hesitation at 3000 RPM

**JWSmythe** · 03-22-2010, 08:56 PM

G'morning all.

I'm working on a friends 2000 Camaro SS. It's an LS1 (obviously) with a 6 speed, and ASR. It has 104,000 miles on it. It's completely stock.

When accelerating moderately (25% to 75% throttle), it goes up to 3k RPM, hangs out as if I wasn't pushing on the gas for about 10 seconds, and then finally accelerates.

I thought it could be the ASR thing on the throttle cable (ugly box on the passenger side with the throttle cable attached) so I hit the switch to turn off ASR. That didn't help. I pulled the electrical cable from the box so it couldn't possibly make a difference. When I took it for a drive like that, the ASR Disabled (or whatever the actual text is) light was on, and the switch didn't do anything, but the problem still exists.

It starts and idles fine. At WOT it doesn't seem to do it. Once it passes the problem at 3k RPM, it accelerates fine after that up to 6k RPM, so that really eliminates most of the normal problems (fuel flow, air flow, clogged cat, worn out plugs). I serviced the K&N air filter only about 3000 miles ago, but the problem existed before that.

There are no indicator lights on. I hooked a scanner up, and there are no pending codes, and glancing through the values on the sensors and they look to be the same as my '00 WS/6 (same config except the ASR, same year and mileage), so I'm assuming the computer is working right, and it's not a sensor related problem.

It has less power than my WS/6, but mine is modified, so that's expected. It seems like it may have less power than it did, but I can't be sure, since my daily driver is the WS/6.

Any suggestions where to start to fix this?

I'm assuming I should start dismantling the air flow system piece by piece and clean them as necessary. It would be helpful to have a target to look for, rather than doing a bunch of unnecessary work.

She doesn't drive it much. Usually to/from the grocery store, and about once a week she takes it out on the Interstate. She doesn't drive as aggressively as I do, so there could be carbon buildup in the heads, but I'm not really suspecting that right now.

Thanks.

**MrMasterCraft** · 03-23-2010, 07:53 PM

Not sure what kind of scanner you've got, but with my actron scanner, I can drive down the road and view alot of whats going on in the computer. This is what I would do before I started to dismantle everything. Also, when somebody tried to play a sick trick on me before in my old M6, it had the same symptons you've described and the MAF sensor was un-plugged. Basically anything but WOT, and the car wanted to stumble at one certain RPM. But if the computer didn't spit the code, I guess that's out of the question

Screen may be a dirty, I duno

**V8MUSCLE** · 03-23-2010, 08:13 PM

check your maf and make sure its clean. i had a similar problem, the rpm hesitation was a little lower 2.3k-2.7k all i did was take the maf out and clean it off, theres a MAF cleaner that will clear it up nicely. whatever you do dont touch the little wires that connect the "bars" inside it, if you break em you just ruined your maf.

**0rion** · 03-23-2010, 08:37 PM

you really need to log it and see what it's telling you but like these other guys have said the MAF isn't a bad place to start if it's been a while since it's been cleaned. Does it feel like the car is missing?

**sweet_revenge** · 03-24-2010, 06:45 PM

I know that with my camaro we had to take out the mass air flow sensor and clean because the oil off my k&n air filter was clogging it. we also removed the screen out of the mass air flow sensor. Never had any hesitation, just a random miss fire we were trying to diagnose. Cleaning the K&N air filter and not putting oil back on it helped my car run better!

**JWSmythe** · 03-26-2010, 10:04 AM

Thanks guys. Sometimes I need a kick in the right direction to remind me what to do.

I'm heading over there this weekend to work on that. Well, and the lawnmower, and pool pump, and just about anything that could break in or around a house.

After I read the comments, I remembered reading that about the MAF sensor. On my WS/6, it kicked the SES light on after I cleaned my K&N air filter. I did both cars at the same time, since I was out working on them. I just had to clean the MAF sensor a couple times, and it's been happy since then. It's weird that hers (the Camaro SS) isn't throwing any codes, but I'll start there and see where it takes me. I drive a lot more than she does, so I'm sure any oil from the filter already got blown through mine months ago.

**0rion** · 03-26-2010, 10:47 AM

Originally Posted by sweet_revenge

I know that with my camaro we had to take out the mass air flow sensor and clean because the oil off my k&n air filter was clogging it. we also removed the screen out of the mass air flow sensor. Never had any hesitation, just a random miss fire we were trying to diagnose. Cleaning the K&N air filter and not putting oil back on it helped my car run better!

you should either run that filter with oil or go back to the paper filter. All that dirt and grit will end up in your oil and act like sand paper in there on your bearings and what not. I run a K&N and have been running it for ~10 years. Just lightly oil it and clean your MAF a few miles after oiling it and you'll be fine. I always lightly oil mine and let it sit for an hour or two outside before putting it back in. Try to give that oil time to soak in. Then I'll put it back in and drive it a day or two then clean the MAF because I figure by then any oil that's going to come off of it has already done so. Now I'm running speed density so the MAF doesn't matter anymore.

**JWSmythe** · 03-26-2010, 10:56 AM

Ya, I meant that it was dry as far as oil coming off into the engine, not actually dry as not oiled.

**JWSmythe** · 03-26-2010, 09:16 PM

Guys, I wanted to say "thanks", for pointing me in the obvious direction.

I feel a little stupid I didn't think of it. I guess I'm getting lazy in my work, and am falling dependent on the computer to tell me what's wrong. I really should get an old Chevy truck or car, so I can stay in practice with figuring things out without the aid of the ODBII scanner.

I knocked the screen out of the MAF sensor. I know, it could be a bad thing, but... It was really nasty. The sensors had some crap on them too. I cleaned it off real carefully with MAF cleaner. While I was there, I pulled the IAC solenoid. It was pretty nasty itself. I cleaned it all up also, sprayed out the throttle body without removing it, and put it all back together. The first time it started, it idled up to about 2500 RPM and didn't want to come down. I guess I cleaned it a bit too well.

I shut it down, and restarted it, and the idle was perfect. I tested it cold at part (like 25%) and high (like 75%) throttle under low load (the proper gear) and high load (way to too high of a gear). Once it warmed up, I did the same. It's working perfectly.