Stumbling, Lurching when stepping on it

[mutti_wilson]

I have an 01 LGT and just the other day i had changed the oil and took it for a drive. I noticed it stumble a bit. The AC was on, so i figured that was it. I kept noticing it though, and now i can really feel it. If i have it in 5th at 2k and floor it, it just starts bouncing and jumpin and feels horrible. It almost died on me yesterday while stepping on it in 2nd. It is fine when accelerating slowly, but anytime you get into it at all, it jumps and stumbles. I was thinking fuel filter. I have no check engine lights on and nothing was changed that would cause this.

[deadlydave]

Did you check your spark plugs and ignition wires? Did you check your air filter?

[boxerpower]

what else did you do when you changed the oil? possibly.... disconnected a wire?

[Huffer]

I call dibs on a vacuum leak or Air Flow Meter being messed up.

[mutti_wilson]

I was thinking about the vaccum angle just a bit ago. I'll check all the lines i can see. I didn't pull anything knowingly.

[shazapple]

I'm going to go with loose/bad plug wire. Mine would stumble if I stepped on it. Come to find out that one of the wires was broken! It still will stumble if the wires are loose at one of the ends.

[Reason]

Did you get the knock sensor wet? Every time mine would get wet (cracked knock sensor) it would do what you are describing.

[mutti_wilson]

I checked the vaccum lines, I dont know where the MAF is. Is is right after the airbox or is that the TB? Where is the knock sensor located. How would i get it wet?

[Huffer]

I checked the vaccum lines, I dont know where the MAF is. Is is right after the airbox or is that the TB? Where is the knock sensor located. How would i get it wet?

You don't have a MAF, you have a MAP sensor. They don't usually fail.

I think shazapple/deadlydave is going to be right with the bad plugs/wires.

[deadlydave]

Sorry to be a pest, but did you check the air filter. I lost an oil cap on my old soob, and my air filter sucked up all the spillage and ran like poop. But the top of the carburetor was right next to the oil filler cap, i suppose it'd be unlikely this would happen in newer cars.

[mutti_wilson]

It's too far away for something like that to happen. I'm just not seeing how a wire would go bad for no reason. They haven't been touched since i owned the car. I'm not against replacing them, but I'd rather not spend 40 bucks for new wires only to find out its something else. This morning it almost idled til it killed itself. If a plug wire is cracked and it's missing, you can feel the rough idle and the miss. A bad plug/wire probably isnt going to make it idle way down smoothly. Seems like some electrical issue. Maybe i'll take it to the dealer. I'm not about to start spending dough replacing sensors.

[Huffer]

It's too far away for something like that to happen. I'm just not seeing how a wire would go bad for no reason. They haven't been touched since i owned the car. I'm not against replacing them, but I'd rather not spend 40 bucks for new wires only to find out its something else. This morning it almost idled til it killed itself. If a plug wire is cracked and it's missing, you can feel the rough idle and the miss. A bad plug/wire probably isnt going to make it idle way down smoothly. Seems like some electrical issue. Maybe i'll take it to the dealer. I'm not about to start spending dough replacing sensors.

Umm... stuff does break for "no apparent" reason... it's mechanical. Sometimes thing fail. An engine is basically an airpump with thousands upon thousands of small explosions going on. There's a ton of vibration in there that you can't see.

Wouldn't hurt to pull the plugs and see - it's a SOHC so it's going to be easier than on a DOHC...

[deadlydave]

a cracked or shorting knock sensor threw a check engine light on my car. It is held against the engine block with a bolt, towards the firewall.

Did you buy this car from the dealer? How many miles have you owned the car for? Are the Ignition wires brittle? You said you haven't touched them for the life of the car, they just go after a while :-? . Are the spark plugs fouled? You can remove them and look at them for free. :smile:

[mutti_wilson]

I've put about 20k on the car since i've owned it and its around 100k now. I pulled wires last night and reseated them and them felt supple. I can pull the plugs and check them, thats no big deal. I'll look at that knock sensor too. I had no idea where it was.

