hupshall Posted May 26, 2009 Share Posted May 26, 2009 (edited) I'm finishing up converting my '87 GL from carb to FI. I have it starting up and running but the idle is extremely fast - 2000 +/- 500rpm. When I unplug the Air Control Valve, the idle drops down to 500rpm. I'd like to get some ideas as to things to check. Edited May 26, 2009 by hupshall Link to comment Share on other sites More sharing options...
GeneralDisorder Posted May 26, 2009 Share Posted May 26, 2009 There are two temp sensors - one for the gauge and another, entirely seperate sensor for the fuel injection computer. You need to run a d-check and see what codes it pulls. GD Link to comment Share on other sites More sharing options...
hupshall Posted May 31, 2009 Author Share Posted May 31, 2009 I spent all day working on the car sorting out the trouble codes. I had 6 to start with - and am now down to just two, 33 and 42. I'm a little concerned about these two since when I followed the diagnostics for trouble code 42, I got to the "replace control unit" - I put in my spare brain and it still was screwing up. I have cruise control in this car, which still works - and requires the speed signal. I've confirmed that the pin on the ECU for the speed signal has continuity with the cruise control so I'm going to be scratching my head on this one as well. Idle is still crap, 2000 rpm's Link to comment Share on other sites More sharing options...
silverhelme Posted May 31, 2009 Share Posted May 31, 2009 GD is probably correct an the temp sender and the idle. I ran into the same thing on my Brat when I swapped in an ea82 spfi. As a quick check unplug the 2 wire temp sender ( not the one wire for the gauge ) and see if it idles down. If it doesn't you probably have a vac leak somewhere but I would bet on the sender. The sender is located down and slightly forward of the gauge sender. Link to comment Share on other sites More sharing options...
kingbobdole Posted May 31, 2009 Share Posted May 31, 2009 It, like said could also be a simple vac leak. You did replace the intake gasket right? Hear any sucking? Also the speed sensor will not cause a high idle. Mine's not hooked up on my SPFI swap and it idles perfect, high when cold and low when warm. Link to comment Share on other sites More sharing options...
Frank B Posted May 31, 2009 Share Posted May 31, 2009 You may be able to just clean the sensors. 17mm wrench and socket. Use a wire brush and/or emory cloth to clean all varnish, baked on coolant residue, and even the outside and electrical connector. Link to comment Share on other sites More sharing options...
GeneralDisorder Posted May 31, 2009 Share Posted May 31, 2009 (edited) You may be able to just clean the sensors. 17mm wrench and socket. Use a wire brush and/or emory cloth to clean all varnish, baked on coolant residue, and even the outside and electrical connector. Cleaning the electrical connection is a good idea. Although cleaning the sensor itself is not neccesary (and more trouble than it's worth to remove it), you should check the resistance of the CTS with a DMM and compare to the specs in the PDF that is linked from my write up. They are very often out of range by several thousand OHMS. In fact if the ECU had a function to recalibrate the temp sensors you would likely never need to replace them. Unfortunately it's expecting them to act as they do when they are new - as they age the resistance values change. It's just an artifact of the materials they are made from. The sensor is a potted thermistor or RTD (resistive temperature device). It changes it's resistance based on the temp of the outer brass jacket. The cleanliness of the jacket is only going to affect how quickly it responds to temp changes - but very minimally and being that the engine doesn't change temp rapidly under normal conditions it's really a non-issue. GD Edited May 31, 2009 by GeneralDisorder Link to comment Share on other sites More sharing options...
hupshall Posted June 1, 2009 Author Share Posted June 1, 2009 Ok, I spent a while working on it today, I can't find any vaccum leaks, but it sounds as if there is one.. but heck, it could be the power steering pump or alternator making that whistling noise... Anyhow, I followed the suggestion and once the system was warmed up, I unplugged the temperature sensor and started the car back up - whoa, it idled at about 750rpm. I will replace the sensor and probably the thermostat just to be sure and let everyone know. Link to comment Share on other sites More sharing options...
hupshall Posted June 8, 2009 Author Share Posted June 8, 2009 Yup, it was the temp sender. A new one at shucks fixed the problem and the car is now idling at the correct rpms. Job Done & thanks. Link to comment Share on other sites More sharing options...
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