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Old 12-09-2007, 01:37 AM   #1
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Default Hesitaion/Missfire under load

hi there all,

I am new to the site and looking for a little help. I have a 01 bonneville SSEi that is mostly unmodified. The only thing that I have done to the car is remove the honeycomb looking air diffuser form the intake, as per a tech article read on the zz performance website. The car has over 200km and has started to develop a really bad hesitation under hard acceleration around 3/4 throttle and 4k rpm. when I first purchased the car this problem did not exsist. The condition has not caused the SES light to come on. Although tonight while returning home it did blink fo a second and then go out.
I run 91 octane fuel, the best availabe in my area. I have had a local shop check it out some and they seem to be stumped as to what it may be. any ideas?? much appreciated!
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Old 12-09-2007, 10:41 AM   #2
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Have you tried putting the maf screen back in to see if the problem goes away? When was your last tune-up, plugs and wires? You may want to try clening the maf, also. Did they check fuel pressure?
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Old 12-09-2007, 11:03 AM   #3
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You can try checking your MAP sensor. My wifes went out last week. Her van would hesitate, low power, surge while on cruise control, stall at idle. When it went out completely it didn't shift right, back fired threw exaust, stalled a lot, and very little power. If this sounds like what your going threw, take a look at that.
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Old 12-09-2007, 11:45 AM   #4
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That will be the first thing that i do will be to replace that piece back into the intake.

The shop where I took it check the fuel pressure and said it was 100%.

I went to replace the spark plugs a while back but when I removed a couple of them they looked great, the gap was ok and the were iridium so i left them alone. the spark plug wires dont look like they have ben changed since new so maybe i will give that a try next.

Having never owned a */c 3800 before especially with that kind of kms, I am just concerned with it not lasting.

Thanks
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Old 12-09-2007, 12:41 PM   #5
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If you take good care of teh car, oil, filters, etc. It shoudl last a long time. I have a 97 with about 90k on it, that'* about 144k km. And it runs like a top.

If you can go someplace like autozone and have them scan your car, they might be able to tell you the problem. Many times they do this for free, but I would suggest tipping the guy $5 or something. You do this and they may help even more.
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Old 12-10-2007, 02:16 AM   #6
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I did as was told and replaced the screen to its rightful home and disconnected the battery for about 8 hours. I also check the spark plug wires and found that the coil nearest the firewall ad some corrosion and rust when I removed the boots. I cleaned it as best I could with some emery cloth and the with electrical contact cleaner. I think I will invest in a new set of wires on Monday.
So anyhow, after reinstallation I road tested and the problem was better but still there under hard acceleration.

The SES lamp started blinking this time and hopefully there is some sort of code when I take it into the shop in the morning.

Does anyone else have any ideas???
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Old 12-10-2007, 02:32 AM   #7
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Default Re: Hesitaion/Missfire under load

Quote:
Originally Posted by thesub265
has started to develop a really bad hesitation under hard acceleration around 3/4 throttle and 4k rpm
Maybe a clogged or cracked catalytic converter? I know when mine went on my SSEi I started to have trouble about 1/2-3/4 throttle and it was very hard to accelerate around or above 4k. It only got worse over time; I only realized what the problem was after I blew a hole in the side of my cat from the pressure.



Ed
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Old 12-10-2007, 08:50 AM   #8
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Your plug wires are original? With all those miles, I would definitely start with a fresh set of wires and plugs.

How old is the fuel filter? It could be clogged causing the engine to be starved for fuel at higher RPMs.
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Old 10-29-2008, 12:44 AM   #9
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problem fixed, i had the same problem,,hesitation under 50% throtle,,,,,just started happening one day,,i changed the plugs(platnium) and wires,,plus emptied a full can of throtle body cleaner into the intake while the car was running. thought i would put a new air filter in as well,,,, the car also had a small missfire when at idle,,the car idles perfect now and the hesitation is totaly gone...the honey comb thing as talked about earlier is also removed....does anyone have the fix for the courtesy light problem..
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Old 10-29-2008, 12:46 AM   #10
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PS my car is a 2002 ssei with 150,000kms original plugs were platnium AC Delco
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