99 Grand am 2.4 hard to find problem, please help

Damname

99 Grand am 2.4 hard to find problem, please help

Unread post by Damname » Mon Aug 23, 2010 9:25 pm

Hey all thanks in advance.

SES code p0507 idle control system, high rpm

What she is doing is:
-idling rough in reverse
-idling rough in general
-while moving if i take my foot off the gas it dives down to 750 rpm and surges between 1000 rpm and 1500 rpm. each surge in rpm (happens 1 per second) equals a lunge. it will surge and lunge maybe 5 tomes in a row then even out. other times it will do it the whole time my foots off the gas.
-from a dead stop and without hitting the gas it will accelerate to 30 mph by itself showing about 1200 rpm
- engine seems to have plenty of power with little to no hesitation. it will squeal tires from a dead stop if i stomp it even while the problems are happening.

This is a very frustrating problem. I have tried several things to fix it so far but nothing works. Sometimes the problem either gets better or worse whenever i take off the air intake from the throttle body to test something.

here are things i have tried so far.
-checked for vacuum leak with starting fluid. no change in rpms or anything noticable.
-changed the TPS sensor
-changed the idle air control sensor
-tested the map sensor
-changed the plugs and boots. replaced the plugs with ngk iridium (7 bucks each)
-checked all the vacuum lines

I honestly dont know what else to check and i am running low on funds. Has anyone had this problem? Might it be possible that this is a tranny problem in disguise?

please help

MeccBoy

Re: 99 Grand am 2.4 hard to find problem, please help

Unread post by MeccBoy » Mon Aug 23, 2010 11:41 pm

Great description. I can almost feel what it is doing.
I would assume you cealaned the bore the idle air control valve goes into. Did you also clean out the throttle plate and bore?
Does not sound like a transmission problem.
Code P0507 is a strict relationship between the PCM and the idle control valve.
The engine is hunting for the correct idle and closed throttle position.
Check the wires at the valve. Broken wire strands inside the colored insulation of a single wire can cause these problems. Pull on each individual wire with one finder while holding the plastic connector with the other. If there are broken wire strands, the colored insulation will stretch.
Can also for the heck of it disconnect the battery for a few minutes, then start car and let it idle on its own for a few minutes, then shut it off for 30 seconds, then start it again. If any work was done prior to this problem, sometimes the PCM needs to relearn minimum idle.

lonewolf
Posts: 1
Joined: Mon Jan 07, 2013 8:24 am

codes po420, po171, po301

Unread post by lonewolf » Mon Jan 07, 2013 9:15 am

I am at my wits end with this it started out with po420 then everything went to crap - replaced battery, plugs, oil, air filter, checked for leaks only thing I have left to do is clean o2 sencors and change fuel filter - repair manual calls for pcv valve on oil air separator but not one - a piece of pipe in its place - can I put the pcv in middle of hose - what else can I try

User avatar
TerryAuto
Posts: 313
Joined: Fri Dec 11, 2009 8:48 pm

Re: codes po420, po171, po301

Unread post by TerryAuto » Mon Jan 07, 2013 1:37 pm

What engine size is in your Grand Am?
How does it run?
Anthything done to the car prior to these codes?

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