1996 Geo Tracker idle

[Garemie]

Hello everyone,

I present you with yet another idle issue.

When the car is warm, and after you accelerate, it will return to normal 800rpm and then drop to 500-600rpm and bog for about 2 seconds before returning to normal rpm.

What could be causing this?

Cheers!

[fixkick]

sounds to me like the classic egr main sticking
each time you stop. and speed goes below say 1/2 MPH, or zero. the ECU commands the EGR closed then or if it sees the idle switch close.
many times it will not, and engine rpm falls like a rock.
its not idle controls, i think.
the fast right foot works but takes lots of action to wake it up this, is the EGR main, dumping exhaust gasses , when it must not.
if the right foot works fast and easy here (stall or near) the ISC failing.. if not EGR leaks.
pretty much....

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what i do, on the cold engine is blip the EGR diaphragm, by hand , with finger. key in pocket.
it must move easy and drop back each time with assuring thud.

push here. (under 96up page)

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see that inside metal ring, that is the test ring, to push it.
one other test is to get it closed. then unplug the vacuum hose NOt larger bark hose)
and then golf TEE the sucking hose side (up stream)
if the stalls now end,? BINGO.
takes like 5min work do this ,this, not test, just hose hack.

[Garemie]

I just replaced the EGR valve thinking it would fix it a week or so ago. It didn't fix the issue.

You suppose it could be the ISC failing? Is this due to vacuum? Or an actual failure of the unit itself. I've pulled the ISC and tried to clean it before.

[fixkick]

automatic or manual trans. ?
NEW EGR OR USED? (the EGR is 5min work to eliminate, close it by hand if stuck open, and plug the vacuum line.
if the throttle, at failure allows you to race rpm faster (super easy,) as it stalls easy, its NOT the EGR. EGR sticking open takes agressive right foot actions.
if super easy to raise RPM with right foot action, it can be the ISC, sticking closed, or the idle switch dead. (open switch , due to calibration of TPS wrong)
if you defeat the EGR, and it's hard to raise throttle at fail ,its low fuel pressure. (low fuel pressure would blog, not misfire, is it misfing at failure (rough)

id need to know what happens in details, at stall. (near stall)
i can see the EGR fail as I stop, is see rpm drop like a rock below 800 (the ecu tries to hold it but cant)
the RPM drop is one of 3 things.
EGR stuck open (hard to save but can)
ISC stuck closed (sticking, or dead because TPS calirbration wrong, and x10 that on automatics in Drive. the M/T has no load on engine, with chutch in, unlike automatic trans.
the engine is misfiring badly due to many reasons.
or is bogging from lack of fuel..

tell me what the right foot action does at the moment of failure.. when you use the right foot, you are adding air, the MAF sees that and the MATCHes fuel to air and engine races.
if it can't race, at failure. no matter how aggressive my right foot is, and it's misfiring now, it can be flooding or if it bogs, hard. it's lack of fuel;....
what it does at failure, with you correcting it , solves, this.
easy to save?
hard to save? tad had but can. EGR leaks)
impossible to raise throttle.?
bogs more?
misfires hard.?

i take it the CEL lamp is not glowing running , right? but does at key on.