Molly

I found a hole in the vacuum line between the intake manifold and KLR. There was no oil in the line but it was clogged completely with a big chunk of soot and grime, right at the hole. The hole.. or somewhat of a crack.. was browned and brittle indicating it has been like this a while. I assume it was sucking in nasty engine bay and road grime air for who knows how long. I fixed the hose. The car has been running a little poorly lately.. though not terrible.. but it pops on decal.. idles a little flakey sometimes.. and does not seem to accelerate as hard these days. It's not slow.. but the boost hit seems mellow by maybe twenty percent compared to how it used to feel. The car is bone stock.. had it since new.. The car hits boost at a little over 3k in each gear.. smoothly and instantly swings over to 1.8 on the factory gauge.. no stumbling.. no odd sound.. revs right through to 5k plus just fine.. simply seems soft.

The thing is.. I thought oh this klr vacuum hose is hosed.. now maybe the car will be back running right.. but alas it only took one drive to see that the car runs identically now even with the hose fixed.. how could it be that such a crucial vacuum line was clearly either completely clogged.. or at bare minimum not holding any vacuum due to a giant crack in it.. yet seems not to have affected anything to fix it? Maybe the klr isn't working at all? Any thoughts are appreciated.

divil

How was the factory gauge behaving before you fixed the hose? The gauge is driven from the KLR, based on the pressure reading the KLR gets from that hose. I would say a leak in that hose is unlikely to cause performance problems, because it just means the KLR will think your boost is lower than it really is. If anything it will actually try to correct your boost curve but I don't think it makes a huge difference either way. I have a KLR with a bad pressure sensor - it reads low, similar to what you might see with a leak, and funnily enough my car has a performance problem that sounds almost identical to yours...but replacing the KLR with a good one didn't help. Your cracked hose would have been a vacuum/boost leak, but if it was very small it probably wouldn't matter. It's a tiny hose after all.

A KLR that's not working at all would give you a no-start condition (no spark), so yours is definitely working at least a bit.

There are lots of things that could be causing your issue - maybe more than 1 thing. Sometimes the catalytic converter becomes a big restriction...since your car is totally stock, that could well be contributing. Vacuum/boost leaks and exhaust leaks are also pretty common causes of reduced performance. If you have never replaced all the rubber vacuum lines under the hood, some of them at least are sure to be in as bad a shape as the KLR hose, and most of them matter a lot more!

Molly

Thank you.. I have replaced a few bad vacuum hoses I knew about already, and will be leak testing it soon. I am going to look in the cat because the tunnel gets very hot inside the car driving it for just a few minutes even on coolish days, which might mean I have stuffed exhaust which is overheating.

Tom M'Guinn

When I first got my car many moons ago, I thought it felt sluggish too for a turbo. After checking everything under the sun, I finally realized the factory wastegate was no longer sealing well, so boost was building slower than it should, and the turbo was not working efficiently at all. Replacing the wastegate with a cheap aftermarket (deltagate at the time, now Tial) made all the difference in the world. Just one more thing to consider.

KLR bonus trivia: Inside the KLR, there is actually an additional vacuum hose that runs from the banjo bolt port to the sensor on the board -- it's just another very well-hidden place a leak can occur.

divil

How did you figure out that it was the WG? Was there any noticeable heat from the dump pipe when it was supposed to be closed?

Tom M'Guinn

Just process of elimination really. It "worked" to keep the pipe cool at idle, but was just too tired to do it's job well at WOT. I'd make an unsubstantiated guess that most original wastegates on these cars are pretty tired at this point.

Molly

Ok so I am going to troubleshoot the WG and see if that's it. And actually as I drove the car more this weekend and paid close attention to how it ran, it is not boosting fully at 3500 like I first said.. it is starting to boost there for sure, but full boost is not til the mid 4s. So maybe the boost is eventually getting there but maybe coming on slower, thus making it feel softer. So WG will be debugged next. Not sure how to test the WG at WOT though, as the things I've found so far seem to indicate testing it at idle.

divil

If it's only starting to boost at 3500 that's definitely very late spool up. Does your car still have the test port attached to the crossover pipe? It would be a thin steel pipe with a blue rubber cap at the rear of the cam tower. That can be used to measure exhaust back pressure, which would be a good way to test for a restriction such as a clogged cat or a collapsed inner crossover/down pipe.

JacRyann

Btw, the KLR hose is ONLY used to drive the boost gauge. On a well-working car, go ahead and unplug and cap it. Boost will remain exactly the same. The KLR has a fixed 3D map using TPS position X RPM for duty-cycle output which drives the CV. It doesn't make feedback adjustments. If you've got leaks or clogged exhaust, it won't care, doesn't even know about actual boost and will continue outputting its preprogrammed map and that's it.

That's why with weak factory wastegate, you'll get lower-than-stock boost and with aftermarket WG, using the KLR/CV will give you higher-than-stock boost.

In Molly's case, it's most likely a mechanical issue with exhaust. Wastegate, collapsed inner tubing walls, cat and/or muffler.

divil

What makes you say it doesn't make feedback adjustments? According to factory documentation it does. Transaxle has a detailed explanation here...I don't know how he found that out but it does match up well with the official documentation. They could have easily driven the boost gauge directly from the manifold...why make it go through the KLR?