2.6L won't start
From Planetisuzoo Wiki
Checking OBD1 codes on the 2.6L:
To check the codes pull out the change tray in the center console and there should be two spade connectors. Connect these two wires and turn the ignition on but don't start the engine.
You should see code 12 (1 flash + 2 flashes) three time on the check engine light, and afterwards it will flash whatever codes it may have. Go to this site to find out what the code means: http://autorepair.about.com/od/obdcodedatabase/The_Exhaustive_Database_of_OBDI_and_OBDII_Engine_Codes.htm
Some codes listed here:
12....No Distributor Reference Pulses
13....Oxygen Sensor Circuit
14....Coolant Temperature Sensor Circuit
15....Coolant Temperature Sensor Circuit
21....Throttle Position Sensor and/or Idle Switch, or MAP Sensor (1989 I-Mark)
22....Throttle Position Sensor Circuit, or No Starter Signal (I-Mark, MPFI), or Fuel Cut Off Relay (Carbureted)
23....M/C Solenoid Circuit (Carbureted), or Manifold Absolute Temperature Sensor Circuit
24....Vehicle Speed Sensor
25....Manifold Absolute Temperature Sensor or Vacuum Switching Valve
26....Vacuum Switching Valve System
27....Vacuum Switching Valve System
31....No Ignition Reference Pulses to ECM (Carbureted), or Wastegate Control
32....EGR System 33....MAP Sensor Circuit, or Fuel Injector (1988-1991 Impulse, others with 2.6L Engine)
34....MAP Sensor Circuit, or EGR Gas Sensor Circuit (Carbureted, Stylus & 1990-1992 Turbocharged Impulse), or Fuel Injector (Impulse)
35....Power Transistor System
36....MAP Sensor Circuit
41....Crank Angle Sensor, or Cam Signal (Stylus & 1990-1992 Turbocharged Impulse)
42....Fuel Cut Off Relay (Carbureted), or Electronic Spark Timing (Throttle Body Injection), or Ignition Control Circuit
43....Electronic Spark Control, or Knock Sensor (I-Mark, MPFI), or Throttle Valve Switch (1988-1991 Impulse, others with 2.6L Engine)
44....Oxygen Sensor Lean, or Fuel Metering (1988-1991 Impulse, others with 2.6L Engine)
45....Oxygen Sensor Rich, or Fuel Metering (1988-1991 Impulse, others with 2.6L Engine)
51....Fuel Cutoff Solenoid Circuit (Pickup, Carbureted) or ECM (all models)
52....ECM (PROM, EEPROM, ROM, RAM, or ECM itself)
53....Vacuum Switching Valve and/or ECM
54....M/C Solenoid Circuit and/or ECM (Carbureted), or Vacuum Control Solenoid and/or ECM (Pickup, Carbureted), or Power Transistor System, or Fuel Pump, Voltage Low (TBI and I-Mark, MPFI)
55....ECM
61....Air Flow Sensor
62....Air Flow Sensor
63....Vehicle Speed Sensor
64....Fuel Injector
66....Knock Sensor
71....Throttle Position Sensor
72....Vacuum Switching Valve Faulty EGR
73....Vacuum Switching Valve Faulty EGR
Checking Fuel Pressure:
Hook your fuel pressure gauge into the return side of the line between the regulator and the fuel rail. The 2.6L needs between 45 and 50 psi of pressure.
Turning on the Fuel Pump:
The 2.6L doe NOT prime the fuel pump (turning it on momentarily like most GM cars) when you turn the ignition on. The fuel pump gets 12v while cranking (key in the start position) through a wire from the starter. Then, when it is running for a moment, the alternator energizes and sends a voltage to a relay that provides 12v to the pump while running. This is done so the pump will shut down if you are in an accident and the engine stops running, so will the pump. That way, if a fuel line is broken in an accident, you won't be pumping fuel all over the place.
Isuzufool says: You can force the pump to prime by turning it to the start (crank) position without pressing in the clutch. The pump will run without turning over the engine.
