2G Idle surge that fixes itself

[Dawson159]

I have a 98 Eclipse gst with 127k miles that has really weird idle surge.

When you start the car will idle surge minorly, not bad, and will do it for a while and randomly spike up to 2k rpms then settle at around 1k rpms where it’s supposed to be (depending on how cold it is outside). But if you tried to drive it before the idle spiked and settled it would get to 2k rpms and sputter and jerk until you hit boost then it would slingshot you forward then would surge really bad if you came to a stoplight between 300-800 rpms which made it pretty much undrivable.

I researched it and thought it was the TPS so I replaced it and started the car and it didn’t surge at start or anything so I thought it was fixed so I went to drive it and it was fine until I parked at Target then started it up again and it was back to surging again. So I drove it to see if it would jerk and sputter and it did but only half as bad (almost unnoticeably) but then when I came to a stop light it would idle surge REALLY bad just like before I replaced the TPS.

IDK what’s wrong I’ve replaced the IAC, the TPS, bypassed the FIAV, and blocked the EGR.

I don’t know what else it could be the weirdest part is that it fixes itself after about 3 minutes of idle then it drives perfectly fine. I really thought it was gonna be the TPS unless I installed something wrong. It was a used TPS BTW.

What do you guys think? Thanks in advance

 

[Dawson159]

Have you gotten any check engine lights yet?

No

 

[AWD-Tony]

I reread your post. Was the tps adjusted properly? .63v in link at operating temp. Also think you should post a log to monitor sensors especially coolant temp. Another thought was you have a bad connection somewhere and when you replaced the tps, it made contact until it came loose again. Consider playing with the harness while this happens. Did you replace throttle body shaft seals yet? They’re only a few bucks but you should also replace both throttle body gaskets and BISS o ring while you have it off.