Elk

This morning, for the first time, my Z06 is exhibiting an engine problem.

On low RPM's (800-1,500) the engine bucks and hesitates under load. I have not experienced it in first or second gear, but it will happen in third gear.

The engine feels fine at higher RPM's, developing plenty of power and is smooth.

There are no codes and all gauges are within normal limits.

It feels like tipping in full throttle on a two cycle engine which is not adjusted properly: light to medium acceleration is fine, but full throttle feels like it is adding too much gas and the engine hesitates.

Another analogy, it feels like an overly aggressive and invasive traction control system. (I am definitely not spinning the tires and this is not what is going on--and the traction control light does not come on).

I am using a Halltech Sidewinder intake, but it has been on for quite a while with no problems so I doubt this is involved. I have not had the time to again perform the idle relearn procedure to see if it might help (I did this after changing the intake, but thought it worth trying again. Anyone know what, if anything, happens if you don't do the relearn procedure after intake mods?)

I welcome any ideas. I'm not panicky yet. But certainly unhappy.

Any ideas or suggestions? :confused:

Thanks!

Elk

ttt

thanks

BruceF

Check the codes stored in the DIC.

And check the connections to the air intake, sensors, etc. in case they loosened up over time.

Elk

Thanks for the reply, Bruce.

No codes of any kind.

I have checked and cleaned the connectors to the MAF, and checked to make sure others are tight.

I reset the PCM (pulled fuses) and did the idle relearn procedure.

I had a little less of a quarter tank of gas and put in nice fresh gas.

No change. :(

Any other ideas? I'd hate to take it in to a <gasp> dealer.

BamaJohn

Maybe a too-obvious suggestion, but did you clean the air filter? My Camaro was exhibiting similar symptoms and woke up big time by replacing the air filter, which had been on for a while.

Blocktrdr

I had a similar problem and it turned out I had a loose plug wire. The plug wire backed off the plug and under load it was misfiring. It would stumble just a bit but would rev fine at less throttle. I got no codes as well.

Elk

Thanks for both the air filter and plug wire suggestions!

I had not considered either.

I should have.; I have both an aftermarket airfilter in place *and* plugwires.

All ideas happily considered and tested.

I'll report back later.

MDT

Elk,

I kinda go along with Blocktrdr's diagnosis, but if that checks out you might want to check the fuel filter for the presence of water.

Good luck.
Mark


[Modified by MDT, 10:38 PM 8/29/2001]

TimZ28

Wait a second...

You tell us that in 3rd @ 800-1500 RPMs the engine bucks. What do you expect to happen?! Your not exactly making life easy for the engine putting it under load in that gear and that RPM range.

Tim


[Modified by TimZ28, 9:07 PM 8/29/2001]

Elk

Happiness!

Blocktrdr was correct! It was in fact a loose plug wire, #8. Of course, it has to be the one that is the hardest to reach.

The engine is perfect once again.

Almost 13,000 miles and alll is well.

Thanks, everyone!!!

Tim: In one way, you are correct ; very low RPM's and high load are not efficient. At some point the engine will lug and die.

Keep in mind however, that while acceleration won't be impressive in this range, the engine should run fine. In sixth, 60 mph is below 1,500 rpm's and I think we all expect the engine to handle this. It would be entiely different with an agressive cam and rockers. My Trans Am WS.6 with a cam, rockers, etc. wasn't worth much at all until the rpm's came up a bit.

Blocktrdr

Glad your problem was solved. Just a heads up, mine came loose again a few times. I tried squeezing it down a bit but ended up having to replace it.

Elk

Thanks for the additional heads up. Hopefully I'll remember the cause if the symptoms ever reappear. I did check all the other wires and they are tight and secure.

Thanks again also for the help. It would have been a while before I tracked this one down on my own.