Engine Help Please Read
Thread Starter
Le Mans Master
Joined: Aug 2005
Posts: 7,890
Likes: 0
From: FL
Engine Help Please Read
Hey Team
My 98 coupe is having some problems.
Car was running perfect and then...Here is what I did.
I Took out the cats (didn't get sims yet) and had 2 straight pipes welded in. 2 codes came up but the car ran perfect still.
The next week I changed out the spark plugs to tr55s with .55 gap. Car still running perfect, gas mileage went up about 3mpg.
Saturday I put in new magnecor 8.5mm wires. Car still runs fine as far as I know...didn't drive it much
Saturday night drove it to a friends house and we changed out the oil pressure sensor. Had the Upper intake manifold off and thought we put everything back right.
I then notice on the highway when I give it full gas at 1000-1900 rpms it bucks, misfires and backfires. After 2000 you don't feel it but I assume the problem is still there. The car also idles a little lower and shakes at idle when it never used to. Feel a big chunk of power is missing. The car runs good until it is warmed up where the problem becomes real obvious.
I had my friend drive around with me with his laptop and the scanning tool and he didn't notice anything wrong.
What can I do? I sprayed some carb cleaner on the uim to look for a leak, I inspected for anything being loose and found the coupler behind the MAF was hanging off (put it on with no change), reset the computer several times.
Please, I think I've shown some effort! If you have any ideas don't be shy.
Thanks in advance
My 98 coupe is having some problems.
Car was running perfect and then...Here is what I did.
I Took out the cats (didn't get sims yet) and had 2 straight pipes welded in. 2 codes came up but the car ran perfect still.
The next week I changed out the spark plugs to tr55s with .55 gap. Car still running perfect, gas mileage went up about 3mpg.
Saturday I put in new magnecor 8.5mm wires. Car still runs fine as far as I know...didn't drive it much
Saturday night drove it to a friends house and we changed out the oil pressure sensor. Had the Upper intake manifold off and thought we put everything back right.
I then notice on the highway when I give it full gas at 1000-1900 rpms it bucks, misfires and backfires. After 2000 you don't feel it but I assume the problem is still there. The car also idles a little lower and shakes at idle when it never used to. Feel a big chunk of power is missing. The car runs good until it is warmed up where the problem becomes real obvious.
I had my friend drive around with me with his laptop and the scanning tool and he didn't notice anything wrong.
What can I do? I sprayed some carb cleaner on the uim to look for a leak, I inspected for anything being loose and found the coupler behind the MAF was hanging off (put it on with no change), reset the computer several times.
Please, I think I've shown some effort! If you have any ideas don't be shy.
Thanks in advance
Drifting
Joined: Dec 2001
Posts: 1,426
Likes: 0
From: Canton Michigan
Check your wires. I had 2 Magnecore wires come loose at the plugs just after putting them in. They're great wires but a pain to get on.
Also, check the metal end caps on the plugs. You need to tighten them just a bit with pliers before installing them. They will work loose if you don't tighten them.
Another thing I was guilty of!
Good luck.
Al.
Also, check the metal end caps on the plugs. You need to tighten them just a bit with pliers before installing them. They will work loose if you don't tighten them.
Another thing I was guilty of!
Good luck.
Al.
Thread Starter
Le Mans Master
Joined: Aug 2005
Posts: 7,890
Likes: 0
From: FL
Isn't there some kind of misfire code?
I was also thinking that it could be ignition related. Maybe the wires were bad or that a coil went out but the car runs better in the higher rpms...I can't feel misfires at least but it's def. down on power.
I was also thinking that it could be ignition related. Maybe the wires were bad or that a coil went out but the car runs better in the higher rpms...I can't feel misfires at least but it's def. down on power.
Le Mans Master
Joined: Apr 2001
Posts: 5,331
Likes: 39
Originally Posted by IDM
Isn't there some kind of misfire code?
I was also thinking that it could be ignition related. Maybe the wires were bad or that a coil went out but the car runs better in the higher rpms...I can't feel misfires at least but it's def. down on power.
