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Question: HIB Some guidance Please- Closed Loop Hesitation-Bat out of hell with open loop

Brian Smith

Well-known member
Joined
Aug 20, 2009
Messages
46
Location
Flower Mound, Texas
Corvette
1993 Viper Red Coupe
93 LT 171,000 miles NO Codes set and I have not connected my computer to see what is happening dynamically -

I replaced original Optispark due to failure last week, plug wires and plugs were replaced as well. I have noticed that the "hesitation" I feel when fully warmed up at part throttle is NOT there at all when cold. I also note that when warmed up at FULL throttle the thing screams as well. If I understand the ECU properly, at closed loop and/or full throttle few sensor inputs are used thus eliminating what I think may be knock retard caused by what the knock sensor interprets as detonation and backing timing out of the ECU.

Added technical data component: I had rocker arms loose and adjusted them, per the FSM, a month or so while back (all required at least 3/4 turn on the locknuts since all had lash). I guess I did a crappy job because one or two still tap when warm (can't hear so good since my time in the military).

Hib are the knock sensors sensitive enough to back timing out when it hears rocker arm noise? Does my assessment of the ECU activity make sense? Is my solution to re-adjust the valves? When I adjusted the valves the engine was cold and hadn't been started that day. Given they are hydraulic elements what are the odds that these lifters are bleeding down or collapsing justifying replacement of the lifter array?

Suggestions?
 
I'm not Halverson but KR is still active in Open Loop and at WOT.
Also, you don't need to be to be fully warmed in order to go into Closed Loop.
 
Before embarking upon an extensive guessing game about false knock, I suggest you take a look at the ECM's serial data and see if any KR is actually occuring when the hesitation you feel takes place.

Valvetrain noise, under some circumstances, can cause false knock.

Your understanding of the ECM at WOT is not correct. When you go to high-part-throttle or WOT, the system goes into open loop, ie: it ignores fuel trim values. Otherwise, all other sensor data, including any KS input, is processed by the ECM. In fact, at WOT, the KS input is the LAST thing you'd want the ECM to ignore.

Given 171,000 miles its very possible you have worn valve lifters, but if that's the case, you need more than just a replacement of 16 lifters. You need an engine overhaul.
 
Maybe this information will be helpful to you. Be sure to follow the instructions carefully.

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Knock Sensor pictures by John-68 - Photobucket
 

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