1995 Pontiac Grand Am surges driving- stumbles at idel

Tiny
DELPHICABLE
  • MEMBER
  • 1995 PONTIAC GRAND AM
  • 4 CYL
  • FWD
  • AUTOMATIC
  • 140,000 MILES
Car will idle fine but every 20 sec. Or so the engine idle will stumble, While driving ( highway speed its most notesable ) the engine will surge not under accelleration but when speed levels out or slightly backing off accellator. Replaced fuel filter, no change. This has been a problem for months steadly getting worse.
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Friday, January 30th, 2009 AT 11:12 AM

13 Replies

Tiny
MASTERTECHTIM
  • MEMBER
When was the last tune up? When I tune these engine up I always change the coil cover too because this is usually what causes the problem. The coil cover acts like a distributor cap
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Friday, January 30th, 2009 AT 6:07 PM
Tiny
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I replaced plugs, new coil and ing. Mod. No change still the same problem.
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Wednesday, February 18th, 2009 AT 10:01 AM
Tiny
MASTERTECHTIM
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What about the coil cover?
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Wednesday, February 18th, 2009 AT 1:39 PM
Tiny
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Yes that was also replaced.
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Wednesday, February 18th, 2009 AT 5:42 PM
Tiny
MASTERTECHTIM
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Well the next step is to do a fuel injector balnce test but you will need special tools to do this. Also check engine compression to make sure there is not a cylinder that has low compression.
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Thursday, February 19th, 2009 AT 6:02 AM
Tiny
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Took car into shop, they test drove it and noticed that the problem only acured when backing off the pedal to maintain speed also sometiimes at idle. They brought it into there shop and did there testing for over one hour and said there is no power going to the MAP sensor, they traced it back to the ecm under the glove box. They told me to get another ECM and replace it, so I did that -- no change same problem. Will take it back to shop on monday unless someone has any other ideas. Ty
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Saturday, February 28th, 2009 AT 3:39 PM
Tiny
MASTERTECHTIM
  • MEMBER
No power on the 5 volt reference wire? Check the gray wire for 5 volts, if none then check the tps sensor gray wire for 5 volts. They share the same 5 volt reference.
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Saturday, February 28th, 2009 AT 7:25 PM
Tiny
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I just check them both, I got 4.98 om the map sen. Wire and 5.01 at the tps.
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Saturday, February 28th, 2009 AT 8:14 PM
Tiny
MASTERTECHTIM
  • MEMBER
Does thie engine have a egr valve? Sounds like egr valve hanging open. This would also cause a map sensor code. If no egr valve then please give me the eigth letter of the vin number so I know exactly which engine you have but if you do have a egr valve then unplug it and drive it.
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Saturday, February 28th, 2009 AT 8:18 PM
Tiny
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I do not see an egr valve, 8 diget is a D
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Saturday, February 28th, 2009 AT 8:32 PM
Tiny
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So you know how I tested the MAP connector, I jumped B lt. Grn accross to C gry wire it was 4.98v, also tested B to battery and got 0.03 with ing. On
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Saturday, February 28th, 2009 AT 8:36 PM
Tiny
MASTERTECHTIM
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There is no egr valve on this 2.3 litre. I just looked at wiring schematics and was lookig for a possible cause. This uses a single wire oxygen sensor which go bad on these alot causing drivability problems but they should be evident on scan tool when monitoring. Also back pressure from a restricted cat converter? Its real hard to give you accurate details on problem because I am not driving it and cant see the data from the scan tool. Sorry I could not be more help. But unless you live near holbrook massachussettes im afraid im going to be of no more real help.
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Saturday, February 28th, 2009 AT 8:44 PM
Tiny
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The problem was a Map sensor wire shorting out somewhere in the wiring harness, I ran a new wire the green wire from the Map sensor to the Pcm. Problem solved no more surging or bad idle. The voltage at the green wire was jumping around from 1.66v down to 0.00v at idle causing the engine to run bad. Now voltage is steady.
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Friday, March 6th, 2009 AT 6:38 PM

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