RPM goes up and down and car runs bad when EGR temp sensor is plugged in

Tiny
AUWE
  • MEMBER
  • 1989 CHEVROLET SUBURBAN
When I unplug the EGR temp sensor car is running smoother. But then the car starts bad.
I already replaced all engine sensors (throttle sensor, map sensor, egr temp sensor, egr valve, CO sensor) and replaced spark plugs+wires.+Distributor. I also replaced the fuel filter + pressure regulator.
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Wednesday, June 26th, 2013 AT 6:22 AM

7 Replies

Tiny
HMAC300
  • EXPERT
Check for a vacuum leak, use choke spray and if a tbi unit check under the unit first as they blow gaskets there. Also if hose going to map is soft replace that.
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Wednesday, June 26th, 2013 AT 6:31 AM
Tiny
AUWE
  • MEMBER
Thanks for your fast reply, I'm going to check the gaskets right now. I already replaced the hose to the map. But could it also be a fuel pump problem or fuel injection problem. I want to be sure before I start buying and installing these.
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Wednesday, June 26th, 2013 AT 6:46 AM
Tiny
HMAC300
  • EXPERT
Check your fuel pressure first it should be 9-11 psi and scan for codes to make sure. Also check wires at top of tbi to see if they are broken
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Wednesday, June 26th, 2013 AT 6:52 AM
Tiny
AUWE
  • MEMBER
Yesterday I took out the TBI, the wires were fine but the gasket looked a bit bad, so I use liquid gasket (silicon seal). I live on a remote island, we do have a NAPA deal but the gasket is not in stock and takes 2 weeks to get here. This morning the cars runs fine and the check engine light is not burning. BUT every time I seem to have found the problem the car runs fine and starts running bad within a day. Keeping my fingers crossed it was a gasket problem.
I don't have the gear to check the fuel pressure, but if that would be the problem I would think it would run bad all the time. And my cars runs perfectly fine this morning, even with the EGR sensor plugged.
Before this morning, when I unplug the EGR sensor, rpm goes up and the car runs a lot better
Really appreciating your input here, been having this problem for a few months and your info finally makes some sense!
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Wednesday, June 26th, 2013 AT 7:16 AM
Tiny
HMAC300
  • EXPERT
Order the gasket and remove the silicone sealer, it will get into your O2 sensor and screw it up. You'll need the gasket so when it comes in replace it.
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Wednesday, June 26th, 2013 AT 8:22 AM
Tiny
AUWE
  • MEMBER
Hey hmac300,
Hope you're still following this thread! I removed the silicone sealer and replaced the gasket. But still when the car runs stationary the rpm goes up and down, not smooth at all. I measured the fuel pump pressure and it is only 2 psi. So probably there lies the problem. I can put in a new fuel pump but I measured another problem. On the wire from the engine to the fuel pump I only get 8 volt instead of 12v. If I change the fuel pump I still have this problem. My question: is it a problem that I only measure 8v and what could cause that low voltage?

Thanks again for your help!
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Thursday, June 27th, 2013 AT 12:42 PM
Tiny
HMAC300
  • EXPERT
Check for a shorted wire touching the bodyframe
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Friday, June 28th, 2013 AT 6:13 AM

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