Car seems to be underpowered at full throttle?

[S600TJT]

As per the title basically, on my '08 Corsa VXR. It seems to be alright at half throttle but at full throttle you can feel the car is boggy.

The car has had MAF & coilpack changed so can rule them out . . Anyone else had similar problems? It does have an aftermarket intercooler (airtec) and isnt mapped, also has forge recirc valve. Runs fantastically otherwise.

Thanks!

[Euro]

Perhaps a rolling road test ? Or garage diagnostic check ?

[S600TJT]

No faults when it was last diagnosed - have tried that. And as it stands RR seems quite a bit of effort, may be something simple.
Currently i would have thought it could be
- spark plugs (would they do this??)
- boost control solenoid
- turbo (although i dont seem to have any symptoms of turbo, smoke etc)
- front mount too large has been suggested to me?!

[vxrmjp]

Possibilities I can think of are the spring in the recirc valve which may be affecting the pressures, vac pipes, solenoid, throttle position sensor. Check all the pipes, air intake etc.
Turbo's can fail without being smokey, but usually they give issues throughout the range if it's the actual core of the turbo. Is the turbo leaking any oil?
Usually a dodgy plug will cause problems all of the time, although the Corsa can be a bit fussy on plugs, from what I've heard.

[GPH69]

No faults when it was last diagnosed - have tried that. And as it stands RR seems quite a bit of effort, may be something simple.
Currently i would have thought it could be
- spark plugs (would they do this??)
- boost control solenoid
- turbo (although i dont seem to have any symptoms of turbo, smoke etc)
- front mount too large has been suggested to me?!

I spent a fortune on my corsa vxr A16 engine with similar fault, changed coilpack, plugs, maf, all usual stuff then spent £400 on a map at Rabbid now been running perfect for last 6 months so I would just get it mapped as it can also show up a fault if car as one


Sent from my iPhone using Tapatalk

[u33db]

I would remove the forge recirc for starters as on mine the rubber end cap seal had split causing the car to feel sluggish/underpowered/erratic at full throttle due to a leak.

(You might be tempted to replace the seals but for the effort involved (taking the inlet off) i'd just replace the full thing with an OE valve, which will last longer anyway...the Forge ones aren't fit and forget as mine failed at 3 years old, and its frankly a crap design...i mean the rubber seal is basically a similar size to a watch seal and it also gets cooked due to engine bay temps!).

Of the other things you suggested;
- Spark plugs - are known to cause running problems so a possibility.
- Boost Control Solenoid - could be duff.
- Turbo - probably not if theres no smoke/oil
- Intercooler when unmapped - no.

It might be worth buying a bluetooth OBD reader off ebay so you can pair it with your phone to get boost readings...that help quickly show if its air related or mechanical

[Noxious89123]

Can't hurt to pull the plugs and check the gap, but tbh I'd expect the car to set a fault code if it was blowing out the spark / misfiring at full throttle.

I drove my car for about 6 months with my FMIC without having the map updated and it ran just fine, although the car had previously been mapped so wasn't on the standard map. The car will adjust for lower air temperatures, just like it does on a cold day, so I'm with u33db on that one, I don't think the FMIC will be an issue.

Have you changed anything on the car recently before the problem started? Could a boost hose developed a small leak for example?