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Isuzu Owners Maintenance and Repair



  • 1993 Isuzu Truck Pickup (4WD) L4-2559cc 2.6L SOHC (4ZE1)
    Vehicle Level Powertrain Management Fuel Delivery and Air Induction Auxiliary Air Valve (Idle Speed) Description and Operation

    Description and Operation

    Air Regulator

    Provides a means for increased idle speed when the engine is cold.

    At the front of the intake manifold.

    The regulator allows air to by-pas the throttle valve, thereby raising idle speed. The regulator contains a temperature sensitive electric element that causes the air bypass to close gradually as the engine warms up. When the engine has run for approximately five minutes, the valve should be fully closed.

    The air regulator is energized through the fuel pump relay and not directly controlled by the ECM.

    1993 Isuzu Truck Pickup (4WD) L4-2559cc 2.6L SOHC (4ZE1)
    Vehicle Level Powertrain Management Fuel Delivery and Air Induction Auxiliary Air Valve (Idle Speed) Specifications


    Resistance 45 - 50 ohms

    Here is a link to a photo of your engine and location: to/v./photo.jpg

    Hope this info helps!
  • You may be able to find an independent mechanic with the Tech 2 tool and Isuzu adapter so that he car read codes. The TOD codes are in the powertrain module, which is easily accessible through the Tech 2 (which is what Isuzu dealers use).
    The trick is getting the codes read right from the powertrain module. The sensors on the transfer case are fairly easy to access, so I cannot imagine why the part or labor is so high!!?? except that it is a dealer!
    The 13 and 14 codes you refer to I am not sure of, but the 24 code is for the brake pedal switch circuit, and the ecm turns off the transfer case solenoid (electromagnetic coil which energises the clutch pack) if it see the brake is applied while the TOD is in action. It does not set the check light but does store in the memory when it is malfunctioning.
    Hope this information helps. One guys opinion.
  • I'm doing the brakes on a 1995 Isuzu Trooper LS 4W with a 6 cylinder engine.

    I have the tires off, and the calipers but can't get the rotors off.

    Direction, suggestions please.
  • The 1995 4wd Trooper has automatic locking hubs on the front. The rotor is integral with the wheelbearing/autolocking hub so, those parts need to be taken apart to get the rotor off. Be ready with the proper grease and repack the bearings and the autolocking hubs while apart.
    The rear of the 1995 Trooper has a drum parking brake concentric with the disc brake rotor.
  • 2000 Trooper w/3.5L Automatic/TOD 4WD, 123,000 miles. Dealer replaced transmission under warranty at 118,000 miles. Since then have experienced problem at startup that has gotten progressively worse. Dealer is at a loss for fix. Symptoms are:

    Startup in morning engine rpm increases to about 2000rpm, then idles down to almost dying, increase upwards toward 1500rpm, down again until it finally levels out at about 1000rpm. Placing gear selector in reverse (any gear) smooths out engine idle and performance is normal except for a flashing check engine light as long as you depress the accelerator. Shutting the engine off, start back up and flashing CEL is gone.
    Drove to dealer this morning with CEL flashing after usual startup rpm fluctuations. Left it running so technician could see what was happening. He confirmed flashing CEL and when we returned to service dept he connected scanner to check codes while engine was still running. Absolutely no CEL codes while in park or in gear while CEL continued to flash. After disconnecting scanner, shut engine off and restarted; no CEL, perfect idle, etc.
    Previous (yesterday 09/12) dealer replaced intake manifold gaskets since they determined a cracked gasket was causing an air imbalance on cold start. The new gaskets haven't changed a thing.
    Am wondering is vehicle may have a faulty electronic idle switch or some other magic piece of electronics/sensor in the Fly-by-wire setup that is causing the problem or if something about the transmission replacement could be causing the problem.
    Am returning the Trooper to the dealer this evening so they can continue the diagnosis. A kudo for the dealer, Duncan Jeep/Isuzu in Blacksburg VA. Service Manager said if the intake gaskets did not correct the problem there would be no charge.
    Any help appreciated.
  • How do you get the auto hub off? I removed the outer clip and I have two springs, a washer but part of the assembly is still
    there. I don't know how to get it off to get to the wheel bearing nut. Do you have an exploded view of assembly?
  • Try this link to see exploded view: - - if/photo/v./photo.jpg

