Ok, I had my 1999 blazer in a shop this week to try and resolve a problem I have been having. Occasionally my car will, bluntly, run like crap. It will be sluggish to accelerate at low speeds. But once reaching 25+ it runs perfectly fine. Sometimes, when idling in drive it will stutter just a little bit. But the big problem is that it is very, VERY, irregular. Like, the friday before I took it in it was really sluggish to go. So I decided on monday I am taking it in because I couldnt figure it out. Then, come monday, it ran perfectly fine. So, they got to it tuesday morning and called and said there were no codes up but there was a stored p0300 and they said there was a leak in the lower intake manifold gasket and it needed to be replaced and inspect the manifold for cracks or damage. Then the proceeded to tell me that I should take it to an engine shop because if it was a cracked manifold that is something they wont replace themselves. A good friend of mine said next weekend me and him will go in and replace the gasket. My only problem is, if it was something like this, wouldnt it be a regular problem? Why would it run perfectly fine for days and then run rough for a day. I dont know if anyone else has had this problem or, maybe if there is something else we should check. Also, I dont know how the shop came to the conclusion that the lower intake gasket needed to be replaced. All they said was they ran some diagnostics and that was what needed to be done.

 

LIM gaskets on these engines VERY commonly go bad. Generally they are diagnosed by coolant in oil, external coolant leak, or vacuum leaks. For the upgraded gaskets (can't remember the part number but it's the Fel-Pro with the metal cage) it's about $80. The job itself can take anywhere from 4 - 12 hours depending on your level of experience and tools at hand. Make sure you have a manual before attempting this procedure as it is very important that you torque the bolts in sequence and to the proper ratings due to the design of them you could wind up with a worse leak or crack the manifold by over torquing.

as far as it being an intermittant problem i'm unsure. I suppose anything is possible considering these engines have cast iron heads/aluminum lower intakes and the expansion rates are different. Reletave heat and humidity COULD cause a difference as well. Is it likely? I don't know.

As for the P0300 there have been MANY discussions on this forum regarding it and many different conclusions to different problems causing it. I recommend checking out the DIY section and searching the forums to find symptoms that most closely seem like the ones you're having and go from there for diagnosis.

 

Who knows if they're shining you on or not? I find it odd, though, that they will replace lower intake gaskets but not replace the intakes themselves.. must be something I haven't heard about yet.

The good part is that almost everyone has to replace those gaskets someday... unlike most parts, when it comes to those gaskets.. one word:
FelPro !!!!!

Read up a lot .. on here and other places. Wells has a good youtube video on the job.. probably to make up for their crap parts.
It's not real hard but two things to pay real close attention to:
The distributor. Line it up carefully before pulling it, Only turn the engine normal rotation to do that... DO NOT BACK engine up if you overshoot. Then mark rotor position accurately before removing hold down.. and CAREFULLY lift until dist gear releases and mark that rotor position as where to start it when reinstalling. If you do that you should not have to line up the pump shaft when you reinstall.

- WHat I'm gonna do when it's my turn is replace the holddown bolt with a headless bolt.. before I lift the dist.. so there's no problem lining up the dist base on reinstall. And I'm gonna pull the accessory belt before starting so there's not the slightest chance of moving the engine accidently by leaning on belt

The torque specs. Seems like the recommendations are all over the map but remember that they're talking INCH POUNDS.

Good luck

 

Pettyfog makes some very good points. The distributor being one. It sounds scarier than it is though just be careful and make sure you mark it.

 

these guys are dead on, its not a terrible job just intimidating.
it took me 12 hours give take, the felpro number has a "t" in the number.
i got my kit from rockauto.com...cost of 90.00 give take.

one thing to, remove the engine harness from the fuse block to get it out of the way..its easier then fighting it the whole time.

i used this how to...is very detailed..down to tools used.

How To Replace Intake Manifold Gaskets On A GMC Jimmy 4.3 Liter V6 To Fix A Coolant Leak - GM Truck Engine Repairs

good luck.

 

Mike... That's why I dont like their spec methods.. 17 in lbs is about 1 1/2 foot lb.
Remember 12 inches per foot

There's a pretty good rule of thumb.. About 25 ft lb final for aluminum manifolds.

 

Wow, thanks for all the replies. I will definitely be getting to this next weekend and will be doing a boat load of homework this week so I understand what I am actually doing. Thanks again.

 

good luck, you should be fine though.

 

Amazon.com: Fel-Pro MS98000T Manifold Gasket Set: Automotive


Is this the correct set? I ordered it already because amazon claims one in stock but I can cancel my order if it is not what I need.

 

That looks like a set for a V8 engine, the set I found has a part # and description of :
Fel-Pro MS98002T Prmdry Intk Manfl Gsk Set

Amazon.com: Fel-Pro MS98002T Prmdry Intk Manfl Gsk Set: Automotive