The ? actually pertains to my '99 Camaro, please bare with me.
What would you do if you had a 244/248/112LSA cam which results in tons of bucking between 1000 and 2000RPM? (Aside from installing a more computer friendly cam)

I have worked with several tables, nothing much works for me. I have taken out alot of timing, but the bucking was only slightly reduced.

Do you think that there is just too much overlap in this cam? I've been thinking about installing a 232/236/114LSA.

 

I do not know about the newer PCM's but I run a .588/280/110 LSA solid roller with a 730 ECM. It took a little time to tune but it works great. I would not say the cam is too big. Maybe you need more converter because it is loading the engine below the RPM range. Just my thoughts?

 

Sorry, I should not have posted my signature which is for my '87 IROCZ.

My '99 Camaro SS is now a LS2 stroker at 402 cubes and has the factory 6-speed tranny. The 244/248 duration is at 0.05" valve lift. I have had several pieces of advice, like reduce the timing; it did not work. Plus there were a few other suggestions, nothing has worked for me. This car bucks very violently.

 

Do you have a way to data-log? That would be the tell-all. Is the problem under normal excelleration. I wouldn't think that it would be timing. I have played with timing alot and it doesnt seem to have a large enough affect to cause a violent reaction like you describe. I would look for holes in your fuel map and in your timing map. Don't rule out a mechanical problem that could have creeped up on you.
If I'm not mistaken those PCM's used both a mass airflow and a MAP sensor. I also think that if the mass wasn't functioning properly the PCM would default to the MAP. Sorry that I can't be more help.

 

Well, the engine is new, but that does not rule out a mechanical issue. The engine has been revved up to 6500 RPM many times now. The bucking was there from the get-go.

I have AutoTap. I can collect way too much data very quickly. I have looked over so many data logs that I am going blinded. This bucking is the must fustrating tuning issue that I have ever dealt with.

You are correct, the '99 PCM uses a MAF and a MAP sensors. The MAP is consulted on transitional stuff, like sudden throotle openings. As I understand things, in or near steady state conditions, the PCM is mainly using the MAF sensor for fueling and only the MAF above 4,000 RPM. Also, the PCM constantly makes checks between the MAF only fueling and MAP only fueling. If they are too different, some blending of the two methods is used.

I am coming to realize that I need to run the PCM in OLSD below 2200RPM to elimenate the bucking. I dont know how to get this done right now with my tuner.

 

Just throwing out a thought,
Is there an adjustment for AE MAP (Either minimum TPS for it to activate) or the amount of AE for a MAP differential.
Might be getting surges of fuel due to the cam lope.
Might see that on a WB if you have one.
Other thing I thought of is the voltage, check logs to see if it varies at low speeds.