New problem. Engine stumbles

[mhuk]

Thanks but yes done the TPS.

Not the codes. I should have!

Now at work but this morning I found out.

Holding the revs it still dips and picks up but when it does the fuel pressure drops 5psi or so with each rpm drop! Drops below 40psi if rev'd and let go.

See video > https://www.youtube.com/watch?v=Q0xZ9EnoqSU

[Laird Scooby]

Originally Posted by mhuk

Thanks but yes done the TPS.

Not the codes. I should have!

Now at work but this morning I found out.

Holding the revs it still dips and picks up but when it does the fuel pressure drops 5psi or so with each rpm drop! Drops below 40psi if rev'd and let go.

See video > https://www.youtube.com/watch?v=Q0xZ9EnoqSU

Nothing wrong with the fuel pressure then, doing exactly what it should do!

The rated fuel pressure is 300kPa above manifold pressure. In English (kPa isn't even an SI unit) that's 43.5psi above Manifold Absolute Pressure (hence the use of MAP sensors on some cars - not yours though!) and 0psi boost = atmospheric pressure of 14.5 psi roughly. Likewise, full vacuum (difficult to attain) is 30" Hg or -14.5psi so on the overrun, the pressure will drop and on boost will rise.

Put another way, the fuel pressure gauge will follow the boost gauge and your appears to be doing that.

Whatever is causing the revs to drop will also cause the drop in fuel pressure, i'd be inclined now to further investigate what Ash suggest, a possible blockage in the inlet somewhere - don't forget the inlet goes all the way from the throttle body to the air intake where the air filter feeds the turbo before sending it through the intercooler and then through the MAF and onto the throttle body.

You could have something stuck in the intercooler for example, removing it and putting the garden hose into it so flow is opposite to the direction of airflow might float out some crud causing a blcokage once airflow reaches a certain level.

[mhuk]

OK thanks so fuel pressure looks good. Glad because I reckon that's a crappy job to sort in the rain and mud.

My inlet side is very modded. See below it's basically a filter and charge cooler on a very short route to the throttle. I'll take a look. Cheers guys!!!!!

FYI. I have sorted those vac lines and it's been fine since (3months) It looks messy in the pics.

[Laird Scooby]

Couple of silly things - what petrol are you running it on (brand and octane rating) and have you checked the wastegate operating rod hasn't come loose? I understand one end is prone to dropping out of where it should be.

Also, can't remember if i've mentioned this, try unplugging the Knock Sensor, you may get the EML up and a fault code for a failed knock sensor but if it runs cleanly that will be a useful pointer.

Also check your timing belt tension.

[mhuk]

One thing I did before all of this was filling the tank with 40 pounds worth of fuel. Tank was about 1/4 fuel. Wonder if it's bad fuel but having said that I managed a good 20miles before the issues. I'll check the knock and wastegate. Also I'll check the fuel tank for vac

Cheers

[mocambique-amazone]

A cone filter isn't good in combination with the LH2.4
A cone filter directly in front of the MAF is even worse

Bad MAF
Bad O2 sensor
Bad ECU

I believe one or two or all three are bad

Good luck, difficult to know problems like this on heavily modified cars, Kay

[mhuk]

I agree Kay.

today's exciting testing.

With the knock sensor off the engine run ok. It did not seem to have a problem.

With the idle valve unplugged. The engine will not rev up.
I thought that's a bit strange.

I have ordered a draper vacuum gauge which is due tomorrow. I did however see my turbo gauge was off the gauge -30Hg for vacuum.

I connected my strobe light and I can see that
when the revs drop the light slows down with the rpm dropping. Also if I rev the engine high sometimes the light will go out. I mean for a split second which in engine terms is forever . This happened on two cylinders.

[mhuk]

forgot to say. I'm screwed the o2 sensor and getting plenty of gases out. in fact I'm surprised how much but the issues stayed.

[mhuk]

just had the exhaust down pipe off. Still showing 30hg on the cheapo gauge. Runs badly and still doing this strange rev dropping business. I thought maybe it might be blocked

[Laird Scooby]

If you do have a blockage, the most likely place is in your cat.

If you're getting a genuine 30"Hg of vacuum, something is wrong on the inlet side. You might get 26-27" Hg on the overrun after doing 90+mph and just let go of the loud pedal but only for a short while.

Also find it strange that unplugging the AICV causes it not to rev up.