3200 idles high after some major work

davy83

davy83

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2,821
I have just completed a major service, including timing belt, and water pump and both idler pulleys, and valve clearance with 6 shims changed out. I changed out the starter too as i was having odd starter issues, so i have had quite a lot fo the engine apart!
It going again, which is always a relief. However its idling at 1500 rpm and some times hunting. If i put it in gear it drops to 1100 rpm roughly, and it drives ok more or less. However it feels like its pulling when you are at a junction or lights. Not driven it much since rebuild, and I may just take it on a longer drive see if it settles down.
I have checked I got all the vaccum hoses back and verified there are no cables not plugged in. Engine sounds ok, and pulls well enough, just the idle. I am thinking throttle body because its been sitting, but wondered if there were any helpful suggestions. when the TB has been off before the idle was drifting around and never steady, this seems to be very steady just at the wrong speed.
 
Rex B

Rex B

Member
Messages
657
Did you renew the O rings on the inlet manifold when you replaced it after fitting the starter motor.
You should also check the temperature sensor because a low temperature reading increases the injection time which would increase the rpm at idle.

Rex B
 
alfatwo

alfatwo

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5,517
Sure you just haven't put the timing belt on correctly this time:) did you just mark the pullies or use the vernier's

Dave
 
davy83

davy83

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2,821
Yes new seals everywhere, rockers covers and all. i did not change the temperature sensor, and the engine temp dial on the dash is working. I initially thought it was just because it was cold but even with the temperature reading 90 it was the same.
and yes i am pretty certain the belt is on the right position, only did that once dude, give me a break! I checked the position before dismantling and also verrified it according to the workshop manual before closing it up. The engine is running nice its just the idle.
 
davy83

davy83

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2,821
Right I took it for a longer drive today and really its driving quite nicely, but still idles at 1500 rpm and hunts a little but on the open road very nice. I had one point where i stopped and did a u turn in a wee car park where i was sure it was idling properly. But once i got back to the garage and pulled up back to 1500 rpm. Brakes pedal was a bit stiff initially (i have also had the brakes apart and discs skimmed) but settled down.

So I am now thinking vacuum leak some where, especially brake servo hose ,explaining why brakes were initially stiff. If I remove the hoses off the throttle body front the butterfly is sitting on its sprung end stop (not quite shut but not actively opening at all) and yet idling high. If I push the butterfly completely closed the engine idles steady (very steady). So where is the engine getting air from? Closing the butterfly completely should choke it surely? I am thinking one of the vacuum hoses is leaking?

The plenum gaskets were all new and also applied hylomar blue to all joints, and it all looks ok no air rush noises. All the vacuum hoses are connected so I have not simply not fitted one. I am wondering where the large vacuum hose for the brake servo that is connected underneath the plenum goes and how i can check that? Any suggestions? it dissapears down behind the cylinder head. Any one know this part of the car?
is there a correct location for any of these vacuum hoses? They all look like they are just connected to the plenum?
 
77GR

77GR

Junior Member
Messages
76
It may be worth simply disconnecting the "large vacuum hose" and securely plugging the exit from the plenum. Then, with the engine warm seeing what the idle speed is (don't try and drive the car though - brakes will be extremely hard work!), if it's still 1500 then forget the brake servo, if it drops to 1000 then it is confirmed as a brake servo leak. At least that could eliminate a brake servo leak without having to dlve around that particular inaccessible area.

It is possible that there is more than one temperature sensor, one for general use (the one that the gauge reads) and another one to control fast idle immediately after cold starting.
 
conaero

conaero

Forum Owner
Messages
34,625
Have you tried a throttle pedal reset?

We fitted a new Mike Roberts TB to a 3200 yesterday and it did the same, idling at 1500rpm and hunting, so I performed the throttle pedal reset and now it idles at just over 1000 rpm, hunts a little but no different to any other 3200 we have seen.

Closed throttle resetting
1/. Put gear selector/lever in neutral.
2/. Flick accelerator pedal a couple of times with the edge of your shoe to ensure full return is achieved.
3/. Switch ignition 'round as far as MAR.
4/. DO NOT START ENGINE!
5/. Leave all pedals and switches alone for at least 2 minutes.
6/. Switch off ignition.

Full throttle resetting
1/. Put gear selector/lever in neutral.
2/. Switch ignition 'round as far as MAR.
3/. DO NOT START ENGINE!
4/. Gently depress accelerator pedal to full extent of its travel and keep it there for 5 seconds.
5/. Release throttle.
6/. Switch off ignition.

If that does not fix it then you are as suggested above on the hunt for an air/vaccum leak. Even though new seals were fitted, you need to thoroughly clean and emery cloth off all the surfaces and check all the vacuum hoses. Listen for hissing and you can use carb cleaner/brake cleaner in suspected areas. If the revs rise you have found your leak.

Obviously, spraying a flammable liquid around a running engine comes with its risks, so extreme caution and common sense necessary.
 
Lozzer

Lozzer

Member
Messages
2,283
davy83 said:
Right I took it for a longer drive today and really its driving quite nicely, but still idles at 1500 rpm and hunts a little but on the open road very nice. I had one point where i stopped and did a u turn in a wee car park where i was sure it was idling properly. But once i got back to the garage and pulled up back to 1500 rpm. Brakes pedal was a bit stiff initially (i have also had the brakes apart and discs skimmed) but settled down.

So I am now thinking vacuum leak some where, especially brake servo hose ,explaining why brakes were initially stiff. If I remove the hoses off the throttle body front the butterfly is sitting on its sprung end stop (not quite shut but not actively opening at all) and yet idling high. If I push the butterfly completely closed the engine idles steady (very steady). So where is the engine getting air from? Closing the butterfly completely should choke it surely? I am thinking one of the vacuum hoses is leaking?

The plenum gaskets were all new and also applied hylomar blue to all joints, and it all looks ok no air rush noises. All the vacuum hoses are connected so I have not simply not fitted one. I am wondering where the large vacuum hose for the brake servo that is connected underneath the plenum goes and how i can check that? Any suggestions? it dissapears down behind the cylinder head. Any one know this part of the car?
is there a correct location for any of these vacuum hoses? They all look like they are just connected to the plenum?
Click to expand...

The later models the vac hose goes to a Venturi type thing buried behind the head, from here it splits into 2 hoses, one goes to the brake servo , the other runs down the near side inner wing through a one way valve into the front of the airbox.
The Venturi type things are prone to breaking btw.
Valve on inner wing
61539

Venturi thingy behind the head
61540

There's a thread here, all potential vac leaks I suppose.
All the best.
61541
 
Last edited:
davy83

davy83

Member
Messages
2,821
Doooh loose jubilee clip on the venturi plastic thingy. still all sorted now and runnig like a top!!! the upside is that i now know how to test if i have any vacuum leaks, just push the butterfly shut and if the engine shuts down then its probably ok, if its still running then there is air getting in somewhere.
 
H

hugy

New Member
Messages
11
My 3200 GT sticks at 1500 rpm when coasting in neutral like coming to a stop at traffic lights.when I stop the revs begin to drop back to idle speed.
I don't know how to fix this!
 
V

vulcan1208

Member
Messages
172
Rex B said:
Did you renew the O rings on the inlet manifold when you replaced it after fitting the starter motor.
You should also check the temperature sensor because a low temperature reading increases the injection time which would increase the rpm at idle.

Rex B
Click to expand...
Can someone point me in the direction of where to get these O rings please ?
 
E

Ebenezer

Member
Messages
4,486
When I was investigating O rings (for something completely unrelated to Maserati), there was al ot more than just 2 measurements that you had to be aware of!
Eb
 
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