EVP Ohm readings

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Oct 21, 2003 | 09:41 PM

DanTana

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EVP Ohm readings

I'm having intermittent idling problems where my 1988 351 seems like the throttle is stuck slightly open. Wants to idle high until I hit the throttle even when hot. I checked the EVP and got a low reading of 500 ohms, is this too high? It went over 2000 ohms all the way closed, but the low reading is what I was concerned about. Or do you guys think this is a TPS issue?

Thanks in advance.

Oct 22, 2003 | 02:30 AM

c96drumm

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From: Colorado, U.S.A!

Have you pulled the codes? My references say a range of 5500 to 100 ohms for the EVP. If the computer thinks it's out of range, it should have set a code.

Oct 22, 2003 | 07:46 AM

DanTana

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No, that's one thing I haven't done yet. Your right I should check and see if the computer thinks it's out of range or not. I've got one of those cheapy light up code readers, it's just a pain to count the number of blinks. I was hoping someone who went through this might of had knowledge of whether 500 ohms was too much resistance.

Oct 22, 2003 | 01:41 PM

HardScrabble

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My book says the same thing as C96's but my EVP has readings like yours. I have not replaced it yet, but I probably soon will.

Oct 22, 2003 | 02:00 PM

gibsonj

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From: north carolina

Had a similar problem with my 92 F150 in-line six. The lower ohm level from the EVP was definitely the culprit. Can't remember specifically what my reading was, but it did set a code---I think 179.

Oct 23, 2003 | 08:48 AM

DanTana

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Yea, my book says the same, but doesn't say how much tolerance allowed in the lower settings. I was hoping the computer could recalibrate itself to the "higher" low setting. The EVP works smoothly other than that.

Oct 23, 2003 | 08:59 AM

dbuck50

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So if the EVP readings are off, what is the result in terms of enging driveablility? Does this just throw a code or is there some other impact?

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Oct 23, 2003 | 10:15 AM

DanTana

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I think from what I read there could be several consequences from the incorrect EVP readings. The low OHM reading is the closed state, the high reading is open. So, you could have either the IAC open at idle, or an overrich or lean condition during normal driving. Depending on the problem of course. When the EGR opens, the IAC compensates some at idle. So your idle doesn't drop too much. On the highway the EGR should be open and send the high reading.