Intermittent hesitation problem SOLVED!!!

[JDW-SVX]

Ever since I bought Jamsvx's SVX, I have experienced the same "intermittent hesitation" problem that many others have been experiencing. (Phil Hill on the European Forum has described the exact same problem!)

That is, every now and again, the engine will not respond to the throttle being opened while on part throttle, and will simply behave as if the throttle was still being held at that part open position.

Then - about 2 to 3 seconds later, the engine will suddenly "wake up" and will rev up, as it should.

Needless to say - when this happened, it was EXTREMELY annoying!

For USDM SVXs, this problem has been traced to an ECU fault (the infamous "bead crush"), but I was convinced that this was not the cause in my case. This was confirmed when I checked with my local Subaru dealer, and found that no recall or service bulletin existed for this problem.

So I start thinking - what else could be causing this problem?

When this hesitation occurs, the engine still runs smoothly - but the power drops significantly. It seems that the ECU is retarding the ignition timing - and this would only happen if knock is detected.

The only explanation that I could come up with for this is that the Air/Fuel mixture has become excessively lean, making engine knock more likely.

However, when I go ahead and check all of the air intake piping and hoses, everything seems fine. None of the vacuum hoses have deteriorated, and all hose clamps are tight.



At this point, I was completely stumped!!!!

Then, in frustration, I double-checked the air intake piping, and concentrated on the two hose clamps that secure the plastic intake "chamber" to the throttle body.

Everything looked fine - until I grabbed a mirror, and looked UNDERNEATH the throttle body!

I couldn't believe what I saw!

At some point in the past, the plastic intake chamber was removed and re-fitted to the throttle body, and in the process, the bottom third of the right-hand flexible rubber coupling had been folded over and crushed by the hose clamp!

This meant that there was an unmetered air leak - which would result in a lean mixture being sent to the right-hand bank of cylinders!

This picture will illustrate what happened!

http://www.subaru-svx.net/photos/fil...-SVX/24443.jpg

Due to the coupling having been clamped in that position for so long, I could not simply fold it back into its proper place, as the rubber had deformed at the point where it had been folded.

I then had to wait nearly 4 weeks for a new intake chamber to be sent over from Japan (Subaru Australia don't seem to keep ANY SVX parts in the country!! )

Thankfully, after fitting the new intake chamber, the hesitation has disappeared!!

So - if anyone else is experiencing this problem - get a mirror, and check underneath the throttle body!

As well, if you are re-fitting the intake chamber to the throttle body, be very careful not to bend the coupling!

Jason.

[lee]

good find Jason.

I only had my SVX for a few weeks when the front differential failed. In the process of removing the transaxle, I took off the air box and found the same situation as you have done.

As an aside, I put two cans of spray paint in the openings (nothing significant about spray paint, it was just the right size round cylinder) and using the screw-type clamps on the air assembly, I clamped it up and let the system sit for a couple of days. It worked for me, so if you haven't already disposed of you old box, you may wish to give it a try.

[svxistentialist]

I discovered this same thing recently on Black Betty.

Whoever had last taken off the manifold had pushed the two rubber boots on carelessly, folded them under and put on the clips.

They looked OK, but were'nt. Even though the rubber had taken on a creased shape, I softened it in hot water, then gently eased it back in place, and secured correctly with the clip.

Not much room to see when that pipe is going in place, so you really have to ensure the bottom lip of the rubber is going onto the flange properly before you push the assembly into place.

Joe