Runs rich, limited power, excessive fuel consumption
Hello there. So I changed the head gaskets on my girlfriend's truck that was severely neglected by the previous owner (not my first time, just my first time on a v6). After getting it back together it was running very rich, very limited power, double fuel consumption and overheating. The overheating turned out to just be the thermostat had decided to stick shut while the manifold was off so it has no thermostat temporarily while I figure this problem out. The only DTC is 45.
I changed plugs, wires, cap, and rotor while doing the gaskets. I checked for and fixed all vacuum leaks and made sure the new gaskets weren't leaking. I triple checked the timing (though I just learned tonight that it's electronically controlled so I'll disconnect the timing wire and check it yet again tomorrow). I followed the procedure in the Haynes manual for adjusting the valves during the gasket change. MAP sensor is working. Injectors don't appear to be leaking and have a good spray cone. The rear bolt on the driver side exhaust manifold did break off in the head during reinstall though, so it does have a small exhaust leak (the first thing on my to-do list once I figure this out). I wouldn't imagine this small of a leak would cause this big of an issue on this truck, or am I wrong?
In my searches tonight I found that TSB 476516 might have something to do with it so Monday I'll see if I can manage to get my hands on the TSB somehow and see what it says.
I've racked my brain and all I've come up with is the exhaust leak or the RTV on the intake manifold possibly have gotten screwed up on install. Any input at this point is more than welcomed and vastly appreciated. I'll admit I'm a little out of my element when it comes to distributor-driven ignitions and TBI.
We all loved these TBI engines -
be sure the ECT sensor is operating If I remember 92 (been awhile), there are 2 one for gauge one for ECM.
The inj wires were prone to grounding and dumping as if WOT - check shake tug wires where they pass under air cleaner assy look for pinch mark.
Correct Base Timing is set with connector open. then connected the ECM will control.
4.3 have to mention EGR - might want to check engine vacuum - they would have issues with stuck open EGR causing low vac and would go rich.
Along that line TPS - check voltage at idle.
SWAG is ECT .
FYI 45 is an obvious o2 sensor hi voltage meaning rich.
What was subject of that TSB? the number does not look like a GM #, a 1992 sould have had the issue corrected by now. But I will give a look time permitting