Engine will not idle when cold ??

Barr

Hey Guys

Starting my car from cold in the mornings it just dies if you take your foot off the gas
Once its hot it runs perfectly well

Any ideas what this could be ?

Henry Ford III

Needs a service?

What is it?

Tipsy Mac

More than likely it's the choke not "opening up" enough and causing the engine to die, as was said a service if it's been a while is your best bet.

stratos

Presuming its a modern car with fuel injection and an ecu, the fault will be with the cold start engine temp sensor. Bring it to a dealer and get the codes looked at. If they diagnose the fault you can change the sensor yourself.

zuutroy

Had this problem a few times over the years, and believe it or not, a new set of spark plus has been the fix more often than not.

Ratchet

Barr wrote:

Hey Guys

Starting my car from cold in the mornings it just dies if you take your foot off the gas
Once its hot it runs perfectly well

Any ideas what this could be ?

make and model of the car would be a help

ambro25

stratos wrote:

Presuming its a modern car with fuel injection and an ecu, the fault will be with the cold start engine temp sensor (...).

Seconded. I had no end of trouble with a Brava years ago with a similar one (but in reverse: ECU flooded engine on cold start, to the point where the spark plugs were dripping with petrol :eek: ).

mike65

Or it could be the cold start valve itself or the power to it (if its got one).

Mike.

AMurphy

Barr wrote:

Hey Guys

Starting my car from cold in the mornings it just dies if you take your foot off the gas
Once its hot it runs perfectly well

....?

need to know some details of the Make and model, year, EFI or CARB and/or any other symptoms not previously mentioned.

either way, given you do not complain of difficult starting when cold, then the cold start sensor or choke must be working to some degree.
And does not appear to have any other running problems, must be tuned OK.

however, after that if could be anything, from not enough air to too much air, and same for fuel.

one possibility, is the Auto Idle adjust system (motor) is stuck and works OK for warn but not for cold enriched fuel, so is flooding.
It coud easily be some thermo-time valve on a vacuum operated carburetted engine.
Or simply some loose/broken vacuum hoses to some idle-up diaphram on the choke.....

Barr

Cheers for the relpys

The car is a 1995 Mitsubishi FTO 2.0 v6

The car has been serviced about 2000 miles ago.

I replaced the stepper motor with another as I thought this may be the root of the problem but it did not help

either way, given you do not complain of difficult starting when cold, then the cold start sensor or choke must be working to some degree.
And does not appear to have any other running problems, must be tuned OK

This is indeed the case , it starts fine put cannot "idle" when cold.Once the needle reaches quarter the way up the engine "idles" perfectly without the need to keep the foot on the accelerator.

I have ordered a temperature sensor today as this seems to be the consensus. Hope the sorts the problem out.

MercMad

Coolant temperature sensor I reckon !

The injection system will give an extra squirt whilst cranking but the above sensor lets the ECU know that the motor is cold and the mixture should be enrichened!

miju

had a similiar problem turns out my choke was stuck, when its cold rev the fook outta the car if you start getting a load of smoke (blackish in color) out the exhaust then it's your choke, you can check it quite easily if you open up your air filter unit take off the filter and have a look see inside when its being revved

MercMad

It doesn't have a choke !

AMurphy

Barr wrote:

Cheers for the relpys

The car is a 1995 Mitsubishi FTO 2.0 v6

The car has been serviced about 2000 miles ago.

I replaced the stepper motor with another as I thought this may be the root of the problem but it did not help



This is indeed the case , it starts fine put cannot "idle" when cold.Once the needle reaches quarter the way up the engine "idles" perfectly without the need to keep the foot on the accelerator.

I have ordered a temperature sensor today as this seems to be the consensus. Hope the sorts the problem out.

2L-V6. That must be a nice drive when warmed up.

OK, so it has an Auto Idle System (AIS) stepper motor setup, good, usually works well where used.
However, while you changed the motor, ..... there are two parts to this sytem, the motor and the valves it controls.

So, as a cheap JIC, verify the AIS ports are free of gunk and oil crud, or just generally freeflowing.

Just for clarification, what does the stepper drive a screw/pintle valve of some form of a flap/shutter type.

A screw/pintle valve can be jammed fast (closed) on re-assembly if not done correctly, the flap/shutter type are immune to this problem.

Did the problem develop some time after installing the new stepper or with installation of the motor or before, but the new stepper did not resolve the problem.
You installed it I assume?.

Does it start and immediately fail to run, or start, run well at higher rpm for 15-30 sec and then develop stalling problems.

If it is crud, a simple throttle body cleaning may resolve the problem.

Barr

Coolant temperature sensor I reckon !

put a new one of these in yestersay and went to start the car this morning and the same problem ahhhhhhhhhhhhhh
Then later on in the day I started the car from cold and it started idling "normally" since the first time I bought it!
I dont know if the promlem is solved since it did'nt work in the morning but during the day all seemed ok which is at least some progress:)

2L-V6. That must be a nice drive when warmed up

Definately a big fan of V6 engines , lovely smooth free revving engine

So, as a cheap JIC, verify the AIS ports are free of gunk and oil crud, or just generally freeflowing.

