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1990 4.5 is possessed


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I have read a couple of posts on this forum (of which I am a newbie today) and am lost without direct relation to my engine type.

My 1990 Sedan (whom I normally love dearly) has begun to decide on her own that a higher idle and cruising without the need of applying the accelerator is better for her personality (I am thinking the "let's go get 'em" type approach). Needless to say I am burning up my front pads trying to hold her back and/or slow her down (black whitewalls... a sin).

I have about 165,000 km (around 100k miles) on it and it has been babied by my parents for about 6 years. I recently replaced the O2 sensor and cleaned the throttle body a bit by spraying some TB cleaner down the throat.

My Service Engine light is on from the time I turn the key until the car is shut off. I am used to other cars activating the light after a short period of driving.

I have heard of adjusting idle and ISC and TPS controls but where to look for them on my car?

The error codes recorded are as follows: E39, E49, then E49 again, then F47, F49, then FF 47 then .7.0.

Any Ideas out there among the gods of experience with my misbehaving mistress?

Thanks, :)

Mike P

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make sure the throttle blades move freely ( no carbon deposits contributing to sticking), clean the egr tubes inside the throttle body with a hanger wire

The saddest thing in life is wasted talent

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E49: AIR injection problem

On mine it was a stuck solenoid on the AIR divert valve. This valve is located above the rear rocker cover towards the front of the engine ( I know it should be right or left bank, but I still get confused which one is which) and has a number of rubber hoses going to it. If I recall correctly about 4 hoses and there are 2 electrical connectors going to the 2 solenoid valves.

The solenoid valves over time get stuck open and this sets of the E49 code & SES light. Its not a big deal and you dont have to worry about it. I just fixed mine coz the black tape kept falling off from over SES light :D and I got tired of seeing that light shining in my eyes at night.

A new AIR divert valve cost a lot of $$$$, is a special order and only available from a GM dealer. My solution was to get a valve from junkyard or salvage yard. I found one for a 89 Deville which has different fittings but I took the solenoids of it and replaced the ones of mine with them.

E39: cant recall what it isthough. Will lookup in the Service manual tonite.

Not sure how fast its idling but have u tried doing an idle learn procedure but then u dont have a n E52 code either.

This is off the top of my head dont have manual in front of me.

IDLE LEARN Procedure:

1). Bring the engine to operating temp. > 80C around 95C, You can check coolant temp when at .7.0 (diagnostics ready mode) hit the Lo button, wait a sec and then the high until u see P.0.4, thats yr engine coolant temp. Exit Diagnostics by hitting the Auto button.

2). Climate control in OFF mode and wheels straight ahead, foot of the gas. Let the engine idle for atleast 10 mins.

3). Foot on the brake, Place car in Drive and let idle for atleast 3 mins.

4). Foot on the brake, Place car in Drive and ECC in Auto let idle for atleast 3 mins. ( You dont need to do this step as I can tell u are out of A/C refrigerant F47, F48 codes)

5). Turn ignition off.

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