I was also thinking that it could be ignition related. Maybe the wires were bad or that a coil went out but the car runs better in the higher rpms...I can't feel misfires at least but it's def. down on power.
Your friends scan tool would have picked up any kind of misfire...there is a code for misfire but that would be for major misfires like with bent valves.
Pro
Joined: Jun 2005
Posts: 593
Likes: 1
If this C5 was tuned sometime in the past the tuner might have turned off codes so they would not trip such codes like misfires.
If battery was disconnected then PCM needs a idle relearn and then a good 40 mile drive to relearn
Maybe the small vaccum hose right inder the MAP sensor ( or MAP itself was not connected) that goes to the intake and then to the HVAC reserve tank was not hooked up properly.
Turn HVAC on and switch where the air should be directed, if it just blows out certain ducts then that tells you that small hose is off or leaking which would effect engine vaccum.
If battery was disconnected then PCM needs a idle relearn and then a good 40 mile drive to relearn
Maybe the small vaccum hose right inder the MAP sensor ( or MAP itself was not connected) that goes to the intake and then to the HVAC reserve tank was not hooked up properly.
Turn HVAC on and switch where the air should be directed, if it just blows out certain ducts then that tells you that small hose is off or leaking which would effect engine vaccum.
Burning Brakes
Joined: Nov 2004
Posts: 822
Likes: 0
From: Grafton Ohio
Originally Posted by boosted_z06
If this C5 was tuned sometime in the past the tuner might have turned off codes so they would not trip such codes like misfires.
If battery was disconnected then PCM needs a idle relearn and then a good 40 mile drive to relearn
Maybe the small vaccum hose right inder the MAP sensor ( or MAP itself was not connected) that goes to the intake and then to the HVAC reserve tank was not hooked up properly.
Turn HVAC on and switch where the air should be directed, if it just blows out certain ducts then that tells you that small hose is off or leaking which would effect engine vaccum.
If battery was disconnected then PCM needs a idle relearn and then a good 40 mile drive to relearn
Maybe the small vaccum hose right inder the MAP sensor ( or MAP itself was not connected) that goes to the intake and then to the HVAC reserve tank was not hooked up properly.
Turn HVAC on and switch where the air should be directed, if it just blows out certain ducts then that tells you that small hose is off or leaking which would effect engine vaccum.
The most difficult part of the intake r&i is making sure the map is hooked up. GM doesn't give you much room to work with back there. Try checking the vacuum connection on the map.
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Le Mans Master
Joined: Jul 2002
Posts: 7,370
Likes: 8
From: Slave to the evil empire
Cruise-In V Veteran
St. Jude Donor '04
Did both vacuum lines get hooked up behind the intake manifold, the one for the brake booster is pretty obvious but the smaller one can and does get missed.
Thread Starter
Le Mans Master
Joined: Aug 2005
Posts: 7,890
Likes: 0
From: FL
Can someone give me a picture? Please tell me that I don't have to remove the upper intake manifold again to access this
I also am having a problem with the A/C blowing air out of the wrong places...it won't switch modes.
I also am having a problem with the A/C blowing air out of the wrong places...it won't switch modes.
Le Mans Master
Joined: Dec 2003
Posts: 5,561
Likes: 447
From: Atlanta metro Ga.
99% sure you have a vacuum leak, and as the others have stated, and by your own admission that your AC controls no longer function..
Looks like you need to pull the intake again, bud. Loose / disconnected lines on the back.
Looks like you need to pull the intake again, bud. Loose / disconnected lines on the back.
Thread Starter
Le Mans Master
Joined: Aug 2005
Posts: 7,890
Likes: 0
From: FL
Wow Magnecor Plug Wires Blow
They don't really snap into place very well and seem loose. They are also too long and touch the side of the headers and 2 of them have had the boot melted already within 1 week of owning them. What a **** poor product and I bought it because I thought it was the best since it was the most expensive at 90 dollars.
They don't really snap into place very well and seem loose. They are also too long and touch the side of the headers and 2 of them have had the boot melted already within 1 week of owning them. What a **** poor product and I bought it because I thought it was the best since it was the most expensive at 90 dollars.
