I'm posting this just for discussion purposes to hear some other inputs as to what may or may not be the issues here.

(93 LT1 A4) and the list is very long as to what has been replaced. Just to name a few related items (IAC, throttle body cleaned, TPS, tach filter, coil, ignition module and connector, new injector o-rings, ECM, plugs, wires, fuel filter, O2s, etc.)

So here are my symptoms and I'm still reading in my manuals and FI tuning book:

Sometimes when I start the engine (it always fires off the moment you touch the start position) it fires off to a very low RPM and slowly builds up to say 650. (Similar to a turbine engine where it starts off at 0 RPM and starts building up to about 25,000 RPMs.) With the AC off no idle roll, with the AC on I get idle roll at compressor on/off cycles. Other times when I start, it jumps immediately to say 1000-1100 rpms and slowly slows up to about 650. Sometimes when I leave work in the afternoon, I start up drive to the street and for a few minutes it acts like it missing and stumbling but then corrects itself and seems fine afterwards while I'm waiting to entry the street. Some times when it's at ops temp I come to a stop and it seems to struggle with idle speed, but it never gets any worst and it seems to try to correct itself.

Now recently in the last few weeks, I've notice an interesting behavior with the oil pressure. It's always solid and steady when constant power is being applied, say idle about 25psi and at running speed say 65psi. But there are times in the morning when it oscilates all over the place the needle jumping wildly from say 65 up but once power is constant it restabilizes. This behavior is intermittent so I've been monitoring it to determine if it is a cold engine issue or both warm and cold, i.e., unrelated to engine temp. Oil temps always run normal at the hottest I usually see maybe 212. Then there are other times I've noted the behavior when the system has been operating not related to a cold start. I've seen the needle just peg the high limit but I back off a sec and reapply power and it restabilizes.

Correct me if I'm wrong but I believe the LT1 uses the same sensor for both fuel pressure and oil pressure? I'm surprised at how little the FSM's address these two items, at least I've not found the areas yet.

I have the FI tuning manual by Probst. And the reason I mention that is I want to do some indepth reading if possible to understand more on the FI system.

I'm thinking that I might be having a pressure sensor issue or perhaps even injector issues (127K on originals). If they are leaking it might attribute the fire off at start after having been running and jumps right to a very high idle then settle down. As well as sitting over night, slowly building up for those start off that slowly accelerate the engine RPM.

I guess I do need to do a leak down test putting the pressure gauge on the system. I'm sure I'll have a better idea too once I've had a chance to research this some more. But I wanted to get you guy's ideas and thoughts on this as part of my diagnosis. Oh and no there are no DTCs being set.

When I did change the intake gaskets, I resolved a major idle miss I've had since I bought the vehicle. And that was obvious besides the oil leak but once the manifold was off I could see the rear ports on 5,6,7,8 cylinders had plumes of carbon in the ports, but the first four were a perfect golden color. That was very obvious on the first start after the intake gasket repair, the miss was gone.

But this new behavior has been going on a month or so now. And I can't seem to put my finger on the possible culprits.

thanks...