I've had a number of electrical problems with this car but it's running
quite well at the moment.
EXCEPT: Every now and then it starts revving up on its own accord. The car
starts and run ok but after driving for a while it takes it upon itself to
vary between 1000 and 2500 revs. This looks and sound bad if you're stopped
at traffic lights and even more so if you're waiting for someone walking
across a zebra crossing. There is also an increase in fuel consumption.
Has anyone got any suggestions?
You sure it is a multi-point and not an SPI (Single Point Injection)?
Also change your Email address to something like firstname.lastname@example.org
otherwise if not already too late the SPAM robots will grab your email
address and SPAM you to death!
Without digging deeper I'm now assuming that the 1.2MPI is essentially the
same as the Magnetti Mirelleli MPI unit fitted to the Tempra 1.8ie.
Locate the manifold inlet tubes at the cylinder head itself. Follow them
back and possibly upwards. They will probably all meet/interface with a
large chamber/body that joins them together. This is the plenum chamber.
At one end of this is the throttle body. After the throttle body is a large
tube assembly that leads to the air filter and beyond. Around either side
of the throttle body there may be two hoses (obe either side) that lead off
to a valve, called the air bypass valve. This may be located at the end of
the cylinder head above the gearbox and between the battery box.
The purpose of this valve is to act as a variable bypass around the throttle
plate thus adjusting the engine idle revs. They are know to stick with age.
Here is the contents of a post I have made on this in the past. (22 April
1) Check for leaks/cracks etc in all air hoses attached to the inlet
manifold. This include the brake vacuum hose. Also operate the brake
pedal and listen for engine speed or note changes.
2) Sticking idle control solenoid - this could be either a mechanical
operation on the throttle butterfly or an air bypass valve. If you have
an air bypass solenoid then one should service this as sticking is a
known problem. Easy to do. Just remove the valve and inspect inside.
Gently remove any deposits. Flush / fill with WD-40 and agitate. If it
is really dirty then wash out with white spirit, dry and give a very
good soak with WD-40. Another trick is to allow the engine management
system to modulate the valve when you have WD-40 in it. Easy to do by
only making the electrical connection, fill with WD-40 and hand/finger
seal the hose connection points and then get somebody to turn the
ignition on (DO NOT START). The ECU will open and close the valve a
couple of times. Repeat ignition on/off cycle a few times.
The valve is officially called VAE Valve.
3) Incorrect static air bypass setting. Tempra Magnetti Marelli fuel
injection systems had this identified by a grub screw and locking nut
located on the throttle body. This sets a minimum air bypass and thus
idle speed so that the air bypass valve has a nominal point about which
to operate. To set this up one has to disconnect the electrical
connection to the air bypass valve. The car should not stall be yours
may. If this happens then reconnect the valve. Adjust the grub screw
out. Initially nothing may happen as the bypass valve will
automatically compensate for your adjustment. Get the revs to about
1000rpm. Now you can disconnect the valve connector and proceed to
adjust the grub screw till the revs are about 650 to 700rpm. Now connect
the valve connector again and the revs will briefly rise to about 1200
rpm or so and then drop back again to about 850 rpm.
Lastly blip the throttle and check that the car does not stall or idle
too low. Test drive as well. You may find that you have to have a
couple of cycles in setting the bypass grub screw. Setting too low revs
will cause stalling etc. and too high will mean too fast and idle.
4) If all of 3) still does not work to your satisfaction then there was
a Fiat service bulletin that modified the original set-up as in 3) to
actually set the grub screw get engine revs of 900rpm (or as low a you
can get to 850rpm) so that when the VAE valve electrical connection is
removed/connected there is NO variation in rpm. I never had to do this
as I found that the method and settings in 3) was perfectly OK for my
Tempra. You may find that you need to go with this 4) method.
Lastly if the Marea uses a mechanical solenoid directly operating on the
throttle body butterfly (Most Fiat single point injection systems like
in the Tipo use this method) then just like the air bypass grub screw in
3 & 4, there will be a similar grub screw to set the base throttle
opening from which the solenoid lifts the engine revs.
I leave the rest for you to sort out :-)
Many thanks for the information.
My 'tame' mechanic has now helped me have a go at this but we couldn't
remove the control valve as one of the screw heads became mashed. So we
tightened the unit up again and gave all connections lashings of WD40 and
it's now running better, not perfect, but loads better (good enough to
sell). This seems to confirm it may be the idle control valve so I am now
going to replace it. I've found them on eBay for £20-25 so it's worth a try.
Although it seems tricky working out which one to get. Have tried reading
the part number on the side of the existing valve but it doesn't match what
the 2 companies state on eBay.
I'll update you when I sort it out.
Yikes, don't use WD-40 on electrical connections. Use DeoxIT
For mechanical us WD-40, for electrical use DeoxIT
Easy to do by
I didn't say, although I can see I badly worded the post, to apply WD40 to
the electrical connections :-)
Having said that I have for many years used WD40 or other very light oil on
NON-SWITCHing contacts, especially engine bay connectors with no problems at
all. If used correctly and sensibly it is not an issue.
dexoit, switch clean/lube are excellent products however. They clean and
lubricate but are however not very good at providing long term moisture and
damp protection. For non switching contacts like connectors there is direct
metal to metal contact of quite high surface pressures. These displace and
penetrate any suitable light oil with easy. The contact area is then
surrounded by a moisture repellent film that ensure the metal to metal
contacts remain moisture and corrosion free.
You can get special custom made lubes that do this but they are not readily
available to most to WD40 is a good substitute if used correctly and
The following are just some of the approved uses for WD40
Cleans gunk from electrical contacts
Drives moisture from electrical wiring in cars
Protects electrical connections in car/truck engines
Lubricates and improves electrical contacts on model train tracks
Cleans electrical contacts on slot racing cars
Yikes, never use WD-40 on electrical contacts. May work for a short
time, but will gum up and attack the plastics and parts after a
while. The only thing to use on electrical contacts and connections
, actually chemically improves connections
after it cleans it. Stuff is amazing and is safe on just about every
Try it, you will not use anything else after you try.
Nearly 20 years use of WD40 on ONE car, from new, on electrical connectors,
including wires, contacts, casing & rubber seals has never produced any
problems. In fact totally beneficial. Plenty of other cars of varying
ages of continual WD40 use all perfectly OK as well.
To each his own. I use products that are specifically designed and
tested on their particular use.
I use WD-40 and other mechanical lubricants for "mechanicall
applications" and DeoxIT products on "electrical applications".