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Discussion Starter #1 (Edited)
Hi folks,

I'm new to the forum and new to Samurais as well. Just picked one up a few weeks ago with a fuel injected 1.3 stock engine. Drove it 6 hours home and discovered it had a few issues...just a few.

The first was the idle was not all that great. At operating temps it would idle around 800 and oscillate down to where it would almost feel like stalling but wouldn't, and then go back up to 800, and do this consistently.

I then discovered the exhaust manifold had two small cracks and decided to fix this first. Couldn't find a stock replacement anywhere within 75 miles so installed a Thorley header with a 2" exhaust. I replaced the cat as well and the O2 sensor for good measure.

After this I checked for vacuum leaks and couldn't find any, but still replaced almost every one of the vacuum lines. The idle now changed...it went from an oscillating 800 to 500 rpm to an oscillating 1500 to 1000 rpm, again at operating temps. I sure can't smog it like this.

I took it to a mechanic who found that the EGR was leaking. I told him I would replace it, which I did after I brought it back home. Took it off and it while it didn't have a lot of carbon buildup it certainly had some oil on the inside of one chamber and outside on the diaphragm. Replaced it, but idle remained unchanged.

I had also asked the mechanic to adjust the valve lash while it was there, and he found a nut/bolt (can't remember which he said) was missing from one of the rocker arms, and another one was about to come off! He fixed that and adjusted the valves.

After I replaced the EGR I noticed that the a/c vsv was making a lot of noise now. I took it off and applied battery voltage to the two terminals. I could hear the solenoid click but I could not sense any air flowing from port A to B. I then tested it for continuity. It should show 24-30 ohms resistance but it showed none. I disconnected it and it ran the Sami with no change in idle.

I then got suspicious of my other components. In testing the ISC solenoid valve, Throttle Opener vsv, and EGR vsv on my multimeter, I get no resistance but they all show continuity when they shouldn't, just like the a/c vsv. I'll be rechecking these with a digital multimeter tomorrow but I don't expect any different results and am wondering just how in the world could all these components be failed at the same time?

By the way, no check engine light is occurring at the moment. Gas mileage is terrible, like 10 miles per gallon. The smell of my exhaust tells me the engine is running very rich. Spark plugs show normal on #1 but then as you go down the cylinders it shows richer burning. It has a new fuel filter, distributor cap, spark plugs and wires as well. All fuses look good.

I am nothing close to a mechanic, and am pretty much at the limit of my diagnosing ability. Does anyone have any suggestions on what I could test further before I take it to a mechanic again? Sorry for the long explanation but I generally try to do as much research and work on my own as I can before asking questions.

Thanks ahead of time if you're able to help.
 

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Here is a link with a wealth of information that pertains to the EFI Samurais as the Samurai's engine management is very similar to the Sidekick/Tracker of the same years. This site is hard to navigate but full of substance and maybe the most information on these trucks in any one place. It sure has helped me.

The FixKick.com Repair Pages, for Sidekicks and Trackers

You say there is no check engine light. Does it come on when you turn the key to the run position? If not, then the bulb is probably burnt out or has been removed. You need this working to get the diagnostic codes when you place a fuse in the diagnostic slot of the fuse panel. With the fuse in place, you want a flashing 1-2 engine light. Anything else indicates a problem with a sensor that needs to be fixed.
 

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Discussion Starter #3
Thanks for the link. You are right...that's a ton of info.

So a little progress today. I used my friend's digital multimeter and all those components mentioned above do show resistance within spec, so my analogue multimeter obviously isn't working correctly.

My friend and I also did a compression test at work and the numbers were 148/150/148/150, so I'm assuming the engine's still good.

I also had my wife pick up a new a/c vsv, and I installed that while at work. Drove it 3 miles home, which brought it to operating temp, and noticed that the idle has returned to 800 rpm, but it still sputters a little down to 600-500 rpm and back up to normal, just like it did when I first got it. Exhaust still smells a little rich too, although in checking the spark plugs today they all look pretty even and normal.

