M20b25 loud pop when flooring

[Julianperezz]

Hey guys! I just rebuilt my head and put in ARP head studs and new head gasket w a bunch of other goodies... I know a lot of people are going to say these cars aren’t meant to be pushed but I’m building it to track it. Anyways I was testing it out in the canyons and I was in third flooring it and I heard a loud pop and the check engine light came on and off for about half a second, I checked and nothing was leaking and it was running fine after, a few days later I floored it again just to check and nothing happened but now it’s really bothering me on what that pop was. I stomp tested the car and code 1444 came up which is “ no faults ” so should I just leave it as a one time thing or does anyone else have this problem?

[15Michaeljoseph]

Hey now, who told you these cars aren't meant to be pushed? The M20 is a great little engine, and they can take quite a bit of abuse! Personally, I would leave your popping noise as a one time thing... Until it happens again! But really, sometimes weird things happen, especially when you've just put an engine back together. Don't sweat it unless you have to! (And don't forget to re-adjust your valves and check the torque on those ARPs after a couple heat cycles) Sent from my moto g(6) using Tapatalk

[roguetoaster]

How loud was it, where was it coming from, where in the RPM range did it happen, what mods have been done to the car so far, any recent maintenance?

Also, drive the heck out of your E30, otherwise I am not sure how you could enjoy it.

[zwill23]

I've had a flickering check engine light that would pop up seemingly every 6 months or so (driven 10-15k miles a year at the time) and when I caught it with the stomp test it was related to my O2 sensor. The code would consistently clear itself so I never bothered with it.

That being said, I wonder if you experienced a backfire and this threw the O2 sensor out of range throwing the CEL.

Also, to echo everyone else's sentiment, my E30's see redline every time I take them out. They're meant to be enjoyed and driven with a heavy foot :)

[Julianperezz]

Hey guys I’m sorry for some reason I didn’t get notified that you guys replied, it just happened again while cruising around 90mph in 5th gear at 4K rpm. I checked a stomp test and it said code 1261, so I replaced the fuel pump relay and it’s still doing it. It’s honestly doing more than before. I’m going to replace the fuel filter next but I’ve already replaced almost everything on the car injectors, engine rebuild, fuel pump. I know some e30’s have two fuel pumps i don’t know if mine does I’ll go ahead and check tomorrow. Thanks for the help guys I you guys have any clue it’ll mean a lot!

[Julianperezz]

https://www.youtube.com/watch?v=SH_cFpT8fog

here's a video of it cutting out

[15Michaeljoseph]

I can't really tell from the video if that little blip was loss of fuel or spark, but since it seemed to pull fine up to the top end of the rev range, my gut sways more toward a fuel issue. If your car is an early model (pre-88 in most cases) you'll have two fuel pumps, one 'traditional' style pump in the tank, with a sock on it (maybe the sock is dirty or pump is weak) and an external fuel pump that's located above the fuel filter on the driver's side under the car. If either is weak or otherwise acting up, you could end up with some starvation. Check the pressure at the fuel rail? Fuel pressure regulator? Aside from that--- If that was a WOT pull, the TPS *might* be a possible culprit causing a hiccup, because it is responsible for bypassing the afm and O2 inputs when you've got your foot to the floor. Could be out of adjustment or gummed up with oil resedue from the throttle body. You used all new ignition components when you did the rebuild correct? I'd also go ahead and replace the O2 sensor if possible just to rule that out. If its original it's probably not in peak condition anyway. Sent from my moto g(6) using Tapatalk

[digger]

a bit hard to tell but looked like tacho did a bit of a blip? which would not be a fuel issue

[15Michaeljoseph]

a bit hard to tell but looked like tacho did a bit of a blip? which would not be a fuel issue

I didn't really catch that since it seems like he let off as soon as it happened, but you could be right. I'm just talkin' 😂 Sent from my moto g(6) using Tapatalk