high idle, sometimes hunts

Azerite · 11-30-2015, 05:16 AM

I purchased a 944 a few weeks back and have been slowly restoring it. It's an 86 base, and was sitting in a garage for a long time before i bought it. Since getting it i have taken the head off, got it cleaned, replaced every seal on the front of the car, and done the general tune up stuff required. I finally got it started over the weekend and it's running great with one exception. When cold, the engine turns over and idles at around 900 rpm, and stumbles a bit. Once it gets warm, the idle goes up to 1100 rpm. If i let it idle, it will move to 1400 eventually, then return to 1100. I took it on the highway and did a pull to 70mph, and was able to handle it no problem, but after i went back home, and dropped the clutch, the idle stayed around 1800. I shut the engine off, turned it back on and it rev'd up to 1100. The whole time i'm 100% sure that the engine was hot, but the coolant gauge was only showing just above the solid white line instead of in the middle. My oil pressure also never went below 5 the whole time. I haven't yet cleaned the grounds, and they could be corroded, not sure.

My assumptions are the following:
1) my oil pressure is artificially high because the idle isn't correct.
2) The high idle could be the grounds on the chasis, which i will clean, and check, assuming it's not;
3) I replaced all the vacuum lines with silicone lines so there is no leak.
4) I rebuilt the throttle body, there is a bit of slack in the wire, and put the brass air valve back the way it was (2 and a quarter turns), the idle screw where the plate hits was untouched, and still has paint on it from the factory. I didn't calibrate the TPS, is this needed? my understanding is that the sensor is on or off and there is nothing to adjust.
5) Lastly, could be the idle stabilizer, can these be rebuilt, or do i need to shell out for a new one?

sausagehacker · sausagehacker's Garage

When it's idling high, can you confirm that the throttle body is completely closed? The new shaft seals you installed when you rebuilt it take a while to settle in, especially if there are remnants of the old seals still in the grooves. The effect is that the seals grip the main throttle shaft, I ran into this as well the first time I rebuilt one.

Re: the idle valve. Late 944s have a closed loop idle valve, so it's controlled by the DME (computer). It could very well be sticking, it's located under the manifold.

Azerite · 11-30-2015, 05:41 AM

ahh, i didn't think of that. The old seals were taken out for sure, i used small picks to get all of it out, but i noticed when i put the shaft back in that it was a tighter movement then before so this could be it. I'll check when i get a chance. So the ICV is rebuild-able in that i can take it apart?

mytrplseven · mytrplseven's Garage

Here's a couple of things to do: Clarks garage has an article on setting idle with a jumper on the diagnostic port next to the brake booster. Second, don't sweat the oil pressure issue until the idle is set. Better high pressure than none. Also, spray a little WD-40 on both ends of the throttle shafts and in the intake of the throttle body, where the shaft goes through and then exercise the shaft. That gets the seals lubed and they'll loosen up. I always spray the seals just prior to inserting the shaft and that makes a big difference. Did you use the street or track seals? The track seals are tighter and take time to settle in. Do verify that the butter-fly closes completely. If not, you may have installed it in improperly (wrong side). It takes some experimentation to get it right sometimes. Also adjust the TPS so that you can hear it "click" just as you move the throttle off idle. The throttle return spring should make sure your butter-fly is fully closed (assuming it is correctly installed). Make sure your O2 sensor is working and connected. Also, the DME temp switch on the front of the engine (blue connector) should be replaced. This makes the engine run richer when cold and that should cause the rpm to be a bit higher after start. Your's is lower and that sounds suspect. They're relatively cheap and easy to replace. You don't have to drain any coolant, just put your finger over the hole and swap them out.

BTW, congratulations on taking the initiative in going through the front end thoroughly before venturing on with other mundane things. I did the same on my last two 944's and it's much more gratifying to know that you got to the things all at once.

Azerite · 11-30-2015, 06:38 AM

thanks for the kind words.

I read the clarks procedure and that's originally why i posted here. I didn't understand if he meant that you could adjust the idle with the brass air valve or the idle screw on the throttle body, my understanding was the second.

On a side note, i also replaced the master cylinder (grommets were caked into the holes) and the clutch master/slave, and the associated lines. The car only has 26k miles which are all original (the spark plugs still say w.germany-Beru haha) the brake fluid was pitch black. When i bled the clutch, i kept getting what looked like small air bubbles in the line. Is this normal? I used a pressure bleeder, and this didn't have enough for (only pushed it to 10psi) so i asked for help and manually bled the clutch. The clutch engages, i just don't know if it's going to drop on me and if I have a leak somewhere.

DannoXYZ · 11-30-2015, 09:19 AM

Quote:

Originally Posted by Azerite

thanks for the kind words.

I read the clarks procedure and that's originally why i posted here. I didn't understand if he meant that you could adjust the idle with the brass air valve or the idle screw on the throttle body, my understanding was the second.

Brass air-valve? Can you post a picture of this? Might be a manual boost-controller by the intercooler pipe.

Follow the Clark's Garage procedure. To set idle, you need to disable the DME's control of the idle-valve first by jumpering the diag-port. Then the idle-speed is purely mechanical adjustments: throttle-body and air-bypass screw. Set idle to 900-rpms, then disconnect the diag-port jumper.

If idle-valve is good, then hunting idle is typically a sign of intake vacuum leaks.

JonA · 11-30-2015, 09:59 AM

Idle Control Valve cannot be rebuilt, rebuild parts are not available. Taking it out and cleaning will sometimes restore function and there is a simple procedure for bench testing that is posted here somewhere.
Finally, there are replacement IC valves available for much less money than the Bosch unit. I have one that is a Chrysler product that has worked well. I can probably dig up the part number if you need it.

