Intermittent starting issue

really good username

really good username

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09 wrangler Rubicon manual transmission. I'm at my wits end with this thing. It's had a phantom starting issue since January. It turns over just fine but takes 3-5 attempts to actually start. Has gotten to where when it starts it stumbles and dies but then it'll crank up no problem at all. No driveability issues other than a few weeks ago it would randomly lose throttle response. I changed the crankshaft position sensor and the ignition switch and I thought it fixed everything but then about a week later the starting issue came back. It has had the fuel pump and entire fuel tank replaced. Map sensor replaced, pcv replaced. New battery. The check engine light is not on so service centers won't even look at it. It idles just fine, no missing, no stuttering, no lagging in power. Might be getting worse gas mileage but not by much.
 
I have aftermarket terminal clamps. The grounds are the next thing I need to look at but at first glance they all look fine. There is not a ground specifically from the battery to the engine, just to the chassis. All the electrical looks fantastic although I bought it the way it is and I did not do any of it myself. There is a winch and 4 small cube lights wired to the battery. Do you think that's too much?
 
really good username said:
I have aftermarket terminal clamps. The grounds are the next thing I need to look at but at first glance they all look fine. There is not a ground specifically from the battery to the engine, just to the chassis. All the electrical looks fantastic although I bought it the way it is and I did not do any of it myself. There is a winch and 4 small cube lights wired to the battery. Do you think that's too much?
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The winch and lights wouldn't have anything to do with it starting because they aren't being used when starting.

One of the first things I did was to run a ground cable from the neg post to the alternator bracket. Clamps and cables are hard to tell if they are good by just looking at them. The Cables can corrode where they clamp onto battery clamps and terminals and not make a good connection.

The Jeeps have way to much electronics these days.

Your battery should be good if it's cranking over good, do you have a small red light on at the top right of the dash cluster?
 
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Ill check the wiring thoroughly this afternoon. Forgot to mention I can smell gas for a few seconds when it does start. Probably just buildup from. Turning over more than it should.
 
BLACKJKU said:
Your battery should be good if it's cranking over good,
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Also rules out the ground issue and any parasitic draw from the aftermarket winch and lights.

Thinking through the basics - spark, air fuel. Since it finally does start and run I would rule out airflow from a macro perspective. If you are smelling fuel there is probably not a fuel flow issue, either. Maybe ignition coil, although I don't recall what the 3.8L has. Is it individual coils or a coil pack? Also the throttle position sensor could be the culprit... Hard starts are a good leading indicator or that.
 
BLACKJKU said:
The gas smell could be a injector issue.

When was the last time it was tuned up?
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Maybe a cracked injector... Usually a pfi injector either works or it doesn't. Or it is semi/partially clogged. Overfuelling would generally be a command issue from the ECU.
 
tJKrider said:
Also rules out the ground issue and any parasitic draw from the aftermarket winch and lights.

Thinking through the basics - spark, air fuel. Since it finally does start and run I would rule out airflow from a macro perspective. If you are smelling fuel there is probably not a fuel flow issue, either. Maybe ignition coil, although I don't recall what the 3.8L has. Is it individual coils or a coil pack? Also the throttle position sensor could be the culprit... Hard starts are a good leading indicator or that.
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It has one coil all the plug wires connect to. The tps is part of the throttle body if I'm not mistaken so I might need to replace the throttle body.
 
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No cost test fix, try resetting the ECU? I'd definitely look at the engine grounds too.

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How to Reset the ECU on a Jeep Wrangler JK

While there are folks that swear resetting your ECU does absolutely nothing, it's a common practice among automotive enthusiasts. The ECU (Electronic Control Module) "learns" your driving style and the parts in your ride by storing information in its memory, information that it gathers using a...
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