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1990 Isuzu Trooper II 2.6 that won't idel until it warms up.

Tiny
STEVESANTOS
  • MEMBER
  • 1990 ISUZU TROOPER
  • 89 MILES
When I check codes I get a 12 code only, which is the normal or OK mode?

Idle is set at 950, the throttle sensor is correctly adjusted. There is no water in the fuel. I have replaced cracked vacuum lines and the EGR valve. I have lubricated the Air regulator. Fast idle does not kick in when I turn on the A/C, for that matter the core fan does not come on either. I pinching off the hose to the fuel regulator has no effect. When you tac up the rpms it back fires. I would say that the system was running on failsafe mode but for the code 12. Fuel pump relay is good. I have tried swapping out the ECM but no change idle. I haven't actually RR the Air Regulator just read on line you can put penetrating oil down the breather tube to free it up. Hope this is enough info.

We live in Africa so swapping out parts willy nilly is not an option. When I order parts they can take as long as three months to get here. I have a 1990/1991 Isuzu Workshop Manual but I am a carpenter not mechanic and non of the locals know anything more than I.
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Saturday, September 29th, 2012 AT 3:05 PM

24 Replies

Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
Check your map sensor see if the vacuum line is soft, it may be sucking together causing this and if you can check your fuel pressure as follows.
FUELÂ PUMPÂ PERFORMANCE Â FUELÂ INJECTED
Application Unregulated Pressure psi (kg/cm2 ) Regulated Pressure psi (kg/cm2 )
Amigo,  Pickup & Trooper 2.6L (1) 42 (3.0) (2) 35 (2.5)
Impulse (3)Â 35 38Â (2.5 2.7) 25 30Â (1.8 2.1)
Trooper 2.8L N/A (3) 9 13 (.62 .91)
(1) There are two unregulated pressure tests. The first is with fuel pressure regulator and pressure regulator Vacuum Switching Valve (VSV) vacuum hoses disconnected. The second is with pressure regulator
vacuum hose connected,  Blue wire of VSV is connected to positive battery terminal and Black wire connected to negative battery terminal. In both tests,  pressure should be as specified.
(2) With vacuum hose connected to pressure regulator and pressure regulator Vacuum Switching Valve (VSV) disconnected.

(3) With engine running and vacuum hose disconnected from pressure regulator.

That is the correct pressure sequence. Hope you have a pressure gauge. 42 and 35 are the specs for pressure.
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Saturday, September 29th, 2012 AT 3:21 PM
Tiny
STEVESANTOS
  • MEMBER
  • 11 POSTS
Wow! Thanks for the quick response, I'm blown away.

I have looked in my manual for the location of the Map Sensor. Apparently this was only put on the California model, which mine is, but I'm not seeing it. I have looked online for a replacement so at least I can identify it. Any help with it's location?

On Monday, I will see a friend about the fuel pressure guage.

Thanks,

Steve
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Saturday, September 29th, 2012 AT 4:13 PM
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
I guess yours doesn't have one sorry for that, but one thing i've been thinking about is check yoru cannister purge valve it should only have vacuum at one side of it at idle. If there id vacuum going through it then the valve is no good. Temporarily you can block off the line until it's replaced.
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Saturday, September 29th, 2012 AT 4:19 PM
Tiny
KHLOW2008
  • MECHANIC
  • 41,815 POSTS
Try this if necessary.

AIR REGULATOR SOLENOID

1. Check operation of air regulator with engine cold. Start engine and note if idle speed is higher than normal after initial start. If idle speed is not higher, proceed to step 4).

2. As engine temperature increases engine idle speed should stabilize. Check air regulator for leakage. Disconnect hose between air regulator and throttle valve body at throttle valve body side. Plug throttle body fitting end. See Fig. 20.

3. Start engine and check for variation in engine speed by closing and opening end of air regulator hose. Variation in engine speed should be less than 50 RPM. Replace air regulator if variation in engine speed is more than specification.

4. If fast idle speed was not higher than normal on initial engine start, disconnect air regulator harness connector at air regulator. Air regulator is located on right side of engine, in front of starter.

5. Using an ohmmeter, measure resistance between air regulator terminals. Resistance should be 45-49 ohms. Replace air regulator if resistance is not within specification. If resistance is within specification, proceed to step 6).

6. Turn ignition on. Using a voltmeter, check for voltage at air regulator harness connector. If voltage is present, replace air regulator. If voltage is not present, check wiring to air regulator and fuel pump relay.
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Saturday, September 29th, 2012 AT 5:07 PM
Tiny
KHLOW2008
  • MECHANIC
  • 41,815 POSTS
Btw the 2.6 does not use any MAP sensor.

