It's doing it again

[jeffcoslacker]

Sweet Mother of the Blessed Acceleration, it's back!

That odd glitch I mentioned a while back where the CEL is on and it wants to run like a bat outta friggin' hell...totally uncharacteristic deep growl from the intake, and a nearly neck snapping rush (by comparison to normal) of acceleration from 3000-4500 rpm or so...it's hilarious...breathing through that punched out airbox it sounds like a Honda when the VTEC comes alive...

It feels more like how the 3.4 in my 2000 Impala would pull when you stood on it...there doesn't seem to be any change in WOT upshift points or anything, so that's not anything to do with it.

So this time I got the codes, since you all were curious (me too)..

It's storing PO125, Insufficent coolant temp for closed loop fuel trim, and PO116 Engine coolant temp circuit range/control problem.

It's not a problem for me! It's a welcome gremlin. Wish it would stay, or I could duplicate it. But typically it goes away in a day or two, we'll see. The difference is a lot like that with engines I've power chipped, only this I would say is even more noticeable. Like I said before, the idle stability is just a bit off...most people would not notice the difference I'm sure...and it doesn't stick around long enough for me to accurately gauge the difference in fuel economy...

I suppose the other interesting thing would be to see what the emissions look like with this occurring...bet it's pretty dismal...I see no soot in the exhaust though, and the front plugs looked very clean....so it's not terribly overfueling, like to the point it can't use it all....

Keep you posted...wish I could quantify it and sell it as a performance mod...

[corning_d3]

Hmm, it sounds like the coolant temp sender or the wiring is bad, which allows the engine to remain in open loop. The PCM uses a pre-programmed fuel table and doesn't rely on the oxygen sensor/'s while in open loop. I'd say your fuel mileage is horrible when this is happening, but as you said, it isn't doing it often. The ECT wiring is usually routed under the upper plenum, and for some reason it along with injector wires is well liked by rodents. It could also be pinched/chaffed. I'm not sure what the resistance of the ECT sensor should be, since it changes with temp, but I could check mine fully warmed and post back if you like..

[maxwedge]

Originally Posted by corning_d3

Hmm, it sounds like the coolant temp sender or the wiring is bad, which allows the engine to remain in open loop. The PCM uses a pre-programmed fuel table and doesn't rely on the oxygen sensor/'s while in open loop. I'd say your fuel mileage is horrible when this is happening, but as you said, it isn't doing it often. The ECT wiring is usually routed under the upper plenum, and for some reason it along with injector wires is well liked by rodents. It could also be pinched/chaffed. I'm not sure what the resistance of the ECT sensor should be, since it changes with temp, but I could check mine fully warmed and post back if you like..

Agreed, or an intermittent thermostat problem.

[jeffcoslacker]

Originally Posted by maxwedge

Agreed, or an intermittent thermostat problem.

The dash guage reads perfectly normal. I'm inclined to agree with the electrical bug theory. Thinking about it some more, I just cleaned the engine last week, and it seems like it was shortly after doing so the last time this happened. So a pattern may be emerging.

Some water sitting in a harness connector, would be my guess. Must take it a couple of days to migrate to where it causes it, though, if that's the root of it.

[jeffcoslacker]

I was just thinking...if water causes a short that brings it on, and I could figure out exactly where and how, a switch could be rigged to duplicate the effect on demand

[maxwedge]

Originally Posted by jeffcoslacker

I was just thinking...if water causes a short that brings it on, and I could figure out exactly where and how, a switch could be rigged to duplicate the effect on demand

Get a switch in the coolant temp sensor circuit, open the circuit, temp goes to minus 41, open loop, will set a code though and run real rich at part throttle.

[tblake]

not necessiarily going into open loop, but maybe causeing excessive resistance in the circuit thus making the computer think the engine is coolar than it is. thus adding more fuel. Is the light still on? Could you hook it up to a tech 2 to see what the engine is recieven for coolant temp, and then maybe check the actual with a guage on the thermostat housing? Just so you know (but i think you already do) there is one coolant sensor in this engine, with 3 wires (two seperate circuits). The green wire controlls the guage, ground it, and the guage jumps to hot. the other two have variable resistance depending on engine temp. I'm sure you know where the temp sensor is located if you want to pull the plug and check for some corrosion maybe.