code 48 misfire diagnosis??? - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 04-19-2008, 04:29 PM   #1
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Default code 48 misfire diagnosis???

Hello all I am new to this. I have owned my 91 Bonneville Le for two years and I couldnt ask for a better car. Since last monday I have been having problems. On my way to work monday the car just shut off after about a 20 min. drive, I sat for a sec. and then she started right back up everthing was fine. Then lastnight on my way to a job she did the same again after 20 maybe 30 minutes. So I figured That I will have to be doing some quick figuring out. Today I drove to wal mart everything was well about 10 minutes. Left wal mart and about ten minutes later I began to lose power I was going about 50 mph stopped for afew and left off again now this is the scary part it is running really rough I barely have any power she wont go above 50 and at anything above 20mph Im afraid she might blow up. Are there any suggestions, or has anyone experienced the same thing? My funds are low UPS dosent pay much and detailing cars right now is slow. I appreciate the help and it is nice to find a family Of Bonneville owners.

PS. I opened the hood while running and the engine is shaking badly I suspected this cause the car was as well. Please help.
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Old 04-19-2008, 04:55 PM   #2
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When was the last spark plug change? If it'* been a while then start there. Are the spark plug wires numbered 1 -6 if so then they're waaay overdo. If you remove the spark plugs keep them in order & take a picture of the electrodes for us.
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Old 04-19-2008, 06:40 PM   #3
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Default MAF sensor???

I changed the plugs when I got her. I guess It could use it again. I rarely slack on maintenance, money has been tight (extremely). I went out to spend a lil time with her after posting and I think the pcv valve needs to be changed as well as the tube going in to it while the car is running the tube pretty much collapses. I disconnected it and the engine seemed to run a little more smoothlybut still rough. I was wondering where the maf sensor is on it and if there was a way to clean it. Its a91 bonneville le. I cant really afford another tune up until my next check (friday) maybe my last from UPS if I cant get to work. Again I am open to any suggestions. Again thanks.
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Old 04-20-2008, 10:35 AM   #4
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well I pulled the code this morning It is a code 48 misfire. So really what should I do. It is I guess sounding like the plugs. Could it possibly something more serious?
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Old 04-20-2008, 11:30 AM   #5
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Quote:
Originally Posted by 91bonnygonewild
What should I buy for tune up brands etc. ? wires, plugs, fuel and air filter etc. I also want to change pcv and the hose going to it. The hose collapse while running. Thanks again I wish I would have found the club sooner.
Go with the stock AC Delco plugs or NGKs.
Delco or Belden Premium wires from NAPA.
Any brand air & oil filter
If the grrommet for the PCV valve is hard then change that also. PCV valvle should fit tight in the grommet.
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Old 04-20-2008, 11:49 AM   #6
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The pcv valve goes into the charcoal canister correct? At least that is what is stated on the cannister. I pulled that off yesterday and there is space around the bottom tube going into the canister is that where a grommet should be? If so will the grommet fix that or do I need tgo replace the canister as well? Thanks for the info on the wires and plugs and other items. Oh I just checked the other thread and I did not know not to do that wont happen again.
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Old 04-20-2008, 12:10 PM   #7
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Check the 8th digit of the VIN & make sure it'* a C. I think all the 91'* were C. If so the the PCV valve is hidden under the three spark plug wires that go to the rear cylinders.
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Old 04-20-2008, 12:17 PM   #8
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The older cars and PCM'* have no true ability to diagnose or detect ACTUAL misfires, and can only detect faults in the components that CONTROL firing.

Your problem will be either the cam sensor, crank sensor, ICM/Coils, or associated wiring. While your plugs and wires may be bad and need to be changed, the PCM cannot see them and does not know they even exist.

1994 was the first year the PCM could detect an actual misfire in the cylinder itself.
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Old 04-20-2008, 02:53 PM   #9
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Quote:
Originally Posted by Technical Ted
Quote:
Originally Posted by 91bonnygonewild
What should I buy for tune up brands etc. ? wires, plugs, fuel and air filter etc.
Go with the stock AC Delco plugs or NGKs.
Delco or Belden Premium wires from NAPA.
Any brand air & oil filter
If the grrommet for the PCV valve is hard then change that also. PCV valvle should fit tight in the grommet.
I'm going to disagree with the "any brand" suggestion and recommend that you use WIX filters and do not use Fram brand anything. It may interest you to know that the NAPA branded filters are made by WIX.
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Old 04-20-2008, 08:01 PM   #10
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Fram anything is evil. Anything BUT fram is OK, but as had been said WIX is good and personally I stick with AC delco.

PCV Valve R and R: http://www.lesabret.com/phpBB/viewtopic.php?t=6107
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