Have the valve clearances checked and adjusted if necessary.
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Saturday, September 29th, 2012 AT 5:13 PM
Tiny
STEVESANTOS
  • MEMBER
  • 11 POSTS
Hello again,

It has taken this long to secure and try the pressure gage. Unfortunately, I was unable to get a working fuel pressure gage. So for the moment let's say it is putting out the correct pressure.

I performed the test on the AIR REGULATOR SOLENOID and found that the rpms change was over 200.

Before I was able to warm up the motor and then it would idle now it wont even do that.

It now sputtering and back firing when you depress the accelerator between 1000 and 2000
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Wednesday, October 3rd, 2012 AT 3:18 PM
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
Gotta do the fuel pressure first
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Wednesday, October 3rd, 2012 AT 3:31 PM
Tiny
STEVESANTOS
  • MEMBER
  • 11 POSTS
Thanks, I will look harder.
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Wednesday, October 3rd, 2012 AT 3:43 PM
Tiny
STEVESANTOS
  • MEMBER
  • 11 POSTS
Hi,

Are you still our there? I was able to get a pressure testes from a couple of pilots and we ran the test and found it was running at 26 lbs vacuum on the pressure regultor or not. Whats next. My inclination its to take the tank down and pull the pump out. Several months ago I had a coating I brought over from the States put on the inside of the tank. The tank had rusted through over the years. Can the pump be rebuilt?

I noticed, now that the internet is up, that the pump cost over $500. Do you know a good inexpensive place to but parts on the internet?
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Tuesday, October 9th, 2012 AT 7:23 AM
Tiny
KHLOW2008
  • MECHANIC
  • 41,815 POSTS
Pump cannot be rebuilt. You should be taking the pump out to check the strainer for clogging.
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Tuesday, October 9th, 2012 AT 9:36 AM
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
Try rock auto. Com inu.S. But it still may be teh same or about the same price due to where you are and it may be the whole unit, pump/sender tec.
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Tuesday, October 9th, 2012 AT 1:40 PM
Tiny
STEVESANTOS
  • MEMBER
  • 11 POSTS
I have the stainer in hand and it clean on the outside but when I suck or blow through it there is a lot of resistance also about 1/8 of it has been epoxied. Looks like there were holes warn in it. Can I run the test again without the filter bag?
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Monday, October 15th, 2012 AT 3:10 PM
Tiny
KHLOW2008
  • MECHANIC
  • 41,815 POSTS
Not advisable as impurities can get into the system and that would cause problems if they were to get lodged inbetween the valves of the pump. If you must, use a degreasing detergent and compressed air to clean the strainer.
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Monday, October 15th, 2012 AT 3:26 PM
Tiny
STEVESANTOS
  • MEMBER
  • 11 POSTS
It looked blackish and and no light would pass through it now it looks whiteish and I can see light through it. I think i'm ready to reinstall it. Okay by you?
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Monday, October 15th, 2012 AT 4:14 PM
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
Yup
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Monday, October 15th, 2012 AT 4:28 PM
Tiny
STEVESANTOS
  • MEMBER
  • 11 POSTS
Reassembled, pressure test, 29 lbs, new fuel filter and inspected the lines. No joy. Won't Idel. Now getting code 26 and 25, respectively. Rev-up the engine it back fires. Smells rich.
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Tuesday, October 16th, 2012 AT 11:20 AM
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
Here are diagnostics for that, hope you can read it.
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Tuesday, October 16th, 2012 AT 1:25 PM
Tiny
KHLOW2008
  • MECHANIC
  • 41,815 POSTS
The non idling and backfiring could be due to the ignition system. Check the ignition timing and spark plug related components. The ignition coil could be weak.
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Tuesday, October 16th, 2012 AT 9:15 PM
Tiny
STEVESANTOS
  • MEMBER
  • 11 POSTS
Both sides checks out. One 37.4 olms and the other 38.1

What do you think about the 29 lbs pressure at the fuel pressure regulator?
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Wednesday, October 17th, 2012 AT 7:37 AM
Tiny
STEVESANTOS
  • MEMBER
  • 11 POSTS
Is there a test for the ignition coil?

New roter, cap, wires. Sequence correct. Having a hard time holding idel to set timing.
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Wednesday, October 17th, 2012 AT 8:56 AM

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