So close, please help!

[SupraChrisMk3]

So hear is my issue. I finally got the car running after a lengthy HG repair job and a few other minor upgrades and am trying to set the final timing. I had the car idleing fine at around 680RPM the other day but found that that the cam sensor was off slighly because the timing mark on the crank wasn't lining up with the timing marks on the front cover. So I readjusted the cam sensor and tried again but now the idle is bouncing up down between 1200 and 1800RPM. The timing marks seem they will line up but I can't tell for sure will the idle bouncing like that. I checked for codes and I have none, no aparent vacuum leaks. I'm just confused on why it just started to do this and all I touched was the cam sensor. I really want to get the car back on the road and I'm so close, it's just setting the final timing that holding me up. Any ideas or advice will be greatly appreciated. Thank you.

 

[zambini]

after i got my engine back together it was suffering from similar symptoms; surging idle while in good timing, that is. try unhooking the iac and tps and see if your idle changes any. if it doesnt with one of them unhooked, may be your problem.

good luck man!

 

[SupraChrisMk3]

That's what I am leaning towards. I disconnected the TPS and the RPMs jump up but disconnecting the ISC changes nothing. So this means my ISC is no good? I was thinking that might be the problem because I had some issues before I had HG go. It had a low idle even on a cold start and If you rev it up when the RPMs fall back down to around idle the motor wants to cut out and stumbles and occassionally will stall. But was fine when driving down the road. Now that it's back together it still stumbles and wants to cut out when I rev it a little and the RPMs come back down. Would a bad ISC cause this? Also, what did you find was your cause?

 

[Kevin]

im having the same problem. I literally just bought a iacv and im gonna put it in tomorrow or sometime this week. as for the timing i found it's real jumpy too. so i try to get it as close as possible.
i'll see if that helps me. i'll let you know.

 

[zambini]

damn man my car would die when revved hard and left to save itself as well.. haha i had the same trouble with a DIFFERENT engine before i swapped a new one in and found the problem hadnt gone away. i installed a new tps and that fixed it.

 

[SupraChrisMk3]

So I think I eliminated a couple possible causes today. I adjusted the TPS exactly the way the TSRM says with a thickness gauge and ohmeter and checked resistances at each terminal and all checked out within specs. I also checked resistance at the terminals on the ISC valve and those were all within spec. However, when it says that immediately after shutting the car off you should hear the valve clicking, I didn't hear any clicking. Tommorow I'm going to test the ISC by jumping the terminals and seeing if the plunger moves like it should. Also though I found that I have a code 24 for intake air temp. I checked the resistance of the AFM though and found that it was in spec so I'm a little confused why that popped up. So after all that the car is still doing the same thing, surging idle between 1200 and 1800RPM and the motor still wants to cut out if you give it some gas and then let the revs fall back down to around idle. Any ideas on what my problem could be, and am I going in the right direction? Also would a code 24 itself cause a surging idle issue? This is really pissing me off because I don't understand why it all of a sudden stated doing this when it was idleing fine last week when I first tried to set the timing. Please guys, any help and/or advice would be greatly appreciated

 

[SupraChrisMk3]

So I just jumped the terminals on the ISC per the TSRM by applying battery voltage and ground to the different terminals and found that the plunger didn't move at all. So I now know that part is bad but what I need to know is is this the cause of my bouncing idle and the engine wanting to cut out after the revs come down?

 

[NewWestSupras]

I'd replace the Iscv and go from there. If the tps specs out good, there aren't that many places to keep looking after that. Pirate air and vacuum leaks come to mind, but if the idle speed valve doesn't work, the ecu keeps "hunting" for a correct idle. So hopefully that will solve your problem. gl.