Thus, with a bad alternator, the truck should fire and start momentarily, but then not be able to continue to run (i.e. it'll get proper crank fueling, but then won't transition properly to "run" mode). So, if there's no combustion at all while cranking, this shouldn't be a bad alternator causing this because during crank the fuel pump will still get a direct battery feed of 12v.
To make the fuel pump run all the time with the key on, pull the engine relay (obviously, keep the fuel pump relay connected). The relays are located with the fuses on the left fender underhood. The purpose of the engine relay is to keep accessories that are designed to operate with the engine running, only operate with the engine running. It's used to reduce engine-off load on the battery, as well as prevent the pump from running all of the time (with engine off).
On the alternator there's a big wire that is the charge wire w/square connector. There is a round connector with 3 pins. Battery voltage comes in on black/yel wire to tell voltage regulator when to turn off and on. White/green wire goes to the engine relay which connects to the dash lights/charge indicator on white/red wire and comes back on black/red wire to the fuel punp relay.
Setting cam/ignition timing:
There is a little protruding plastic strip on lower plastic timing cover near the damper (harmonic balancer) - this is the timing tab. Look to the left of center (towards passenger side) O degs (TDC) is on the far right side of the tab. But, the marks on the balancer may not be accurate as the rubber on the 2 piece balancer is known to get loose and allow the 2 rings to slip. Factory spec for ignition timing is 12 degs BTDC.
The black plastic timing belt cover is in 2 pieces. Taking the top timing cover off (four 10mm bolts) revels the cam gear. The little triangular pointer that is part of the edge of the aluminum piece behind the pulley at the top (at 12:00 position) and the notch in the cam gear line up when #4 piston (cylinder closest to the firewall) is at TDC. Thus, an alternate way to read timing instead of using the harmonic balancer and lower timing cover tab is to use an adjustable timing light set to 12 degs on the #4 cyl and shine it at the cam gear.
If you have the damper and lower timing cover off, the lower toothed pulley has a notch in the rear flange which lines up with a pointer on the aluminum crank seal retainer (it has an inch long straight line on top). You will probably need a mirror on a stick to see it with radiator in. This is the best tdc reference, consider it #4 tdc.
Factory setting for the distributor is halfway between retarded and advanced - there is a cast line on the distributor and the base that should line up. Note that the distributor rotor turns in the clockwise direction, and the terminals are numbered on the inside, and they're not numbered as you'd think just from looking at the cap as they're routed internally.
If you're not getting spark: (the distributor, coil and Igniter)
Note: the rotor doesn't just pull off - it's held down by a bolt. Bump the engine until the rotor is pointed straight down, and the hold down bolt will be pointed straight up.
The 2.6L has the crank angle sensor (a degree wheel) that has notches and slots cut in it for ignition and injector timing inside the distributor.
The Igniter (power transistor) is located on the underside of the intake mainfold near the rear two ports. Its bolted up against the manifold flange and is about 1"x2" square black plastic with little cooling fins on it and dual lead connector. The power switch that controls the spark is under the intake manifold. Some refer to this as the igniter. When it stops working, you get no spark. Do not test with anything other than a 1.5V flashlight battery, anything else will fry it. See this link for a picture: http://forum.planetisuzoo.com/viewtopic.php?t=16533
Ignition coil: 2 wires, black with a yellow stripe and black with a red stripe. The black and yellow one is switched power. The black and red wire goes to the Power Switch (ignitor) and then on the the ECM.
Check the condensor that's bolted onto the valve cover near the backpressure transducer. Its got nothing to do with the radio, it is the main condensor for the ignition system. Frayed wiring only running current through a couple of strands results in a very weak spark and inconsistent fire.
See these threads for more info:
http://forum.planetisuzoo.com/viewtopic.php?t=16846 http://forum.planetisuzoo.com/viewtopic.php?t=18595
Idle Speed adjustment:
To adjust idle speed use the air bleed adjustment on the back of the throttle body pointing toward the firewall that is adjustable using a flat-head screwdriver. It's a slot type screw pointing upward at about a 45 deg angle. Unlike the TBI systems like the 2.8 V6 uses where this IAC motor is electronically controlled by the ECM and plays a major part in the operation of the motor, the IAC screw in the 2.6l works similar to a regular mixture screw on a carburetor. Only that instead of the mixture being changed like in a carb the whole amount of incoming air is changed to adjust the idle speed. In the TBI systems the screw (IAC) is electronically controlled and adjusted by a servo, determining the idle speed of the motor from the ECM.
