Thread: Rough Idle After Replacing Radiator

Car: 2001 Grand Prix GT - 199k, basically stock.

My car was overheating pretty badly, so I went to replace the radiator and noticed that the motor mount on the passenger dog bone was broken clean off. So while doing the radiator I replaced that. Once everything was back together, the car sounded good and ran good for about a week. Then randomly it would have a chopping idle while driving, and it seemed to be loosing power. This happened more and more. Now it's really rough.

Once I start the car, it sits at like 1300 RPM's until I put it into gear or the car is warm.

While sitting still, the idle jumps from around 800 down to 650 and back forth. If I put the car in neutral, it seems to help a little bit for awhile, then it starts to idle down to 650 and back to 800 again.

While driving, it feels like I have no power and it takes forever to accelerate and the engine on and off jumps really hard. But randomly it will stop and the car will drive just fine and have no issues with the idle. There have been no codes or SES light showing.

I'm not sure if I should start with plugs and wires and go from there or what.

sounds like a vac leak. spray some carb cleaner around the engine at the vac lines when its at idle. if the idle jumps up you found you vac lea area.

I sprayed all around the throttle body vac line and the lines that go close to the MAP and fuel rail and nothing happened. I unplugged and checked the edges for cracks and didn't find anything. The vacuum seemed strong. It seemed to be running a little better after messing around with the lines. Going to drive it tomorrow and figure out if it fixed anything.

you could try un plugging the maf, then starting up the car. if it runs better the maf is bad.

That was the absolute first thing I checked. It ran kind of close to the same really, which makes me wonder if that's bad still. Because the car shouldn't start with the MAF unplugged. Or if it's started and unplug the MAF it should turn right off, right?

you unplug it then fire the car up it now runs in closed loop, like when its cold. if it runs better the maf is bad. in your case id say its fine.

you never want to unplug it when its running.

So I tried unplugging the MAF again and it kind of ran better. Not too much better, but it ran a little better.

I forgot to mention that the sensor that is in the air intake was missing on my car. I also replaced that when I did my radiator. Any reason that might have acted up and messed the MAF up?

not sure, check around the rad, make sure you didnt mess up some wires or a vac line. one may run across the front of the car rad support. if that broke it could cause a vac leak.

Not quite sure how old they are. Just bought the car this past summer.

So I just found out that the SES light isn't even working. So I went in and had it scanned. Over 20 codes came up.

Here are the following codes:
P0137
P0141
P0201
P0300
P0420
P0650
P1107
P0102
P0107
P0113

Seems like a lot of these are caused by one thing. So far I've tried unplugging the MAF and even replaced it with another one I had (new) sitting around. Didn't seem to make a difference in how it ran. Swapped the MAP out with another one I had and it made it a little better, but not completely. And I've changed the vacuum lines on the top of the engine that run along the fuel rail.

Hopefully I can get some insight on this, it's driving me insane.

Thanks.

Shoot man, honestly when I see a car with that many codes I would clear them all and drive the car untill the light popped up again and deal with the code(s) that came up first.

http://www.gmforum.com/obd-ii-troubl.../p0650-286007/ this po650 worries me. bad pcm, and that could be the whole cause of the rest.

hows your grounds? the battery cables are clean and tight, the grounds on the tranny bell housing are good and tight, the wires are tight in the eyelets still?

I second what Scottydoggs said. Did you screw with any electrical grounds? I moved my battery ground like half a foot to a different location because the bolt sheared off in the factory hole, and it totally screwed everything up for like a month. My gauges were wacky, abs lights, trac control lights, charging system failure, etc.

I finally had to drill and tap a new hole right next to the old one and everything magically got fixed.

So I went and had the codes cleared. Turns out it was just the misfire on cylinder 1. The injector was throwing a code, too. So I unplugged the wire from the spark plug end, looked at it, put it on nice and good and checked to make sure all the wires around the injector on cylinder 1 was plugged in right. Went to start it and it ran just fine.

Thanks for all the input.