1995 GEO PRIZM ENGINE IDLE AND LOW RPM CUTOUT

  • Tiny
  • frypan2112
  • 1995 Geo Prizm

Engine Performance problem
1995 Geo Prizm Front Wheel Drive Manual 174, 00 miles

My engine is a toyota 1.6 vin 6 inline 4 cyl. My engine idles low and rough. As soon as the rpm's reach about 3000 or so (just guessing at the amount as I don't have a tach) the engine runs fine until I go to shift and the rpm's drop under 3000 or so. At these points the engine will cutout for just a split second or so causing a "bucking" action, as the rpm's increase the engine runs perfect.

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Saturday, October 30th, 2010 AT 5:57 PM

7 Replies

  • Tiny
  • KHLow2008
  • Expert
  • 41,997 posts

Hi frypan2112,

Thank you for the donation.

You would need a tachometer to monitor the idling speed. Seems the idling speed is too low and there could be a misfiring.

Get the throttle body and IAC cleaned and spark plug wire checked. We start from here.

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Sunday, October 31st, 2010 AT 2:48 AM
  • Tiny
  • frypan2112
  • Member

Hello,

I cleaned the throttle body and IAC. The throttle body and IAC were'nt very dirty. The IAC was'nt clogged at all, just a little bit of black soot-looking dirt that came right off with some carb cleaner and a rag. I also replaced the 2 water hoses and the vaccum line that goes to the IAC. Problem still remains unchanged. Spark plug wires have about 14,000 miles on them. Going to get new ones in the morning. Spark plugs themselves are brand new. (NGK Platinum) Still no tach. I must also add that the problem is'nt occuring until engine is warmed up. Thanks for the reply.

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Monday, November 1st, 2010 AT 3:01 AM
  • Tiny
  • KHLow2008
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  • 41,997 posts

When engine is warmed up, the cold start feature would cut off and this would result in the idling rpm being lower. In your case the idling seems to be lower than expected and since cleaning the throttle body and IAC did not work, the next thing you should do is to check the ignition timing and valve clearances.

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Monday, November 1st, 2010 AT 10:35 AM
  • Tiny
  • frypan2112
  • Member

Thanks for the information. New wires had no positive effect. I do have a couple of questions about the ignition timing and valve clearances. As for the ignition timing. Can that be changed by moving the distributor like the old days or is that controlled by the ECM? I'm not exactly sure what you are refering to with the valve clearances. Can you elaborate a little more?

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Monday, November 1st, 2010 AT 6:38 PM
  • Tiny
  • KHLow2008
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Yes, the ignition timing is adjustable by turning the distributor but the DLC terminal E1 and TE1 have to be bridged while checking and adjusting.


http://www.2carpros.com/forum/automotive_pictures/192750_DLC95PrizmGif04_1.jpg



Valve clearances is the amount of clearance between the camshaft lobes and the valves. You need to remove the valve cover to do that.

Shims are used for adjustment and you need to measure them and then change the shims to trhe correct thickness to get the desired clearance.


http://www.2carpros.com/forum/automotive_pictures/192750_ValveClearance95Prizm16Fig01_1.jpg

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Monday, November 1st, 2010 AT 7:16 PM
  • Tiny
  • frypan2112
  • Member

Hello. Thank You for your information and time. I am happy with your answers. My vehicle has been repaired. Although it was somethng that would have been difficult to diagnose without actually being present to see what was happening. What had to be replaced was the ignition coil. That solved the cutting out at low rpm "bucking" issue and was partly to blame for the low idling thing. The other part was a short in the signal wire for the tps causing a check engine light to flash and giving a code for a map sensor. That was found by accident upon just moving the wires around while having the scanner hooked up and everything being good 1 second and not the next. Anyway, like I said before, thank you for your time and answers. You may keep the small donation.

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Tuesday, November 2nd, 2010 AT 8:06 PM
  • Tiny
  • KHLow2008
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  • 41,997 posts

Glad to know you have fixed the problem.

Thank you for using 2carpros and have a great day.

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Wednesday, November 3rd, 2010 AT 7:18 AM

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