negative integer in vacuum field?

[Nasty-Z]

Use an actual vacuum gauge to verify , could be a sensor bad but I doubt it . I was looking at one of your earlier logs that you sent me and it didn't show a negative MAP value while I was looking at it . Might be another glitch in the 7747 data stream and the XDF file you are using to view it. Which .XDF are you using ?

MAP values generally start high (100) at high vacuum and decrease as engine vacuum goes down (0) Usually on a N/A engine you will not see true 0 MAP .

MAP values on high performance or altered engines can be useful to track down intake tract restrictions , such as with TBI engines .

One note : As for the engine , you have a Gen1 small block , not a Gen II , Gen II small block Chevrolet is the 92-96 LT1 and LT4 platform , Reverse flow cooling , gear driven water pump , Optijunk distributor , etc.... Might save some trouble down the road asking for parts as aside from them also being 350 CID there are vast differences.

TOM

[89S10_Project]

Tom-

Again, many thanks.

I swear, you are a font of information. I need to know half of what you've forgotten. :)

I've come to the conclusion that most of my sensors are of questionable age (other than TPS, temp, knock, oil pressure, O2, and now IAC, which I've replaced recently). Knowing that failures in electrical components can be intermittent related to temperature and many other factors, I have just decided to replace them all.

Yes, it's expensive, and may well be money wasted. I am saving the old ones for my next build, "just to get it running" sort of approach. Meanwhile, with this truck, at least I stil ldon't have a car payment!

Also, after convo with you and a few local guys, I am going to add an aftermarket (mechanical where applicable) gauge pod with engine temp, oil pressure, and vacuum gauges, as a "second opinion" for this sort of thing. Example: my Oil pressure on the factory sensor (also new, BTW)ranges from showing 60PSI to just about 0, and it's not temperature or RPM-dependant. I had 60 pounds when I installed the engine, and nothing about the engine's operation tells me I have an oiling problem- ie, no noise at WOT from the valvetrain or journals, etc).

Also- big thanks to you for correcting me on the typing of my engine. I don't know where I got the GenII thing from, thought it was when I looked up the block ID. IIRC, the Optispark ignition is at the front of the engine, right? This definintely isn't that, as the dizzy is where you'd expect it on an oldschool 350. Also, it's brand new as well, so there's a new ignition module and pickup coil to add to my list of new electrical bits.

One thing I am starting to ponder about this issue with my engine (intermittent stumble at idle and throughout the RPM range - most notable at idle though)... it only occurs when hot, near as I can tell. I have an Accel Supercoil bolted to the firewall, that has been in service in various vehicles (Fiero, Jeep, S10 since about 2002) since I bought it in 1995 or so. Yeah.. the coil is 21 years old... it might just be time for retirement. I'm going to get a stock replacement coil (which I understand is probably all I'll ever need- blame purchase of the Supercoil on being young and dumb), fabricate a bracket since I stupidly threw the old one away, and see what that does for me.

EDIT: also, to address your question- I don't recall off top of mind, what XDF I used. I agree it might be a glitch along the lines of the Injector Utilization and Spark Advance issues we've previously noted. Those are going to be my first forays into burning new chips- getting the patches applied so I know I have good data in Tunerpro.