19 replies to this topic

[02_Liberty_RX]

Hi guys, 
 

When I lift off the accelerator and the revs drop below roughly 2500, the whole car shudders and jolts. The only way to stop it, is to put the clutch in, change to a lower gear (so the revs become higher) or to go to neutral. This happens whether the car is cold or at running temperature. Does anyone know what could be causing this because I don't think its good for the car to be shuddering constantly.

 

 

2002 Subaru Liberty RX 2.5 Sedan

Cheers guys

[surge]

Could be a few things.

Hopefully a simple service would rule them out.

Id clean the MAF sensor.
Change the spark plugs.
Fuel filter.
Air filter.
Check the TPS.
Check the ecu for any fault codes.

[02_Liberty_RX]

I did the spark plugs and leads recently because the engine was misfiring. Tho I think I could still use a new coil.

 

Nooby quesions but what is the MAF sensor and whats the TPS. And how do you check the ecu?

[surge]

Not a subaru but this guy has a pretty good explanation and it would be located in approximately the same place in your engine bay.

https://m.youtube.co...h?v=gRfaPfTcfOM
Also to check the ecu you could get an obd2 adapter (Bluetooth ). Download toque on android and then follow the steps in the video. Also check fault codes using that.

The TPS is a throttle position sensor.
You might need to research how to inspect it.

It may also be an O2 sensor being out. That should be something you can check with the scanner.

Also couldn't hurt putting a tank of bp98 through it.

Don't forget the subaru upper engine cleaner as well. Might just help it run a bit better.

Obviously start with the cheaper and easier things before you move on to replacing any expensive parts like the coil pack.

[skillionaire]

[02_Liberty_RX]

Thanks for that, I'll have to give the MAF sensor a clean once I get some cleaner.

Would any mounts be causing the car to shudder? This is all new to me so Im not too sure on what causing it.
 

Or is there anything else that could be causing it, because its only in the lower rpms that its happening?

[surge]

Could be mounts. Could also be driveshaft or gearbox related.

Hard to know without getting the car raised and inspected.

Sort of have to rule things out one by one as it's just one of those common problems that can be a result of different problems and possibly more than one at the same time.

Sometimes a good specialist will be able to take it for a drive and narrow down the possibilities.

[duncanm]

when you say lower RPMS - does it differ with engine load (throttle position)?

 

if it only happens at low RPMS + throttle, then maybe suspect spark (coil, plugs, leads) or fuel system problems.

 

Does it idle cleanly, or do a little shudder/miss every now and then?

 

Is the engine nice and stable in the bay when you blip the throttle? - may indicate worn mounts if its not.

 

As surge says - a good mech should be able to narrow down the possibilities pretty quick.

[RX25SE]

Hi guys, 
 

When I lift off the accelerator and the revs drop below roughly 2500, the whole car shudders and jolts. The only way to stop it, is to put the clutch in, change to a lower gear (so the revs become higher) or to go to neutral. This happens whether the car is cold or at running temperature. Does anyone know what could be causing this because I don't think its good for the car to be shuddering constantly.

 

 

2002 Subaru Liberty RX 2.5 Sedan

Cheers guys

 

 

I'm going with a driveline issue. Broken mounting or similar.

 

Things like coils, plugs, leads etc are usually at fault when the engine is under load. (this is when a greater volume of fuel is delivered, thus stressing the ignition system)

 

 

 

 

 

Forget cleaning your MAF, you don't have one.

 

The n/a 2.5 uses a 'speed density' engine management system, therefore it uses a MAP, not a MAF.

 

 

MAP= Manifold Absolute Pressure sensor

(measures the air pressure in the inlet manifold and compares it to atmospheric pressure, combined with the Inlet Air Temp sensor it allows the ECU to calculate air flow into the engine)

 

 

MAF = Mass Air Flow sensor

(measures the volume and temp of incoming air to calculate air flow into the engine)

 

 

 

 

 

 

Sorry for the detail, but I see this mistake often made and some days it bugs me more than others.

 

Today is one of those days.

[CRUISN]

Have a beer or 5 Jase.

Ive been cleaning and painting the undeneath of the Chev. Im filthy, my neck is sore but beers make everything better.

[RX25SE]

Haha

 

I'd be painting my calipers if not for the fact I can't find my blow gun!!!

[02_Liberty_RX]

when you say lower RPMS - does it differ with engine load (throttle position)?

Only when I take my foot off the accerator completely and the car is pretty much 'rolling'. As soon as I accelerate it goes away or changed down it goes away.

 

 

if it only happens at low RPMS + throttle, then maybe suspect spark (coil, plugs, leads) or fuel system problems.

I recently replaced the spark plugs and leads so I hope it wouldnt be them. Though when we looked at the coil one of the terminals seemed to be burnt, all we did was sand it back and that seemed to fix it. Though sometimes I think I feel or hear it misfire, only slightly though

[02_Liberty_RX]

I'm going with a driveline issue. Broken mounting or similar.

 

Things like coils, plugs, leads etc are usually at fault when the engine is under load. (this is when a greater volume of fuel is delivered, thus stressing the ignition system)

What mounts would be ones to look at? Are there any in particular or ones that can have this sort of characteristic?

[02_Liberty_RX]

Also, when the car first arrived it would shudder dramatically when on full lock and at running temperature. So we have already had the viscous coupling replaced with one that is refurbished and done up. This wouldnt effect the shuddering when my foots off the throttle?

[allpaw4]

I've found out the hard way that coils do not like running without a plug/broken lead for any period of time. I'd suggest replacing the coil that you sanded back as one of the first items for replacement/checking. Borrow one from a working car for and go for a drive before buying a replacement. See if it makes a difference before shelling out lots of dollars.

[02_Liberty_RX]

Okay I'll have to have a look.

 

Does anyone know of anyone who is in the Mackay area. Anyone on here that might be able to have a look at it or come and see it?

 

Or are there any specialists that anyone recommends around here (other than the Subaru dealer). Or anyone around who knows Subys and might be able to come have a look?

 

Thanks for the replies guys

[RX25SE]

What mounts would be ones to look at? Are there any in particular or ones that can have this sort of characteristic?

 

Engine and transmission mounts.

 

Also worth checking the pitch mount (firewall to engine) as well as the diff mounts.

[Andyjs2]

Same problem man, even with clutch in rolling with foot on the brake close to stopping, just like a shuddering feeling
After having the centre diff replaced (violently shuddering while turning when car was heated up)

An engine mount was recently replaced too, and I've been told that the pitch mount is worn out (I've got one sitting ready to go when I can be bothered)

But I'd like to see if you get it fixed and how
I'd probably look at a tranny mount if it's not the pitch stop

never had a problem until the cv popped out while I was replacing the ball joints, problems ever since
Replaced cv shaft, center diff and now I'm getting the same kinda shudder at slow speeds

[Bumpty]

That is concerning.

[Andyjs2]

It has recently come to light tjay my left cv shaft was replaced by a shorter cv shaft... could be something to do with it?