[Reason]

You know with heat,vibrations and 6 years of driving wires can break no problem. You are most likely due for new plugs and wires so just changed them to see what happens. I figured the same thing but thought I throw something else at you like the knock sensor.

[Chicago96GT]

It could be the plugs, but im having the same problem and i have new plugs and wires. Still havnt figured it out and i have no clue, no vacuum leaks or anything. Although my knock sensor is bad and it has been. It didnt do it before when my knock sensor was bad maybe it just got worse though. Getting a knock sensor soon and i will see what it does.

[mutti_wilson]

Post here when you get that replaced. I want to know how that works out.

[bubaru21]

i am also having the same problem as well. i just did plugs,wires,fuel filter. i am cleaning the air filter now though so we will see. but the knock sesnor how hard is that to replace?

[mutti_wilson]

Well, it's gone now! I changed the plug wires, drove it, no difference. I unlatched the fuel filter, shook it, relatched it and took a drive. Runs perfect and has the rest of tonight. Whatever :-?

I did notice something wierd (to me at least). When I changed the plug wires all 4 wires were covered in oil of some sorts. Whats up with that? Is that some sort of weatherproofing maybe?

[deadlydave]

Well, it's gone now! I changed the plug wires, drove it, no difference. I unlatched the fuel filter, shook it, relatched it and took a drive. Runs perfect and has the rest of tonight. Whatever :-?

I did notice something wierd (to me at least). When I changed the plug wires all 4 wires were covered in oil of some sorts. Whats up with that? Is that some sort of weatherproofing maybe?

was this the part of the wire that plugs in to the plug?

and Bubaru21, the knock sensor is easy, at least it was on my 2.2L. just make sure you wait for the engine to cool off all the way, so you don't burn yourself like I did.

[Huffer]

Well, it's gone now! I changed the plug wires, drove it, no difference. I unlatched the fuel filter, shook it, relatched it and took a drive. Runs perfect and has the rest of tonight. Whatever :-?

I did notice something wierd (to me at least). When I changed the plug wires all 4 wires were covered in oil of some sorts. Whats up with that? Is that some sort of weatherproofing maybe?

You might want to change out the fuel filter - or check your lines don't have obstructions.

The "oil" on the wires is probably dielectric grease to help the plugs make better contact with the wires - or it's a grease to help facilitate easy removal when they need to be replaced. It probably also helps to seal out water around the plug boot.

[mutti_wilson]

Cool. I was thinking that too. I was just shocked when i pulled the first one off. Never seen that before. I am going to pick up a new filter, i'm just glad it's running good now so i can drive it in the meantime. Any recommendations a filter. I found a bosch online for 30 bucks shipped.

[Huffer]

Cool. I was thinking that too. I was just shocked when i pulled the first one off. Never seen that before. I am going to pick up a new filter, i'm just glad it's running good now so i can drive it in the meantime. Any recommendations a filter. I found a bosch online for 30 bucks shipped.

I just buy the AC Delco or Bosch ones from my Autozone or Murray's Autoparts store. As long as the construction is good, it should be fine. I paid $30 retail.

[Reason]

Wait what end was the oil on? If it looks like engine oil on the spark side you may have bad seals.

[deadlydave]

Wait what end was the oil on? If it looks like engine oil on the spark side you may have bad seals.

That's what i was thinking before.

[TRUBLU]

Time to replace that fuel filter buddy!!You are replacing it every 15,000miles right?

[studum]

Wait what end was the oil on? If it looks like engine oil on the spark side you may have bad seals.

Been there, done that. The part that connects to the spark plug itself should be dry. If you have oil on the outside of the plastic tube that goes over the spark plug your valve cover gaskets need to be replaced. Now is the time to take a peak and see if any of the washer / gaskets are leaking at the bolts that hold on the valve covers. If you have any leakage there (would be external) you might as well replace those too.