So, I'm back to square one it seems.
 

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Discussion Starter #4
I almost forgot...in regard to the check engine light, it did work just previous to my replacing the EGR valve. After replacement the light went off.

Tonight I also put a fuse in the diagnostic slot, and I do get a 1 flash then 2 flashes closer together.

Back to the idle. This thing is really making me scratch my head. At times it will idle at 800 and dip down and back up; at other times, it will idle at 1100 and dip down, and then sometimes the idle returns to 800 rpm. I tested the ISC valve electrically and mechanically and its working properly, yet I hear like a quick and successive sucking sound coming from the vacuum hose leading from the ISC to the plastic T at the throttle body, and this is when the engine idles a bit higher. When I pinch that hose the idle seems to go back down to 800 and act about as normal as I can expect it. If I pinch the hose beyond the T, the one that leads into the a/c vsv, there is no change in idle.

Am I right to suspect the problem may have to do with my throttle body?
 

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Personal experience. Had it happen on my old CRX, and my old Volvo.
If the valve is bad, the idle will surge up and down just like you say. The IAC is what the computer uses to set your idle.
There should be a code related to it.

TYPICALLY To bench test, these are the correct specs... disconnect the IAC from the Zuk.

using multimeter : positive lead on signal wire, negative on other wire.

-7ohms or 13+ ohms and it's bad.

You can also try to clean it. Using CARB CLEANER (DO NOT USE BRAKE CLEANER!!) you can hose the crap out of both the inlet and the outlet. Wiping them out really good. A lot of carbon accumulates in there.

Could be bad computer too.
 

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Discussion Starter #9
Yeah, I'm hoping the computer isn't the culprit here. I'll try testing the IAC either today or tomorrow and post back the results. Thanks for the tip!
 

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12 code shows ecu is ok, i'm betting the IAC valve is either bad, or blocked. if you clean it and the problem reappears after a couple of days, then start hunting for a new one.
 

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Discussion Starter #11
The IAC is what the computer uses to set your idle. There should be a code related to it.
I am getting no code for it.

[TYPICALLY To bench test, these are the correct specs... disconnect the IAC from the Zuk. using multimeter : positive lead on signal wire, negative on other wire. -7ohms or 13+ ohms and it's bad.
Wait...isn't the IAC part of the throttle body on my 1992? It doesn't just disconnect. I have no wires going into the IAC, unless I've misidentified the IAC on my vehicle? I am new to Zuks but see the pics below and tell me this isn't the IAC for my specific year vehicle:





The only wires I see here are the six in the connector in the last pic: two for the injector and four for the TPS.
 

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So turns out it only pertains to fuel injected models. Now that I think about that, it makes sense. Carbs run all on vacuum. Sorry for the goose chase.

I wish I had better answers for you at this point, but I have yet to familiarize myself with the Zuk's carburetor enough to be worth a damn.

But historically, from a carb standpoint, a vacuum leak somewhere would be a strong culprit.

  • Bad carb gasket possibly.
  • Check all hoses (I recently discovered my choke valve hose was smoked. Replaced that and made a big difference in how it runs).
  • Spray some soapy water around the sealed areas and see if that changes the idle. If the idle changes while that "joint" is covered in water, then that gasket is bad, or possibly a loose joint.
 

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This image is of the IAC installed in the original location by the PCV. The top nipple that is broken off is for the hose that goes to the big vacuum line at the base of the throttle body.



The IAC in this image is right above the thermostat housing with the to 5/16 hoses coming from it. The black cap on the IAC is part of my fix for the broken nipple. Had to move the IAC when I put the 1.6L intake manifold on as the IAC bracket did not just bolt on.

 

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Discussion Starter #14
So turns out it only pertains to fuel injected models. Now that I think about that, it makes sense. Carbs run all on vacuum. Sorry for the goose chase.

I wish I had better answers for you at this point, but I have yet to familiarize myself with the Zuk's carburetor enough to be worth a damn.

