Strange issue

[TG Goose]

Been having some issues with my track car lately. I never used to daily it, but have been for the last month while I do work on my other car.

Cold starts - starts fine, but idle is low. Never idles over 1000rpm when cold. usually a solid 600ish. Sometimes just straight out stalls if really cold outside (zero Celsius)

Hot starts - no problems. idles 650-700rpm

warm starts - excessive cranking required to restart, idles fine afterwards.

I have a fuel gauge inline. In all situations, pressure goes straight to 45ish when starting. maintains 40psi at idle, rises with throttle accordingly. Tried two different FPR's, both identical.

Things I have done -
Valve adjustment
Ohm'd the TPS, CTS, ICV - All in spec
Swapped ICV's, both act identically.
Replaced CTS, no affect
Adjusted the TPS, no affect
Valve cover gasket, Throttle body gasket, new PCV hose, new clamps, new vacuum lines - no affect

Now here is the kicker. If i swap DME's, or unplug the battery, the car will cold start perfectly and idle at 1500 and slowly come down to a perfect idle as temperature reaches operating temp.

The car is an ETA body with a m20b25 motor swap. I have the round plug connector so its a very clean swap. All gauges work, check lights. Car had a 6 button OBC, but I yanked it, would that affect anything?

[jlevie]

It sounds like adaptation is wandering off into the weeds. The likely causes of that would be intake leaks or a bad O2 sensor. A smoke test will find any leaks and the O2 sensor can be replaced.

[TG Goose]

I just put in a brand new NTK o2 sensor, I'm going to smoke test it and hopefully narrow it down.

[TG Goose]

OK so ran the smoke test, instantly found leaks at the ICV elbows on the boots and the EVAP hose under the TB. Fixed those leaks and no other instances of smoke leaks after 10 minutes. Car was already somewhat warm, temp gauge at 1/4, but idle seems dead stable at about 700ish rpm now. Will know the cold results in the morning!

This goes to show just how important a smoke test is. I ran a homemade version and came up empty a couple weeks ago. Used a Redline Smoke Detection Pump system that I was lucky enough to borrow at no charge. This machine is brilliant and saved me so much time, I was almost going to yank the intake off and redo the gaskets!

[dnguyen1963]

Every noob should read this and learn the lesson.

[dnguyen1963]

of how important a smoke test is...

[AlphaE]

SMOKEEM IF YOU GOTTEM! its your freind.

[TG Goose]

Ok, so this morning was the cold start of all cold starts to see if my rough cold start/stalling issue would go away......Fucking cold started like a boss. No roughness, no stalling, idles like a motherfucker. So wish I did a proper smoke test a long time ago!

[TG Goose]

So after fixing all my vacuum leaks, I was still intermittently having misfires on cold starts just like before. I broke out the smoke machine again, no leaks. When ever it misfires, it always smooths out after 5 seconds and drives fine. But I have been getting terrible gas mileage. 380-420km tank, never getting the same result in consecutive fill-ups.

I primed the fuel pump and checked my fuel pressure gauge. Would hold pressure for 5 min, then start dropping, slowly but consistently. Fuck, leaking injector. Decided to downsize to 17lb M50 4 hole injectors from the 19lbs i was running. Yanked the old injectors, sure enough there were issues. These were brand new injectors too, but it only took 1 to fuck up everything. 1 injector had a busted Pintle, but looked fine otherwise. Going to rig them up and try and find out which one was really the culprit. I pulled all the plugs, but they all had great wear and was impossible to find out what cylinder was the problem one.

Put in new injectors, primed pump, held pressure over an hour, over 2.5 hours only lost 5psi. Well within spec. Now hopefully I didnt fuck the cylinder rings up, I just did an oil change a week ago and it didnt smell like gas, so hopefully I got lucky.

This morning pressure dropped from 43psi to 25 overnight (around 12 hours). Car fired up instantly with no hesitation or misfire.

[TG Goose]

So been a couple days, cars running awesome with the M50 injectors and the new tune I wrote for it. But still one issue, cold idle is 600-ish, car turns over perfectly and fires right away. Once warm holds a rocks ready 750rpm.

Any reasons for the low cold idle?

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