Idle...unsurged? Possibly a Jonas Q/A

[FujiwaraTofu]

I wasn't quite sure whether or not to put this in the Electrical section...

I have an 87 gts with the notorious, somewhat mythical idle surge. So initially the car on a cold start would idle anywhere from 900-1200 rpms. Once warm, it would start idling at 1100rpm and it would surge to 1500 and then go back to 1100. Rinse, wash, repeat. So, with IACV as the main suspect of failure, I looped the two lines running to and from the IACV in order to completely block its usage. It slowed the surge quite a lot, but didn't fix it. So a good friend of mine unplugged this

the idle control circuit, I believe, and the surge stopped. The car idles 500-600rpm on cold start, and idles 1200rpm once warm. Its at least stable, but its still backwards haha. Any ideas where the circuit is going wrong? Just a bad plug?

[dr.occa]

I was just on the phone with Mark (mbehrens) the other day and he had the same thing with his GTS. He's got a nice blue point tool for bleeding and filling his coolant system. If you don't have one you can pick one up OR just go out there, take the cap off, start her up and let it warm up regularly checking the coolant level in the rad. Squeeze the hoses (may be hot so be careful) to get out as much air. Fill your coolant reservoir bottle and almost top off your rad. Then cap it and open the coolant bleed bolt (if you have it) on the left side (driver side here in the US) of the block. Don't mistakenly loosen the oil pressure sender (the big round sensor that's about the size of a bicycle ringer). Coolant bleed screw would be next to it.

[FujiwaraTofu]

Oh I know what you mean. I have had to flush the coolant system several times since I got the car. Once a week or so. It sat for 10 years so the fluids were all sorts of nasty, so I've just been changing I routinely to get some of the sludge/rust/whatever else out. And I always fill it up completely and burp it. As for that bleed screw I'm very well acquainted with it. It was one of the first things I replaced when I got the car because it was the source of my coolant leaking out. No o ring.

I'm gonna start just using distilled water since its works for the application and it's much cheaper than changing coolant once a week. Once the systems clean, then I'll start using coolant again.

Anything else I should check? Tps reads the right ohms, throttle body is good, iacv isn't the problem. Apparently the maf sensor is in proper working condition though I haven't tested that myself. Probably forgetting something. Thanks for your help!!!

[dr.occa]

I use just distilled water on my dd as well until I know for sure where my coolant leak is. I'm having a sneaking suspicion that it's my radiator.

Sounds to me it's your IACV.

Here's a great illustration on what should be blocked or routed on the throttle body and intake mani:


pictures are from http://www.locustbuilders.co.uk" onclick="window.open(this.href);return false; - as if you didn't already know

[FujiwaraTofu]

Thanks. I think I'm gonna go on an adventure to Wally world and see if I can find any goodies. Maybe toying around with the car a little will help lol

[FujiwaraTofu]

Wait...maybe this is dumb, but wouldn't capping the pcv be bad? And sorry for my second question in advance but what is an fpr? My knowledge of cars and lingo is very partial haha. I only just started looking at this stuff seriously like 2 months ago

Update: looped the lines on top of the t-vis, dont the ones on the bottom that the pic said I should plug keep the engine from stalling when using power steering to turn during idle?
Also I plugged the idle control circuit back together and it is holding a steady idle now

[wizzurp]

Dont cap the PVC on the valve cover side. Cap it on the IM side and stick a breather on the valve cover side. I'd personally just leave it connected, there isn't much reason to delete it.

[wizzurp]

For reference, capping the Pcv on the vc side would probably make your car smoke from the blow by.

[FujiwaraTofu]

Gotcha! Probably gonna avoid that. And I don't trust myself not put the engine into idle while I'm turning late at night lol
So now I just need to figure out how to get it to idle high at cold and low at warm.

[dr.occa]

Dont cap the PVC on the valve cover side...

+10000000000000000...

[wizzurp]

For the cold we can just set your dash pot to actually push the tb slightly.

[FujiwaraTofu]

Gotcha!!
Anyone have any clue about the backwards idle??

Edit: meant to put the warm idle being so high

[wizzurp]

The dashpot will make it idle up when cold.

[mbehrens]

For reference, capping the Pcv on the vc side would probably make your car smoke from the blow by.

Not to menssion all the oil that gets forced into your intake and throttle and intake boot from the intake ports the crankcase pressure has to go somewhere if you really donte want the pcv hose t
o the intake then put a breether on it rapped up to rsoak up the oil..nut then that just looks dumb lol... But to each tjere own ...