But historically, from a carb standpoint, a vacuum leak somewhere would be a strong culprit.

  • Bad carb gasket possibly.
  • Check all hoses (I recently discovered my choke valve hose was smoked. Replaced that and made a big difference in how it runs).
  • Spray some soapy water around the sealed areas and see if that changes the idle. If the idle changes while that "joint" is covered in water, then that gasket is bad, or possibly a loose joint.
1992 Zuks, like mine, are EFI. But I don't have an IAC attached to the throttle body; instead, I learned the manual calls it an air valve that opens/closes based on water temperature. That's what you see my pics and I have yet to take it apart to test it.

Interestingly enough, when I tested the electrical components last week using my friend's multimeter I didn't bother to see if the readings were in spec. I just noticed they showed resistance as opposed to my old analogue meter that was showing continuity. So, I purchased a digital multimeter yesterday to see whether the readings were in spec or not.

Both the Throttle Valve Opener and EGR vsv should read between 33-39 ohms, and they just barely read over 33 ohms, which means they should be operating properly.

The ISC valve, on the other hand, should read between 30-33 ohms but reads 29.4, just out of spec. This makes sense because when I disconnect the ISC the vehicle idles close to normal. So, I plan on replacing it this week and then I'll tackle cleaning out the air valve.

No carbon buildup to speak of in the throttle body or on the back side of the plate, nor could I find a vacuum leak (although it's always posible) so I suspect this is mainly an issue where extra air is constantly being added to the mixture by the faulty solenoid, causing high idle, and possibly a little air bypassing the air valve (or something else) as well.

I suppose the good thing about all this is that I'm becoming VERY familiar with my Samurai's engine and how things work on it.
 

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Discussion Starter #15
Thanks Haptown, I see where the confusion is. What you and graphicjunkie are calling an IAC, the 1992 service manual is calling an ISC. And yes, it appears mine is running just out of spec and needs to be replaced.
 

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Discussion Starter #18
Okay, back with an update. I replaced the ISC solenoid and idle after warmup has dropped from 1500 to 1000-1100 rpm. Again, if I pinch the vacuum hose leading from the air filter to ISC the idle drops 2-300 rpm. Also, it sounds as if the ISC is stuck on, sucking air from the air filter. Same thing as when the old ISC was on. I'm beginning to wonder if this could be an electrical problem.

The previous owner did wire in a light bar and an auxiliary fan that can be turned on manually by a switch but also turns on automatically when the a/c is turned on. So it's quite possible he screwed something up electrically.

Or, could this be indicative of an ecu malfunction? Wouldn't I get some sort of code if it was?

I've about had it trying to figure this thing out. I don't mind fixing stuff when I know what needs to be fixed, but I just haven't the skills to really diagnose these kind of problems on my own. I'm sure it will be a fun vehicle, though, once all the bugs are sorted out.
 

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I don't have the answer here, but what seems to me that is needed is to find out what the signal is from the computer to the ISC is when it's supposed to be "open/closed". This would tell you if the computer is sending the right signal.

I don't know. But at the same token, have you ruled out the most simple piece by testing all vacuum lines for seal and vacuum? (entire vacuum system...) It might be something else causing incorrect air volume that the ISC is having a problem compensating for.
If you don't have one, a mighty-vac is a POWERFUL and cheap tool!

Also, did you spray soapy water as suggested?
 

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Discussion Starter #20
I actually replaced all vacuum lines, except the one to the evap cannister. Interestingly enough, the vacuum hoses I got from autozone seem to have a tad larger ID. I'm gonna swap back to the old ones just for giggles.

I've also sprayed carb cleaner, not soapy water, all over the new vacuum hoses, egr, intake manifold (where the spray could reach) and I haven't been able to detect a change in idle with this method.

I think my friend has one of those mighty vacs. I'll have to ask him.

I'll also have to check the service manual on how to check the wires leading to the ISC. I'm not good with electronics but I'd like to try doing what I can before I resort to a mechanic.
 
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