1994.5 - 1997 7.3L Power Stroke Diesel

Intermitting idle at startup---Normal?

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Dec 20, 2005 | 07:42 AM

#1

RichPSD

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Joined: Sep 2005

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From: Amherst, NH

Intermitting idle at startup---Normal?

After I finished the GP/GPR job I stated the truck, it now seems to have small surges in RPMs at idle. As soon as she’s warmed up it doesn’t seem to happen anymore….is this normal? And is there a type of chock system on these beasts?

as always,
Thanks,

/Rich

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Dec 20, 2005 | 09:33 AM

#2

chapguy

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I just finished GP/GPR's last weekend. I disconnected the batteries when I switched out the GPR so I could clean all the posts/contacts. When I hooked it back up I found that my truck now has a high idle when cold that it never has had in the 2 plus years that I've owned it. Only first start and only when very cold. Of course, I couldn't start it when it was this cold without plugging it in until now. It's not really a surge but it starts out with the low idle, runs a little rough and then idles up to around 1000 rpm for a minute or two then back down to low idle and all is normal.

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Dec 20, 2005 | 11:57 AM

#3

stroker2

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Joined: Jul 2005

Posts: 261

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From: North Carolina

Quote:

Originally Posted by RichPSD

After I finished the GP/GPR job I stated the truck, it now seems to have small surges in RPMs at idle. As soon as she’s warmed up it doesn’t seem to happen anymore….is this normal? And is there a type of chock system on these beasts?

as always,
Thanks,

/Rich

I think it might be your EBPV system if it's still hooked up. The closing of the EBP valve causes a back pressure to build up in the exhaust manifolds. This back pressure forces the cylinders to work a little bit harder to force the exhaust gases out of the cylinders and may cause a momentary slight slowing of the engine. The PCM is trying to hold the engine RPMs at a certain RPM level and "sees" this slow down from the CPS (camshaft position sensor) pulses, so it adds a little bit more fuel to get the RPMs back up. It may over shoot the RPMs it wants and then has to reduce the fuel input to get the RPMs back down. This may go on, back and forth, until everything is stablized, probably at a slightly higher idle RPM than when the engine is warm and the EBP valve is open. Try disconnecting your EBP valve solenoid connector and see if it goes away. If it does it's your EBP system causing the problem and you can leave it disconnected or reconnect it and know it's normal operation.

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