So help me diagnose my engine sputtering

georryan · Post by **georryan** » Tue Jun 13, 2006 4:39 pm

Ok, so now i've soldered the internal wire together and used some heat shring tubing to seal it up. Then I took that external wire and as best I could, I brought them together and put some solder on them to keep them together and put some heat shrink tubing around that. I then wrapped all the wires back up and connected everything back as it should be. Would anything done to the knock sensor wire prevent my car from starting up? Now it won't start. It won't even act like it will start up. It turns and turns, but it never catches. Almost like the fuel pump isn't on. The only thing I touched was the crank, cam, and knock sensors, and the knock being the primary one. Could any kind of a screw up on the soldering job cause a problem like this?

vrg3 · Post by **vrg3** » Tue Jun 13, 2006 4:47 pm

Nothing with the knock sensor can keep it from starting. I suspect the cam or crank sensor. If you pull the trouble codes you can find out which one -- if one of them gives a signal and the other doesn't, the ECU stores a trouble code for the one with the missing signal.

georryan · Post by **georryan** » Tue Jun 13, 2006 6:19 pm

That was it Vikash, thanks. The cam grounding wire had snapped from my last job. I hate brittle wires.

Starts up like a beauty now.

vrg3 · Post by **vrg3** » Tue Jun 13, 2006 9:22 pm

Great.

georryan · Post by **georryan** » Tue Jun 13, 2006 9:39 pm

Well it ran like a charm on the way to work, but after getting off the freeway I pushed it again and this time when the boost reached about 10 or so the car acted real funny. Not like timing was thrown back more like like it just hit a wall and there was some sputtering, but not the kind of sputtering where it feels like your engine is trying to stay running. If I eased onto the boost at that point it was fine. It just didn't like the sudden punch under a load. Maybe I need to start looking at my MAF now, or maybe I need to go back and look at all my wiring jobs I just did on the cam and crank sensors. I'm not sure what this could be, but at least my sputtering at low speed, the "leave me dead in the water" kind of sputtering, is gone.

vrg3 · Post by **vrg3** » Tue Jun 13, 2006 9:42 pm

Is your ignition system in good shape? It could just be misfire at high load because of worn plugs or wires or something.

Splinter · Post by **Splinter** » Tue Jun 13, 2006 9:50 pm

When my car was doing that, it was because spark plug #3 wasnt in all the way, and the high-pressure combustions you get under boost were forcing gasses through, and knocking off the sparkplug boot.

Maybe its time to replace your plug wires?

georryan · Post by **georryan** » Tue Jun 13, 2006 10:21 pm

All good points. The very first time my car acted like this it was because I needed to regap my plugs. So I'm hoping it is ignition, plug, plug wire related. Now it is just time troubleshooting. The wires are only a couple years old, so I think they are fine.

Splinter: It was blowing off your spark plug wire? Crazy.

-Ryan

georryan · Post by **georryan** » Wed Jun 14, 2006 4:53 am

Well back to the drawing board. First I'll check my wiring, then start playing with the MAF and the other fuel delivery/spark delivery components.

The sputter that leaves me limping came back just a bit ago. Almost didn't make it across the intersection before it was red. Once I did the car picked up and drove normal. GRRRR....

An odd question, but can a failing turbo cause this sort of reaction? Just something else to watch out for.

Splinter · Post by **Splinter** » Wed Jun 14, 2006 8:36 am

Not unless theres big holes in it

Even with blown gaskets, a turbo cant really cause any problems when you're not under boost.

Unless youve got huge tracts of oil swathing into your engine, but I think youd know about that by now.

georryan · Post by **georryan** » Wed Jun 14, 2006 5:08 pm

Also, how would a gas tank leak affect things? I just found out I have one. Only when the car is full an parked with the nose significantly higher on a hill than the tail. I'm going to have to figure out where that leak is coming from.

I'd figure if it was a fuel pressure thing due to a leaky tank, I'd notice it all the time, not just randomly.

free5ty1e · Post by **free5ty1e** » Wed Jun 14, 2006 8:03 pm

Leaky gas tank just will manifest as poor mileage and a smelly parked car. Most times gas tank leaks with our cars is where the filler neck mates to the tank, although I did have to patch up a hole in the rear with some JB weld. That stuff is the shizzle.

Have you ever replaced your stock fuel pump? I highly recommend a Walbro 255lph with the WRX install kit on general principle.

georryan · Post by **georryan** » Wed Jun 14, 2006 8:28 pm

I have the walbro pump already. I put that in before I put in the vf8.

Ok, so I don't need to worry about the tank or a turbo issue as I diagnose this renewal of sputtering. That's good.

georryan · Post by **georryan** » Wed Jul 12, 2006 10:01 pm

So I MAY have solved it. We'll see. I swaped out a coil back to another diamond coil, and while I was fixing my oil leak from the turbo I noticed that the signal wire on my 02 sensor was melting, or getting rubbed away. Half of the shielding around the signal wire was gone and the wire itself was exposed. I replaced it with a NA 3 wire sensor (I had a 4 wire one). All today the car has run pretty stable. No sputtering. It hasn't even sputtered when I'm pushing it at full boost (which it would do often before, and I felt it was related to the sputtering I was feeling at random times). So if this fixes it I'm going to guess it was the 02 sensor giving the ecu some funky readings and messing with the fuel delivery of the car. We'll see. Only time will tell now.

-Ryan

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So help me diagnose my engine sputtering