    There is a hub nut which must be removed, requires a deep well socket to reach. It sounds like you have gotten to that point. Good Luck.
  • I found a snap ring I missed, and I got the rotor off.
    My mistake, well, it looks like i took the clutch assembly apart... I rented a deep well socket set - didn't have the right one (they all had 4, i needed 2). I'm trying to reassemble now.
  • Check the Fuel Pressure Regulator, Idle Air Control Valve and Mass Air Flow (MAF) Sensor. Also, make sure the Alternator and Battery are good, a low voltage from the Alternator/Battery can confuse the hell out of the ECM and hence creates random symptoms like you have described. In the morning when you first start the engine (Cold Start) it first idles at higher rpm till the engine warms, after that it will idle around 750-800 rpm, the reason for this that the ECM runs in a open loop form till the O2 sensors warms up to 600F or so, this is by design. The CEL light flashing when you start the engine for few times and then disappearing also seems to be normal, untill and unless it is happening way after the start of the engine is completed. Have you changed the Timing Belt recently by any chance, if that is true then it could be incorrect installation or Belt jumping which could be the cause of these symptoms.
  • HELP!!! Just got done replacing head gasket on trooper, changed all the gaskets and the water pump gasket, started to fill with fluid and it comes gushing out from underneath, it appears to be from above the transmission area, i am machanically exhausted with this truck but it really is a love hate relationship, I really want to see it in the mountains again, any ideas would be really appreciated.
  • Which engine are you working on...there is a L4 and V6 for your year vehicle.
  • Thanks bahmed for the diagnosis and insight. I have been thinking about the possibility of some type of idle control sensor being out of wack. The flashing CEL remained active for about 15-20 minutes. When I got to the dealer I left it running so the tech could check codes. After he found none I then shut off the ignition. Immediately restarted the engine with no flashing CEL and perfect idle. I will discuss your comments with the service rep. Appreciate the info and will post the outcome. Thanks.
  • It's the 4 cyliner 2.6
  • I am not familiar with the 4 cyl., but in general, there may be a freeze plug on the back of the head. If not or if that is not the problem, you indicate that the coolant is coming from the transmission area. If you have checked above and around the heater hoses to be sure they are not leaking, and the head was installed and torqued properly (means you don't see any coolant around the gasket area, then you may have a freeze plug on the rear of the block that chose this time to leak. It seems like it would be a small leak that would gradually get worse over time though. If the coolant is gushing, I would look for something I (you) missed while reassembling the truck. Have you checked the engine oil for coolant as well? That might show an improperly installed gasket and the need to retorque the head bolts. Sorry I can't be more specific. Let us know what you find. good luck
  • There were a bunch of water coolant hoses around my 1984 1.9L L4 engine and on my 1995 V6 as well. I suggest looking at all the hoses. Maybe one end of a hose fell off, or the hose has failed. The hoses are difficult to reach and therefore are usually only changed if they fail.
    A positive note: At least you have a visible and verifiable and traceable non-intermittent consistent problem which can be solved without risk of damaging the engine.
  • Thanks for the info, I should have said it does not start leaking until I get to a certain point like filling a bowl with a leak, the freeze plugs would make sense, I plan on looking at them this week and will let you know thanks.
  • No problem, let us know what will be the final fix, another thing to check is the 'Transmission Mode Switch' also known as 'Range Switch' or the 'Mode Switch', it is a Electro-mechanical switch located on the side of the Auto transmission on the Driver Side, this Switch tells the ECM which gear the truck is in, the switch goes bad around 80K and the symptoms are rough shifting from 1st to 3rd and vice-versa, I did had the howering idling in the first start in the morning and it settled down after the engine warmed up, search for my other post on the transmission mode switch, I did not have the rough idling since I changed the Mode Switch, by the way the Mode Switch went did not produce any CEL or Check Transmission Light, but the Dealer did pull the codes about the switch, so not codes will bring the light on the dash. If you also have sluggish power, it sounds like the Timing belt issue.
  • Dealer called this morning. Said problem is with MAP (Manifold Absolute Pressure. The service rep said the voltage was off causing it react much as if there was an intake manifold gasket leak. The MAP was replaced yesterday and codes checked. The Trooper was restarted this morning (outside temp around 58 degrees) with no abnormal idle or flashing CEL. Hope this takes care of the problem; I'll drive it myself for several days to see what happens. The dealer (Duncan Jeep/Isuzu in Blacksburg VA) had already changed the intake manifold gaskets based on the symptoms. I did not have to pay for the gasket change since that did not fix the problem; kudos to them! Appreciate the help and I am sure your input help put them on the trail to the problem. After your initial assessment I asked the service manager if they had checked to ensure the ECU and any related sensors were within specs. He was pretty insistent that it was the manifold gaskets since they have had problems with them in the past. Unfortunately, sometimes we zero in on the "usual" problem and same old solution when that is not always the case. I think you gave me some insight to make them think about it a bit more. Again, thanks and will keep you posted if the problem reoccurs. Cool site! :shades:
  • I have a similar problem with my 2001 trooper (2WD). I have determined that the sound is coming from my right rear wheel. From in the car, it sounds like a "waw, waw..." noise starting at about 10 mph, and the only thing that makes it quit is by stopping the car. From spinning the wheel, it sort of sounds like a grinding noise. I am not sure if it would be the wheel bearing, or an axle bearing.

    Anyway, what would be the best way to determine which it is, and how difficult is it to replace? I am fairly mechanically inclined, and have access to tons of tools (auto-hobby shop on base).

    Also, where can I find a maintenance manual for my 2001? I have looked and looked, and cannot find one anywhere.

  • Hi, Are you sure it is not some component of the brake system that is causing the noise? That would have the highest probability of causing a noise. You have an internal parking brake shoe system that can cause an intermittent noise. Removing the caliper and rotor may help you isolate, but if it is a bearing, the outer usually is the one that goes first. They are not too hard to do, and the seal will need replacement too. You could try an online manual at if you cannot find one locally. I am sure that a Chilton or other publisher can also be found, if you have the time. I bought mine on ebay, used. Hope this helps. /photo/v./photo.jpg
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