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Old 09-28-2017, 11:13 AM   #8
Claybury
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Join Date: Oct 2016
Location: Mille Lacs
Posts: 178
Default Re: Limp mode when I accelerate or use air codition

I hope the ECM fixes your problems. Many bad ECM diagnosis are actually poor grounding issues.
I don't know how your mechanic measured the throttle body power. The throttle motor is driven in current mode by a bidirectional push/pull amplifier. Voltage measurements are largely irrelevant and specialized equipment and a break out harness are required to make the current measurements. Also ECM's don't "put out power", normally the circuits are all sinking power to ground. Power comes from the DC buss voltage. Looking for voltage on the ECM pins is pointless except to see in the power is getting to the ECM.
If the Throttle body or ECM were the problem you should have had P0121, P0221, and possibly a P02135 code. These would mean the throttle is not responding properly to the computers requested position.
An other part of the throttle system is the accelerator pedal position sensor. It is easy to test these parts if you look at live data from the APPS and TPS sensors while slowly depressing the pedal. They should go up and down hand in hand.
The big clue you have is the problem happens when the A/C is turned on. If it were me I would watch the DC buss voltage at the fuse box connections and see what it is dropping to with the car running and when the A/C is turned on. If it is dropping excessively check the cables, ground, battery, battery terminals, and alternator.
Next thing would be to check the engine load live data to see if the the A/C is putting an excessive load on the engine.
After that check the O2 sensor data and the MAF sensor data.
The MAF sensors on these cars are problematic. They will feed bad data to the ECM long before they will throw a code. This can make the ECM think the throttle is open far enough when it is not. It should be reading between 3 to 7 grams/second at idle and increase smoothly as the throttle opens.
The MAF is easily damaged by water. The L series intake is susceptible to ingesting water into the air cleaner box if you drive through a puddle or heavy rain, or a car wash. They even put drain holes in three of the boxes four corners.
One other thing is the 3.0's do not like ethanol. The factory put out TSB's basically saying there will be drivability problems if you put over 10% in the tank. The engine and it's controls were developed prior to the European ethanol directives. It's an Opel engine built in England BTW.

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2002 SC2 1.9L
2007 Vue 3.5L
1985 Fiero SE 3.1L
1974 Triumph Spitfire 3.1L V6
2002 Ram duelly diesel 5.9L
1975 Honda PA50 0.05L (Swarm and destroy)

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