I did both my valve cover gaskets and both upper and lower intake manifold gaskets on a 3800 Series II GM V6 engine. Also replaced the upper plenum with a new Dorman one.
I seem to be getting a vacuum leak from somewhere around the throttle body. You can hear a hissing, and when I hit the gas, it whistles, and then the vacuum leak goes away. It seems like the new plastic plenum does not sit flush with the throttle body. Some parts are flush, others are not. You can see the new throttle body gasket through some of the gaps between the throttle body and the plenum. That's the other thing, the new throttle body gasket seems to stick out from the plenum. The old gasket sits flush against the plenum. I took the throttle body off to make sure everything was on evenly and the gasket was OK. Everything looked OK. Both times, I torqued the 3 nuts to 89 in lbs.
Despite the weird gaps and it not looking flush, there is no change in idle when I spray it with carb cleaner. As a matter of fact, I can't get the idle to change by spraying carb cleaner anywhere. I tried where the lower intake meets the heads, where the upper intake meets the lower, at the EGR tube, at the throttle body, at the rear vacuum tree, the brake booster hose, almost everywhere I can think of. I put all the new orings on the PCV valve, and have double checked both the PCV valve and the other black plastic piece that goes into the intake.
I'm stumped, and even though I'm not losing coolant, and there doesn't seem to be any coolant leaking from the intake manifold to heads area, the only thing I can think of that it would be is that I didn't install the lower intake back properly.
Only CEL code I'm getting is a P0102 low MAF sensor input. I measured the output voltage and it seems to stay around 2.6 volts, even when you rev it up. It barely moves at all, and it seems like revving the engine has almost no effect on the output voltage. Is this a symptom of the vacuum leak or is the MAF bad? This code wasn't on before, but I also forgot to remove the MAF when I cleaned the throttle body.
Any ideas on what more to check? I don't have any access to a smoke machine but I am thinking of trying to make something homemade.
I seem to be getting a vacuum leak from somewhere around the throttle body. You can hear a hissing, and when I hit the gas, it whistles, and then the vacuum leak goes away. It seems like the new plastic plenum does not sit flush with the throttle body. Some parts are flush, others are not. You can see the new throttle body gasket through some of the gaps between the throttle body and the plenum. That's the other thing, the new throttle body gasket seems to stick out from the plenum. The old gasket sits flush against the plenum. I took the throttle body off to make sure everything was on evenly and the gasket was OK. Everything looked OK. Both times, I torqued the 3 nuts to 89 in lbs.
Despite the weird gaps and it not looking flush, there is no change in idle when I spray it with carb cleaner. As a matter of fact, I can't get the idle to change by spraying carb cleaner anywhere. I tried where the lower intake meets the heads, where the upper intake meets the lower, at the EGR tube, at the throttle body, at the rear vacuum tree, the brake booster hose, almost everywhere I can think of. I put all the new orings on the PCV valve, and have double checked both the PCV valve and the other black plastic piece that goes into the intake.
I'm stumped, and even though I'm not losing coolant, and there doesn't seem to be any coolant leaking from the intake manifold to heads area, the only thing I can think of that it would be is that I didn't install the lower intake back properly.
Only CEL code I'm getting is a P0102 low MAF sensor input. I measured the output voltage and it seems to stay around 2.6 volts, even when you rev it up. It barely moves at all, and it seems like revving the engine has almost no effect on the output voltage. Is this a symptom of the vacuum leak or is the MAF bad? This code wasn't on before, but I also forgot to remove the MAF when I cleaned the throttle body.
Any ideas on what more to check? I don't have any access to a smoke machine but I am thinking of trying to make something homemade.
