ZD30 flat spot - no power

[mickn]

Hi guys, tried a search but nothing really jumped out at me....

I have a 2003 GUIII auto with 153k on it. It has the dawes setup, 3 inch Scott's Rods exhaust, EGR plate, auto fully rebuilt and nomad valve body. Serviced every 5 k and always use Delo 400.

Until a couple of months ago it was driven daily, a round trip of at least 70 km, but has since sat in the driveway, maybe doing a short trip to the shops once or twice a week. All mods have been in place for ages. I noticed the other day that it had a bit of a flat spot, really a hesitation when accelerating. Then yesterday, the same thing but much much worse, almost undriveable. It moves off ok, however any attempt to accelerate further just sends it down this deep hole and it almost dies. lift off the accelerator and it comes good again. It will build speed but very slowly. It is almost like it is hitting a rev limiter as it is quite a sudden drop.

I was thinking that the turbo, intercooler or associated pipework might be leaking boost, or in the case of the turbo, not producing any, but the fact that the boost gauge is indicating the levels of boost I have always experienced leads me away from that as being the culprit. I thought it may have been some dodgy fuel, however I always buy fuel at the local BP which has a pretty high turnover and I always run some chemtech diesel power in the juice, so I think I'll discount that. Also changed the fuel filter for no improvement.

Not being terribly experienced in diagnosing diesel issues, could you blokes provide some of your knowledge in pointing me to the components I should be checking to isolate the problem?

It's frustrating for me,if it was a petrol engine I'd have no problems in working out what's wrong, but diesels are relatively new to me and the only experience I have is through servicing it myself and avidly reading these forums regularly. I don't post regularly, but I do make comment when I can help someone out. I'm hoping someone may be able to help me out this time.

[threedogs]

What is it boosting to, and have you cleaned the MAF sensor recently.
Sounds a bit like its going into limp mode??
Check all hoses for splits especially the blue one in the pic, it can blow off

You will need to remove the engine cover to check

[mickn]

Boosting to about 15 psi before the dawes drops it back to about twelve. MAF has been cleaned, might try pulling the intercooler off and cleaning inside, make sure the catch can is doing its job..........

[threedogs]

You may have a large crack/leak in the IC if its still OE chances are its leaking/oily
, test it when its out not too much pressure though

[P4trol]

A longer shot, but make sure all your sensors are plugged in properly.

[mickn]

Thanks threedogs, but if it was leaky, would I still be seeing 12-15 psi boost? I'm heading down the TPS path at the moment, as it seems to drop out both under load and when coasting and then accelerating. Sort of happens at a certain position of the right foot if you know what I mean. Have ordered an ECU TALK cable so I can do some real time testing, but its starting to drive me crazy.

[boots]

TPS or maybe ECU relay .

[mudski]

Does it happen in any weather? Or only when its raining etc etc? I'd go over every hose and clamp real close first off. Sort of sounds like you have a slight boost leak and the leak is holding off to a certain pressure then letting go. But it could be anything, but boost leaks is the first port of call I reckon.

[dirtygu]

I had a similar prob on my zd30 gu11 turned out to b a head gasket

[mudski]

Wow! On a GU11? Well OP. Remove the cap, start her up and have a look see.