No idle when hot, Update on recent tests Options

[ltex]

Hello again ..

Update on recent testing results regarding idle dropping to zero when the car is hot.

Fuel pressure is a steady and constant 36 lbs. Maybe a bit on the high side, but apparently is not the cause of the problem.

Vacuum measured out at 10-12, until the idle went south, then it went flipping all over from 1 to 5. Jack up the RPMs and vacuum went up as high as 20, then settled down at 10-12 for idle, then back to 1-5 when the idle decided to go south.

I did find a vacuum line that comes out from under the air cleaner that has been cut and plugged. As far as I could read the diagram, I think it goes to the oil breather.

If I pull the plug on this line (open it up) the engine races madly, which may be why it is plugged. If I run a line to the oil breather, would I be able to tone down the idle from 4500 rpm?

What would cause such a situation?

Thank you again for all the assistance, I'm having such a wonderful time not driving my car! *sigh*

Lonny

[redshift]

2.0? What year?

The vac connections at the plenum, passenger side: forward to suck side of decel valve, rearward bung connects to OEL filler bung.

People do remove the decel rig..


M

[Dave_Darling]

How's the head temp sensor? Is it plugged in? I've had symptoms like these when it was...

--DD

[Bleyseng]

QUOTE (ltex @ Aug 8 2005, 10:45 AM)

Hello again .. Update on recent testing results regarding idle dropping to zero when the car is hot. Fuel pressure is a steady and constant 36 lbs. Maybe a bit on the high side, but apparently is not the cause of the problem. Vacuum measured out at 10-12, until the idle went south, then it went flipping all over from 1 to 5. Jack up the RPMs and vacuum went up as high as 20, then settled down at 10-12 for idle, then back to 1-5 when the idle decided to go south. I did find a vacuum line that comes out from under the air cleaner that has been cut and plugged. As far as I could read the diagram, I think it goes to the oil breather. If I pull the plug on this line (open it up) the engine races madly, which may be why it is plugged. If I run a line to the oil breather, would I be able to tone down the idle from 4500 rpm? What would cause such a situation? Thank you again for all the assistance, I'm having such a wonderful time not driving my car! *sigh* Lonny

Reset the fuel pressure to 29-30lbs as the injector doesn't spray right at 36lbs.

Probably the AAR valve hose is plugged leave it that way.
You should have the 710 hose plugged into the plenum if it has a PCV valve onit.


CHECK THE ENGINE FOR VACUUM LEAKS!

Everytime I help someone local with this problem its a vacuum leak from a bad hose or mis-connected hose.

See pic for correct hose layout.

[reverie]

A bit off-topic, but at the bottom of the picture it says:

MPS hose stuck in fuel pressure regulator NOT RIGHT.


Okay.... so what IS RIGHT?

[ltex]

Sorry, this was results from last posting regarding same problem.

It was the 'No idle when hot .. or starting' topic.

I.E., head temp sensor checked out at 60 ohms when hot.

this is a 1972 1.7, runs great while cold. After getting nice and hot, the car will still run great above around 2000 rpm. Will not idle. Idle drops to zero and have to blip the gas pedal to get the revs back up.

Makes stopping a pain, as you have to have a foot on the gas and a foot on the brake.

Whatever it is, it is affected, or activated/deactivated by heat.

Thanks for any assistance, this makes me nuts.

P.S. The ECU checks out good, the MPS is also good. Has electronic ignition.
Contact points are new. Uhm .. recent tune up including valve adjustment and replacement of guide seals.

[p914]

In mine the #3 valve tightens up quicker than the rest and I generally have to adjust valves every 4 months to keep that hot idle operating right.

Your problem sounds just like what my 2.0 does when it needs that valve adjustment.

[Dave_Darling]

QUOTE (reverie @ Aug 8 2005, 07:53 PM)

Okay.... so what IS RIGHT?

The hose plugs into the manifold pressure sensor (MPS) over on the right side of the engine bay. Check the diagrams on the Bird site (Pelican Parts) and you'll see where the MPS lives.


To ltex--I would check the head temperature sensor (as mentioned above), and also the auxiliary air regulator (AAR). "How do I check those?" We could spell it all out for you, but you'll learn a lot more if you read up on those tests (and others) over at http://members.rennlist.com/pbanders .

--DD

[Bleyseng]

At this point I would follow DD advice on getting a new CHT, they are cheap.
Plug the AAR valve hoses.
Check for vacuum leaks!
Check the timing- Set it too 28 degrees BTDC @3500rpms
Drive around until the engine is hot
Now adjust the idle, using the ECU knob and the airbypass screw on the TB to set it at 950 rpms

Get some PB Blaster and squirt alot of it in the AAR valve to free it up over several days. Then hook it up and see if you get a cold idle of 1500 rpms and then it should drop to 950 in about 5 minutes.

(IMG:http://www.914world.com/bbs2/html/emoticons/beerchug.gif)

[mike_the_man]

Just taking a guess here, but I'm betting it's running too rich. On Brad Ander's page, rich running is a cause for hot idle problems. I'm having the same problems, and I'm pretty sure that I've elminated all other culprits. If you could test your mixture at idle, I'll bet you'll find it's rich.

Good luck,

[Bleyseng]

(IMG:http://www.914world.com/bbs2/html/emoticons/agree.gif)


That's why you set the idle mix hot. The symtoms described are a rich idle condition. Combined with a sticky AAR valve you get goofy idle problems that change like the wind. Having a new CHT that is known good is a start. Timing must be spot on, valves adjusted, ignition set correctly......

[ltex]

Thank you again.

So the plan for next week is as follows :

Bring the fuel pressure down to 29.

Recheck the CHT.

Check the AAR.

Verify the timing and valve adjustments.

Recheck for vacuum leaks.

Check the idle mixture.

*whew*

I'll let ya know!!

Lonny

[ltex]

Okay, check this out.

I brought the fuel pressure down to 29, and I could HEAR the difference while I was doing it.

And .. Yes, I found a vacuum leak.

One that was easy to miss on first examination.

The AAR has a short line leading directly to the manifold. It's about an inch and a quarter.

It looked fine, but the engine revs varied when it was twisted.

The bottom (Yup .. the bottom) was cracked. I'm guessing it leaked worse when it got hot.

I replaced it with another hose, let the car get warm, and set the idle to about a grand.

Now I need to check the mixture, as I am sure it's running rich now. ( It blows a little soot, which also tells me she be running rich ).

Thanks for the help, and THANK YOU for that link Dave. I've been reading up on procedures and the injection system. Kindly relay my thanks to Pelican Parts for hosting that kind of information.

After I check the mixture, I will be testing it out under circumstances that would have been a bear before, and if it is STILL not playing well with others, I will continue down the list!

Good job, and again .. thanks.

Lonny

[bd1308]

how do you adjust the mix if you have D-jet???!!!???!?!?!

[Bleyseng]

After 71, the ECU comes with a idle adjustment screw on the top of it. Pretty simple compared to carbs really........... (IMG:http://www.914world.com/bbs2/html/emoticons/biggrin.gif)

[bd1308]

psssh. mine idled like a drowning dog no matter what that was set to.

I think my ECU was bad honestly.

[Bleyseng]

Its pretty rare that the ECU was bad unless battery acid ate thru it. Usually, bad idle is caused by vacuum leaks, bad timing, crappy valve adjustment and hose mis-routing.

[bd1308]

see mine was doing the exact thing that itex's engine was doing.

i had some crazy missing action and alot of stalling like 89% of the time.