andrew54

I purchased the car with what i was told was a GIAC tune (probably 10 years ago). Car runs great 99% of the time and pulls hard, not missing a beat.

Occasionally (I haven't been able to replicate the exact situation repeatedly), when transitioning from either idle or low rpm and beginning to accelerate, the car surges as if it is too lean. Engine shakes badly and then i let off immediately, and then can resume accelerating.

Any thoughts on what could be causing this? Think it may be a issue with the tune?

rmc1148

Hate to go the usual but check MAF.

andrew54

Oh man, totally slipped my mind but sounds like a very real possibility! Will investigate

Kevin

As you have wrote, your engine could be running lean. Check your fuel pump for hose failures.

If your previous tune was written for better octane 94/93 vs 91, you could have heavy timing intervention. Are your tailpipe tips heavily sooted?

I would check for any soft codes (CEL) that are stored? Misfires and such.

Boost leaks, plugs, wideband O2's, MAF and throttlebody adaptation are on the list of Check items.

You can run some race gas, if your conditions clear up, you have a timing issue.

Wealth Manager

Do you get any sort of popping noises?

andrew54

Kevin, I normally run 94 Octane to keep things on the safe side actually; with no excessive soot. I just did the plugs (was happening prior to plug change)

Wealth Manager, No popping or backfires. Runs perfectly smooth except during those circumstances.

I will start by cleaning the MAF as the car does have a BMC filter.... and work my way down your check list there.

I will probably begin to tackle this tonight.

Kevin

Cleaning the MAF is "fools gold" The MAF works when within spec and it doesn't if fouled..

Unplug the MAF and see if how the car runs, (you'll have to clear codes>after you do this) Take a picture of your BMC, is it oiled? The oil coats the MAF filament.. Then with the current running thru the hotwire, you electroplate the carbon, dirt, cr@p to your MAF..