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Discussion Starter · #1 ·
Hello. I am having some issues with my 1.6 8v EFI Vitara. It starts very hard when cold (-3 degree celsius) and only if i press just a little bit the acceleration pedal. Once it starts it's not staying on idle but if i press a couple of times the acceleration it idles good (about 1500 rpm or lower).
Once it gets hot it runs and starts perfectly
I read the repair manual and I have suspected the ISC valve wich it was bad (tested with a battery acording to the manual ). I have replaced it, and it was a small improvement.
I suspected the IAC and chaged the whole throttle body, still does the same.
I changed the distribuitor rotor, and the spark plug wire set.
I get an check engine code, it's the VSS because my cable is broken, but I have been runing this way before and nothing happened.
Spec:
1.6 8v 1993 with ISC and EGR
-2 VSV, one for dash pot and one for egr
-water temp on intake
-o2 sensor on exhaust
-MAP
-air sensor on intake

Short recap what I have changed till now:
-ISC (tested)
-throttle body (injector, TPS, fuel regulator, ISC, dash pot)
-brand new distribuitor rotor and the spark plug wire set

I am very frustrated because of this problem....please help :)
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The different requirements between a cold start & a hot start are a richer fuel mixture when cold, and a higher idle speed to reduce the likelihood of stalling.

Since your only code is VSS related, and the vehicle runs well once warm, I would suggest you remove and test both the IAT (intake Air Temperature) & CTS (Coolant Temperature Sensors) sensors, you'll need an ohm meter, a thermometer and hot water - instructions can be found in the manuals at the link below


There's a possibility your ECU doesn't know that the engine is cold so let's see what the sensors are telling it.
 

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Welcome to the forum. Aside from Fordem’s good suggestions, note that just pressing the throttle pedal slightly on cold start actually gives your engine more air. At cold start, the idle speed sensor, the throttle opener (dash pot) at the rear of the engine, and the mechanical wax pellet valve are involved. Without issues, when your engine starts from cold, it should rev to about 2000 rpms or so, and within 5 to 10 seconds, you should hear a VERY definite drop of rpm to about 1500 rpm. Then your idle should slowly drop as the engine warms up (and the wax pellet in that mechanical valve melts, to cover an additional vacuum port that is uncovered at cold start).
The throttle opener is open in its default position, when the engine is off, so it’s easy to check to see if that valve is open or not. When the ECU comes online, it provides vacuum to the throttle opener VSV, and closes the throttle opener. You don’t advise that you actually hear the idle drop, and it would possibly be that your throttle opener is closed at cold start??? You might also want to check the mechanical wax pellet valve which, if you are standing in front of your engine, is just to the left of the throttle position sensor, behind a metal plate. If you remove the metal plate, you should see that the valve is pushed far back, so that the port on the right side of the housing is exposed.
 

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Discussion Starter · #4 ·
Happy New Year and thanks for you quick responses!
@fordem I didn't checked those sensors but I have another vitara and I removed the coupling from water temp sensor and the car has similar symptoms, and mine ran the same with or without the sensor, so I bought a brand new one - still the same.
@Bex the valve works fine. I suspected the wax pellet before and that's why I've changed the whole throttle body. If i remove the plate the valve inside it's just a bit open, there is a small gap.
As a desperate measure I just changed my distribuitor rotor, cap, spark plugs and ignition coil, it starts a bit better when it's hot but when it's cold there is no change.

Sorry for the late response.
 

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Discussion Starter · #5 ·
One more thing, in the manual at the "Trouble diagnosis" section it says ""if the engine is hard to start only when it's cold, check air valve first and then engine starter signal circuit" . What is "engine starter signal circuit"?
 

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@Bex the valve works fine. I suspected the wax pellet before and that's why I've changed the whole throttle body. If i remove the plate the valve inside it's just a bit open, there is a small gap.
As a desperate measure I just changed my distribuitor rotor, cap, spark plugs and ignition coil, it starts a bit better when it's hot but when it's cold there is no change.
When you remove the plate to view the wax pellet valve, the valve should be all the way rearward, and you should see a completely round, open vacuum port on the right side of the housing. Do you? By the way, the valve is adjustable. See Ranger’s posts here:
 

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What is "engine starter signal circuit"?
The "engine start signal circuit" is a connection from the starter circuit to the ECU - it's how the ECU knows the starter is cranking the engine over.
 

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Discussion Starter · #8 ·
The "engine start signal circuit" is a connection from the starter circuit to the ECU - it's how the ECU knows the starter is cranking the engine over.
So if the connection is bad and the ECU doesn't know I am cranking the engine, the engine will still start?
 

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The start signal circuit would not be affected by a cold vs warm start up. If your engine is difficult to start under cold start conditions only, then normally it’s an ‘air’ problem. You advise you have to depress the throttle pedal slightly to get it to start. That provides additional air to the engine.
Post #3 indicates exactly what your engine/idle should do, from cold start. The throttle opener forces your engine to rev at about 2000 rpm for about 5 to 10 seconds, before closing, at which time the idle will drop to 1500 rpm. You don’t advise that this is happening. Personally, I’d check your throttle opener.
 

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