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Lack of power at top end

ConradBuff

Trainee
Joined
5 Mar 2021
Messages
73
Hi all. My '99 3.4 Cab has developed an issue whereby it seems to lose power in the top half of the rev range. It will get to c.4-5k pretty quickly and then take an age to rev out at 7k, if at all. I used to be able to feel the Variocam kick in at around that point but I can't currently and the lack of power is obvious. I had the Cam Solenoid on Bank 1 changed back in April so I know the symptons (rough idle etc) but the car isnt showing any of those currently so not immediately pointing to the solenoid for Bank 2, unless they behave differently?

There are no fault codes showing. I've had a recent issue with the AOS bellows but this has recently been resolved but wondered if a vac leak could cause similar symptons?

Any ideas on where to start?

TIA - Rob
 
The sypmtoms you had before with your solenoid were due to it being stuck in the advanced position - rough idle, etc.

The syptoms you have now sound like it's stuck in the retarded position. I wouldn't rule it out until you've had both of them tested with a PIWIS.
 
Alex said:
The sypmtoms you had before with your solenoid were due to it being stuck in the advanced position - rough idle, etc.

The syptoms you have now sound like it's stuck in the retarded position. I wouldn't rule it out until you've had both of them tested with a PIWIS.

Thanks Alex. It certainly feels more Variocam related and having had Bank 1 replaced it woudnt surprise me if Bank 2 was needed as well - just wish they were easier to get at on the .1!
 
Bank 2 solenoid failing is rarer than bank 1, but your symptoms are opposite than normal. First thing I'd do is check bank 1 solenoid hasn't come unplugged (check bank 2 whilst you're at it as well). Also check your solenoid fuses/relays if there are any.
 
Alex said:
Bank 2 solenoid failing is rarer than bank 1, but your symptoms are opposite than normal. First thing I'd do is check bank 1 solenoid hasn't come unplugged (check bank 2 whilst you're at it as well). Also check your solenoid fuses/relays if there are any.

If it was unplugged would it throw a code?
 
mikeeb said:
Don't they have variable length inlet tracts in the inlet manifold. I think they're vacuum operated. Could that be faulty?

Had something very similar on GT3, reso flap was stuck closed. Car just didn't want to Rev out. I know it's a totally different engine but symptoms were just as the OP described.
 
ConradBuff said:
Alex said:
Bank 2 solenoid failing is rarer than bank 1, but your symptoms are opposite than normal. First thing I'd do is check bank 1 solenoid hasn't come unplugged (check bank 2 whilst you're at it as well). Also check your solenoid fuses/relays if there are any.

If it was unplugged would it throw a code?

Doesn"t on the 3.4, least it didn't with mine when disconnected.
 
Alex said:
ConradBuff said:
Alex said:
Bank 2 solenoid failing is rarer than bank 1, but your symptoms are opposite than normal. First thing I'd do is check bank 1 solenoid hasn't come unplugged (check bank 2 whilst you're at it as well). Also check your solenoid fuses/relays if there are any.

If it was unplugged would it throw a code?

Doesn"t on the 3.4, least it didn't with mine when disconnected.

OK, thanks. I've been having a few issues with the AOS bellows and as they are in the same area I wonder if the solenoid harness has been pulled/disconnected. Will take a look later today.
 
So I got under the car and had a look at the cam solenoid connections and they seem fine. Borrowed a friends iCarscan to try and diagnose further - the car is showing NO fault codes, however when you look at the data fro the cam variations (one of the identifiers that was the issue prior to having the solenoid replaced) it shows some irregular values. On a drive out last night it was 0° when I first started the car and then suddenly showed 1006°! Parked the car up and plugged in again on the way home, then showed a solid -8.25° so I'm guessing something isnt quite right.

The actual cam angle seemed to be a live reading that changed however the deviation was frozen on a fixed number each time. Any ideas on what could be giving/causing the 'false' readings? I say false, this is most likely the cause of my missing power but having had the solenoid replaced and the car showing no fault codes I'm inclined to think its something electrical or a sensor rather than something more mechanical but I'm guessing at this point.

TIA
 

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