R25 idle speed

Ren25

Ren25

Member
Fellow Frogger
Joined
Dec 12, 2002
Messages
298
Location
Perth
First post guys, so be kind. I have an '86 R25 and have a problem with the idle speed. It seems that the cold start sensor isn't working or some such. If I set the idle cold at 8-900rpm, when the motor warms up it idles at 1500. If I set the idle when hot, the motor, when it's cold, cuts out at idle due to low revs. The aircon idle solenoid works ok. Any ideas?
 
Hi

It could be the air/fuel mixture valve that sits in the fuel injection manifold. If this has a small perforation in it it will cause your idle to be out of whack. I had a similar problem on my 1985 R25. This was the cause, and after repairing this little diaphram it worked like a dream.

If you are unsure of where to locate this valve diaphragm e-mail me and I shall send you a scannned pic of the potential area at fault.

Hope this helps a little

Regards

Luke
 
What injection system is used on the R25?
I have the exact same problem with my P505 GTi (Bosch L-Jet injection) and have been chasing my tail on it for AGES :mad:
 
Welcome, Ren25!

If it's L-Jet I'm sure it has an idle speed stabiliser, which is an alloy housing with a rubber pipe attached at each side, with a round thing in the middle that looks like it houses a diaphragm. It actually contains a sliding gate type of arrangement. This controls how much air bypasses the throttle to trick the injection into adjusting for the requisite fuel to be injected, and so increases the idle speed until the engine warms. This unit is therefore open when cold, and almost closed or closed when hot. If you take it off and wahck it in the freezer, you should be able to look through it, and the aperture will be three quarter moon shaped. It closes when it warms up, from both engine heat and a heating element inside (on most). They're mounted on an appropriate part of the engine like the rocker cover. so the right amount of heat gets to them at the right time. This unit has to be all right before you can get the idle set properly.

Hope this is a start,

Stuey
 
Stuey:
Welcome, Ren25!

If it's L-Jet I'm sure it has an idle speed stabiliser, which is an alloy housing with a rubber pipe attached at each side, with a round thing in the middle that looks like it houses a diaphragm. It actually contains a sliding gate type of arrangement. This controls how much air bypasses the throttle to trick the injection into adjusting for the requisite fuel to be injected, and so increases the idle speed until the engine warms. This unit is therefore open when cold, and almost closed or closed when hot. If you take it off and wahck it in the freezer, you should be able to look through it, and the aperture will be three quarter moon shaped. It closes when it warms up, from both engine heat and a heating element inside (on most). They're mounted on an appropriate part of the engine like the rocker cover. so the right amount of heat gets to them at the right time. This unit has to be all right before you can get the idle set properly.

Hope this is a start,

Stuey
Click to expand...
Oh... You mean the Supplementary Air Device. Yes, i have one, and yes it works just fine :)

I'll have to keep looking.
 
Nyah Nyah Nyaahhh! Well Bosch call it an idle speed stabiliser and that's good enough for me...considering that's what it does. :D

I've got an excellent Robert Bentley Bosch FI service manual - when I can dig it out (I think it might be borrowed out) I'll see what else they reckon you should check.

Stu

<small>[ 13 December 2002, 05:23 PM: Message edited by: Stuey ]</small>
 
The 25 uses Renault's own Renix system that has a MAP sensor. (no flap) There are two temp sensors on the thermostat housing. The top one has two pins and does the dash and warning and the other is smaller with one pin for the injection. Disconnect the wire, measure (with the motor off)2200- 2800 ohms at 20 deg and 280-370 ohms at 80 deg. Toward the back of the passenger inner guard there is a black plastic cylinder aout 40mm long 15mm across that adjusts the idle mixture. The circuit board comes out of the cylinder and has a 270 deg. pot. Adjusting the pot clockwise is richer, and you obviously know about the the big plastic air knob at the left front of the engine to modulate idle speed. The temp sensor would be first choice. If you need drawings etc. email Ian at rccq@iprimus.com.au
Alan.
 
Jason, it's an independent publication by Bentley, a US publisher. Their manuals are the best I've ever seen (they do car ones as well). The Bosch FI one covers all Bosch from D-Jet to Motronic, around 1992 or so. Great book. Incidentally, a local bookshop (Rellim) sells a large stock of proper Bosch service booklets for practically everything they make, from alternators, to dizzies, etc. etc. Not sure about FI though, but they've got a big rack of them.

Stuey
 
Thanks all, looks to me as though Alan might have cracked it. As far as I can tell on my 20yr old $9.95 Dick Smith analogue multimeter the switch (it has 2 pins though, Alan, and a FI looking connector with the wire clip around it) is reading about 5 ohms at operating temp. Havent done the cold temp yet for obvious reasons, but will tomorrow am, will keep you posted. Thanks again
 
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