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Discussion Starter #1
Hello from Serbia!

Recently I bought a 1986 Supra 3.0 N/A from a friend. The car hasn't been driven for the past 7 years, and prior to putting it in storage he rebuilt the engine after a head gasket failure. The car ran perfectly at the time, and was parked in perfect working condition.

The car has an LPG fuel system installed (back then it was almost a regular old car and he was looking to cut expenses). It's a sequential system, so 6 injectors and a computer to control it all. Supra is Gulf-spec, and doesn't have an O2 sensor. I drive it only on petrol at the moment, but the LPG system can help diagnose some issues.

Fast forward to today, it runs, but with a list of issues. My suspicion is that most of them are caused by the engine flooding, but since there are virtually no qualified mechanics for the Supra here, and parts availability is quite bad, I'll have to do most of the work myself. I'm handy so it shouldn't be too much of an issue.

The list of issues is as follows:
  • When cold, the idle is hunting from 500-1500 RPM and will stall. Once every 10 cold starts it will be steady, but as soon as I bop the throttle the engine will die.
  • Once the engine gets warm, the idle stays at 1300-1400 RPM, and stalling very rarely occurs.
  • If I switch from petrol to LPG, the idle will be at around 1000-1100 RPM.
  • When driving the car, the power delivery is never smooth. It runs ok at low RPM (below 2000), then it will often sputter and lose power above 2000 (like it's drowning in fuel), and if it gets to 3700-3800 it will go like hell. Sputtering is very bad on petrol, to the point where the car can't stay running anymore. On LPG it's better (although the power delivery is still far from ideal).
  • Even on occasions when there's no sputtering, the car acts like a turbo one, and delivers a huge kick in the back after 3800 RPM or so, it goes at least 50% better than before it hits those revs. This is the case on both petrol and LPG. I don't know if this is normal, though.
  • At times, it has trouble starting when warm, but very rarely. 90% of the time it starts right up.
  • The temp gauge never goes past the 1/8 of the scale. I replaced the thermostat, situation remained the same.
  • I cleaned the rotor arm and cap, and the IAC valve, no changes.
Any ideas on what should I do next? I did a search of the forum and came to a conclusion that I should replace temperature sensor(s) and the IAC valve. Since I cannot source these locally, do you have any recommendations on what brand to look for, and also if I need to order anything else?

Thanks in advance!

Uros
 

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Discussion Starter #3
There is a separate computer for the LPG, but as far as I know it's getting the data from the car's ECU and then controlling the LPG injectors off of it.
 
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