[Rhinoman]

I built device to replace the IAC which I could use to mimic the IAC manually with a screw. I can make an adapter to go between the IAC and the TB to limit the air but not increase it. The manual idle needle does not have much effect which makes me wonder if there is a blockage in the bypass?

What are the voltages (relative to vehicle ground) on the IAC?

 

[magician35]

What are the voltages (relative to vehicle ground) on the IAC?

I'm about to look at it myself but the shop that I just got it back from said it was battery voltage out of the ECU with the connector off the IAC which dropped to "zero" when connected to the IAC. The IAC measures 12 ohms.

After I confirm that the IAC opens with the connector off and external voltage applied, I'm going to verify that the TPS comes back to .5v at idle, then bypass the harness from the ECU to the IAC.

It's been a long time, but I think I recall that the idle control gradually got worse and worse with time which may indicate a harness problem. I would think that the switching transistor would fail completely.

 

[Rhinoman]

After I confirm that the IAC opens with the connector off and external voltage applied,

If you can determine in which state the IAC is open then that will help to diagnose the fault.

 

[Bex]

The IAC measures 12 ohms.

Just to be annoyingly out of my depth here (don't be annoyed, Rhino!!) that reading is within factory spec of 11-14 ohms. Does sound like your problem lies elsewhere.....

 

[Rhinoman]

Just to be annoyingly out of my depth here (don't be annoyed, Rhino!!) that reading is within factory spec of 11-14 ohms. Does sound like your problem lies elsewhere.....

I'm not annoyed, I don't have the spec for the 1.8 IAC, it is unique to that model.
If it rattles then the spring is probably broken.

 

[magician35]

If you can determine in which state the IAC is open then that will help to diagnose the fault.

Here's where I am: A 12v pulse on the IAC gives it plenty of RPM.
The ground input wire from the ECU to the IAC connector shows no significant resistance.
Measured at the ECU plug (disconnected, ignition on) the TPS sensor output to the ECU is 0.5v. with the throttle at idle.
I think I need to look for an ECU repair or exchange.

 

[Rhinoman]

I've had quite a few ECUs with a dead IAC driver, often they've come in for another fault and the owner wasn't aware that the IAC was faulty. I suspect that the first IAC burnt out and took the driver with it.

 

[Bex]

Measured at the ECU plug (disconnected, ignition on) the TPS sensor output to the ECU is 0.5v. with the throttle at idle.

While it very well may be the ECU that is at fault (and logically it must be something at fault that has affected all the IAC's that you have put in, ie, wiring, ECU, etc.), I think the point of the above test is to have the TPS sensor connected properly, backprobe the gray and gray/yellow pins, turn the key on, see what the voltage is with that gas pedal fully up, push the gas pedal slowly down and see that the voltage swings from 0.5 upward toward 4-5 volts, without any glitches, hesitation, etc., and then release the gas pedal and confirm that the voltage drops back to 0.5v. The TPS must be connected.

 

[magician35]

While it very well may be the ECU that is at fault (and logically it must be something at fault that has affected all the IAC's that you have put in, ie, wiring, ECU, etc.), I think the point of the above test is to have the TPS sensor connected properly, backprobe the gray and gray/yellow pins, turn the key on, see what the voltage is with that gas pedal fully up, push the gas pedal slowly down and see that the voltage swings from 0.5 upward toward 4-5 volts, without any glitches, hesitation, etc., and then release the gas pedal and confirm that the voltage drops back to 0.5v. The TPS must be connected.

Just finished doing that. Voltage at pedal full up was .37 v. I adjusted that to .50 v. (warm with fast idle off) Then, with full pedal down it reads 4.0 v. Lack of IAC function unchanged.

 

[Bex]

Presumably you have also confirmed that, as the throttle pedal moved downwards, the voltage increased without 'dead spots', etc, but coordinated with the movement of the pedal - and also, when you release the pedal, that it goes back to .5v. Anyway, it was worth a shot to see if this was a cause of your problem.

 

[magician35]

Presumably you have also confirmed that, as the throttle pedal moved downwards, the voltage increased without 'dead spots', etc, but coordinated with the movement of the pedal - and also, when you release the pedal, that it goes back to .5v. Anyway, it was worth a shot to see if this was a cause of your problem.

I appreciate that. I found several sources for repair/exchange of the ECU. I'm looking at a diagnosis, repair, functional check and warranty for $299 U.S. My only hesitation is the possibility that there is something I've overlooked.

Do you know what the RPM signal to the ECU is supposed to look like? Is it analog or digital? What is the source of the input? Is it the same as what the tach sees?

