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View Full Version : headers in, now car barely holds idle...thoughts?



6Speed
04-19-2009, 11:48 AM
Pulled off the hooker lt in favor of some LPP lt. Finished everything up this morning and when I cranked the car it will barely hold an idle. It does have a 306 cam but it never had a problem idling (pcm4less tune, daily drove the car for years). It used to idle around 850 or so, and after the headers it's idling at 1k and then dipping down almost dying and then bouncing back up. I'm wondering if the oxygen sensors need to be changed?

I noticed last night that somebody spilled some oily substance on the shelf I had my oxy sensors sitting on and some got on the end of the sensor. I wiped them off but wonder if that's the problem? They weren't completely soaked or anything, but there was definitely oil on the ends.

I also wonder if there is a sensor I forgot to hook back up. I got the pcm ground on the block, knock module hooked up, both starter wires, both oxygen sensors, cps, just tryin to remember all the connections I unplugged underneath.

Not getting a check engine light yet but I've only let it run for about 2 minutes. thoughts?

Colossus
04-19-2009, 11:54 AM
Its your O2's. Before I bought new ones, just me cus I'm cheap, get some electrical cleaner and spray it down in the connectors. Don't wipe or anything just spray it, let it dry, spray again a few times and try it again. In both connectors because when you plugged them in you would have now gotten the connector in the wire harness dirty. Try that and see what happens. If no go clean out the harness connnector again and go for new O2's. Your car will run off a pre-set O2 reading until it warms up and 2 minutes isn't long enough to get you there, hence the lack of SES light. Good luck man and I hope its that simple.

6Speed
04-19-2009, 11:57 AM
Well, the oil wasn't on the pigtail, it was on the metal end that screws into the pipe. Should I try the same steps but on that end, or no?

Also if the o2's are the problem and the car is running in open loop right now, shouldn't it run fine until it warms up and hits closed loop?

The only other thing I wondered about is I changed the plugs and wires too, and wonder if I crossed two of the wires. I highly doubt it since I double checked everything...just trying to run all the possibilities through my head.

97lt1camaro
04-19-2009, 12:16 PM
Check the plug wires. Im putting money on that before o2'ss. I changed my headers last summer (lt's coated) and am now just replacing the o2 sensors on mine.

VendettaV8
04-19-2009, 01:57 PM
after my last header changed i had a o2 sensor that failed...

Adam
04-19-2009, 02:03 PM
You guys sound like you're on the right track. It's really hard to tell if an O2 is bad without scanning your vehicle with a device. Do you have a cable that may have been used to upload the new tunes to your pcm? Or did you mail your pcm in to get it tuned? If you have the cable, than i can give a link to some free software to determine if and which O2 is bad. Pay careful attention to burnt plug wires as well. I'm not sure how you have them routed but on my lt1, I burnt 3 sets with similar idling issues until i brought the wires up and over the valve covers.

Typically with burnt plug wires the car won't idle correctly and stumbles harshly under lower rpms and then smooth out at higher rpms. If it stumbles for long enough it will throw a check engine light.

If the O2's are bad you will typically run very rich and have alot of exhaust fumes. The car might not throw a check engine light at all. Your fuel economy will suffer, and you need to get new ones asap to prevent an extreme rich condition which could cause to much fuel getting into your oil which leads to ring and bearing damage.

6Speed
04-19-2009, 02:13 PM
wires are routed in the stock location on the passenger side through the stock looms. On the drivers side they are all in stock location except for the #5 wire is routed over the valve cover. I do have a akm cable that I upload tunes with. what free software is there? I had lt1 edit but the laptop it was on crashed long ago and I haven't had much of a need to upload any new files recently so I haven't bothered with trying to get another copy.

Adam
04-19-2009, 02:17 PM
Try running this and post what your 02 readings are cold and warm.
http://www.geocities.com/MotorCity/Shop/1624/pcmcomm.zip

6Speed
04-19-2009, 02:19 PM
awesome thanks! I will have to wait till my g/f gets here with her laptop. I unfortunately only have a desktop. Gives me more of a reason to pick up one of those little Asus 10" netbooks. :D

95formula383lt1
04-19-2009, 02:22 PM
i highly doubt its o2s, i have a cc306 long tubes ported heads intake bigger valves, no tune and no o2s at all for right now and mine idles great 950rpms and sounds great. is it a SD car or MAF? i agree with plug wire issues, maybe fuel issue or MAF if its not SD, or intake gasket leaking?

Colossus
04-19-2009, 03:28 PM
Go quadrouple check all your plugs wires. You could try cleaning the O2's as well. I Only burned one plug wire on my LT's routed mostly stock. There is some Zip Tieing I will admit. But as soon as that wire burned through I knew exactly what happened. Good luck, man.

Adam
04-19-2009, 04:33 PM
awesome thanks! I will have to wait till my g/f gets here with her laptop. I unfortunately only have a desktop. Gives me more of a reason to pick up one of those little Asus 10" netbooks. :D

Every time i retune my car, I have to setup my desktop in my garage. Ha, it sucks.

6Speed
04-19-2009, 05:23 PM
I'll check the plug wires. Does anyone know if any of the lt1 software will work with linux? One of the mini laptops I'm looking at comes pre loaded with linux instead of windows.

gregrob
04-19-2009, 06:07 PM
How could it be 02's since it doesn't even use them during cold startup? Just an observation

6Speed
04-19-2009, 07:48 PM
well the problem went away on its own mostly. The only other thing I noticed is that one of the primaries is hitting the k-member at times and I noticed the idle gets funky when i feel it vibrating/knocking against the k-member. Could it be that the pcm is pulling a lot of timing when it senses this "knock"?

gregrob
04-19-2009, 11:44 PM
I would bet so. I would get that fixed, you dont want your nice headers hitting the K member. You could do an LT4 KM for extra insurance although you technically dont "need" it until you do Roller Rockers.

Or so I've heard.

Adam
04-20-2009, 04:14 PM
I had to get an lt4 knock module just for my roller rockers. So it your headers are hitting the kmember I would definately assume it's pulling timing. That program i sent you will also pick up knock. Find a windows computer and scan it to be sure. The software is rare enough in windows, if you want it in linux expect to paid big $$$.