[Mk2] [Turbo] Stutter under boost

[mikey2]

I tried that, didnt make any difference when i wiggled the plug. I disconnected it and started the engine and the difference was huge, it blew a cloud on start, it bogged down as soon as i even tried to accelerate, it idled ok, but anything above it didnt want to know.

[Lewis Jay]

Have you checked the resistance values in the BGB for the AFM?

Have you checked the base timing, rotor arm and dizzy?

Are all the leads in good condition?

Did you check the gap on the iridiums I have seen plugs wrongly gapped out of the box and cause issues.

Try the stock plugs see if its till the same.

[mikey2]

I have not checked the values on the afm no.
I have not touched the timing, i dont know what i am doing and would rather not play with something which i could get horribly wrong!
I had the dizzy off earlier, i cleaned the contacts as there was some erosion on the contacts, the rotor arm looks ok, but i couldnt get to it very well so was only really a limited inspection.
The leads look ok, they dont look big enough, but that may just be me.
They are all seated right too, i had them off again today, and it made no change.
The plugs, i was told not to mess with the gaps on the iridiums by Peter at Sbits, so i didnt. I have the original plugs, but it was doing the same thing with them in, thats the main reason i changed them.

[Lewis Jay]

I have not checked the values on the afm no.
I have not touched the timing, i dont know what i am doing and would rather not play with something which i could get horribly wrong!
I had the dizzy off earlier, i cleaned the contacts as there was some erosion on the contacts, the rotor arm looks ok, but i couldnt get to it very well so was only really a limited inspection.
The leads look ok, they dont look big enough, but that may just be me.
They are all seated right too, i had them off again today, and it made no change.
The plugs, i was told not to mess with the gaps on the iridiums by Peter at Sbits, so i didnt. I have the original plugs, but it was doing the same thing with them in, thats the main reason i changed them.

O.k well get the stuff I`ve mentioned checked and then we can go from there.

I dont mean mess with the plug gap on the iridiums as Pete told you they shouldnt be changed, but that doesnt mean they are right out of the box. You should still check them before fitting atleast visually anyway.

[djpkins]

I had some good plug advise from guys on another thread in the modifications forum..."back from my iridium plug mishap" i think it was called...if your running under 1.2 bar then a 6 grade plug is ok with a .6 gap...my rev 2 is almost exactly the same as yours but it's random as Lewisj says...but then it seem to power through it after it's warmed up...also you could carefully check the sensors on the water elbow...I have a broken cold start timer sensor which I'm sure contributes to the problem...I replaced the plugs, leads, dizzy cap,coil and igniter...everything seemed to work for a bit and then start playing up again...I now have the original leads,dizzy cap etc back on and still get the problem randomly...my money is gonna be on the AFM and when I get the chance I am going to do as Lewis recomends and test it...I noticed the water was getting through the engine lid and dripping on the AFM plug, when I fiddled and tidyed the Wire up and lightly sandpapered the connections it was running as sweet as a nut for a week or so...

[Lewis Jay]

I noticed the water was getting through the engine lid and dripping on the AFM plug, when I fiddled and tidyed the Wire up and lightly sandpapered the connections it was running as sweet as a nut for a week or so...

The contacts are copper coated and flexable, they wear and get corroded.

In your case djpkins I would remove the old connectors inside the plug competely and replace with new connectors.

You can replace them with these small spade connectors by cutting some of the plugs middles away and then it still all looks stock and tidy.

[mikey2]

I will have a look for the values for the AFM, the plug is very clean and lacks any corrosion, i dont doubt the continuity of the connection, as i said, when i wiggled it it made no difference, but removing it, made a massive difference.
My standard plugs are gapped at 0.75mm at the mo. I can close this down to 0.6 and try that.

Would the fact the Tvsv is still electrically connected make any odds?
The boost guage on the dash still works, but i cant remember where the feed is taken for that, or is that the turbo pressure sensor thats connected to the inlet vacuum?
The turbo is running from the pressure side to the boost controller, then from the boost controller to the actuator, the other actuator feed is blocked off.

[mikey2]

I have the manual or a rev1, but not a 2, i have the values for what it should be, but will get the values that it is now.


Right, interesting!

THe book says:

vs + e2 = 200 - 600 Ohms
vc + e2 = 200 - 400 ohms
tha + e2 = 2-7 ohms temp dependant

Results

585 ohms
281 Ohms
insulated, there is no connection for the temp range, it briefly flashes very high 1600+ then nothing.


My Bad, the temps supposed to be Kohms, thats why! 2 mins!

THA + E2 = 1.95

[mikey2]

Right, small development today, i had a thought about the boost controller, whether it was actually working properly, because, when it stutters, the boost guage needle fluctuates like mad, and i wondered if it might be the solenoid, so i turned the boost down, right down, 0 gain, and it still boosted to 10 psi, so i turned it up, to a gain of 40, and it boosted to 12psi, i did this on both settings, so no i wonder if thats causing my problems.
Hopefully i will be able to borrow an MBC off a mate and test out the theory!

[b4rk3r]

I'd try changing the lambda sensor. You can get a cheap second hand one and they only take two mins to change, worth a shot.

[mikey2]

i am going to work through the possibilities, i would be surprised if it turns out to be the lambda, i cant see why that would make it stutter.
Incidentally, it behaves the same way with the actuator directly connected to the compressor, boost rises to .75 bar and theres a bit of a stutter there.

[Lewis Jay]

AFM values look o.k. so that box is ticked.

[b4rk3r]

i am going to work through the possibilities, i would be surprised if it turns out to be the lambda, i cant see why that would make it stutter.
Incidentally, it behaves the same way with the actuator directly connected to the compressor, boost rises to .75 bar and theres a bit of a stutter there.

I thought the same thing... I had virtually the same symptoms, the lambda cured mine

[mikey2]

i will look into that then, saying that, the turbine did hit the lambda on its way out!

[mikey2]

The problem would appear to be gone now, the only thing i have changed is the fuel, i used tesco 99 today instead of sainsburys.
I used tesco before, but it was with a load of sainsburys anyway, so was diluted! wil see!

[chri5]

Mine has started doing this but only when warm.
I did have a boost leak which didn't help.
But my engine is in a lexus is200 and where the radiator is filled is right over the dizzy cap
could water of got in and caused a fault???

[mikey2]

Right, the fuel made no odds, everything I tried made no difference.
However, when I fitted an afr guage I noticed the plug on the lambda was real loose, as in it came apart in my hands, so I put back properly, and bingo! No more stutter!! It doesn't flame like it did, but it runs infinitely better than it did!!
I remember someone telling me to check the lambda as I had had it off, and me saying it was fine cos I had it off, now I feel a little daft as I didn't put it back properly!!
Thanks for the help