97 Pontiac Grand Am GT 2.4L Quad 4 - Multiple Misfires

[Harper76]

I have a 97 Pontiac Grand Am GT 2.4L Quad 4, my problem is that it misfires and the engine runs rough. You can smell fuel, but there is no fuel leak. I have about 155k miles on the car, never had no serious issues with the car, the car has been great, I’ve owned it since early 2000. Little history on the parts I’ve replaced this year is the following spark plugs x3, spark plug boots x2, timing chain, Timing chain tensioner, camshaft positioning sensor, throttle positioning sensor, fuel pump, fuel filter, air-intake manifold gasket, throttle body gasket, IAC, ignition coils, ignition coil housing, ignition coil wiring harness, swapped the Ignition control module, checked the fuel injectors for solenoid clicking, replaced water pump, thermostat, swapped EGR’s. Maybe some other parts I can’t remember but I have done a lot trying to figure this out. Also took it to a garage and told them what I have done and the first place they looked was the fuel pump and said it tested at 20psi and called for 40-60psi so they replaced it and problem was still there. They had it for a week and half and couldn’t figure this problem out. Thinking about replacing the ignition coil housing again just to see maybe bought a bad one. Also done the three checks for head gasket blown, milky white oil, anti-freeze bubbling from the reservoir and compression check, all checked out fine. Ran gunk fuel injector cleaner through it several times. I don’t know I’m at a loss on this. If anyone can send some information my way please it would be much appreciated. I've read all the other post about this issue, and just thought I would start a fresh one of my own.Thanks

[thephantom1492]

Seems like you replaced lots of things unrelated.

First thing to look at is: the spark plugs! be sure to use the OEM one for your engine. I do not know the specs for your, but mine call for iridium spark plug from ac delco. Other tried other brands/type and "saved" a few buck, but ended up having multiple misfire due to the plug that ain't the right type.

Today, they design the engine around the spark plugs! So they are extremelly important.

[Tech II]

Do you have a timeline for all the parts your replaced, or were they ALL REPLACED to fix this misfire problem?

In my shop, we had a "top" from a 2.4, that we salvaged from an engine that spun bearings.....whenever we had a misfire, pop off 4 bolts, and add the top, and if the misfire was gone, we new it was the housing, coil(s), or ignition module.....usually, in that order.....

You say you replaced all 3......were they new or used?

Plugs OEM?

Check compression?

Check fuel pressure regulator vac line for fuel?

Check vac line to MAP sensor for cracks?

Was misfire there before the timing chain was replaced, or showed up immediately afterward?

Injectors can't be checked by just hearing if they click....

If you pull the plugs, are they all the same or is one wet or carbonned?

[Harper76]

The problem didn’t seem to start till after we replaced the water pump, which we had to take the timing chain off to get to it. We made sure the timing was correct. Had a print out from Chilton’s and Haynes manual; also had a gentlemen that knew what he was doing. All the parts were replaced from the beginning of this year. All the parts I have replaced have been new from a parts store with the exception of ignition coil packs, but I ended up replacing them with new ones. We checked compression and the same guy that helped me said it was good. I will check the map vac line for cracks also replaced that as well manifold airpressure sensor. What do you mean about fuel pressure regulator line for fuel? Should there be fuel present or no? Cause I think when I take it off there isn’t any, but there is a vacuum I believe. The sparks plugs are Ac Delco Platinum, they only sold or had 2 different ones in stock a $7 and $5, I went with the $5 and they were rapid fire platinum, parts store said they would work. But of course they sold me autolite or something and the mechanics told me I had wrong plugs in there, But I replaced them. The plugs are not wet but they all look the same with white carbon where it was misfiring. I replaced the ignition coil adapter again today 01 Jul 12 and it seems to be doing better. I’m going to keep an eye on it. Also what I thought was weird, is that when all this started my check engine light was coming on, and then it went off and never came back on with all of this going on. I appreciate all the valuable information and help that is coming in since the post. Think I’m going to replaced the fuel pressure regulator next time I get payed.

[Tech II]

Don't replace parts unnecessarily.....I mentioned the f/p regulator, because they are known to leak....if they leak, you will find fuel in the vac line...if fuel pressure is ok, and it's not leaking, don't replace it....

2.4L engines are the easiest to time......you time the engine, makes sure the tensioner is fully extended, and then you manually rotate the crank twice and RECHECK THE TIMING....if everything lines up, you are good to go.....

You've replaced just about everything......when does this misfire happen? At idle, or under a load up a slight grade?

[Harper76]

The majority of the time it would spit and sputter when under a load. Especially when on main highway or interstate or somewhere you have to get up and go You could feel it when at idle and when you would give it gas while in park you could hear it spitting and sputtering. Seems that I have now replaced for the second time the Ignition coil adapter or housing however you prefer to call it. And it seems to be doing better now since the test drive. And I would not call timing the 2.4L Quad the easiest, I’ve had that section of the motor torn apart three times within the past seven months now, to just verify the timing, I’ve got it down to about four hours with just myself. I think since I’ve replaced just about everything you can think of, I’m going to just replace the fuel pressure regulator so I don’t have to worry about it. The car is 15 years old with 155k on it, this is the first time I’ve had this much trouble out of it. Everything on the car was original till now; well minus the upkeep stuff .I don’t know about anyone else, but my last three cars all have been Pontiac starting with 89 Pontiac Formula Firebird when I traded it in 251k miles same engine same transmission, 97 Pontiac Grand Am GT 155k miles, and 02 Pontiac Bonneville SLE 164K miles. I think personally and this is just me, that is you take care of your car, it will last as long as you own it. And the fuel pressure was at 22 PSI when I took it to the mechanics and they ended up replacing F/P. Said it needed to be between 40-60 PSI according to the specs.

[Tech II]

You sound like a guy who keeps his vehicles for a long time....you've spent a lot of money on this vehicle....I think it's time you take the vehicle to a good GM tech....

Some people try to avoid the dealer like the plague.....but believe me, if you get their top driveability guy in the shop(specifically ask for him), he will fix the vehicle....you've spent enough time(checking timing 3X's in 7 months) and money on this vehicle....they have the expertise, experience, and equiptment to figure this out.....