"Rev Hang Slows My Roll" (RevHang)
02/24/2015 at 16:52 • Filed to: None
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"Rev Hang Slows My Roll" (RevHang)
02/24/2015 at 16:52 • Filed to: None | 1
| 13 |
i have been rehabilitating a 1990 Mitsubishi Mighty max with the 4G64 Sirius 4 cylinder engine. It has been suffering from a rough idle and bad drivability which i have narrowed down to a fuelling issue. I pulled the fuel rail and placed all four injectors into plastic bottles then cranked the engine a few times. Each bottle had the same amount of gas in it except number 4, which was basically dry.
I just paid $85 to get all four injectors ultrasonically cleaned and im still having this problem. I am beginning to suspect a wiring issue somewhere. what should i do?
RamblinRover Luxury-Yacht
> Rev Hang Slows My Roll
02/24/2015 at 16:56 |
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They're not individually wired where you can swap them around? A test light would at least indicate whether you're getting a pulse, but whether you can hook one up if you can't get at the wiring... If you *can* swap the wiring, do that and repeat - an injector can be scrupulously clean and still have a faulty coil, for example.
deekster_caddy
> Rev Hang Slows My Roll
02/24/2015 at 16:56 |
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Here's a "cheap and dirty" way to narrow down the problem to a specific injector or wire.
At idle, one at a time, pull a spark plug wire. The engine should run a lot worse. Put the wire back on, do the next cylinder... one of them will not get as much worse as the others. That's the one that isn't firing.
Now, swap injectors with the suspect one and a different cylinder. Repeat step one. Does the problem move with the injector or stay with the cylinder?
If cylinder, (you know the cap, rotor, wire and plug is good, right?) that's the injector wiring to test. If injector, try replacing it.
Even cleaning injectors may not resolve an injector problem - it could be a bad injector. Were they flow tested as well?
505Turbeaux
> Rev Hang Slows My Roll
02/24/2015 at 16:57 |
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did you try them after they were cleaned? Could be an FI harness issue, try all 4 with a test light. Spark good at all 4 holes?
bob and john
> Rev Hang Slows My Roll
02/24/2015 at 16:57 |
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the injectors may be clean, is the fuel rail good? is the fuel pump good?
if injectors start to go, just replace them and dont worry if its a good injector or bad.
crowmolly
> Rev Hang Slows My Roll
02/24/2015 at 16:58 |
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First, I'd swap the non-spraying injector to a different cylinder (therefore part of the harness) and see if it sprays normally. If that's the case then it's confirmation of the OK injector.
Then I'd trace the harness back and look for any kinks, cuts, or sharp turns. See if it's detachable from a main engine harness.
davedave1111
> Rev Hang Slows My Roll
02/24/2015 at 17:02 |
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You can get injectors which have stopped working rather than got clogged up. Check the resistance across each of them - if the suspect one is out of line with the others, that's a good indicator it's buggered. According to a quick google you should be looking at 13-16 ohms on working ones, but if the three good ones show something different, google's probably wrong.
You ought to be able to find either a junkyard replacement dead cheap, or a new one for not too much. If it's a generic part, you may find it much cheaper under a generic listing rather than a model-specific one.
handyjoe
> crowmolly
02/24/2015 at 17:03 |
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This. See if the problem follows the injector or not. Hopefully it does, because injectors are cheap enough.
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Rev Hang Slows My Roll
> deekster_caddy
02/24/2015 at 17:04 |
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yes, I have a report from the company i sent it to showing they awere all cleaned and flow tested.
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Rev Hang Slows My Roll
> davedave1111
02/24/2015 at 17:05 |
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The place i sent them too sent me a report showing that they flow tested all four of them, so i have no reason to believe the injector itself is dead.
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Rev Hang Slows My Roll
> bob and john
02/24/2015 at 17:08 |
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the three other injectors seem to be working fine, so I think the issue is with the wiring to the number four injector. The fuel rail on this vehicle is just a hollow metal tube and i didnt see any blockages inside it.
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Rev Hang Slows My Roll
> 505Turbeaux
02/24/2015 at 17:08 |
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New plugs and wires. Spark is good all around. Issue is definitley fuel related.
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davedave1111
> Rev Hang Slows My Roll
02/24/2015 at 17:15 |
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If you have an ammeter it's really simple to check, so you might as well - but I take your point. Then again, I had a 'dead' injector that only went wrong above a certain temperature, so they can be a bit funny.
If you can swap a couple of the injectors over, that would absolutely rule out (or in) a faulty injector.
The next thing I'd check is the fuel rail itself, since it's #4 which isn't working - I assume that's the far end, so there's the slim possibility of a blockage between 3 and 4. Very slim chance, but should be the work of moments to check and rule it out.
Assuming all that's checked-out, you'll want to start looking at the wiring and electronics. Where it takes a separate path to each injector, you'll want to check each bit end-to-end for resistance and make sure all four paths are the same. Keep going backwards piece by piece until you find what's wrong.
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deekster_caddy
> Rev Hang Slows My Roll
02/24/2015 at 19:34 |
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You can still find the 'weak' cylinder with the pull-a-plug-wire test. Then figure out if it's fuel or not. The plug with a lot of white is too lean...
http://www.onallcylinders.com/2012/12/20/rea…
If it's too dark/fouled looking it could point to an ignition problem.