Intake Manifold Gasket Symptoms

[Nicolai8775]

Over the last week I've been having trouble starting my '01 Tahoe in the morning. One morning it wouldn't start at all but it started later that day after it warmed up outside a bit. This morning I had to turn the key over for like 5 seconds before the car started. I had o'reillys check battery, starter, and alternator and they all passed. I didn't think it was the battery cause it wasn't a slow crank like with a dead battery. It turns over normally but just has trouble starting. One of my friends said maybe a vacuum leak due to a bad intake manifold gasket.

I also have misfires when i go through the car wash. When I bought the Tahoe last January I had a shop do the plugs cause I couldn't get them out, they were seized pretty good. They said that a couple of the plugs were really fouled up but I'm not sure if that was because they were original plugs or something else. I haven't noticed a coolant leak either which I thought was typical with an intake manifold gasket leak. The level in the reservoir hasn't changed since January.

Check engine light doesn't come on either (unless I'm in the car wash for misfire) and I'm not even sure if there are any codes thrown for this type of issue.

what do you guys think? could moisture be making its way past the gasket when I get it washed? Could the cooler temperature be affecting the gasket in someway where there is a vacuum problem?

 

[01ssreda4]

Car wash maybe wet connector on the 02 sensors since they control fueling, common during heavy rain. Not starting id check running fuel pressure AND drainback/pressure bleed with the key off. Easy to do with store bought kit.

 

[ISU-152]

Cap n rotor time

 

[David Paul]

Cap n rotor time

Please share with us where these are located. I can't seem to find them on mine.......

 

[David Paul]

While intake manifold gaskets are an issue with these trucks, I doubt it is causing your no start problem. Most of the time it will cause a rough idel when cold and set an MIL.
Did they change the plug wires when they did the plugs?
Something is getting wet to cause the rough idle.
I agree which checking the fuel pressure to see if it is draining back while off. That could cause the long crank times while the fuel pressure builds up.

 

[ivin74]

It could also be the crank position sensor

 

[Chip18]

I seriously doubt the "vacume leak thing" also, but easy enough to check. Just get it started and spray carb spray over the manifold area, if the idle raises ... you've found a leak.

If water is an issue?? WD-40 is your friend, do the car wash thing again and if no start ... spray it over all electrical connections, WD-40 displaces moisture.

You can rent a Fuel Pressure test kit at just about any Auto Store. One of the less obvious issues "could be ... bad battery cables?? They could look good at the terminal connections but could be corroded on the inside further down?? You could just change them out or check them for resistance with a DVOM. I've never experienced that happening but I have heard of it happening.

That aside ... next step would be to think it thru and "troubleshoot the issue:

 

[Nicolai8775]

I will check all of these things and get back to you guys. I ended up doing the intake manifold gaskets anyway and damn were they nasty. I was doubting the vacuum leak thing too, so I'm kind of expecting it to have trouble starting tomorrow morning. i was also thinking maybe a short in the battery wires but wouldn't that result in a slow turn over or no turn over? i did spray water on the coil packs once out of a bottle to see if i could hear any change but nothing happened. I hope its not fuel pressure cause i just did the fuel pump on it last month.

Car wash maybe wet connector on the 02 sensors since they control fueling, common during heavy rain. Not starting id check running fuel pressure AND drainback/pressure bleed with the key off. Easy to do with store bought kit.

usually starts misfiring when the spray is in the front of the truck not the sides or underneath, so I didn't suspect O2 sensors. I hope its not fuel pressure related because I just did the fuel pump a little over a month ago.

While intake manifold gaskets are an issue with these trucks, I doubt it is causing your no start problem. Most of the time it will cause a rough idel when cold and set an MIL.
Did they change the plug wires when they did the plugs?
Something is getting wet to cause the rough idle.
I agree which checking the fuel pressure to see if it is draining back while off. That could cause the long crank times while the fuel pressure builds up.

I also did have new plug wires put on but for some reason they didnt keep the little metal insulators that were around the original plugs, could that have something to do with it?

 

[retiredsparky]

So if it isn't plug wires, what about the knock sensors? Mechanics often change them out when doing the intake gaskets on this motor because of the knock sensors being a common problem.

It is certainly worth pulling apart the wiring harness connectors under the hood and looking for evidence of corrosion, especially at the crank position sensor, map sensor, etc. When reassembling these connectors, put a light coating of dielectric grease on the rubber seal or o-ring of the connector.

One spot in these vehicles that is prone to corrosion is the fuse block just behind the battery. Mice love to inhabit this area, because of convenient openings left for them by GM. You can often see their "calling cards" in this area. Mice also urinate where they travel-this urine is very corrosive, and when in a moist environment can cause electrical problems.

One other rather strange cause can be a battery that tests ok, but has bad connections internally. This can generate electrical noise in the 12 volt system. I don't think this is the cause of your no-start.

 

[01ssreda4]

Get you a tube of dielectric grease, take off your plug wires and add some to both ends of each, then unplug your front 02s and fill the connector with it to then go back to the wash and see if that fixes it. I might know a little something about making stuff "weather proof"