Paulyy

So i've finally got my car back together after bending a 2nd set of valves.
It drive flawlessly before it all happened.

Apart from the valves getting replaces, the pistons got cleaned up and a new set of gaskets and fluids.
I have replaced the spark plugs & leads. That's it

I am looking at it's either 1 of the 2, but the miss fire stops at load.
It's not a big missfire, it's like i can feel the car very slightly jumping while cruising. As soon as i give it throttle, it goes away and pulls. Car feels the same as it did previously except this missfire.

The sparkplugs are my standard NGK ones i use. IICR they're BPR7
The leads are BURU but not the porsche ones. They are the ones that the leads are pushed and crimped onto the plugs. I know this because one fell off and i pushed it back on. I'm thinking that could be the issue. I think i have my old ones (i know one is broken) but i can replace the one that came off.

What im thinking is though, if it's 1 lead that's the issue, shouldn't it missfire more at higher RPM or be more noticeable with more load?

Humboldtgrin

I would look at your fuel injector wire harness and your speed/ref sensor gaps.

Paulyy

fuel injector wiring harness has been fixed with new plugs. there shouldn't be an issue there. Car would shut off if it arcs out, and it would be more rough i suspect with a not good harness?



The gaps on the S&R sensors are good. i marked them before taking the housing off and put back on the same spot. And when installing (new) them, i gapped them properly per manual. wouldn't this cause an overall issue, not just part throttle cruising?

It's a very low missfire, you need to pay attention and look for it to notice it. I thought about data logging it, but unsure how. RPM doesn't move. neither does the vacuum.

Humboldtgrin

Could it be a bad spot(worn out) on your TPS? Or AFM if you still run one. Both are potentiometers.

Paulyy

running M-tune so i have a maf.
i have a known good TPS as i have changed it. But i changed it before it all happened and it had 0 issues.

Tonight i'll try my ignition leads for a piece of mind.

Darryl H

Checked the rotor arm/distributor cap? Mine did some funny things when I’d accidentally damaged the rotor arm.

Paulyy

It's pretty new, maybe a few years old. I'll double check it though. It did look new when i put it back together.

I had my rotor break once, that was missing quite badly top end

Humboldtgrin

You may want to change the TPS back out and see if that resolves the problem.

Paulyy

Can't the other one is stuffed. I'll set up my logger and see how the TPS acts, but i'm not confident it's that.

Paulyy

Im not sure if it's a missfire now. I dont know how to put this in words. But when i changed my cam to this big cam i have, the car would jolt? like it'll want to go accel then stop and continue doing that, so feels like it's jolting and that'll happen while cruising on a freeway or something from time to time. To stop it i just accel and it'll go away immediately.
But now i can feel it slightly while cruising.

I had Josh make changes to the tune and it did help. I know there's something causing it at the moment, I'll just have to go though and double check things now.