same harness on the engine as you had before changing engines? Make any other wiring changes?

i had something very similar happen but it olny happened once. my TII had a fuel cut switch wired in before i bought the car, while looknig to buy the car, I clicked the switch (to test it) off but instead of dying down like it should,the car sputtered and surged between 100-500 rpm. I never figured it out, and it never happened again.