 

[Bex]

Sadly, I don't know the answer to any of your questions - the Sport is poorly supported, as there were not many of them sold. In the 1.6, the tach signal comes off the wiring at the noise suppressor, but whether the Sport is the same or not....??? Thus far, at least on this forum, there have not been many (actually, any) repairs that I've known of to the OBD2 computer (the older ones have had to replace capacitors, etc.) unless there was some occurrence of shorting wires or similar. Rhino (who is an expert in this) has previously spoken about the IAC driver being damaged in some way - have you opened up the ECU to actually look at the board/drivers to see if you notice any type of damage that would have occured from shorting wires - burn marks, etc.?? Often if faults occur this way, the damage is somewhat obvious - and then it might be possible to replace just the IAC driver - if that's where the damage is. Do you know what the model number of your ECU is? (Sorry, I haven't read through this post again). Rhino's theory about the there being a problem with the first IAC (which may have damaged wiring, etc) and thus the driver may have been fried, so that all the new IAC's exhibited the same problem, may very well be a good theory. I had a burned injector driver - it was quite visible when looking at the board.

 

[Rhinoman]

Do you know what the RPM signal to the ECU is supposed to look like? Is it analog or digital? What is the source of the input? Is it the same as what the tach sees?

Its a VR sensor so its analogue, there is a toothed wheel on the crankshaft, I think the ECU generates a PWM signal to drive the tach. If you post a picture of the ECU I may be able to identify the driver.

 

[magician35]

Sadly, I don't know the answer to any of your questions - the Sport is poorly supported, as there were not many of them sold. In the 1.6, the tach signal comes off the wiring at the noise suppressor, but whether the Sport is the same or not....??? Thus far, at least on this forum, there have not been many (actually, any) repairs that I've known of to the OBD2 computer (the older ones have had to replace capacitors, etc.) unless there was some occurrence of shorting wires or similar. Rhino (who is an expert in this) has previously spoken about the IAC driver being damaged in some way - have you opened up the ECU to actually look at the board/drivers to see if you notice any type of damage that would have occured from shorting wires - burn marks, etc.?? Often if faults occur this way, the damage is somewhat obvious - and then it might be possible to replace just the IAC driver - if that's where the damage is. Do you know what the model number of your ECU is? (Sorry, I haven't read through this post again). Rhino's theory about the there being a problem with the first IAC (which may have damaged wiring, etc) and thus the driver may have been fried, so that all the new IAC's exhibited the same problem, may very well be a good theory. I had a burned injector driver - it was quite visible when looking at the board.

Thanks again (and to Rhinoman) for the input. My exact next move is to get the ECU out and look for damage. (Not easy to get out because of no slack in the harness) I would expect the damage to be in the switching transistor rather in the driver since that's what interfaces with the IAC, but we'll see. Can't do it until after the weekend since we need the car right now.

 

[magician35]

Thanks again (and to Rhinoman) for the input. My exact next move is to get the ECU out and look for damage. (Not easy to get out because of no slack in the harness) I would expect the damage to be in the switching transistor rather in the driver since that's what interfaces with the IAC, but we'll see. Can't do it until after the weekend since we need the car right now.

Here it is: R347 & 348 fried. They must be at least 3 watts so they took quite a hit. Next move is to find best option for repair/exchange that won't keep it a month.

FYI: Take out the driver's seat so you can lay on your back and get both hands under the dash to get mounting screws in and out. Also, do not un-bolt until all of the connectors are pulled (release on back of connector) It take a lot of force to pull them out and you can't do it with the ECU loose.

 

[Bex]

Ta dah. Rhino should be able to give you info on those drivers - however, it will be a good idea for you to thoroughly check that wiring circuit, as whatever fried those drivers, if not repaired, will obviously fry the new ones as well.
Good advice about the difficulty of removing those connectors - note that they are practically impossible to find, so it is wise to take some extra time (with the locking tab, etc) and take them out carefully. It's also a good idea to have the negative battery cable removed before you start this disassembly, just in case.
Glad you found the source of your difficulty. Now, on to the repair!! Since you have the ECU out now, you should post the model number of it, so that it's easier to give you info on that specific ECU.

 

[Rhinoman]

Please post a picture of the complete PCB so I can identify it.

 

[magician35]

Here they are. The top of board photo shows the burned resistors in the lower RH corner. The ground signal pin to the IAC is in the connector at the far top left (pin 23). That pin is in the third layer down to the far right of the connector. The upper ends of both resistors read near zero resistance to pin 23. The resistors both read 9.3 K-ohm across them.

