Idle issue

[davemilton]

I just bought a 1990 Eclipse GS Turbo about 3 weeks ago. I work a lot so I really don't have enough time to read up on forums and what not to troubleshoot my issues. When I first bought the car, I noticed that it idled funny. When I start the car, it runs at about 2grand. After it warms up for about 3 minutes, it drops to 900rpm. When I start driving it, then come to a stop light, it revs from 1grand to 1500rpm, then back down to 1g, and back up to 1500, and it does this for about a minute, then drops down to 900rpm. It doesn't seem like it's running smoothly at 900rpm, either. I have changed the oil, oil filter, spark plugs, air filter, radiator, and thermostat. After all these changes, it seems to be idling better than when I first bought it (because it would take a few minutes longer for it to idle back down to 900rpm), but I'm noticing that my mpg has dropped quite a bit. I noticed this about a week and a half ago, when this flex pipe that connects the downpipe to the cat, blew off from the cat. Also, after this happened, my car backfires once i get up to 5grand in 3rd gear; and this is after the oil and oil filter change, spark plug and air filter replacement. I figure that there could be a ton of things that need to be looked at, but where should i start? Any help would be greatly appreciated. Thanks!

 

[Dsmkauai]

I would do a boost leak test and also check your iac and verify its within spec.

 

[LiquidX]

Boost leak test and go through the idle surge test procedures. Post back after that is done.

 

[92AWDHX40]

Terry's Talon Troubleshooting Tips #3 - Fast Idle (aka. Idle Surge)

i had the same problem when i first got my dsm found out it was the isc, after talking to my buddy
matt here i swapped it out and, problem was fixed.

 

[davemilton]

Okay. So i tweaked the throttle body, new tps, swapped out the 14b turbo and the stock exhaust manifold with a super 16g and a tubular and it idles perfectly.

 

[USAF 98 GSX]

Good to hear, I had the same issue for about a month and I was fed up with people giving me the run around of what it might be. So I did the same thing you did, REPLACE everything that might be the problem.

 

[davemilton]

I also replaced the stock 2 1/4 downpipe with a 3 inch downpipe cat-delete, but it connects back up to the 2 1/4; if anyone knows where I can find a 3 inch catback, let me know. But yeah, it's running great!

 

[rEclipserGST]

Ebay.

 

[DSM1G90]

..Bet you had leaks like crazy and it took a major changeout to cure the issue.....fun.

 

[ariman]

something happens to me similar, this weekend i'll do boost leak test and clean the TB

 

[davemilton]

The 60 lb cat that I ripped off was clogged up also. It wasn't even the stock cat that was hooked up. Haha, looked like it came off a 92 Lumina. I did the downpipe swap before everything else and still had a little idle surge, but it was running better. That cat created too much back pressure.

Ebay.

The only catback I saw on ebay for a 1g dsm was for an awd. And the only fwd exhaust that I have found in my area, on Craigslist, is for a 2g. Doesn't work. Jacked up the back of the car and put his exhaust under mine. Probably going to have to go to a local fab shop and have it custom made. I went to an exhaust shop and they wouldn't bend pipe over 2 1/2 inches. Ridiculous. I went their planning on piping out my intercooler setup.

 

[slidesidwayz]

Did you have to replace your isc?

 

[davemilton]

Nope. I was going to do that next though, if my idle surge got any worse after the turbo and manifold swap. It makes pretty good sense that it fixed it; less back pressure with the downpipe cat-delete, and better exhaust flow with the tubular. I am having a separate issue entirely, though. Power steering fluid leak out of the rack. $117 for the rebuild kit . This will be fun. Not! But I just got my boost controller in today, so I'll at least have that to look forward to for tomorrow.