Thread: Advice on Hard Cold Start

IF its fuel, would would it only do it on cold start and why do i not have any other symptoms of the car running? Spark plugs showing no signs of a lean condition...etc. Fuel pressure is always on point even at start up. Today i pulled the dist cap just to have a look inside (still looks new) and that basically all i did, went to start it and now I'm getting an issue where the car will drop RPMs to almost dying (sometimes even colder it will and has died out) after a rev of the engine. I had a simliar issue like this before I cleaned the IACV about a year ago. I adjusted the screw and it seems to have helped it (funny thing is all i really did was adjust it more open then ended up adjusting it almost back to where it just was). So i'm gonna go ahead and replace that first and see what happens. Sounds like its asking to be replaced anyway, just so i can rule it out for future issues if not anything else.

I had the exact same issue. Turned out my ecu had a burned channel for controlling the idle air control valve. Hitting the pedal slightly cracked open the tb, allowing air to enter the engine and it would start. Warm starts are ok without extra air. Something to check.

ECU was already swapped for a different one, no change

Oh, missed that. But still, check the wiring between the ECU-IACV

One pin is constant +12v with the ign on, the other pin is controlled by the ECU, switching PWM ground. It can be checked with a multimeter, but scope is best.

No need to throw more parts at it before checking simple things with a multimeter.

I agree it sounds like too much fuel.
It's worse on a cold start, due to the ECU adding extra fuel - cold enrichment.
I've seen a bad ECT cause this, but you already checked that.

The troubleshooting order in the FSM for hard cold start is:
- Check battery and starter
- Check fuel pressure
- Check air regulator and AAC valve
- Check injectors
- Check ignition spark
- Check spark plugs
- Check ECU harness connector
- Try a known good ECU

You can measure the resistance on the injectors - should be 10-14 ohms.
If the resistance is too low, could explain the extra fuel.
Could also be a leaking injector / bad o-ring(s).

I would still hook up a scanner if you have one or someone you know has one and check all the data just to be sure, I've seen it plenty of times where the resistance of a sensor was in spec but the sensor is still bad and causing problems

Well let's see, battery and starter are good, no cranking issue ever. Distributior looks like new, again fires every time not cold, fuel pressure never drops under 3 bar and I pulled the fuel rail to look for leaks even though fuel pressure holds for like 2 hours. Harness looks good, new known good ecu swapped in, spark plugs and wires are basically new. Engine is effected unplugging each injector at a time so I know they are at least working and not leaking. I'll try checking resistance. Only thing I'm not sure how to test except for swapping is the IACV and AaC which I'm in the process of trying to find to swap in for testing

If you look in the third video i show data via consult, everything looks good to me except AAC cuz I'm not sure how to understand it's parameters

Read through this, interesting issue. When it actually is running, have you tried pulling individual plug wires to see if there is a change? I'm curious if all cylinders are firing correctly.

But I keep coming back to the IACV or something related there, not enough air getting into the cylinders while cold. Take the vacuum line off that goes to the brake booster and see if the car starts better. This will allow extra air into the intake and it's an easy hose to get to. If the IACV is stuck closed, this would resolve that.

That's what I am leaning towards. As mentioned right before ur post engine gets rough when unplugging each injector at a time while running, I can also even hear them all firing. But haven't unplugged the wires, however there's no misfire at all while running, I'm 95% sure it's an air issue

The other day when fucking around with stuff I actually got it to the point where it almost didn't even wanna keep running. When I'd rev the engine the rpms would drop below the base idle and even cut off the motor a few times. Adjusting the idle screw (with TPS disconnected) then reconnected helped, but it was already too warm at this point to test cold start and it was late at night. I gut feeling is telling me it's that aac shit. I had a low rpm issue 2 years ago I solved by cleaning it. Worked fine up to parking it in November, now I got this issue waking it up in May.....

I don't see that he mentioned it so I will..

it will start cold if you spray a little starting fluid in it. It will also start if you wedge the tps tab open (leaving to closed)

It may start up rough but better than not at all, at least it gives us a direction to look which has been making me thinking enough fuel..