My camaro has been acting funny for about a month now, and I haven't quite pinned the cause down yet. While changing my plugs today, I noticed that my K&N filter was MISSING!!!! Would something like missing a K&N Filter Cone be the reason why my car seems to stumble ~500 RPMs while under load between 2000 and 2500 RPM? The stumble only happens while maintaining my speed or very gentle acceleration. If I press the throttle more than 50%, it accelerates beautifully and without any hesitation. Also, my idle is smooth & steady, but sometimes it will bog down and sputter off the line if I don't accelerate hard. I've already ordered another filter, and I'll be receiving it tomorrow, so I guess I'll know then. I just wanted to know sooner whether putting a filter back on will solve my problems...

 

I dont think so. You may have dusted your engine though. I hope it isnt dirty where you drive.

 

Dusted my engine? Is that slang, or are you referring to the literal term? It's fairly clean where I drive...

 

Yes it would cause it.

Clean your MAF and I bet the car runs better.

But be careful with it. The Mass Air Flow sensor is kinda fragile. I never had to clean mine, but I would say your best bet is to maybe spray it down with Break Clean, or something of the nature that will evaporate but pull the dust/oil/dirt off.

A dirty MAF will cause drivability issues.

 

I have a 93, the only year they made it with Speed Density (aka, w/o MAF). Could the air filter still be a possible cause for the car's odd behavior?

 

I would say that unless you got something in the engine due to not having the air filter on, you should not experience the stumbling that you are. Think about it, no filter means free-er flowing air. May actually give you a little boost. I was agreeing with the post regarding the MAF until you shared with us about not having one. You may have another issue somewhere else. Some may say opti. Do a search on opti and you can probably get a plethera of symptoms to go by.

 

CRC makes a MAF cleaner that is supposed to be less harsh than Brake Cleaners.
My local NAPA had it.
Mike

 

My car has a Delteq DIS on it, so if it was the Opti, it could only be the optical sensor. Would a bad optical sensor allow the car to even run? Would it cause RANDOM stumbling? My car stumbles at 2000-2500 RPM, but only while crusing, and even then, it only happens randomly and occasionally. If the Optical sensor was bad, I'd like to think that the engine would behave poorly in the upper RPMs, but that's not the case at all. In fact, any throttle above 50% and the car accelerates without any stumbling and very smoothly.

I've done a number of searches, using key words like "opti", "ignition", "vacuum leak", etc., but I've come up with nothing (those threads aren't quite describing/resolving my problem).

As far as running better w/o an air filter, I'm gonna have to disagree. The air is more turbulent w/o an air filter, and shouldn't flow as well. Don't forget that I'm running a K&N CAI Kit, and it shouldn't be any more restrictive with the filter on, than it is with the filter off...

 

Do you have an A4 or M6? What are your rear gears? Does it do this around 55-60 mph, more-so up a hill?
I have had my A4 do this (3.23 gears) only on light throttle. THeres a huge post on the board somewhere. Coles notes: I've replaced alost everything and never been able to fix it, a few other people have the identical problem.

 

Mine was originally an A4, but I did all the necessary mods to convert it to an M6. I used an M6 from a 96 Camaro, so it's got the later gear ratios. I've mated that to a set of 3.73 rear axle gears. This stumbling happens in any situation, even downhill. It's completely random, though. I mean, sometimes it'll do it, sometimes it won't at all. Length of trip or engine temp makes no difference either. The only thing that's consistent with the stumbling is that it only occurs around 2000-2500 RPM, and in that range it will sporadiacally dip and surge ~500 RPMs...

 

It maybe a failing throttle position sensor. One can test it with an 'old school' needle type ohm meter connected to the center terminal and one of the outer terminals. Obiviously done with the motor off and its connector disconnected. The meter needle should track the sensors position exactly. Any jumping of the needle during its range of motion would indicator a failing sensor. They normally don't fail all at once, unless wet, they get flakey, if you know what i mean.
Doug

 

The TPS, MAP, Oxygen, Knock, and IAC sensors are all brand new (~2 months old). Could the TPS have been messed up by not having an air filter? BTW, I replaced the air filter cone and that didn't change anything. Also, I've changed about half my spark plugs and that hasn't fixed it yet (not that I'd expect it to, if I only replaced half of them). A friend suggested maybe one of my Delteq coilpacks may be going out...is this a possibility??

 

Sounds like your tip in fuel in your tune is to lean. Get Bryan or Madwolf to fix it.

 

Okay, I'm having a local shop (friend of mind) use his Snap-On diagnostics tool tomorrow, so hopefully that will reveal something. My next door neighbor (who has tinkered with hot rods for over 40 years) rode in it today, and he seems to think it's something electrical, like a loose connection or a wire grounding out...

 

If it was electrical it would do it worse under full throttle.
The Snap On machine may find it if it's not related to the fuel tables.

Do ALL the plugs before having it scanned.