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[C4V V6]

Hoping to pick your brains!

On my way back from a show this year car was really sluggish. Just didn't have any go at all , I immediately presumed it was either back box collapsed or blocked CAT. (As that's what it felt like having had my gsi Zafira spit all back box out tail pipe)
Checked and back box, that was fine so pulled lambda sensor to see if it ran any better with a release for any back pressure a blocked cat may cause. It seemed like it was a little better. So changed CAT and lambda.
This didn't help.
Car when ticking over will red line. But once you drive and it's under load it won't rev past 3K.
I have swapped a few other bits in the hope to solve this problem but won't list just yet as more want to hear everyone's thoughts what it could be, or they think I should try
It's a C25XE so the 2.5 V6

[Robsey]

When Troy and I were working on James' V6 Cav, it was found that his amplifier was fubar'd.
Three of the six channels were duff.

Without load it would be easier to rev, although I presume it would be lumpy depending how many channels are down.
Under load, it would be like running a much smaller engine.
A basic continuity / resistance check of all the pins of the amplifier should point it out, or rule it out.

The only other thought is a failing fuel pump.
When I fitted the C20NE (MPi), but ran it with a lower pressure C18NZ (SPi), it could be coaxed to 3 or 4 thousand revs, but it was totally gutless on even a mild incline.

That is two potential causes - sorry they are so far apart.

[James McGrath]

Hmm, my first thought would be a blocked cat as this has happened to me but if you've changed it, it can't be that.
Could it be anywhere else along the exhaust? You say that removing the O2 sensor helped a bit, did it get worse again when you put the new one on?

[C4V V6]

Hmm, my first thought would be a blocked cat as this has happened to me but if you've changed it, it can't be that.
Could it be anywhere else along the exhaust? You say that removing the O2 sensor helped a bit, did it get worse again when you put the new one on?

This is why it's a head scratcher . No , it didn't get any worse once new one went back in. For the first 5min of driving car thought cat and o2 sensor fixed it.
It's had a new fuel pump so unless it's a faulty one I've ruledtgat out. But will try the other option mentioned .

[C4V V6]

When Troy and I were working on James' V6 Cav, it was found that his amplifier was fubar'd.
Three of the six channels were duff.

Without load it would be easier to rev, although I presume it would be lumpy depending how many channels are down.
Under load, it would be like running a much smaller engine.
A basic continuity / resistance check of all the pins of the amplifier should point it out, or rule it out.

The only other thought is a failing fuel pump.
When I fitted the C20NE (MPi), but ran it with a lower pressure C18NZ (SPi), it could be coaxed to 3 or 4 thousand revs, but it was totally gutless on even a mild incline.

That is two potential causes - sorry they are so far apart.

Do we have a "how to" on testing the amplifier?

[Robsey]

All the books say to use an oscilloscope,
With the negative probe on the earth pin,
And the positive probe on each of the remaining pins, one at a time

But to use the continuity method.
Rather than using an oscilloscope, use a test meter.
I am not certain of the specific resistance, but an open circuit should imply an internal fault in the amplifier between that pin and the common ground.