1mzfe cold starts, hesitates, almost dies. then runs fine

[dorifuto.boi]

hey guys,

What I believe normally happens during a cold start is that the engine turns over, then the rpm shoots up to around 2k then stays there and slowly drops back down to normal idle rpm as the car warms.

What my 1mzfe does is it turns over, rpm jumps up only a little before quickly dropping back down to slightly under 1krpm (feels like its about to die). a second later, it'll slowly go up around 1.5k and stay there and slowly drop down to under 1k as the engine warms.

Today, it took slightly longer to turn over the engine. After turning over, the rpm didn't shoot up much. came down past under 1k and relaly felt like it was about to die. but then after half a second, it went back up to around 1.5k

the car runs great. when i floor the car it still runs around 11:1 afr. so would there be fuel problems or spark problems only during startup ?

thanks guys

[chronoti]

check the idle air control prolly needs to be cleaned

14.7:1 is ideal a/f ratio, your running a little rich is this only at cold start or when the engine is fully warmed up?

where in for that check the engine coolant temp sensor, also the 02 sensors

[fenixus]

running rich on cold start is normal. as long as ratio gets near ideal after car is fully warmed up (ECU knows that when reading the ECT for EFI sensor) it all right.

dorifuto.boy, as I mentioned in your other thread a month ago or so, you should check the ECT for EFI sensor on car by measuring its resistance when car is cold and when it's warm. all you need to do is to unplug it (on shut off car) and touch terminals with ohm-meter leads (lowest dial setting on warmed up car, and up to 20k ohm setting on cold car) and compare if readings fall into proper ranges according to this diagram (print it out and use ruler to see exactly where the range should be):


recently on my V6 I found out that ECT for EFI was misreporting resistance/temperature at around 0C degrees (at every cold start in Winter).

your IAC valve may be dirty too, not allowing enough extra air to pass to engine to raise the RPM while it's warming up from super cold start.

[dorifuto.boi]

Hey guys thanks for the replys. i will check out my iac when i get some time.

after that, i will check the ect sensor ? is that what it is ? the coolent temperature sensor ? is that the same thing as the thermostat ?

thanks,
d

[fenixus]

Originally Posted by dorifuto.boi

after that, i will check the ect sensor ? is that what it is ? the coolent temperature sensor ? is that the same thing as the thermostat ?

thanks,
d

ECT for EFI is the sensor used by ECU for monitoring coolant temperature, it has 2 wires and is located on passenger side of engine, below the coolant/radiator cap (where you fill it up).

here is a pic, look at the center of this pic, below the coolant filler (with rad cap on it), it's the sensor on left side, it has a shiny gold bottom because I've just replaced it (the one on right side is the dash gauge coolant temperature sender 1-wire).



thermostat is something completely else, it's a mechanical valve installed on driver side on engine where the water inlet pipe connects to engine (thermostat housing), this is thermostat picture:

[dorifuto.boi]

where is the IAC valve ? do i just spray intake manifold cleaner in it ?

[pmesfun]

under the throttle body, there is a port inside the throttle body and you spray TB cleaner in there.

[dorifuto.boi]

the ect sensor's resistance is within the normal range both hot and cold.
the iac valve's resistance is within the normal range both hot and cold.
i cleaned the throttle body plate.

i'm still getting the problem. during a cold day when i start my car, the rpm's wont jump up as high as when its warm right after the engine turns over. also, the rpm's drop to a really low value really quickly before going back up again to around 1.3krpm (really low because when its warm out, it'll idle at 1.6krpm for a bit). then when i start to drive, it will start idling higher at around 1.6krpm.

here is a video to show what i'm talking about. it was really cold outside. sorry about the quality of the video. its from my phone.

You Tube

You Tube

[fenixus]

it could be a dirty IAC valve still.

[AlmightyCamry777]

your 1fmze v-6 may not have an IAC valve. I have a 2002, and it does not have an IAC valve.
I'd try cleaning the throttle body and throttle plate though - (make sure the engine is warm first or it will be really hard to restart). It's not too hard, you remove the big rubber hose where it meets the aluminum throttle body, and you will see inside the "butterfly". Clean it both sides, and the interior of the throttle body as much as you can see using throttle body cleaner, or spray sea foam, and rags and old toothbrush (BE SURE and hang on that little red hose from the spray can of throttle body cleaner - or just don't use it! If that little red nozzle hoseflies off inside your plenum you will have a heck of a time getting it out!)

