Question about 1990 Isuzu Amigo

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Cold Idol problem/ Bad gas milage

When I fire up my 1990 amigo (2.6L Multi-Port fuel-injected) in the mornings it will not idol. It will only idol after the engine has wormed up to full operating temp. It also has a fuel oder (cold or worm). It doesn't leak fuel. However i'm only getting 17MPG. I've changed plugs, wires, rotar bug, cap, changed the air filter and tested the timing, Tested mass-air flow sensor, EGR, PCV. and checked for air leaks both from housings and air hoses. After it reaches operating temp it runs like a champ (still bad gas milage and slight loss of power) . I love this little vehicle and wold very much like to work out this problem.

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Check the cylinder pressure. Mine does the same, and is suspected to be due to a worn cylinder or worn valves leaking. (do your valves click too?) Supposedly, the leak in pressure is causing less efficient combustion which leads to the fumes and slight loss of power / MPG. I haven't been able to open the engine to test mine yet. I am waiting until I can put in new valves, etc. before I go in.

The other thing that you may want to check is the thermostat. When my got stuck open a few years back, it had similar symptoms. Turns out when started, the engine wasn't allowed to warm up to normal operating temperature because the cooling system was triggered by the faulty temperature sensor to try to cool the engine down. Once it warmed up everything was back to normal. The most noticeable thing about this is prior to the problem, the engine would idle really high at start up for about 30-45 seconds, then settle into it's idle pur. One day it just started and immediately went to idle, and sometimes would require gas to keep it from stalling. The problem would not occur if the engine was warm. Putting in the new temperature sensor solved it.

90 Amigo, 2.6L, 2WD, 5-Spd Manual

Posted on Oct 09, 2008

  • 90amigo Oct 09, 2008

    oh.... forgot... mine has 240,000 miles, keep that in mind while trouble shooting. Let me know what happens!

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