I done this at the time and checked if any wire were frayed going into it but it seemed ok

Just for clarification, what does the stepper drive a screw/pintle valve of some form of a flap/shutter type

I'm not to sure which type it is but I have attached a picture of this would help stepper motor.jpg

Did the problem develop some time after installing the new stepper or with installation of the motor or before

Problem existed before I installed the new stepper motor

You installed it I assume

Yes,I Dont know alot about engines but this job was very simple even for a novice.

Does it start and immediately fail to run, or start, run well at higher rpm for 15-30 sec and then develop stalling problems

It immediately fails to run

If it is crud, a simple throttle body cleaning may resolve the problem.

I got the carb cleaner out last nite and gave it a good clean when the temp sensor was replaced

Ratchet

here is some ftorelated info

[This courtesy of Adrian Wright] The ISC (Idle Speed Controller) is a small stepper motor, capable of moving up to 120 steps, bolted to the side of the throttle body. It controls the opening and closing of the idle butterfly, which obviously should open when the engine is cold, and close completely when warm and under normal load (it will open if the engine is loaded, with either heavy alternator load or aircon, etc.). It's normally the cause of idling problems.
Problems (1) : The 120 steps appears to be a notional figure rather than an actual - ie 0 is not closed and 120 fully open. Depending on the car, how it was serviced and whether this 'steps' figure has been reset, many FTOs typically have around the 40 'steps' mark as fully closed. Problems can arise when the fully closed 'steps' gets too high, as the ECU will only step up to 120 max. Therefore if the fully closed number of steps is, say, 80 you only have 40 steps until max - which will only partially open the idle butterfly and hence the car will not idle when very cold or under very heavy load. Apparently a Mitsi service should reset this (steps figure to a lower value), providing they've got the kit to do it.
Problems (2) : The ISC gets covered in black carbon deposits which prevents it working properly - typically causing hunting at idle and general eratic idling. Remove it (two bolts hold it to the throttle body) clean the hell out of it (WD40 or something), clean the hole in the throttle body where it fits and finally clean and lubricate the main throttle butterfly and interior of the throttle body just for good measure.
Problems (3) : The ECU needs to 'learn' where the idle point is - so an ECU reset can sometimes help to force it to relearn!
Problems (4) : Due to the position of the ISC and the wiring loom, the wires to the ISC are prone to fracture and complete breakage. Simply pulling back the black plastic looming material on the six wire connector should show whether all wires are in fine fettle. If you doubt the continuity of the wires, the Owners Club have the Electrical manual and it's not TOO difficult to trace all 6 wires on the connector back to the 1st ECU connector and one of the junction blocks, both in the passenger footwell.
Problems (5) : Low idling, but everything else is OK - just need to pump up the idle. The throttle body has a recessed idle screw, on the top - towards the front, normally covered by a very obvious circular black rubber dust cap (about half an inch in diameter). Simply remove the dust cap, and turn the screw in or out to increase or decrease the idle speed.

also have chat with guys on
www.fto-ireland.com/

AMurphy

The Photo does not tell me much about it's innards and how much of this assembly you exchanged.
Anyway, if this is correct;

clean the hole in the throttle body where it fits and finally clean and lubricate the main throttle butterfly and interior of the throttle body just for good measure.

Then you do not have the "pintle valve" type, but do have the "shutter" type.
Based on the previous detailed description, it appears to be a little adaptive and adjusts for wear, bunging up, etc. However, it does appear as though this adaptive process can force it over the edge on occasion.
Usually disconnecting the battery for a while (30 min or so) erases these adaptive parameters in most ECU's.
And it certainly could have been a faulty Temp sensor. Easy way to check, put the old sensor back for a while.
Although, faulty temp sensors are also attached to a difficulty in getting started in the first place PLUS post start running problems.

As for the wiring, certainly a consideration, connectors and sharp turns are traditional failure points. I don't know the method for FORCING the motor to rotate in your vehicle, but there is a method I'm sure, however in the absense of ECU interrogation tools, this usually involves removing the motor assy from the AIS assembly or throttle body while connected to the wiring loom and observing it.

Barr

The new temperature sensor seems to have helped matters somewhat. It is only first thing in the morning it cannot idle but during the day it is fine.

Problems (4) : Due to the position of the ISC and the wiring loom, the wires to the ISC are prone to fracture and complete breakage. Simply pulling back the black plastic looming material on the six wire connector should show whether all wires are in fine fettle.

Had a look at these a bit more closer and discovered that a red wire has frayed completely. I am getting a mechanic to have a look at this on Thursday.

Thanx for the advise .I am hoping that this is the root of the problem!

AMurphy

Easy check, just get someone to make the contact on the broken wire while the motor is ideling, if it responds favorably, you got a hit.