Question...All of a sudden my 1999 Pontiac Firebird started shaking when turning it on..and also it sounds a lot louder than usual! This is happening right when the car comes on..it shakes harder when it is reverse, and when you slow down at a red light or stop sign and take your foot off the brake. It also seems as though it has lost power, when you start to accelerate from a stopping point. There are no smells or fumes coming from the car...just erratic shaking and like I said the exhaust or something sounds louder... I'm not sure what this could be since it was running fine as usual just a couple hours before I got back in it and started up and drove for about 2 minutes???
Any ideas to what this could be...??? Any help would be appriciated...Thanks guys!!!!

 

Thirdgen not Fourthgen

As far as your car. Any ses lights on? Hows gas milage and when was your last tune up? How do the plugs look. How old is the cat? Fire it up and lift the hood. Any sound when revved or idling?

 

Yes, the service engine soon light is on... It was solid at first now flashing..!
I notices this past week, I don't think my gas mileage was too great... I had 3/4 of a tank and got about 110-120 miles...
but that was before it started doing this obviously...
I'm not sure when the last tune up was...I'm kind of embarrassed to say, but I just bought the car about 2 weeks ago...
So, this has been a little stressful..needless to say...
Sound just louder than usually when reving and idling...
I'm not sure about the cat...? Plugs, I think look decent, but haven't gotten under the car to look...Thanks for your help...

 

Also, someone told me, I could be having this problem b/c I need new spark plugs..or a torque converter..solenoid or something?
Sorry...not too familiar w/ what that is....????
Oh yeah, and I'm sorry..I'm aware it's thirdgen...but I'm 21/female...need any info. that can help me slightly...??
Thanks a bunch...

 

Being female doesn't mean we can't help ya here
BUT seriously
your car ignition system can have "items unique to 4th gen set ups" and we may not be hip to all those goodies...
I strongly can say it may be your ignition system.
Why did it just happen?
Why not?
Serious, the worn down part may have just finally caught up to ya.
AND TEH BEST ANSWER I CAN SAY IS THAT
IF the problem persists, then it will be easier to track down. That may not sound so appealing but on a Saturday night, that beats being at home or ? seeking answers than broken down side of road this time of night!
What ya can try and this is fun...
go start car, in area with no lights, open hood, see if you see any electrical arching going on.
IF YES TO THIS, your problem is electrical. What exactly, well that depends... but you can narrow down problem this way. IF no electrical arching, then it's "something else". Oh joy!

 

half solve this real fast....go to autozone and have them scan the comp real quick and put the code on here it makes things ALOT easier

 

Yeah, no kidding. Get the codes scanned.


Could be a bad ignition module, could be a collapsed lifter, could be a squirrel trapped in the combustion chamber, who knows...

 

I wanna say o2, clogging cat, even an egr issue......don't sound like ignition.

 

lets first see what the comp is telling you. Theres something wronge and thats why your ses light is on. Go to autozone and see why

 

See sometimes I know what I am talking about.

 

so got the codes.. it says DTS (codes)

p0306
cylinder 6
Misfire detected

was told could be spark plug, wire, or ignition coil..?
could it be anything else??
Bought all those parts anyway to have all three replaced..but could it be anything else?

Thanks again guys...

 

Aha.

Just messin' with ya, dadsbird.


Uh, yeah, I thought it was a misfire. I had a misfire on my car not too long ago. It turns out it was [the thing that controls when each spark plug fires, which is different on my '86 and your '99 because yours is the ign coil and mine is a distributer], so I replaced it, problem solved. You shouldnt have wasted your money on new plugs and wires just yet though. You should have checked them first. Same goes with the ign coil. But hey, replace 'em, and if the problem goes away, you will know that those parts are brand new.

 

I was talkin about goin to Autozone na na

 

You might want to try www.firebirdnation.com i know there are 4th gen people on there.

 

Spark plug is a good possibility. Pull it and note the color. If it's black and dry, then you either have too much fuel entering the intake cycle, or a weak spark caused by a bad cable. I would guess that since you don't have a code for cylinder 3 that the coil is okay, since the coil fires both cylinders 6 and 3 at the same time. (1999 model year does have DIS, right?) If the plug is wet and black, then you have an oil leak. If the gap is bridged, then you have a problem that should be looked at by a professional. If the plug is white, then you don't have enough fuel coming into the cylinder.
Check your fuel injector. If it doesn't have a signal, or a bad one, it's won't fire properly and then you won't have enough fuel. Check this with a "noid" light. If the light shows that you have a signal, then resistance check the injector with a multimeter. If the resistance is not 12.5 ohms or close to it, then you have a problem with that injector, whether it is shorted or has broken wiring. If the injector passes the resistance test (I should note that this should be done with the harness disconnected so you don't fry the ECM ), then pull the fuel rail out of its mountings and prime the fuel system by turning the key on and then back off after five seconds. If the injector leaks any fuel in five minutes, then you have a problem. If the injector passes this test and it's still not running right, then you might want to look at replacing the injector since it may be clogged or mechanically broken internally.

