99 Firebird hard to start when hot

firebird1999 · #1 03-09-2009, 12:44 PM

Ok, to start out I'm not really good at automotive terminology and I appologize for any misconceptions but I am thankful for any help i receive. The car is a 1999 3.8l firebird with 133,000 miles on it. I've got a huge list of symptoms so I hope that this description is specific enough to get a good diagnosis.

Symptoms:
Check Engine Light - Random Misfire, appears on start up and goes away, sometimes appears during idle, happens randomly, 3 occurrences in last 30 starts.
Really hard to start when hot(above 30 degrees).
Starts perfect when cold(like 30 degrees or colder).
Dumps large amounts of fuel when first starting(Black smoke after finally started and stumbles extremely bad, eventually "mellows" out).
Backfiring after accelerating and letting off.
Extremely bad fuel mileage (<15 mpg)
Idles really rough.
My manifold reading from a scan tool said 10.3 hg at idle.

I've had the fuel pressure checked by a local mechanic and he said it was fine. He also checked for vacuum leaks but I don't know how good of a job he actually did. I recently replaced 4 of the 6 wires and plugs to try and correct the problem, it made the engine idle and run better but still did not fix the problem. I did a fire test on each wire by taking off each individual wire while it was running and all are firing. I'm thinking about doing a coil test but I don't think that it could be the problem.

What should I try next? I am really interested in learning about cars and I want to fix this myself so if anybody can give me a direction to go I will try my best.

Oh yea, changing the spark plugs was a major pain in the ass....I find the 2 rear plugs on the passenger side are nearly impossible to remove much less replace. Is there a trick to changing them?

Thanks!

Also, I just remembered something. Sometimes when I go to a stop sign all of my lights will dim like my car is goin to die and my voltage gauge in the car will drop down into the yellow and then the engine will pick up and everything will be ok. Also I'm not sure what the voltage is supposed to be at but its almost in the red constantly.

wrightz28 · #2 03-09-2009, 04:31 PM

Your battery should run around 13.5 volts with no load on it when the engine is running.

You can get a multi-meter from just about anywhere for around $20 now-a-days and use the voltmeter function of the multi-meter and confirm what your dash gauge is telling you.

You starting issue to me sounds like a coolant temp sensor what are the codes from the Check engine light coming up as?

firebird1999 · #3 03-10-2009, 05:07 PM

The check engine light is a:

P0300 Random/Multiple Cylinder Misfire Detected

Although, like I said this only happens when my engine is trying to start and acts like its flailing for help as it stumbles and studders. It eventually mellows out and a few miles down the road the light will go out. I'll be sure to check the voltage, should I check directly at the alternator?

Lol, thats funny because I've had 3 people tell me that its the coolant temperature sensor but wouldn't that make my engine temperature gauge in my car read wrong? I ran a scan tool on my car a while back to try and eliminated that possibility and the scan tool said the engine was about 34 degrees when it was about 20 oustside and by the time the engine was completely warmed up it was at about 205.

Also I just replaced a coil pack that had a rusted plug post to try and solve the problem. It runs a good bit better but still has all of the problems as before.

Thanks for your reply I really appreciate the help!

firebird1999 · #4 03-10-2009, 05:19 PM

Um, wow, I just checked my voltage on my battery when it was connected to the car with it off and the voltage was 14.5 volts and with the car running the voltage was 17 volts. I checked this right at the battery. I know car batteries are supposed to run at 12 volts so is this really weird or what?

Scrapper · #5 03-10-2009, 05:40 PM

it could be that it's out of time you could put a new cps (crank sensor) on it. also sounds like your catalatic converter could be pluged up or egr. i doubt it could be the module under coil pack. take your neg. battery cable off for about 15 minutes then put it back on this will reset your computer and see if that does anything.

firebird1999 · #6 03-10-2009, 05:55 PM

Crank sensor is a deffinite possibility right now but I hate to just start throwing parts at it without testing first. It just had a new catalytic converter put on around 100,000 miles and EGR does sound possible but is also very expensive, I hate to spend without more testing. Could my extremely high voltage be causing some of these issues, I know sensors are very sensitive and I would think that an incorrect voltage might create incorrect readings.

wrightz28 · #7 03-11-2009, 09:06 AM

Yeah, that voltage is high. Unfortunately now the PCM controls volage regulation versus a regulator in the 'old days'.

You may want to check all connections at the battery, alternator and starter for corrosion.

firebird1999 · #8 03-11-2009, 06:26 PM

Well I can check all the connections for corrosion but if I completely remove the battery from the car and test the voltage it reads 15 volts so would corrosion really make that happen?

wrightz28 · #9 03-12-2009, 07:27 AM

It's being overcharged for a reason, and start with obvious first. Wouldn't it completely blow to put a new PCM in and it turns up there's a funky battery connection on the starter?

firebird1999 · #10 03-24-2009, 11:14 PM

Okay I just took my car to a really good local mechanic and he was able to fix it for me it turned out that the fuel regulator was bad and was leaking. He replaced the regulator and the fuel rails as well as 1 coil pack for the missing in the engine. Thanks for all the help! I hope this helps anyone else that runs into this problem.

wrightz28 · #11 03-25-2009, 08:49 AM

So what happened with the charging issue?

firebird1999 · #12 03-26-2009, 05:47 PM

Ok wow, big issue, this is just what happened. I drove my car this morning when i went to the doctor and when I started it I got a strange noise but then it went away so I went onto the doctor. When i got back i let my car sit for a while and i went out to start it and huge amounts of white smoke came rolling out the tail pipe, it rained pretty bad this morning so I'm not sure if that could've caused this amount of smoke but I'm just scared to drive it. The smoking went away after about 2 minutes and went down to a very slight smoking. My coolant is full, my oil is full, they are not contaminated?????? help!

wrightz28 · #13 03-27-2009, 09:15 AM

Can you elaborate on this strange noise a bit?

firebird1999 · #14 03-27-2009, 10:22 AM

Kind of like a screeching metal noise but I just throught it was my surpentine belt slipping because it was rainy, it needs replaced. It is a possibility it was something else though.

firebird1999 · #15 03-27-2009, 10:57 AM

Ok today i started my car and now there is no smoke what so ever and when i drove it home from work still no smoke....this is really weird....is there any prank u can play on someone to make their car do that cuz i could've sworn i heard a car door/hood shut a couple nights ago.

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