Engine hesitation at high revs under a full load

Hey Richard, did the coil packs arrive?

 

Hi Lukas, I haven't been back here for awhile obviously. As I said before, coil packs didn't make any difference. Certainly seems to be centred around the turbo. The other day I got the idea of disconnecting the wastegate actuator, which should tell me something. I pulled off the tubing and closed it off with forceps. The result is no change. So, can the wastegate be opening and closing by itself? I am thinking of getting the stock turbo you've got up on ebay and swapping it. What else could it be? I've got to stop this behaviour somehow.

 

Hmmm... Perplexing.

I've had a look back through your intro post and you mentioned that there was an engine hesitation issue and then this:
"It wasn't until I got to Rockhampton that I realised the trouble was a broken wire in the engine loom. I was able to locate the section of the wire bundle where the problem was, and tie it to the air conditioner low side pipe, which stabilised it and it gave me no further trouble the rest of the way home."

Have you checked if this has returned as the cause?

As much as I'd love people to buy my parts, I'd prefer you didn't go to unnecessary expense!

 

Hi Lukas, no, that problem turned out to be the plug to the engine ECU was halfway out. I just removed the glove box and pushed the plug back in and it hasn't missed a beat since. Anyway, the symptoms were completely different; it would start misfiring on one or more cylinders, and eventually would quit altogether. I found that I could affect it significantly just by moving the wiring loom around. Looked exactly like a broken wire. But no, it was just the plug. This problem is quite different, and repeatable. And it seems it must have something to do with the turbo. I've got a boost gauge, but haven't fitted it yet; I've been preoccupied with my home solar power plant; more specifically, getting a supply of adequately hot water. Cool showers were ok in summer, but not now. I've made a heat pump out of a dehumidifier, with the help of a friend who does air conditioning. It kind of works, but something is wrong, it's not refrigerating like it should. I'm going to have to take it out and take it up to his place.

Anyway, I'm pretty sure the boost gauge will show the bottom dropping out of the boost in time with the kangaroo hopping. So, what else can cause that?

 

It may be fuel not an electric fault - I had a hesitation when accelerating and sometime a cut out at junctions and was told it could be water in the fuel tank or dirt - a bottle of STP fuel system cleaner in the fuel tank did the trick.

 

Thank you, Ceri, I appreciate any and all input. I finally installed the boost gauge, though I had trouble figuring out where to put it. I finally removed the ashtray and wedged the gauge in the space for the time being.

What I see is that every time the boost approaches 20 psi, which is the maximum reading on the gauge, there is a sudden drop, which coincides with the sudden loss of power. This suggests that the waste gate is opening when it shouldn't be. But I tried earlier disconnecting the actuator, and it made no difference. Maybe Lukas knows if there's some other way the waste gate can be activated, as an emergency pressure release; I don't know if 20 psi is dangerously high, or normal. I also don't know if it should operate so violently. I worry that the engine mounts could be damaged. And what about the blow-off valve? I guess if that was opening when it shouldn't, I would hear it? There's a lot I don't know. I'm about to take it back to my mechanic, but mine is the only Copen he's ever seen, so he might not know much more than I do.

 

Nice work on hooking up the boost gauge. It makes diagnosis of this issue a lot easier.

Yep, 20psi is a bit too high and is more than what it should be set at. When I had the car, I'd set the boost via the wastegate to around 15psi to keep it under boost cut and prevent any reliability issues. That car has an aftermarket turbo that uses a threaded rod to adjust boost, not a boost tee or anything like that.

Please, whatever you do, don't disconnect the wastegate. That's probably one of the worst things you can do because you're preventing the wastegate flap from operating correctly and it's going to increase the boost level, not decrease it.

What I'd be looking for now is a split hose or an exhaust manifold leak, as it sounds like the turbo is overspooling due to an air leak somewhere. Also, check the adjustment of the threaded wastegate actuator rod or get a mechanic to adjust it to decrease boost.

As I'd mentioned previously, I'd suggest going to another mechanic for a second opinion, as it seems this guy isn't really up to speed with nuances of Copens.

 

I've got a friend who knows quite a bit about turbos in general, and he says that 20 psi is way too high. He thinks it sounds like the ECU is sensing excessive boost pressure and is shutting off the fuel and spark as an emergency measure. That seems pretty plausible to me. Is there any way the wastegate can get stuck closed? And what actually operates it? Is it operated by the ECU? Does it work on vacuum or pressure? I've never had reason to contemplate this component before. Anyway, I'll look at the hoses and connections again, maybe replace them. I noticed there's a T connection at the wastegate, I was wondering where it goes from there.

 

I. give. up.

 

Eureka! There was a hole in the tubing, caused by rubbing on something. No way to see it until I removed the pipe to the intercooler. There it was, a hole about 6mm diameter. As big as the tubing itself. I replaced it, but it was a bitch getting enough fingers in there even with the intercooler pipe gone. Got it done, though; put it all back together and went for a spin. Lovely, boost maxes out at 14-15 psi now. No more hopping. Thanks for all the encouragement, I might have given up otherwise. In hindsight, it explains why disconnecting the wastegate made no difference. It was effectively not connected anyway.

 

Its probably got a manual turbo boost controller teed in between the turbo and activator. Just screw/adjust the controller, mine scews in to reduce boost, if its hitting fuel cut at 19psi it has som sort of piggyback ecu modification.