Just thought I'd share a bit of knowledge with you that I recently learned. My 85 Deville (34,000 miles) has been battling a hesitation problem for some time now, but I just discovered the issue. The car just didn't seem to have much pull once I hit the gas (it would hesitate, then gradually build power), and if I mashed it, I sometimes got a backfire (didn't do that again once it did it the first time).
Well, believe it or not, my problem was a plugged-solid crankcase breather filter in the air cleaner. I had replaced the PCV when I bought the car, but never touched the breather pad in the air cleaner. Then, when I was messing around the other day, I noticed it was VERY dirty, and I wondered how any air could pass through it--then it hit me. I disconnected it from the vent hose and drove the car around the block. The hesitation was gone!
I've driven it for 500 more miles, and it appears to be cured. Just a tip to you all, this element is supposed to be replaced every 30,000 miles, so for $5, you should probably invest in one, and maybe it'll help!
I swear awadecki, you and I are living in some twighlight zone parallel universe with a 4100 at the center. I'm picking up a breather filter at the local AC/Delco parts place today. Will report back if my hesitation vanishes.
Haha, if nothing else, your oil consumption will go down. I went from burning a quart every 1,500 miles, to about a quart every 3,000. My breather filter was plugged solid--I think it happened when the intake gaskets blew. The part is cheap and it takes all of 2 seconds to replace, so why not just replace it.
Hope it helps yours too. Try just removing the breather filter once and driving your car around...it won't hurt it. See if it helps.
Many people replace the PCV, but forget about the breather (myself included). On newer cars, there is usually not a breather filter because the engine sucks air in after it has been filtered through the airbox. This is the case on the 4.5 and 4.9 engines with the swoopy air intake.
On the HT4100, it sucks air in before the filter; hence, it needs its own element to filter the air. It is supposed to be replaced every 30,000 miles, but I bet everyone's is original. Right after I found it cured my hesitation, I went and replaced the breathers on all of my cars (my 86 Cutlass Ciera and my 82 Trans Am).
You might want to try advancing your timing one degree above base. I found that this gives a great mix of performance and economy. If you don't like it, just put it back. I get an honest 26.5 mpg highway consistently.
I carried a 15mm wrench in my car for about a month trying to figure out the best timing setting for performance and economy, and that was it. I fill up with mid-grade and there's no spark knock.