Hi guys,
Bought a 2000 turbo wagon (1999) earlier this year and constantly trying to iron out issues.
The most recent one is a series of flat spots under max load (4th, 5th gear) when on full throttle. Its a bit like letting off the throttle - they are smooth not boost cut. It's not the generic dip between 4k and 5k as there are about 3 of them as the revs climb.
The car is completely stock and I have recently replaced the plugs, intercooler hoses and vacuum lines which have made the world of difference (was plagued with a stutter on boost).
I'm running out of ideas. No CEL lights. Everything seems to be in good order. It occasionally starts to idle a bit low but nothing too problematic and has never stalled. The maf has been replaced by a previous owner, but a few years ago.
Only thing to add is that it's running 1.1bar of boost instead of 0.8bar.
Could it be that it's potentially running lean on boost?
Any suggestions would be great!!!
Tom

 

I suppose there's a possibility that it's pulling the timing back slightly to avoid det but these things run really rich as standard so should be ok. How old is the fuel pump, plugs etc?

 

Well I need to do some more checks but I was running 0.5bar as my restrictor pill was missing but it was running stoichiometric on boost so I assume it still is at 1.1bar. Will need to verify this though.
Have no idea the age of the fuel pump - was considering replacing but I took the inlet pipe off the filter and it's priming and fuelling well.
Plugs are 100 miles old. The old ones weren't a matching set and were degrading under load.
Fresh out of ideas really.

 

Plugs gapped correctly, could it be maf starting to play up?

 

https://www.scoobynet.com/general-te...limp-mode.html

Second hand good coil pack fixed my problem!!(£5 from ebay!!)

 

They are gapped at 0.7mm which seems fine. There aren't any losses in power in other gears and no misfiring so I believe all is well there.
As for maf - could be degrading slowly? I have only been able to try one that was broken so wasn't much help. I don't want to swap parts for the sake of it either!!

 

It's not missing or in limp mode. Coil packs are usually fine or not and it only does it under peak load. So don't think it will be? Especially with no misfires!

 

Running stoich on full boost? That would be a bad thing.

 

Sorry under light load it is running stoichiometric. All lambda values are where they need to be when under load so its not a AFR problem i don't believe.
Need to put the band sensor back on now it is at 1.1 bar but im not convinced it will be ratios.

 

Best getting a wideband on to see if the AFR's are ok. Has the car had a remap or anything in the past?

 

I have a spare maf for a '99 you could try, I replaced it with new when I ppp'd the car, as a preventative measure. The car ran fine with it. I'm in Bristol.

 

sounds like MAF (but seen it has been changed - was it a genuine one?)

 

I don't believe it has as there is nothing in it's history. It's just had a genuine owner who's looked after it very well.

 

I have no idea. I'll have to recheck invoices and I'll have a look under the bonnet later. Do mafs degrade slowly like this and cause problems? I've taken it off and sprayed some cleaner in there but it was spotless before I did that.

 

Awesome. I may take you up on that. I'm in Oxford for the next few weeks but if I'm in Gloucester for a weekend I'll message you beforehand!! Thanks very much!!

 

Might be a silly question but what fuel are you using?

 

I was using just normal unleaded as it is a UK not import. Switched over to super a few weeks ago but no change at all!

 

Mine is a UK car and it says on the inside of the fuel cap to use super unleaded. Did the problems get worse when you used unleaded?

 

Yeah you are correct so does mine. There wasn't any difference between the two fuels but I think I'll run it on super from now on to keep it a happier.

 

Probably for the best mate. Especially if you're running raised boost on a standard map. I assume you've got some kind of boost controller fitted?

 

Yes I think you're correct with the fuel. Actually I'm running a restrictor pill off a VF28 turbo which is a smaller diameter. Giving me 1.1bar rather than 0.8/0.9bar.
This problem hasn't occurred due to more boost though. I've been slowly diagnosing and clearing issues and the flat spots are a mystery.

 

I have heard that boost controllers do smooth the boost out a lot. Should this be something to look into?

 

I personally wouldn't bother with a boost controller as such. There was a Turbosmart manual controller on mine when I got it but then I came across a cheap Blitz dual SBC and fitted that in its place. It actually gave me the best and most stable boost I've ever had. I since fitted ESL and am now using the Subaru system again. It's more complicated to set up but I'm guessing it's the best job for the car. Raising the boost without checking the timing and AFR is just asking for trouble. The only thing that saves us is that the cars run really rich from the factory.

think you'd benefit from some data logging like boost, AFR, timing etc. Is your car OBD2?

 

Not obdII unfortunately.
MY99-00 uk cars have a reputation for eating mafs. Some owners treat it as a service item and replace it every year. Also, I can't imagine 1.1bar boost is good for it with the standard map and exhaust, how about trying the correct restrictor pill?

 

Thanks for the advice. I will put some time aside at some point and run some data logging. I'll let you know if there's anything unusual happening.
Tom

 

The old pill went in the bin unfortunately but i can run a 1mm drill bit through this one if necessary. I'm under boost cut as well so I'm not too concerned about it being unsafe. The problem seemed to be present without the boost running higher anyway.
I'll do some logging and update everyone on the progress!!
But yes, MAF could be degrading but no way of telling. No CEL and engine cuts when disconnecting. Data logging may reveal!

 

Got a boost gauge?

 

UPDATE:
It misfired again and the flat spots still remain. I now have a boost gauge and I have similar problems to this man here:

When full throttle, the boost fluctuates about half a bar (not fuel cut). Its gradual and the car continues to build rpm.
It wont be a boost leak - I have brand new intercooler hoses and I secured all vacuum lines again at the weekend so I'm certain I have no problems there.
Since owning it the CEL has intermittently come on and off. I cleared the ECU (few months ago) and it recently illuminated again. Code 22 - Knock sensor.
Forums suggest this isn't because it is knocking but rather the sensor is buggered. I will take it off to inspect as they are susceptible to cracking.
Furthermore, I have a replacement MAF inbound as its a few years old and a lot of the low idling problems and boost problems can occur from a failing one, so im swapping it out for a piece of mind.

Does anyone have any of these symptoms and codes and can pinpoint what it is exactly?

Many thanks guys. Sorry about the slow progress, I will be able to do with spare time over Christmas.

Tom

 

has it been mapped?

 

Are you sure its a standard car, an easy upgrade was to fit the PPP ecu this would give you 1.1bar, if you have removed the center cat, your boost could be rising to quickly, once it spikes it gets pulled back, try building the car up slowly, don't floor it and see how it reacts, the boost control solenoid could case this problem.
To see if the Ecu has been changed, lift the carpet in the passenger footwell and remove the cover plate, it should have a pink sticker if its PPP, otherwise it should be a 801 or 800 series dependent on month.