Well the two guys that worked on the car cant find whats wrong so I am taking to all the shops in the area, so far no luck. Its a 2000 C5 with a heads and cam package. After having the plugs and wires done it started a lean miss-fire condition in both banks. Most noticeable at lower RPM cruising as the car stumbles etc.

Took to AZ Auto Masters here in Phoenix and they confirm a lean condition but cant think of anything other then block learn problems with the computer programming. Thing is its been over two years before the problem suddenly came up. They checked for intake leaks but we will have several other shops look as well. Intake leaks make more sense to me as the computer was fine before. Going to try swapping the MAF sensor first, then redo the computer before tearing the engine apart and redoing all gaskets etc.

One person mentioned engine replacement and I laughed, sad thing is I have to start pricing engines out as it looks like this problem can not be solved by the experts.

 

Keep it simple..... No problem before the plugs and wires....suspect a problem with the plugs and/or wires. May be something as simple as the wrong heat range plugs.

Go back to the plugs and wires that you had no trouble with and see if the problem goes away.

 

Well we did replace the plugs and wires, twice. We even tried different temp plugs. Now we are running cooler ones but plug and wire replacement did not see to fix the problem. The people at AZ Auto Masters said they did read a lean condition on both banks when the hesitation occurs. I am thinking some sort of an air leak but cant figure out what it suddenly occured.

We could try another plug and wire swap but I doubt it will do any good.

 

I'd run from anyone that is talking about "engine replacement". Most likely when the original plugs and wires were changed, something got bumped or disconnected. If you are sure that the problem started right after the swap, I'd be looking for the lowest common denominator.

Hopefully, someone who has changed their plugs and wires will be able to shed some light on what else may have been disturbed.

Good luck and keep us posted.

 

If it occurs when the engine is stumbling, (I am assumming you mean from cam lobe overlap and not from the lean condition) I would take a WAG and suspect that extended engine rocking may have caused a leak or crack in the power duct that opens and closes with the engine movement, causing a momentery erroneous MAF reading (lean out).

 

Not sure if you have acess to it, but I would hook up a scanner of some type (ie EFILive) and log while driving. You could then go back and review the logs to get a better idea of what is going on and further isolate the problem.

 

maybe it's a situation with the 02 sensors.. I'd put them on a scope and check them out. or could be a vaccuum leak. just 2 ideas I had.

 

Did you by chance bring it to the dealer for anything? If so they might have re-flashed your computer loosing whatever tune you had in it.

If it was me i'd run a program like autotap and record exactly what your engine is doing and also take some fuel pressure readings.

 

I agree. Did someone reflash your PCM by chance? SOundslike the tune is bad to me. If you have air leaks....you should be getting codes? Hold the Options button and hit the Fuel button 4 times fast to get the codes......................

 

Use some sort of data logger and check all of the engine sensors that could effect AF/Power, ie MAF, Air Temp Sensor, Throttle Position Sensor, Manifold absolute pressure, ect

When the problem occurs do you get any codes? Do you ever see a CHECK ENGINE LIGHT and see a P0300 Code when it is on? (Engine Mis-fire)

You could also have a bad coil!

Check the air intake tract and make SURE that it is properly sealed.

My 2 cents.

BC

 

Well I think we may have found it. I took the car to Extreme Motorsports here in Phoenix. I had a Halltech intake I bought in 00. Well the guy who changed the plugs and wires did not like the gaps in the radiator shroud so he decided to plug it all up with some black goop looking stuff, make more of a seal. Well this must have caused a bunch of turbulance and thats seems to be the problem.

The MAF readings were jumping from 26-28 all the way down to 8 and back. Extreme has removed the black goop restoring the gap between the hole in the radiator shroud and the Halltech intake. He told me on the phone the hesitation is there but less the 1/4 of what it once was.

So far my plug and wire change has resulted in 3 months of no car and over 300 in parts and labor. Nice huh? Now I am not sure what to do. Extreme recomends installing the blackwing WITHOUT the cold air cutout on the shroud. That and a new shroud will run 300 or so. They claim the MAF readings wont jump at all. Is it possible with the Halltech that I had crap MAF readings from the start? The black goop just made it worse? If so maybe I should stick with the old Halltech system and work in stabilizing the air flow a bit more.

Any suggestions? I pick up the car tomorrow and will see if the problem is indeed gone, at the very least I will be happy to have my car back! Sorry for not answering replies here, the forum stop notification. Thanks again for all the help. Looks like its another "cold air intake turbulance" issue.