View Full Version : Misfiring on start up, bad intake manifold gasket?
04-23-2009, 12:43 PM
I have a 2002 Grand Am Gt with 3400 in it. When I Start the engine it misfires for about 30 seconds and the runs fine. The exhaust smells funny and kind of sweet (coolant?) I have to put about a cup of antifreeze in once a week. I have not noticed any oil in the reservoir. I haven't noticed "milky" oil or an increase of oil on the dip stick. It just seems like the antifreeze is slowly leaking into the intake when it's sitting and when when I start it up the coolant runs through and is getting burned up. The exhaust isn't really smokey or white either. I've brought it to a few mechanics and since there are no visual leaks found and it's not going through a ton of coolant they can't be 100 % sure it's intake gasket. I want to change the intake myself but can't afford to if it's not the problem. Can anyone give me confirmation on what is actually happening and what needs to be done to fix it? Please let me know if more information is needed, I will respond quickly.
04-23-2009, 01:31 PM
dave, here is what i would do...
start with having an autozone or similar place scan it..... after all it could be a lot of things, including the intake gasket... which very well may be your problem....
this may not be the best set of test, or all-inclusive, and you can do these in ANY order... others will chime in soon with more/other ideas
1.check your plugs and wires... free to do
2.check your fuel system, you may have a clogged fuel filter, have you changed it ever? if not, i would consider doing that, the filter is like 7-10 bucks and easy to change and is a good thing to do even if the intake gasket is bad
3.check your coolant cap, if its not working right, it could be leaking some coolant, causing your loss, clean the area below the drain spout on the fill resevior, and then watch to see if it is leaking out there, if it is, repalce the cap and watch it....
4.perform a pressure test on the cylinders if you have the tool, if not, you may be able to borrow one from a friend or parts store... report back with results
those are just a few tests... now for a few questions...
Does it act like that every time you start it? like when you take a trip somewhere and it reaches opperating temp, then try starting it 5-20 minutes later? i ask because this would allow the cooling system to build pressure, then leak if it is leaking, and cause your problem... or does it just do it after a long rest/cooling period? which could point towards other things...
does it run hotter than usual? does your heater put out good heat? these can also be signs of gasket leaking...
let us know, and we will try to help you
04-23-2009, 02:22 PM
That sounds like a good place to start.
I will double check plugs and wires. I'm assuming if these were bad misfiring would happen all the time and not just on start up. I changed plugs about a year ago and wires looked good. I'll make sure there isn't any fraying or major gunk/build up on plugs.
I'll also take care of that fuel filter. Can't remember the last time I changed it. I better start taking better documentation of these sort of events.
I'll also double check the coolant cap.
Comp test might be tricky but I'll ask around, someone might have a tester.
It really only misfires bad during warm up. It does it bad after it sits over night. When we're done shopping at a store it's not noticeable.
The temp holds good and the heater blows hot. We just got over winter here and had no trouble keeping warm. I'll reply more after I check/change everything.
04-23-2009, 08:56 PM
Plugs look good, wires look good. all connections are solid.
Coolant cap looks good and clean. No cracks or dirt.
Got a fuel filter and started taking the rusty one off. Had to borrow 13/16 wrench from the neighbor. Thought I depressurized the fuel line but still shot fuel all over the floor. Once I got that old one off and noticed how dirty the fuel was inside I was pretty shocked. Really don't know why I wait this long to change it. Also changed my air filter and put some fuel injector cleaner in the full tank. It was on sale. Started up pretty nice but the final test will be in the morning to see what happens. I can only pray this was the issue.
Considering I've been running dirty fuel through the engine for awhile is there anything I should to to help clean this system out? Would putting a can of sea foam in the next gas of tank be enough to clean this system or should I use something more powerful (expensive)?
I'll post again when I start up in the morning. Thank you again for any and all help.
04-23-2009, 10:42 PM
sounds good, keep us posted....
I really hope its not the manifold gasket...
04-28-2009, 09:09 PM
Still starting the same as it was. :(
04-29-2009, 12:08 PM
when looking at the car from the front with the hood opened look at the right of the UIM and LIM and look to see if theres any antifreeze around there, if so you need a new intake gasket this happened to me, also could be time to change the catalitic converter or resonator, I mean for the smell not sure on that one. hope this helps.
04-29-2009, 06:44 PM
hate to say it.... probably the intake gasket....
05-01-2009, 10:34 AM
I'm going to change the intake gasket. It just seems to me it's an internal leak. I can't see anything on either side of the intake. Hopefully I can get it all done Saturday. I'm just going to use the walk through I found in the forum.
05-01-2009, 10:49 AM
the first time I did my intake gasket i followed that walkthrough and it was awesome. So just take your time and make sure you dont screw up the order of the pushrods when you put it back together.
And also make sure you put enough RTV in the valleys.
05-01-2009, 11:00 AM
So just take your time and make sure you dont screw up the order of the pushrods when you put it back together.
And also make sure you put enough RTV in the valleys.
we took a cereal box and made a cutout and put all the pushrods in and everything in the order they were suppose to be in .. it was a lot easier to do it that way.
05-01-2009, 11:59 AM
the way i do it, is the shorter pushrods go on the rockers that are further forward the middle of the motor
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