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2000 GT Rough idle + hesitation around 1500-2000 RPM

  • Thread starter Thread starter Sams2000GT
  • Start date Start date Apr 26, 2011
S

Sams2000GT

Member
May 8, 2002
41
0
6
Michigan - Around Detroit
Apr 26, 2011
#1
  • Apr 26, 2011
  • #1
Having some sort of problem with my GT. About 2 months ago it overheated on the freeway and coolant ended up going all over the engine because the radiator fan was not functioning and turning on to cool the car. That has since been fixed but I have noticed since this incident whenever it rains or is humid out the car hesitates and has a rough idle to it, normally only in the morning on the way to work. When driving it I can feel the engine miss like a plug is bad throughout all gears around 1500-2000 and 3000RPM as well. There is no CEL and when I drive it home it doesn't seem to have the issue in the evening. The problem is very sporadic and only happens some days.

The mechanic that fixed my car suggested to bring it back so he could check the spark plugs. He said since the car overheated it could have cracked the porcelain around one of the plugs. He of course wants to charge for this but I figured I would see if I could attempt to figure out what the issue is first myself.

Any ideas or tips?
 

trinity_gt

10 Year Member
Jan 31, 2003
3,125
81
99
Canada
Apr 26, 2011
#2
  • Apr 26, 2011
  • #2
The mechanic might be on to something re the plugs.

Pull the COPs (coils) out of each hole and visually check each plug well for coolant/water left behind from the overheating. If there's any moisture in there it may cause a problem. Also check the COP boots themselves for contamination.
 

GDawg

Founding Member
Mar 22, 2002
1,469
19
68
Nevada
Apr 26, 2011
#3
  • Apr 26, 2011
  • #3
trinity_gt said:
The mechanic might be on to something re the plugs.

Pull the COPs (coils) out of each hole and visually check each plug well for coolant/water left behind from the overheating. If there's any moisture in there it may cause a problem. Also check the COP boots themselves for contamination.
Click to expand...

Absolutely. Heck with the mechanic, pull them your self. Have a look at each one and look for individual problems. And clean any water out of the plug holes before removing them.
 

wmburns

SN Certified Technician
Aug 14, 2009
5,892
514
204
Houston Texas
Apr 26, 2011
#4
  • Apr 26, 2011
  • #4
FWIIW, if moisture gets into the spark plug holes and grounds out the spark, sometimes this will damage the COP insulator boot. The misfire will continue even though the moisture has been removed. If this is the case, consider replacing the COP boot insulators. Autozone (Durlast) sells a set of (8) insulators for less than the price of a single COP.
 

jayrw

Member
Sep 2, 2007
156
0
17
Clovis, California.
Apr 26, 2011
#5
  • Apr 26, 2011
  • #5
I have a 00 GT and last year my intake manifold cracked which caused coolant to spray all over the motor, a couple of the sparkplug wells became filled with coolant causing a misfire, It was a pain getting out all of the coolant without removing the spark plugs but we managed to do it and the car has been running fine since.
 
D

Deleted member 38176

Apr 26, 2011
#6
  • Apr 26, 2011
  • #6
Yup, definitely a COP/plug issue. Ive had this problem in the past.
 

Maxpowers

Member
Sep 9, 2009
859
2
19
Pittsburgh, Pa
Apr 26, 2011
#7
  • Apr 26, 2011
  • #7
I agree with the statements above. The symptoms sound exactly like a COP/plug issue.
 
S

Sams2000GT

Member
May 8, 2002
41
0
6
Michigan - Around Detroit
Apr 27, 2011
#8
  • Apr 27, 2011
  • #8
Thanks all for the suggestions. Is the COP just held on by the one screw? If there is no moisture or coolant should I assume the COP is bad? Anyway to test the COP with a multi-meter?
 

trinity_gt

10 Year Member
Jan 31, 2003
3,125
81
99
Canada
Apr 27, 2011
#9
  • Apr 27, 2011
  • #9
Yes, one screw. Once the screw is removed the COP can be removed by weaseling it past the fuel rail. (There's no need to remove the fuel rail in case you were wondering.)

The COP can be tested with an ohmmeter to provide a go/no-go test of the primary and secondary windings. However, such a test does nothing to test whether or not the COP has insulation issues. That is, a DC test might show a 0.6-ohm primary resistance and a 6Kohm secondary resistance (for instance) and you might think it's okay. However, when that coil is asked to deliver a 25,000 volt potential to a spark plug it may have an internal winding insulation problem that (a) basically shorts the HV causing much less to be delivered to the plug and (b) doesn't show up with a DC ohmmeter test.
 
S

Sams2000GT

Member
May 8, 2002
41
0
6
Michigan - Around Detroit
Apr 28, 2011
#10
  • Apr 28, 2011
  • #10
Thanks trinity, i'll check them out this weekend
 
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