From http://www.asashop.org/autoinc/feb98/techtips.htm
Problem: Hard surge on a warm engine, at idle only between 1700 and 1200 RPM and is constant until the throttle is opened.
The 2.6L has a fuel-cut mode to limit engine speed at idle to 1700 RPM, with the idle switch indicating closed throttle and the engine warmed up. The vehicle computer responds by shutting the injectors off until engine RPM falls to 1,250 RPM. This could give the hard surge the customer is complaining of.
The idle switch (located on the throttle body) has a blue wire with a yellow stripe on its connector - the signal return to the ECU with 12 volts at idle and 0 volts off idle telling the ECU if the car is on or off idle. By disconnecting the switch, the computer thinks it is off idle and this should eliminate the fuel cut function.
On this Trooper, idle speed is controlled in the following manner:
1. Cold idle speed increase (or "fast" idle) depends on the amount of bypass air through the air regulator (aka the auxiliary-air valve) located under the intake manifold attached with 2 10mm bolts and has a 12v electrical connector and two large vacuum hoses attached, on top and bottom. It's a bypass that pulls metered, measured air (measured by the MAF sensor) from before the throttle blades and ducts it into the intake manifold behind the throttle blades, bypassing the tbrottle blades. It's a bi-metallic valve with a heating element that opens and closes with temperature.
It's wide open on a cold engine allowing air to bypass and increasing cold idle speed. When ignition is turned on, the heating element powers with 12v and heats the bi-metallic spring and closes the valve - returning the vehicle to its normal idle speed of 850 to 950 RPM. This valve is bolted against a coolant passage in the intake which keeps it warm for hot/warm restarts and keeps the valve closed. A quick test of this valve can be made on a warm engine by pinching the vacuum lines. Engine speed should not change. If it does, the valve may be hanging open, causing a higher than normal idle.
A faulty one of these (if the little clock spring goes out) can cause hard starts, and high idles. It is possible to readjust these. There's a little bolt with red sealant on the underside that winds the clock spring on the little flapper valve to determine when it should open. I'm sure you could readjust it but getting it to open at the right time with the temp of the engine is the trick.
2. Hot engine idle is controlled by a thermal valve and increased load causes idle increase by a fast idle solenoid. The thermal valve, located on the thermostat housing, will bypass air past the throttle plate if engine temperature is more than 198 degrees F. It has three vacuum lines - one to the air intake tube near the center of the valve cover, one to the intake, and the final one to the fast idle solenoid. There should be no bypass air through the thermal valve until the engine reaches more than 198 degrees F coolant temperature. To test the valve, pinch the vacuum line to the intake. If the engine speed changes and the vehicle's coolant temperature is below 198 degrees F, the thermal valve is faulty. The thermal valve's other vacuum line runs to the fast idle solenoid. This vacuum line is always a fresh air source unless the coolant temperature is above 198 degrees F. The fast idle solenoid is controlled by the air conditioning signal. With A/C on, bypass air will pass through the fast idle solenoid and increase idle speed. With A/C off, no bypass should occur.
3. Base idle is adjusted with a simple air bypass screw located in the throttle body. If all the other systems are working correctly and there are no vacuum leaks, idle speed may be adjusted using this screw.
Idle Speed adjustment: Auxiliary Air Regulator Valve
As mentioned above, these 2.6L have an Auxiliary Air Regulator (AIR) valve for fast cold idle, located under the intake manifold. It's basically a bypass to add extra air for cold starts. The temp sensor input to the ECM richens the AF ratio for cold starts.
