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Old 03-27-2007, 11:45 PM   #4
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Re: hard to start when warm

what happened jetendersandhu, forgot your lukerseth password?

I have a 1992 isuzu trooper 3.2 V6, same as your 1993.

this is how my 1992 has acted since new almost...
the almost is :: : When it starts, the rpms are slow to come up. ::: that part doesn't happen with mine -- once mine starts it is fine.

i took it back to the dealer and even got the isuzu district service representative involved way back then. and the answer i got each and every time was ' that's normal '. to which i could only reply -- yes that's the problem, it's normal, it's just not right. i figure it sells them more starters.

anyway, i have come up with my own theory: namely, it is indicative of a hot rich start condition (like that reply relating to a carbureted engine). in this case, the culprit would be, i theorized, either the Manifold Temperature Sensor (MTS) or the Coolant Temperature Sensor (CTS). i figured since both these would cause the computer to mistakenly enrich the mixture if they sent the inaccurate temperature input data.

recently, i decided to track the CTS, mimicking the condition of a restart after sitting for various amounts of time. the way it works is, the sensor sends a different voltage signal back to the computer depending on the temperature; the computer takes this voltage (temperature) input and prescribes an air/fuel ratio according to its program.

the voltage changes should correspond to the changes in the coolant temperature. what i discovered is that in my case, these changes were not consistent, they fluctuated rather than followed a curve. they became weird exactlly in that window where starting was problematic. shortly after shutdown, the temp would spike (as expected) and starting would be fine, then it followed the imagined curve, but eventually started indicating values opposite what would be expected; then after that period it would settle in at what one would expect.

so that's my theory and that's my analysis and diagnosis. if the CTS were in an easily accessible place it would be a no-brainer to just swap it out and see what happens. but it's on the coolant crossover pipe at the rear of the engine up against the firewall and near impossible to get to, so i continue to live with the symptom until i need to take off some stuff and/or tilt the engine to get back in there. (and the time is probably coming soon since i am going to have to replace the heater core and/or the hoses also back up between the firewall and engine.)

well that's my story...and i'm sticking to it : it's the Coolant Temperature Sensor.

does it make sense to your situation?

1992 trooper 3.2L v6 sohc is

i love a good intermittent electrical challenge. . .especially when it's someone else's.
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