The bottom of the board shows the heated area around the resistors which is in the cluster at the lower left just above the first mounting screw.

With the connector which carries the IAC ground signal disconnected at both ends, the two pins at the IAC read open (no short.)

Conclusions: The two burned resistors are in the IAC circuit and other components of that driver are probably damaged as well. There is no short in the harness between the IAC and the ECU. There must have been an open circuit in the original IAC (more likely than a short .) One of the mechanics who had a hand in it shorted the board output somehow. The other 2 "bad" IAC's were either mis-diagnosed or damaged in testing.

Please post a picture of the complete PCB so I can identify it.

 

[magician35]

Sadly, I don't know the answer to any of your questions - the Sport is poorly supported, as there were not many of them sold. In the 1.6, the tach signal comes off the wiring at the noise suppressor, but whether the Sport is the same or not....??? Thus far, at least on this forum, there have not been many (actually, any) repairs that I've known of to the OBD2 computer (the older ones have had to replace capacitors, etc.) unless there was some occurrence of shorting wires or similar. Rhino (who is an expert in this) has previously spoken about the IAC driver being damaged in some way - have you opened up the ECU to actually look at the board/drivers to see if you notice any type of damage that would have occured from shorting wires - burn marks, etc.?? Often if faults occur this way, the damage is somewhat obvious - and then it might be possible to replace just the IAC driver - if that's where the damage is. Do you know what the model number of your ECU is? (Sorry, I haven't read through this post again). Rhino's theory about the there being a problem with the first IAC (which may have damaged wiring, etc) and thus the driver may have been fried, so that all the new IAC's exhibited the same problem, may very well be a good theory. I had a burned injector driver - it was quite visible when looking at the board.

I'm "happy" to report that the '97 Sport idle speed control and everything else is working fine. I sent the ECU to a repair shop (Klien) to repair for $140 including return postage. They said it was too far gone (?) and sent it back after charging me a $50 fee to look at it. So I posted the need for it through a salvage yard search site ($10 fee) and bought one for $200 including shipping. The case had some rust but the inside was clean and the board looked good. I popped it in and all is well (for now.)

I learned to not be too hasty in buying one. I thought there were very few used ones around so I snapped up the first one I found. It was clear across the country so I had to wait nearly a week to get it. After I bought it, I started to get more response from the posting, most for less money and some closer to home which I could have had the next day. But, after fighting with this for several months and even stumping two ex-Suzuki dealerships, I'm just glad it's over. All it took was pulling the ECU and looking at it.

Since the repair cost and the cost of a salvage unit are about the same, I'd recommend finding a used one with a warranty rather than trying to repair your old one.

Thanks for the help from all on the Forum who offered suggestions. Now all I have to do is go back and try to recover some of the money I was charged by 3 shops to do nothing but throw parts at it.

Malcolm

 

[Bex]

Just as an aside, it is good to 'study' before jumping into this - and with the internet, there is now no excuse not to do so. I brought my Tracker here from NY, when I moved here 18 years ago. When I had been here about 3 years or so, and before I found this forum and started learning the specifics about this car, my car wouldn't start - diagnostics indicated that it was the computer. In my desperation and haste, I found some guy in England who advised he could repair the computer - I was happy enough, as I was afraid that I would have had to trash my car. The FSM, of course, does not indicate anything about 'repair', only 'replace', which I was pretty ignorant about. Anyway, I sent the ECU over to England, and about a week later it was returned in working order - to the tune of about $300 (somewhat expensive for the replacement of $5 worth of capacitors). About a year later, I began to have the same problem - I pulled the ECU, and saw burn marks on the circuit board. This time, I found a replacement ECU (from California) for $100 core exchange. After waiting 2 weeks for the replacement, I plugged it in, the car started and then stalled again. As these replacement cores advise that the 'warranty' is voided if you open the unit, I never opened it, but sent the unit back for another replacement. And waited another 2 weeks. The same thing happened again. This time I opened the unit, and saw the burn marks in the same place - and that is when I found this forum. With due respect, Jerry diagnosed the problem for the forum - it wasn't the caps this time, but the injector driver. With his info, I found replacements, ran new injector wiring (rather than searching for the culprit that was continuing to cause the problem), had the new drivers soldered in at my local computer shop, and also installed a 5v fuse on the line, so that, if a wiring problem occurred again, the fuse, rather than the injector driver, would blow. So, a real learning experience - and my car is still on the road, thanks to the myriad of people on this forum who take the time to share their experience and information.
Hopefully your 'adventure' is over, and it has been a learning experience for you, as well.....