Unstable idle when cold

[elwesso]

First off, I dont think this is related to the transmission because it did it before somewhat.

What will happen is when I start the car first thing after its been sitting for a while, it will start right up, then the RPMs fall down to about 650 or so, then it will start hunting, dropping down almost stalling then back up to about 1000, and it will keep going up and down for a while.. If you let it do that for a little bit, or manually hold the throttle open to 1500 RPM or so for a few seconds to let it "smooth out", it will be fine.

Any ideas? Again, I dont think its related to the manual transmission because a) no one else has had issues like this b) it did it occasionally when I still had the automatic.

[Q45tech]

Analyse the ratio of rpm created by hot wax idler cam and IAC duty cycle.

Determine what duty cycle of IAC delivers what rpm when hot.10-15% should lift rpm by 50 above disconnected IAC. 80% should provide 1100-1300 rpm depending on cleanliness of TB Measure the hot wax throttle lift vs coolant temperature.

The point is: it takes both system to get to 1500 rpm cold.

Why Consult has a screen to adjust IAC duty cycle in 1% increments for testing and a test to check IAC at zero, 10,20, 100% [functional 80%]

The manual IAC bypass and the hot wax adjustments are the only 2 MANUAL ADJUSTMENT POINTS but all the other things [ ign advance/CAS and cleaniness and coolant temp] make changes.

You must monitor all sensors and mentally correlate what is going on.

Read and data log coolant temp to ecu during warm up phase [intermitents/errors/ corrosion]..................coolant temp affects rpm until it exceeds 140-160F.

The other place to look is data long MAF voltage for a weird cold to warm hiccup.

Monitor fuel pressure pump voltage/current for the same thing as the FPCU warms up.Remember ecu sends higher voltage to FPCU during start and for a time after crank.

[unknown007]

I have the same problem.Mine sometimes also stalls when I'm driving and take off at a green light.Maybe the vacuum leak that I have causing that?

[bullittandy]

Sounds just like a vacuum leak.

[unknown007]

I hope.I can't seem to find it but sounds like it's on the throttle body.

[Haitian_King]

First off, I dont think this is related to the transmission because it did it before somewhat.

What will happen is when I start the car first thing after its been sitting for a while, it will start right up, then the RPMs fall down to about 650 or so, then it will start hunting, dropping down almost stalling then back up to about 1000, and it will keep going up and down for a while.. If you let it do that for a little bit, or manually hold the throttle open to 1500 RPM or so for a few seconds to let it "smooth out", it will be fine.

Any ideas? Again, I dont think its related to the manual transmission because a) no one else has had issues like this b) it did it occasionally when I still had the automatic.

I was experiencing a similar issue before the car went into the shop. I attributed it to the alternator being bad. It seems to have cleared itself up after the alternator was replaced.

[unknown007]

Any alternator?Really?I doubt it mine was replaced last year around Feb.Before I bought the car in May I think it was.I don't think an alternator would cause that though.My IAC is leaking as in air keeps going through whether I push the screw all the way in or not.So could be that.I can't seem to find a vaccuum leak in mind either.

[Haitian_King]

Yeah. Turning the car on, the RPM's would bounce from almost stalling and up past 1k. Especially when coming to a stop, like in a parking spot. It would go away during regular driving, but it's caused the car to stall at least twice.

[unknown007]

My alternator looks OEM hows it bad already?Not another repair. Well firt I rather fix my IAC issue to confirm it's the Alternator.

[Haitian_King]

When was the last time you changed it? To the best of my knowledge, mine was the original. 17 years, 101k miles.

I know the OEM alternator is Hitachi.

[unknown007]

previous owner changed it last year in feb.I saw the receipt which I got in the car.

[Infinitiguy19]

Is it New OEM, used OEM, re-manufactured or aftermarket "New"?

[unknown007]

Looks New.I'll check when I drive later.Some how coolant still leaving the radiator. It's getting into the alternator.

They day was saved thanks to the NEW RADIATOR!!! It just came in I'm gonna replace it tomorrow.Whoo.

[paranoidjack]

Looks New.I'll check when I drive later.Some how coolant still leaving the radiator. It's getting into the alternator.

They day was saved thanks to the NEW RADIATOR!!! It just came in I'm gonna replace it tomorrow.Whoo.

You have coolant getting into your Alternator? Never heard that one before!!!

[unknown007]

I said I think.My radiator cracked.I put some sealant until the new came in.Some how coolant is flying from somewhere,up to the valve cover of the passenger side,hitting the side wall.side battery/all the way up to my ABS. Tell me about it I'm confused because I did a compression test yesterday and the seal was holding.