arad99

iTrader: (2)

I searched for this problem but didn't have any success. I have an S4 T2 with about 700 miles on a rebuild. After it is fully warmed up, one time it will idle at a steady 700 rpm and another time it will idle at a steady 1500. It might idle at 1500 for a whole day or so and then the next day drop back down to 700 for a day or so.

Any thoughts?

cmanns

The 1,500 idle is the accelerated warm up idle.

It's controlled by the wax pellet in the throttle body I thinks, coolent runs through the intake heats up the wax, idle drops.

HAILERS

Possibly the cam isn't falling off the roll pin.

arad99

iTrader: (2)

OK, next time it idles at 1500 I'll check the cam. Today it has a steady 750 idle. Yesterday, it idled at 1500.

HAILERS

************************************************** ************
See the Cam Adjusting Screw in the jpg? It rests on top of the piston in the water thermowax. IF you screw it clockwise, the cam and roller will seperate sooner. You have to remove the intercooler to access it. Make sure it's THAT screw and NOT the other screws.

If turned in all the way, the roller and cam seperate completley if memory serves.

Water almost MUST pass thru the throttle body for this thing to work. So, if you've removed the water hose on the bottom and or top of the throttle body, the cam and roller will not seperated for a loooooog time and only if the engine bay gets hot enough to drive the thermowax piston outwards.

Texas_Ace

iTrader: (18)

Yep, sounds like the cam is not coming disengaged. I had to adjust my cam to get it to come off of it, now idles perfect.

jmkogut

Sounds moderately like my issue (which I have yet to fix) of a super damn high idle and even with a TPS adjusted to 1.001kOhms +- .003k and the idle screw adjusted ALL the way clockwise (with the initial set jumper) and the engine warmed up it still idles at 1500 and surges from 1300 to 1600 rpm.. I can't find any vacuum leaks.

Texas_Ace

iTrader: (18)

I had tons of high idle issues when i got my car. Ended up being a combo of the thermo wax not working right and the TB being adjust so that it didn't close all the way.

Adjusted the TB and adjust the thermowax cam and now it idles perfect.

jmkogut

Which adjustment do you spreaken of? There are a few that I can think of.

Texas_Ace

iTrader: (18)

In my case it was the stop for the sec ports, it kept them open just a tad. but i would check all of them if i was you, pull the TB off the car, it is by far the easiest way.

HAILERS

This needs to be a sticky or just written in very large letters at the front of the second generation page:

THE DARN TPS DOES NOT SET THE DARN IDLE SPEED!

And adjusting the tps using an ohm meter is pointless if the cam isn't off the roll pin and throttle plates CLOSED all the way.

jmkogut

I understand the TPS doesn't adjust the idle speed, but I was referring to the adjustment because of my crapass idle that I would occasionally get.

HAILERS

FULLY heat the engine up. Best to go drive it for a half hour. Then idle the car and backprobe the green/red wire at the TPS connector. NOT the test or check connector, but the TPS connector. On the harness side of the plug is the green/red wire that is the output wire of the TPS. It should read what the FSM says it should read, approx one volt dc at idle. (This is assuming the cam is off the rollpin and throttle plates fully closed).

One way to prove the cam is off the roll pin, is to lift upwards on that adjust screw I pictured in a post above, and while you lift up, watch the linkage. It should not move any more towards the closed position. You'll understand what I mean if you do this on a stone cold engine. Lift up on that screw and the linkage WILL move more to the closed positon.

Then get a timing light and set the timing per the FSM.

Then adjust the screw(s) the FSM calls for. Right now I forget if you have a non turbo or turbo.

If you have a turbo, then remove the intercooler and substitute a run of PVC piping from HomeDepot for the intercooler. If you do that you can idle the engine and make adjustments and the cooler won't be in the way.

I don't find a picture of the PVC, but this thread describes it a bit: https://www.rx7club.com/showthread.p...&highlight=PVC

jmkogut

Thanks mate, I have an NA. I didn't check voltage, I was checking resistance on the TPS.

I have the timing light and the full FSM right here. I'll get to this on Saturday while I'm up at a friends house.