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Discussion Starter · #1 ·
I have a 1997 geo tracker with 1.6 4 speed auto 4x4 here is the problem I have when I pull out with a steady gas pedal the trackers engine is cold and it want to surge like you would feather the gas pedal on and off, but if you push down on the gas pedal and give it more gas it wont do it. I was thinking it might fuel I don't know, if anybody has any idea? I change the Tran. oil.....
 

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Discussion Starter · #3 ·
No it does not. After 5 min of driving it all good. Just after start up. Don't know what going to happen when it colder. I only had the tracker for three months...
 

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Maybe give a bit more info as to what is actually happening. If you are just idling and not moving, at cold start, are the rpms ‘surging’? When you are moving, is the truck movement actually speeding up during the surge? What is your cold start idle, and what does it do as the engine warms up?
 

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Discussion Starter · #5 ·
First thing in the morning start up( 5deg.C) it goes into high idle 1600 rpm not much warm up put in drive pull out of my drive way start to pick up speed shifts into sec. gear ( 4Sp auto) then it starts its like you have a large 1/2 fill water tank in the back sloshing forward and back. The rpm and speed go up with each sloshing it will go away if you step on the gas. Slow down to a small acceleration and it will start again. Come to a stop sign take off and it start all over again for about 5min. temp. gauge has not moved yet. This will only happen first thing in the morning. Things I have done change thermostat,(180 d) engine temp sender (not the gauge sender) , ambient air sensor , Tran. oil and filter. One thing I am going to try is manual shift the auto. Tran. I will try that today. I am waiting for a for a fitting so I can check the fuel pressure at the fuel rail. Should be here this week.
 

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Good idea to manual shift. If you disconnect the tranny computer, you will be able to shift through the gears (you will lose 4th gear - it will be like the 3 speed mechanical tranny). See if you still have the same symptoms. Also advise if, during this ‘sloshing’ - does your O/D light or check engine light come on or flicker?
 

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Discussion Starter · #7 ·
When I first start up in the morning the O/D and service light come on briefly. The O/D does not come on when it surges. I tried the manual shifting no change.. I will unplug the tranny computer in the morning. It also has a power switch I will turn it on and see what happens.
 

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In order for your transmission to be really shifted manually, you must disconnect the tranny computer, and then go through the gears manually. Disconnect the computer, and see if the ‘sloshing’ continues.
And does this rpm surge occur when the car is just sitting and idling? When you first start up, rather than immediately driving, will your rpms surge?
 

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Discussion Starter · #9 ·
First thing in the morning start up no surge at idling. It surge with the power switch on does the same thing until warm up. I will try the computer tomorrow morning when it cooled off. I shod have the fitting for the fuel pressure check today and check it at the fuel rail and let you know...
 

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First thing in the morning start up no surge at idling. It surge with the power switch on does the same thing until warm up.
Can you explain more about this?

The reason I'm curious is that the "power" switch is a transmission controller input, it has nothing to do (as far as I know) with engine operation, what it does is change the transmission shift points, holding the lower gears longer, so the engine stays in the power band longer, it's useful for hill climbing or towing, but impacts fuel economy negatively.

I'm wondering if the surge is possibly caused by the transmission controller shifting back & forth between gears.
 

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Discussion Starter · #11 ·
Just checked the fuel pressure and with in sp. 37psi cycling the key 4 times .Started it up with the vacuum on 37psi and 41psi with vacuum line disconnected . Tomorrow I am going to unplug the tranny computer.
 

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Perhaps confirm that the engine does not surge with the power switch turned off???
 

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Discussion Starter · #13 ·
It surge with the power switch on and off.. Unplug tranny computer and still surges. Going to hook up the pressure gauge with a longer hose to the fuel rail and watch and see if the pressure drop off under load. What are your thoughts?
 

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Unplugging the tranny computer, and still having this issue, has at least removed the tranny controller from the equation. I don’t see that you’ve answered whether or not the idle will surge with the car just sitting in park, at cold start, before you begin to move.
Is your car OBD1 or 2? I am unsure as to when Canada switched over (or what market your car was initially manufactured for). If you are OBD2, it would be advisable to plug in your scanner at cold start, to see what the computer is seeing.
Your cold start idle is controlled by the additional air that is fed into the engine, via signals from the idle speed controller, as well as the open port on the mechanical wax pellet. You advise that your engine starts up at about 1600 rpm at cold start, which is normal. The question about watching the idle at cold start, without driving or a load on the engine, would indicate whether your surge is actually the idle going higher than that 1600 and then dropping back, or if it’s from the idle dropping lower than the 1600 rpm and then coming back up again…..????
 

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Discussion Starter · #15 ·
First thing in the morning start up no surge at high idling. I have a OBD plug it just reads codes. Today I will let the engine warm up and go into idle before I start driving and see what happens. Is there a check/test for the idle speed controller valve or service it ?
 

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Discussion Starter · #16 ·
Ok Today let the engine warm up until the idle dropped to 800rpm from 1600 rpm about 5 min. temp. gauge just started to move. Went for a ride and very little surge not like when it was cold. Checked the IAC Valve and ohms 13.6 and the voltage at the plug was 8.6V . Can this valve be with in speck and may need cleaning ? Their is coolant and vacuum lines going to it...
 

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OK, so Canada was still OBD1, unlike the US…..I don’t see any indication of what engine you have, in your signature. I assume you are 16v, correct??
The resistance across the ISC (the idle speed solenoid) should be 11-14 ohms, and yours is in spec. However, the voltage you should get (on the light green wire) should be 12v, not 8.6. Do NOT test this solenoid with 12v going directly to it, however, as you’ll burn it out. If testing the ISC on the bench, you apply 12v for one second (to see if the plunger is vibrating) and then let the solenoid rest for 10 seconds before applying voltage again.
However, there are other ways to test, prior to removing it. Do you have A/C? If so, when you turn the A/C on, the ISC is meant to raise the idle about 200 rpms. When your engine is warmed up, if you put an electrical load on the engine (headlights, etc.) does the idle drop or stay the same? It shouldn’t drop.
If you pinch the vacuum line going to it with a pliers, what does the idle do? It should drop considerably.

Your 8.6v reading is out of spec, and you need to chase that circuit.
 
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