Taubr Unit

iTrader: (32)

My buddy has a '00 camaro with a lq4 swap, cam, ls6 intake etc..basic combo and 6sp. Bought the car about 6 months ago and it ran perfectly fine and strong! Car sat for 2 weeks while we put a rearend in it and now it has nothing but problems. First start and drive it runs perfect and strong, one it gets up to operating temp (closed loop) it runs like ****. It will idle fine but anything over half throttle it just falls on its face. Let the car sit and cool off and runs fine again until it gets hot and runs like **** again.

Car never showed signs of issues before it was parked for 2 weeks so why all of a sudden it runs like **** when hot? We put new o2 sensors in it and it got even worse when hot so now I'm really lost. Any tips or anything else we can try?

G Atsma

Something is putting it in "limp-home" mode.

computerz

When you worked on the rear end, did you remove the exhaust? cats? If you did, maybe it's related. you already replaced o2 sensors though.

Does he have any error codes? Maybe the o2 sensor wiring harness got pulled and tugged something loose?

If you rap the cats with a rubber mallet, can you hear any pieces rattle inside?

2xLS1

iTrader: (25)

There is no such thing as limp home mode. You really need to stop.

Taubr Unit

iTrader: (32)

Car has no cats and we did have to cut the exhaust off but it's right I'm front of the rearend and that I don't see doing it. People run open y-pipes and cutouts on stock cars without issues so I don't see why that would make a difference. He did say it got way worse with the different o2s in the car vs the ones that were in it.

When he bought the car the cel was on for a bad bank 1 o2 sensor but still drove fine, even drove it home 2 hrs after buying it. Ever since then it's ran real strong until it sat so that's why we changed them out figuring that was it. Put different ones in and he said it felt stronger when cold (open loop) but again after a half hr or so when hot and goes into closed loop it runs even worse now vs the bad ones, lol.

98redorangeta

iTrader: (10)

Try tuning closed loop off even when it's hot that will narrow down what you are looking for.

A log of it will help too if you can get it.

G Atsma

I will stop when other knowledgeable people quit using the term to describe when ECM detects a fault and decreases power by a BUNCH. It is a slang term, but it does exist.

BigEd_72455

iTrader: (7)

Did you guys check the fuel system? Fuel filter(s)?

Maybe from having it sit, something may be settling
and opening up the fuel flow, but once you start driving
it, the blockage returns.

See if you can put a fuel pressure gauge on the rail and have it somewhere you can see it easily. When it starts to run like crap, start watching the fuel pressure to see if it is getting below normal pressures. Some engines ran at 48, some at 60 psi.

I may be completely wrong, but it cant hurt anything to check.

Compsystems

without a data log or more facts to help narrow it down, youll get 1,000 guesses.

Your best bet is to data log all the sensors (coolant, TPS, O2's, MAP,Spark..ect) so we can see whats causing it to run bad.


if you have no way to data log, you can try disconnecting the battery overnight to reset the pcm, and unplug the 02 sensors. This will force it into open loop. If the problem goes away you know its related to that.