What are the symptoms of a failing turbo? I've been experiencing a random loss of power on acceleration and it's most noticeable when I don't rev the motor before slowing engaging the clutch. It seems to do it more often when I'm not in Sport mode and if I'm not mistaken, it's simply because the engine responds quicker off idle in Sport mode and therefore I've built some revs and got the turbo spinning.

I'm going to plug my OPD II module in one day soon and see if I can characterize the boost vs RPM for when it seems okay versus when it's a dog!

And while I'm on the subject, does anyone know exactly how boost is controlled? I'm an old school hot rodder with limited knowledge of boosted systems but waste gates were how boost was regulated in the days before computers.

 

Boost is still controlled by a WG, but the WG is now controlled by the ECU (unless you've installed a much bigger turbo and / or MBC).

Tell us about your mods, if any. Maintenance history, mileage, etc --- anything related to your turbo or general performance.

Common "gradual loss of performance" causes for N14's are ---
-loose WG
-plugged cat
-leaky DV
-loose / leaking hoses
-worn out plugs / coils
-low compression
-loose timing chain
-dirty fuel filter
-etc, etc. Tuff to diagnose online with limited info. Your previous experience / knowledge on hi perf engines should help eliminate some of my listed causes.

Keep us posted ---

 

Translation for pdeinc:

WG= Wastegate
ECU= Engine Control Unit
MBC= Manual Boost Controller

 

The loss of power isn't consistent so most of your items wouldn't necessarily apply.

Most of the time it runs like the proverbial raped ape but on occasion it can't get out of its own way from a dead stop. And the only thing that seems consistent when this occurs is that I've bogged it a bit coming off from a stop. Once I get rolling, I can push in the clutch, let the revs drop to idle, rev it slightly (2-3K) it a few times, then proceed with normal power most of the time. No mods that I'm aware of, purchased it with 99,000 miles and have put another 15,000 on it with no issue. I do have a thermostat issue in that it doesn't run up to full temp all the time but it does run over 180-190 so I haven't bothered to replace it yet.

You forgot DV! Seriously though, WG and ECU were common terms for me, MBC and DV were not, so thanks.

 

I've read that a faulty t'stat --- low temps, can cause random problems --- ECU doesn't like low temps after a given time lapse, unless it's been re-programmed. Maybe fix the t'stat and try again?

 

When I plug in the OBC II and track boost levels, I'll also monitor temps to see if there's any correlation.

 

Update: Well, it seems I can not duplicate the loss of power issue at will! I took a couple trips around town with my OBD II and Dash Command app and try as I may, it wouldn't bog down on starts. I'm beginning to think it might be more of a fuel pressure issue as it's similar to what I would experience when I had a fleet of boats and had a high pressure pump going bad. But I don't know how that correlates to bogging the engine from a dead start and the problem I've experienced only happens then.

Regarding the water temperature, it stays between 180 and 193 once warmed up and while that's probably a little less than optimum, I can't imagine those temps can affect performance to the degree I'm seeing. And it's probably not low enough to justify replacing the thermostat...for all I know someone put in a 180* version at some point in the past. What is interesting though it that it threw an error cold while at 178* only a few minutes after leaving home after a warm start. I would think there would be some delay after starting to allow the system to reach operating temperature, something longer than 2 minutes anyway.

 

Details on my coolant temp suggestion --- when manic lowered my coolant temp to 180, they either forgot to adjust something, or adjusted only one of two settings. Result was a code after a short driving time from a cold start. Seems the ECU is looking for a hot engine (over 180 deg) after a few minutes. This was done a few years ago and I don't remember the details or all conditions, but after some discussion with my tuner, I pulled the ECU, sent it back to him, and the fix was programmed in. Haven't had that code since. Pretty sure the t'stat only comes with one setting --- about 220 deg F. I don't know the time delay used in a "warm start", but it sure sounds like your t'stat is faulty, and that can definitely cause random problems --- ECU is compensating for low coolant temp. You should definitely replace the t'stat before chasing a fuel pressure problem.

 

Thanks for that info, that's helpful and while I agree that the t'stat is likely faulty, I still believe the randomness along with the very short duration of the problem isn't related to coolant temp. I had another occurrence yesterday and didn't have my app running at that instant so wasn't able to correlate it to anything but within a minute, the coolant temp was over 200. In fact for short time I did have the app running yesterday, both before and after the low power insance, temps were 199-203*, contrasting with previously where they ran from 180 to 193".

I have found that I can monitor the fuel rail pressure in real time but I may have to use the data logging feature of the app to pin this problem down to any particular source. But even if I find the problem is related to fuel pressure or coolant temperature, I'm not likely to do anything immediately considering both how rare and short term the problem is.

 

I am having a very similar problem with my 07 jcw and it is driving me crazy occasionally it Boggs from a stop feels like it has no power feels like it’s running rich but the weird part is when mine occurs it over boosts to 20 21 psi but takes for ever to get there? I don’t get it normally it pushes 16 17 psi but feels 10 times faster I can not trace the problem not throwing and codes and it’s real intermittent any ideas?

 

Sounds just like my symptoms and I'm a bit surprised that until your post, no one else has experienced anything similar. And sorry, I haven't been able to pin it down to anything in particular but like you I no longer believe it's turbo related. I'm tracking fuel pressure in the rail now but having my app running when it happens is a challenge.

 

any update?

 

No, nothing yet. Been busy with other projects and have only run the Mini on short errands. I did download the full version of Carly and checked for any codes my other app may not have reported and found nothing. Made a few code changes regarding lighting and reset a brake error but that's all so far.

 

I have done spark plugs and valve cover gasket so far with no luck have a new downpipe coming and pigtail for the maf bc 2 of the wires on mine are nicked hopefully that’s it also want to do the rubber seal on the turbo inlet but I don’t believe you can get just the rubber seal without buying a whole intake pipe which I don’t necessarily want to do

 

Update #3

I've tracked fuel rail pressures and they don't seem to vary from when it's running well to when it's not. But I think I've correlated the poor performance to one factor - heat. Not coolant temp and not necessarily intake air temp but more like under hood temperature!

My reasoning is that this occurs most often after sitting still for what is typical a long cycle traffic light after running hard or running when ambient air temp is in upper 90s. Plus this fits with my experience that after I travel a couple of miles from the extended dead stop and poor performance, it's back to normal. I know these cars suffer from certain plastic parts that age and warp and this may be related but not sure how. The idle is always fine so if it were some significant vacuum leak, that would be immediately obvious.

So experts, what else under the hood is adversely affected by high engine compartment temperatures that would contribute to a significant loss in power?

 

Maybe it's a bad electric fan?

 

Coolant temps are within normal.

 

Do you notice this happening after you've been running hard or the ambient temps are high and you've sat still for several minutes? Mine never does it when cold or during normal driving when ambient temps are cool.