Jon

Jon

Azerite · 11-30-2015, 10:19 AM

Quote:

Originally Posted by DannoXYZ

Brass air-valve? Can you post a picture of this? Might be a manual boost-controller by the intercooler pipe.

Follow the Clark's Garage procedure. To set idle, you need to disable the DME's control of the idle-valve first by jumpering the diag-port. Then the idle-speed is purely mechanical adjustments: throttle-body and air-bypass screw. Set idle to 900-rpms, then disconnect the diag-port jumper.

If idle-valve is good, then hunting idle is typically a sign of intake vacuum leaks.

The brass air valve is the air bypass screw that you screw in with a 7mm socket and has an oring that is replaced with the throttle bottle rebuild. The other screw is where the throttle body plate rests against on idle and when the throttle body flap is closed. This hasn't been adjusted, has the paint from factory.

Dont have boost controller non turbo.

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Azerite · 12-01-2015, 05:52 AM

i'm an idiot, the clark's procedure shows the brass air valve as the adjustment mechanism. I ran the jumper and took the idle down to 950 with the screw. As soon as i released the jumper, the idle went back up to 1100rpm's, i reved the throttle and it went to 2000 rpm, and came down slowly (seals in throttle body) but it didn't stick, the throttle body was closed, and the rpm's stayed at 1400rpm. I'm going to check electric grounds next and the temp sensor from the thermostat.

Azerite · 12-06-2015, 06:46 PM

i started taking about the throttle body to get to the DME temp sensor, i'll see if that fixes the problem, but the problem is likely my ICV. Is there a way to bypass the valve? what is the part number from another brand so i can swap a new one in if i can't bypass? Don't want to spend $300 on a new one.

fiily · 12-07-2015, 06:58 AM

I am in the same boat, 25+ year old electronics, mechanical idle control valves, and hardened/cracked rubber seals = hunting idle.

I have replaced the vacuum hoses, but I am also suspecting the ISV is bad on my 944. I have found a couple of aftermarket ISV, but not really looking forward to playing a $125 guessing game per ISV to see if it fits and works just yet.

JonA · 12-07-2015, 11:02 AM

The valve in my 924S was a Bosch 0280140501 and that crossed to an AIP Electronics valve IAC42. I think it is a Chrysler product. Mine has been in for about 6 months with no problems.

I ran my 924S with the valve removed and the hoses plugged to verify that the ICV was my problem. There is also a simple bench test for the valves that you can probably find by doing a search.

You can get these valves apart but there is a pair of contacts (brushes?) inside and all wear with time and parts are not available so the only solution is to replace the valve.

Jon

sausagehacker · sausagehacker's Garage

Try shaking the actual IAC, like a shake-weight. You should be able to feel an internal mass moving, you'll know it when you feel it. If it's all solid inside it's gummed up probably from oil getting in there.

Azerite · 12-07-2015, 01:37 PM

Anybody relocate the valve to that it can be serviced? If I take the intake off again, I'm sure going to leave the valve on the outside of the intake not under.

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Azerite · 12-07-2015, 02:58 PM

Anybody use alibaba? I know that a chinese aftermarket isn't going to be as good as bosch's original, but the cost to produce the valves are anywhere from $10-40 or cheaper if you go with someone who has a worse rating, which makes you think about porsche profit margin. Just so there are no misconceptions, i don't think the original bosch units are made in germany anymore, they're probably made at the same place that makes these, it's common practice in china to run the shifts for legimate businesses, and at night to run another for off market goods using the exact same tooling.

Idle Air Control Valve For Porsche/fiat/volvo/citroen/peugeot. - Buy Idle Air Control Valve For Fiat/volvo/citroen/peugeot,Iac Valve For 91541077 7401317057,0280140501/136317073781628e0 60574613 1317957 Product on Alibaba.com

It looks like these are the guys that make the IAC 42 item, or very close to it.

There's no way i'm paying $300+ for a bosche replacement, and can't be sure how much my original will last (only has 25k miles, but has been sitting for years).

Azerite · 12-07-2015, 03:20 PM

ep nevermind, i went on ebay and looked up the original porsche number and i think i found a german supplier. If you look in alibaba under this guys profile, they made a shipment to (DE) germany for several thousand dollars. LOWE automotive in germany offers the part on ebay for $54. Looks like a viable replacement.

Leerlaufregler Citroen Peugeot Porsche Renault Volvo Entspr 0280140501 | eBay

JonA · 12-08-2015, 04:08 AM

If you leave the mounting clamp off and position the hose clamps carefully you can get this in and out without removing the manifold.

Jon

Azerite · 12-10-2015, 05:10 PM

I think i found the problem. It's the TPS, when i put the throttle body back together (seals) i didn't align the click. when i took it off, this basically meant that the unit always thought the throttle body wasn't in idle hence the extra gas. The pin for WOT also didn't give a reading so i think the WOT sensor is busted. Ordered a new one, we'll see if that fixes it.

Azerite · 12-20-2015, 04:44 PM

The new tps properly adjusted took the idle down to 1000rpm.i think think the system is wonky somewhere but this is liveable.

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gtroth · 12-28-2015, 01:15 PM

You might double check that your throttle is actually always closing all the way. When I rebuilt my throttle body, I reinstalled the throttle disk ('butterfly') slightly misaligned and it would slightly rub the throttle bore and sometimes fail to close all the way. Caused a bouncy hunting idle in my case. The S controls its idle, so the behavior may not be exactly the same as yours if you did what I did. With the throttle cable slack, I could feel the subtle rubbing when I opened it by hand.