This AIR valve is impossible to get to from the top of the engine. To access it, you'll remove the passenger side front tire and go through the wheel well. 2 10mm bolts that face towards the passenger fender hold it in (so the head of the 10mm bolts are facing the drivers side so you can't see the bolt heads). To remove the AIR valve, you'll disconnect the electrical connector (wire clip similar to the MAF plug style holds it in - use a small screwdriver and pry away the wire clip and the connector will drop out.) You'll also need to disconnect the 2 hoses that attach to the valve - one on top and one on bottom. Disconnect the hoses not at the valve end (impossible to do) but at the manifold end. Both hoses go to the intake manifold - one attaches on the bottom, one attaches on the top. Disconnect the hoses, remove the wiring, unbolt the valve and it'll come out the bottom.
Testing the AIR valve: the wiring harness should have 12v between the 2 connectors when the fuel pump is turned on. This means to check it, turn the igniton on and remove the Engine Relay - this will turn the fuel pump on as explained above, you should now see 12v between the 2 terminals. If not, you have a wiring issue. If you power the AIR valve with 12v, you should see the shutter door move and start closing - closing completely in about 3 minutes. The resistance between the 2 terminals on the valve should be around 40 ohms.
For a picture go to these links: http://forum.planetisuzoo.com/viewtopic.php?t=24715 http://forum.planetisuzoo.com/viewtopic.php?t=14944 http://forum.planetisuzoo.com/viewtopic.php?t=12999
For more AIR regulator info go to this link: http://forum.planetisuzoo.com/viewtopic.php?t=20389
For more cold idle problems go to this thread: http://forum.planetisuzoo.com/viewtopic.php?t=14397
TPS (Throttle Position Sensor & Throttle Position Switch:
The 2.6L with manual transmission has a Throttle Position Switch, not sensor.
The prongs on the switch are labeled top to bottom, I, P and F. With the throttle closed, you should have no continuity between P-F and continuity between I-P. Slightly depressed gives no continuity between both of those sets of prongs and with it fully depressed (Wide Open Throttle), you should have continuity between P-F, but not I-P.
To adjust the switch, hook up the Ohm meter to I-P and place a 0.012 feeler gauge between the throttle stop and the throttle lever. Adjust the gauge until the point where the continuity is just established. Then use a 0.020 feeler gauge to make sure continuity is broken. At that point, it is adjusted.
If you have a 2.6L with automatic transmission, you have both a switch and a sensor. The TPS on the auto 2.6 trooper has both the 3-position switch as the manuals do, and the variable output pot for the auto tranny computer. You cannot adjust them independantly so this is still the proceedure to follow for adjusting it.
It sounds confusing because it is tough to do on the engine. The location of the TPS on the firewall side of the throttle body, the location of the screws that lock the TPS in place (lower screw requires a LONG right angle teeny phillips), the angle of the TPS and the proximity of the valve cover make it pretty difficult to clip leads for the ohm reading with any assurance that you are not clipped to two at a time. The best solution is to grab a connector off a wire harness at a junk yard, strip the insulation off the end, plug it in and use that to clip to. The time consuming solution is take off the throttle body and do the setting in the bench. If you are doing a valve setting and clean up of the throttle body and common chamber anyway that's a great time to set the TPS. It's just like the instructions said, top to bottom take the readings. It's only three prongs.
Throttle Lever - That's the part that moves. If you look at the throttle cable and follow it to where it hooks on to the throttle assembly you have found the throttle lever. Just cause it looks more like a circle doesn't mean it doesn't act as a lever. The lever opens the throttle.
Throttle Stop - If you turn the throttle lever by hand you will see on the lower part of it a flat spot that always returns to the same position on top of a little screw on the lower part of the throttle body. That screw is the throttle stop. It's usually painted with a red strip so that you know to never mess with that screw! You place the feeler guage between the flat spot and the screw.
Adjust the gauge - That's just bad wording. It should read "loosen the locking screws and push the TPS connector plug down (clockwise as you face the firewall) until the point where continuity is just established."
And just a reminder this applies to the 2.6 I-TEC . It's not a complicated device. I thought there was some mysterious electronic gizmo inside of the TPS until I took it upon myself to take one apart. It's a make-break-make switch. One contact for the throttle "closed" position, one contact for the throttle "full open" position and a contact on a strip of metal that goes between them. My understanding of the function of it is in the "closed" and "full open" positions it drops the O2 sensor out of the ignition sequence for a smoother idle and better pedal to the metal acceleration.
