car hiccups

[tsi95]

i recently had to fix my radiator and put in new struts both at two different shops. when i get my car back the CEL is on and find out its my O2 sensor. find out that it some how got disconnected. after connecting it the CEL goes away. take it out for a test drive and the car does fine for a while. then while i was driving i came to a stop and the car idles at 200rpm but doesnt die it struggles to stay on. I pull over and look for anything loose but nothing disconnected. turn the car back on and it runs fine again. take it home and find out the firing order is wrong 2 and 3 were swapped. car runs fine now except when driving it kind of hiccups if that makes any sense. it drives fine around 2500rpms then it just falls down to about 1500rpms for a brief moment then jumps right back up. can anyone tell me why its doing this?

[97GSTspyder]

Check your spark plugs for proper gap, any oil on them, clean them/replace, etc. Check for any boost leaks. When you say it 'hiccups' it sounds like it probably does this in the boost range? If you don't know how to do a boost leak test, search the forums there's plenty of info.

Also, check the MAS connector. My car did something similar to this before. On a long ride from Pittsburgh, I got off the freeway and the car was sputtering and struggling to keep idle (was around 200rpm). I popped the hood, couldn't see anything that would be causing it, but when I jiggled the MAS connector, the motor came right back to normal idle and ran perfecty fine.

[tsi95]

Actually it did it in the boost range when the firing order was wrong. Now that the firing order is correct it runs fine when boosting. But under normal driving is when it does it once in a while. Theres no boost leaks and I checked all the hoses. I will check out the spark plugs and check the MAS cause there are some exposed wires. Thanks

[tsi95]

ok checked the spark plugs and their fine. checked the MAS and i made sure all the wires were connected. rechecked all the hoses and then took it out for a test run. car seems to be better but at one point it tried to drop the rpms but then it just kept running fine. i will need to take it on a good long run tomorrow

[tsi95]

Took the car out for a good run boosted and came to a stop after that the car idled again at around 200rpm. CEL code p0300. Pulled over and checked the connections and it was still idling at 200rpm. I unplugged the battery to reset the code and turned on the car. It ran fine. Checked the coil packs and connector are fine. I replaced the crankshaft sensor a while back. After I put everything back together thought to see if I get the CEL again. The car has never run better. So i'm all out of ideas I guess I'll keep driving it until I get the CEL again. Anyone else know what I can check?