Thread: Stumbling then stall cold and warm start.

So ever since I got my exhaust work done my car has been acting odd. First I'm thinking its the for but I'm not sure. On cold and warm starts it stumbles and stalls if I don't press on the gas to at least 1k rpm sometimes 2k rpm. Some times I get the p0420 code. My o2 sensor seems to move slowly and doesn't even reach 9mv according to my torque app. My iac is around 58 My maf use to be around 5.4 now its over 6 and goes up when it starts to stumble. Also when it does stumble I can hear the vacuum pulling close to 0 before it stalls. Please help.

No I was going to do that when I do my lim gaskets, but my boost gauge stays at -20 so it can't be a vac leak

Well the cleaning didn't help, nor disconnecting the battery. So now I'm thinking the o2 sensor? On another note, I broke a stud in the TB.. Great. Now it's leaking coolant.......I just can't catch a break.

Update: since the cleaning it's been acting normal somewhat, but when Idling it feels like the engine is slightly misfiring. You can't notice it unless you're actually paying attention.

check your vacuum lines, mine was giving me fits and I ended up tywraping all of the hose connections and the stumbling went away.

I already went over those and replaced most of the line fittings with silicone hose

Subscribed - this happens to me on both cars too, and I've cleaned out the intake tract.

Did you change any ignition components? This is what I'm doing next

On a former car, I changed out all of the ignition except coils. On the two cars I have now, I have only changed out plugs & wires.

In my mind, even a poor ignition is still sufficient to get the job done under startup conditions - since my engines run great under much heavier loads, it seems that the ignition should have a "breeze" of a time getting the job done at idle.

So it must be my o2. I got code p0133 and p0440

Or you could still have a vacuum leak...

True but where? The lim? This started happening after I had my stock downpipe but in, a resonator, and mufflers.

I guessing you checked the EVAP lines? Have you tried the propane torch test? The O2 slow response and EVAP codes can and have been known to be caused by vacuum leaks. I have chased vacuum leaks for a week and still seem to find another one just about every day. Brake booster vacuum line, the other end of the line. The connection to the MAP (both ends, at the MAP and the tube to elbow). Fitting at the front of the SC under the snout, the other 2 connections on that T. The bypass solenoid and the line to the bypass solenoid itself. The other end of the bypass valve (each end). You have to remember a lot of these lines are not only under vacuum but pressure as well and with it flip flopping between vacuum and boost so it's pushing and pulling on the lines all the time (the ones on the outlet side of the blower anyway).

Jeff

What's the propane torch test? I'm going to order some silicone hose and replace everything

Are any of the lines by the charcoal canister by the drivers side rear wheel a place to check for leaks?

The propane test is using a propane torch with a length of tubing fit over the end. Start the car, preferably cold, slightly turn on the torch. Not enough to light it but just enough so you can use the tube end to probe areas that you think may have a leak. When you get to the vacuum leak the idle will change. If you don't feel confident doing it don't. Mechanics have used this sinc way before I was born.

Can't help you with the routing, I've had several BOP cars with the 3.8, but most weren't SC'd and my GP is an 05'. I'm sure someone else will chime in though.

Jeff