I had this exact same problem for a year now and finally got rid of it last week with the replacement of two fuel injectors, either one or both of which could have been bad. Good luck in chasing your gremlin...

 

Nono I meant when you said it didnt sound like ign.

 

Check out this article on diagnosing misfires:

My last email promised an interesting topic for this week. I think the misfire detection feature is one of the most impressive and useful parts of the OBDII system. I'll describe how it works in a minute, first let me tell you about the experience I had with my car just about a month ago. (This is a pretty long email, if you want to skip to how-it-works, just read the last few paragraphs).

Returning from a late dinner, 25 miles from home on a very cold night, my check engine light turned on ('98 Chevy, 3.1L w/64,000 miles). At the same time the idle was rough, and power was down. The check engine light was even flashing for a little bit (not good!), then went to steady-on.

Being an engineering-type (my wife might substitute the word "geek") and an AutoTap-addict, I always have my Palm PDA with me and keep my AutoTap in the car. So - I plugged in AutoTap and read the codes. There were three misfire codes, but the most telling was the following:

P0304 Cylinder 4 misfire detected
Now that I knew the problem, I also knew my light was flashing was because driving with a misfire can wreck the catalytic converter. The right thing to do here would be to call a tow-truck. But, I didn't. We drove home very gently. I was able to use AutoTap to monitor the live misfire counts in cylinder four and was able to find some "sweet-spots" where the misfire seemed to mostly go away. I really don't know if that was effective, but it made me feel better. A couple miles into the drive, the MIL stopped blinking and turned steady-on.

The next morning I headed straight to the garage. I'm going to go through this part quickly because I still want to tell you how the misfire detection system works.

I hooked AutoTap back up (the PC version this time, I keep an old laptop in the garage for just such an occasion). I configured the screen to show real-time misfire counts on all cylinders. Cylinder four definitely showed up as the culprit. Now I need to decide if it's an ignition or fuel problem (I ruled out a compression problem on purely on the basis of thinking positive). I swapped spark plugs and plug wires and coils with a different cylinder. With each swap AutoTap still showed #4 as the problem. That confirmed it wasn't a spark problem.

The next day I paid to have the car hooked up to a professional fuel-injection cleaning system. Magically, all my problems were solved (funny how money can do that). No more misfires, and the tech tells me he sees a lot of this. The pintle-valve in the injector gets clogged with varnish from fuel deposits. As preventative maintenance, he recommended using an injector cleaner additive each time I change the oil. Sounds like good advice. I should add that when I brought in the car I told the mechanic about the ignition system tests I had done. He agreed that he didn't need to do any further diagnosis and hooked it up to the cleaning system. I suspect that saved me close to an hour of shop time.

Happy days…for about three weeks. Then the problem reoccurs. AutoTap confirms it's the same cylinder. I do a little research and decide to change out the fuel injector. Those professional cleanings aren't terribly cheap and I don't want to do this once a month. I pick up a new fuel injector and o-rings for under $100.

I definitely underestimated how much work it was to change an injector on this car. There was a LOT of stuff in the way. Quite a few hours later, my new injector is in and everything's buttoned back up (no parts left, the measure of success in my garage). I start the car. Seems like its running smoothly. Check AutoTap for misfires - cylinder four is looking good. I pull up the DTC page of AutoTap and click the magic (and very satisfying) "Clear DTCs" button and the light turns off. I use my Palm a few times over the next few days to check for Pending DTC's and watch cylinder four. Success!

This was a pretty involved project on this car. A professional tech could have done it faster than me, but there's no way they could have gotten it done in less than three hours, not including any diagnostic work. I never did check what the repair charge would have been, but I suspect I saved a few hundred dollars on this one.

Now - How it works. Here's what I find amazing about the OBDII misfire detection system. Not only did it tell me about a misfire, but it pinpointed exactly which cylinder had the problem. That's a huge timesaver! How? Read on!

The computer monitors crankshaft position. It needs to know this for a number of reasons so this sensor is nothing new. What's clever is that it uses this sensor to measure how much the crankshaft accelerates every time a cylinder fires. So if a cylinder isn't pulling its weight, the computer can tell which one was supposed to be firing at that time and reports that info back through the OBDII port. That it can do this at any RPM and load impresses the heck out of me.

If the computer detects enough misfires in a cycle, it turns on the light. It even does some clever things to detect if it's just a bumpy road causing the crankshaft to accelerate erratically. There are some other types of misfire detection systems, but I understand that this method is the most common. The system is also quite sensitive. It can detect a misfire long before you'll feel it as a drivability problem. Slight misfires can cause a Pending DTC (remember that email?). If they re-occur it turns on the light. Severe misfires cause the light to flash because it could mean that unburned fuel is getting to the catalytic converter (damaging it very quickly). Any misfire means your car is polluting.

That's it for this week's (long) email. I'm getting lots of great suggestions for more topics. Next week I'll share a reader's story of how to diagnose a bad coolant temperature sensor.

Happy Repairs,

Mike Fahrion
www.autotap.com