One more running issue to sort

[Daveyboy20]

Hi guys, CApri performing daily driver duties admirably! After years of running problems with this project - a full wiring loom strip down revealed that the lambda sensor wires had been cut and taped back up as had the AAC valve wires amongst others. With every electrical component now hooked up and working properly, it is a joy to drive! No more hesitation or missing on steady throttle once warM! There is one (maybe 2, if unrelated) less annoying 'problem' left. I thought I'd tell you all the symptoms to see if anyone recognises them, and it turns out it's simple to fix.

No issue when cold.
w
When warm, if i give it a rev, the revs drop down too much and it coughs and then they come back up but it seems slightly confused and can't hold a smooth idle. I can usually 'remind' it of what to do by holding the revs at, say, 2000rpm for about 5 seconds and gently dropping back to a smoother idle.

It seems that when i come off throttle completely, there are about 2/3 seconds where nothing is happening, for example, if i drop the clutch and the throttle at the same time it'll sometimes cut out, but if i drop the throttle first and allow it to coast for a couple of seconds, i can feel and hear the moment at which it would've cut out or idle dropped too low if it didn't have the momentum of the car/gear to chug it along.

This is also occasionally noticable in 5th, if i accelerate and then back off i can feel the two seconds or so of what feels like 'no input'.

Sometimes when i back off the throttle it makes terrific crackling noises from the straight through exhust, but most of the time it just makes a smooth sound. Almost as if the values are different between the two noises (i feel like it has something to do with the 2 second moment of seemingly 'no values/input' after i come off throttle.

Does any of this tie together and ring any bells?

Should i just be happy it's finally working and shut the hell up!?

[Actual_Ben_Taylor]

You got a dump valve fitted, I'd so it sounds like that would be the culprit

[Daveyboy20]

Nope, just a very chatty T28!

[pointz]

How is your inlet paperwork setup? Between afm and turbo?

[Daveyboy20]

A very short bit of straight pipe, basically, as short as it can be!

[Daveyboy20]

[pointz]

I would say there is a good chance that's your problem, it ideally needs to have a bend in it as basically when you lift off the accelerator air that has passed the afm goes back through the afm (air reversion) or whatever its called!
It confuses the afm.

Anyway you can alter it to have at least one bend?

[Daveyboy20]

Interesting, would that cause a problem when cold too? As it's faultless when it's cold.

[pointz]

I cant say personally but i would imagine not so much as more fuel gets injected when cold anyway and i expect you wont be boosting much when cold if at all.

Even if you could try running it with a bend and see if it improves it then that can be ruled out! I do know that afm's do not like 1. Being close to turbo and 2.being on a straight pipe ie- no bends.

[Daveyboy20]

I had no idea about that but it makes sense, thanks mate! As you can see from the pics, space is tight! The filter is right next to the rad though, so it would benefit from moving for that reason alone. I'll have to extend the AFM wiring and source some suitable pipe work. Oh... headlamp bowl - induction headlight - rude thoughts... Thanks again matey

[Hugh Janus]

I would say there is a good chance that's your problem, it ideally needs to have a bend in it as basically when you lift off the accelerator air that has passed the afm goes back through the afm (air reversion) or whatever its called!
It confuses the afm.

Anyway you can alter it to have at least one bend?

as i started to read this the length of the AFM pipe was my initial thought too

[pointz]

No worries mate! Space does look very tight lol stick it out the bonnet lol.

Post back and let us know how you get on

[Kev]

Afm might be the issue, but my thought would be aac not set right or dirty inside.
When cold, the air regulator under the tb let's more air in.
But when hot it's blocked off.
To test, warm her up then sit on idle for 30 secs to let it settle.
then take the plug off the aac.
idle should stay the same.
If it goes down or cuts out then it tells you the aac is needing to engage to hold idle which it shouldn't really.
This would be the easiest fix as you would just back off the 10mm bolt on the back of the aac assembly, the one that points to the back of the engine.

If all is ok then screw the 10mm bolt in until the idle starts to get ropey and then plug the aac in, it should recover... I'd it doesn't then aac ain't working