I Need help diagnosing weird idle

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Ratrodtaylor

New Member
Jan 24, 2013
22
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0
Utah
I bought an 87 supra about 4 months ago with a BHG so i have slowly been fixing it, by getting a cometic mhg, getting the head machined a bit, putting in arp head studs, and got it all back together but it still has an idle problem it had before (Although i'm not burning through coolant anymore which is good). It surges and kind of chugs I know the timing is perfect because i triple checked myself. The car originally had the egr valve bypassed, but there was one in the trunk of the car so i put it on when i put it back together because I need to be able to pass emissions. I do know that there is an intake leak now because you can hear it whistle or whine (near the EGR valve area) when you rev the engine. could this be a bad egr valve that came with the car? is there a way to test it? my only guess as to the reason why it is running rough is because of this leak. Any thoughts or ideas? or anyone in Utah that would be able to give me a hand with it? I'm to the point that i am running out of ideas and may just turn my car over to a shop to fix it but i can't find any that seem to be real confident on the 7mgte engines.
 
IndigoMKII

IndigoMKII

New Member
May 9, 2011
2,181
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Madison, Virginia
I've found the problem but can't find out why my car won't act right without fixing this problem.

Perhaps make sure that you installed the EGR correctly along with all the needed gaskets and didn't strip the stud on the head when installing the EGR valve. http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?Section=EC&P=16

Also, on this perfect timing issue, I'm curious. How did you perfectly set the timing on the engine without it idling nicely at the required 650 RPM with t1/e1 jumped?
 
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Ratrodtaylor

New Member
Jan 24, 2013
22
0
0
Utah
ya i know it sounds silly but if you give it a tiny bit of gas the idle runs fine so i just had the gas pushed slightly bringing the idle to about 850rpm ( I thought thats what it was supposed to be at?) and the idle on it's own will run rough for about a min. then fix itself and idle perfect for about 15 sec. so i was kind of using that little window of opportunity to time it lol. thanks for that diagram that will probably help me test it. I didn't strip the bolts and i double checked the gaskets by taking it off and reinstalling it at everything looked fine. someone suggested that i hookup a fog machine (like one you would use for halloween) to the intake and turn it on and just watch for a leak. any thoughts on this? lol thanks for the suggestions guys sometimes it just takes another mind to straighten my thinking out lol
 
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Ratrodtaylor

New Member
Jan 24, 2013
22
0
0
Utah
just an update on what was going on. first the intake leak was pretty bad and it ended up being on the intake manifold which is weird because it was a brand new gasket. So i just trashed the gasket and used some RTV sealant instead and it sealed up perfectly now it runs much better. It still had a surging idle though, meaning it was jumping up and down between 1000rpm and 2000rpm. I found that this was being caused by the ISC Valve? (I think that's the one) It has one of the bigger vacuum lines going to it from the intake and it's right next to the TPS sensor. The way i found out the valve was the problem was by starting the car then pulling the vacuum line off and quickly covering both ends with my hands and the idle evened right out. anyway I tore it apart and one of the bearings inside was seized up so it wouldn't allow the valve to move. I soaked it in wd40 and the bearing spins freely now. I then cleaned it all up and put it back and the idle is perfectly steady now at around 850-900rpm :)
 
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