Grounds and wiring issues:
The ground cable on the Troopers is a common problem area (where it bolts to the block). Sometimes responsible for bad cold starts.
Look in at the right rear tire. There's a wire loom that comes along the gas tank from behind and splits to two places. Two of the wires go to a plug that runs the fuel pump at the top of the tank. The other wires go to the front, middle of tank (sending unit). Unplug that top plug and check it for corrosion. I had to just cut the plug out and wire them straight together. Any drop in voltage and the pump won't push enough gas.
For 2.6L ECM pinout and photo of where some grounds go see diagram at this link: http://forum.planetisuzoo.com/viewtopic.php?t=16846&postdays=0&postorder=asc
Vacuum Leaks:
Not so obvious areas to look for vacuum leaks: Check for hole on underside of plastic air inlet pipe. Check the series of vacuum lines that go to the fast idle sensor, located directly behind the battery. They tie into little sections of plastic tubing where they run behind the battery. The two middle lines are usually only shoved on there about 1/8" or so, and have a nasty tendency to pop off from the battery vibrating. What fooled me, is they are almost impossible to see without removing the battery.
Idle problems when cold can be caused by failure to hook up a manifold vacuum line to the intake tube to provide high idle. There is a hose that goes from the front of the intake tube to a valve on top of the radiator outlet. It splits into two hoses, one goes to a valve on the passenger fender and comes back to the plenum. The other goes directly to the plenum. The short one (the last one I mentioned) could very easily cause cold idle symptoms.
Here's a link to an explanation and photos of vacuum tube routing: http://forum.planetisuzoo.com/viewtopic.php?t=14304 http://forum.planetisuzoo.com/viewtopic.php?p=109784
Here's photos of Vacuum tube routing: http://www.planetisuzoo.com/articles.htm?id=113&Isuzu_2.6L_Vacuum_Hose_Photos
EGR, TVV (Thermal Vacuum Valve) & BPT (Back Pressure Transducer)
See these threads: http://forum.planetisuzoo.com/viewtopic.php?t=8631 http://forum.planetisuzoo.com/viewtopic.php?t=8793
The TVV doesn't allow vacuum to the BPT until the engine warms up.
Adjusting 2.6L valve lash:
2.6L valves lash should be adjusted every 15,000 miles or the #3 exhaust valve will burn. This is mainly because with the early 2.6s the valves were not lapped at the factory and will settle back into the seats as they wear in. most of the time they'll settle back enough to make contact with the rocker arm making the valve hang open and eventually burn. This is why isuzu reccomends that the lash be adjusted ever 15k miles.
Check the torque of the camshaft/rocker arm caps before you adjust the valves. Set to 16 ft-lbs, if you don't torque properly, the lash adjustment tends to be off all the way across the board. Note: only rocker bolts 1-8 are torqued to 16 ft-lbs. Bolts #9 & 10, the ones closest to the transmission, are not rocker arm bolts and are torqued to 6 ft-lbs.
Set lash to .008 on both intake and exhaust with as little drag as possible to leave them a little loose to prevent burnt valves.
1. Remove the valve cover. 2. Rotate engine to #1 TDC (cam mark at bottom) 3. Adjust intake valves on cylinder #1 and 2. 4. Adjust exhaust valves on cylinder # 1 and 3. 5. Now bring #4 cylinder on top dead center (line up cam marks at top) 6. Adjust intake valves on cylinder # 3 and 4. 7. Adjust exhaust valves on cylinder # 2 and 4.
Loosen the adjusting nut and the screw enough so that you can fit the feeler gauge blade in. Tighten the screw so that the blade has a bit of a tug on it. Leave the feeler gauge in and tighten the nut till the feeler again has a bit of a tug on it. It's almost like you have to adjust the valve twice because the lock nut definitely will change the clearance.
See this link: http://forum.planetisuzoo.com/viewtopic.php?t=3466