Now double check you didnt leave anything inside the plenum and re-attach the hose and tighten the clamp. Start the engine. (Easier said then done). Hold the pedal to the floor, it will take much longer to start then normal, then release the throttle as soon as the engine starts. It will then smost likely stall. Now hold the throttle part way, maybe half, and restart. Enjoy large clouds of smoke from your exhaust for several minutes (if this is a problem in your area and somebody is going to drop a dime when they see the smoke, do it at night so the smoke is less visible).

[fenixus]

well, his 1mz-fe is 2000? it has the IAC valve since he measured resistance between its terminals

anyways, I see that coolant temp gauge rest at super cold position, so pretty much it is cold soaked over night. the engine's RPM should get around 1,600-1,800 and sit there for a while upon initial start, his drop almost immediately to 1.2k-1.3k. that's way too fast. just like ECU get input from ECT for EFI that the temperature of coolant is way higher than it really is.

dorifuto.boi I would remove that coolant sensor, throw it into freezer with multimeter probes attached securely e.g. using mini-aligator clips (scale set to 20k ohm) and see what it says in freezer after a few hours, then remove it from freezer and rest it on the table and watch how the temperature of it rises (non-contact digital thermometer from HFT at $9.99 is handy for that) and watch how resistance drops (note you will need to toggle the dial to lower setting so it catches the lower readings). this way you can measure it throughout the full cold-warm cycle and note down the results (both temperature it reports at its tip and resistance between terminals) then compare ALL to the diagram.
that's how I tested mine, but I replaced it with new one upfront and played around with the old one (it had a misreporting behavior at certain ranges).

BTW, what were the results of resistance reading both cold (what was the OBD2 saying about temperature of coolant?) and when warm (again what was the obd2 reporting on that?).

what obd2 reports is what ECU *thinks* it gets from ECT for EFI sensor.

how is that the idle when driving jumps to 1,600rpm after it warms up? that's totally weird. mine when in Driving gear (even when super cold) will never climb above 1,300rpm, usually 1,100rpm when its warming up.

any chances you have a loose vacuum hose somewhere?

[dorifuto.boi]

Hey,

Cleaned TB (did that a few days ago)
Cleaned IAC (just did that yesterday)

Its 17 degrees (celcius) today and went down to start my car. It still does the same thing so cleaning the IAC valve doesnt help. I had my obd2 scanner in and watched the ECT start at 15 and go to 60 then I came back in. I also watched the IAT go from 15 to like 25.

Are you sure that the ECT reading from the OBD2 is the ECT for EFI sensor ? There are two other ECT sensors. One at the radiator and one by the thermostat. What are those two for ?

If you are sure that the ECT reading from the OBD2 is the ECT for EFI sensor, then that sensor is not broken because I watched it start reporting "a temperature of" 15 degrees all the way to 60 degrees. (I didnt wait until the car was warm because my problem is cold starting). Also if you are sure that the reading is from the ECT for EFI sensor, then I'd rather not use the freezer method because I can get the translated resistance reading from the OBD2.

The engine RPM doesnt jump to 1.6k after it warms up. It will start idling at 1.6k (when its still cold) after my car starts moving. If I start my engine (cold day) and I remain parked, the idle remains at 1.3 (when its still cold). After it warms up in either case (when i stay parked or if I start to drive), the RPM will drop to a normal warm RPM.

[fenixus]

did you unbolt the TB and removed IAC from it for thorough cleaning?

[dorifuto.boi]

no i just sprayed a third of a can of tb cleaner into the hole in the tb lol

do i need to remove it to clean it ?

[fenixus]

that's the whole point which made a world of difference on my wife's car. at some point spraying more TB cleaner down the hole couldn't improve anything further, yet the valve below was dirty and useless. I actually swapped it with a new one ... and bam car is healed no more trouble with extremely slow take off from stop lights or too low idle.

regarding the OBD2 coolant temperature you see. you cannot trust it for checking the ECT for EFI. why? because that's the resistance reading in fact which ECU translates into temperature according to its "map".

the whole idea of a freezer and warm up test is to measure both temperature and resistance at same time and over time and then compare the results with a diagram (mine was seriously falling out of range at around 50F).

Originally Posted by dorifuto.boi

no i just sprayed a third of a can of tb cleaner into the hole in the tb lol

do i need to remove it to clean it ?