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Seems like a fuel problem...


Boxer4turbro

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Okay, so today I let someone else drive my car for the first time. I know I know that was my mistake.

 

Any way here's the issue;

 

It has no power. The engine still runs fine and the timing is ok. If you gradually let it rise under load to the primary turbo it will cut as if not getting enough fuel. If you keep the engine revs constant at this rev range (3200-3400rpm) it splutters and loses all idle until it resets itself back to 900rpm.

 

When the driver was under full WOT and secondary turbo starting spooling there was a very strong pop. It sounded like a vacuum pop or a diaphragm/hose splitting. Possibly backfiring into the intake manifold (that type of sound) It definitely seems fuel related, as if not getting enough. Its starving. The engine now will ping or cut if any load is applied at that primary turbo level. Otherwise it drives and runs fine.

 

Preliminary checks of hoses etc show no sign of splits or hoses not connected.

 

Any suggestions would be greatly appreciated. I don't really want to take it to a moneychanic just yet if I can help it.

 

Thanks in advance.

 

D

 

 

 

Sent from my SM-N950F using Tapatalk

 

 

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8 minutes ago, Boxer4turbro said:

Any suggestions would be greatly appreciated. I don't really want to take it to a moneychanic just yet if I can help it.

 

Hey,

 

Try inspecting the spark plugs. Or anything ignition related (coils etc). Had similar symptoms in my car when I purchased it. Inspected yesterday and the spark plugs were pretty much gone, so I replaced them. Some would call it a "hesitation" in the engine. If the clearance on the spark plugs are over 1.1mm, I'd suggest replacing them first. See if that helps.

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Hey thanks man.

Could it be an ignition issue when the car runs totally smooth while driving normally below boost pressure?

Also in terms of the coil, it didn't fail over time and become problematic it just suddenly went pop. It doesn't seem to fit the symptoms.

I should add that when I replaced the engine I had a wahlbro 255lph fuel pump installed. I'm not sure if this will help, it's the only modification to the fuel system.

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2 minutes ago, Boxer4turbro said:

Could it be an ignition issue when the car runs totally smooth while driving normally below boost pressure?

Also in terms of the coil, it didn't fail over time and become problematic it just suddenly went pop. It doesn't seem to fit the symptoms.

I should add that when I replaced the engine I had a wahlbro 255lph fuel pump installed. I'm not sure if this will help, it's the only modification to the fuel system.
 

 

Hmmm I've had no experience owning a turbo, but in the engineering point of view, as soon as the car is running under load, it could be an ignition issue (but don't quote me on that haha, could very well be something else). At least, that was my issue on my non-turbo. However, you pointing out that it 'suddenly went pop' could mean something else. 

 

It's also very possible that whoever used your car put in a low octane fuel (91?). Try using a Subaru Fuel Additive next time you fill up with a 98 octane. Add in the additive just before you fill up the tank so it mixes well with the fuel. They cost about $30 from any Winger dealer. It may not solve the issue but it's a good maintenance check to have anyway. Actually it's recommended by Subaru to use their additive every 6,000 kms or every oil change, so that wouldn't hurt. Just make sure to use up all the fuel after using the additive so that you don't lower the concentration by adding more fuel halfway through.

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Hmm. Does your car struggle to reach 50-60km/h? Use a lot of gas? Trigger a CEL? Run fine off boost? If so, it is running in limp mode. 

 

From what you've described I would probably check the spark side of things first. This is because reaching X amount of rpm and then cutting out is usually signs of something bad with the spark. Check plugs and leads for obvious signs of wear. It could be bad coil(s) but you'd have to check first. Advise you to check check check before spending money as it'll get expensive :)

 

I've fixed a Nissan sr20de auto with similar issues, was Cam angle sensor not sending right messages to ecu to deliver spark, plugs leads dizzy were all rooted. Plus my gf8 recently had a gaping hole in compressor-ic pipe and I had cleaned out intake parts with brake kleen after it had sat for 8+ months. It blew black smoke used a lot of gas and did not want to boost. Replacing the worn/fouled plugs fixed my issue but I also ran through injector cleaner and replaced fuel filter for peace of mind. 

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1 hour ago, swamp said:

Hmm. Does your car struggle to reach 50-60km/h? Use a lot of gas? Trigger a CEL? Run fine off boost? If so, it is running in limp mode. 

 

From what you've described I would probably check the spark side of things first. This is because reaching X amount of rpm and then cutting out is usually signs of something bad with the spark. Check plugs and leads for obvious signs of wear. It could be bad coil(s) but you'd have to check first. Advise you to check check check before spending money as it'll get expensive :)

 

This. 

 

I've just changed my plugs on Saturday and I can confirm it's what fixed my issue.

 

The symptom was: The car would jolt and hesitate under load and slight acceleration but only at about 2000 rpm. This meant that, during cold start, I'd get a hesitation while accelerating from a full stop to 50-60 km/h. And also on the motorway (warm engine), if I step on the gas at 4th gear (Max in my AT), I'd get a hesitation at the 2000rpm area. 

 

I then inspected my plugs and saw that there were 2mm gaps on 2 out of 4 cylinders. Don't think they've ever been replaced before because they were well worn out, So I replaced them with the factory recommended NGK platinum spark plugs. 

 

Today, I tested the car in cold start and under load on the uphills. Hesitation was gone. Have a bit more power when accelerating and engine is a tad quieter. I also noticed a small elimination of the delay in my gas pedal as I accelerated from full stop (didn't know that would be affected). 

 

May be well worth checking out those spark plugs.

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It doesn't make a difference hot or cold. It's not a jolt or hesitation. It's literally when the boost pressure builds the rpm suddenly drops as if being choked. It's either a vacuum problem or mixture/ratio problem.

 

Spark or ignition usually stutters or aggressivaly jolts under load.

 

Under hard boost there was a pop like a backfire into the intake manifold. Almost sounded like a diaphragm that couldn't hold the pressure.

 

I'll check plugs and coils tonight to be sure.

 

Sent from my SM-N950F using Tapatalk

 

 

 

 

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