PeterSchurms
Isuzu Junior
Black 95' 3.1 MU Auto in Melbourne
Posts: 132
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Post by PeterSchurms on Sept 23, 2004 22:41:29 GMT 11
I have noticed that the engine idle RPM is not always the same when the engine is warm.
It is set to 750rpm. When warm is may be between 750 & 1100. I have found that a short sharp press of the accell peddle and it will drop back to 750.
Under the bonnet the accell cable is not tight or restricive at idle, the throttle boddy appears to stop just before the adjusment screw. If you manually move the throttle body to the correct position with your hand, there appears to be some small resistance but no too much.
I have started to look into the water temperature control valve that Mat discussed in a earlier topic but have not been had a win yet.
Has anyone come accross this before?
Cheers!
Pete
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Post by tourist on Oct 13, 2004 18:10:35 GMT 11
Idling problem. Same here in both my 4JB1-T and 4JG2-TC engine. Hated it but nothing can be done about that.
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Post by geeves on Oct 13, 2004 19:42:03 GMT 11
could be to do with the aircon. When the air con compressor is running this operates a relay that increases idle speed This compressor dosent run continuously when the aircon is on The relay might be sticking.
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2much
Isuzu Baby
94 Bighorn 3.1ITD LWB
Posts: 20
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Post by 2much on Oct 14, 2004 12:54:27 GMT 11
Also check out your EGR and small rubber pipes for leaks and valves sticking open (if you still have it connected) I recall something about when the EGR valves are open the revs increases or something...the system also connects into the fuel injector pump (on the 3.1)
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PeterSchurms
Isuzu Junior
Black 95' 3.1 MU Auto in Melbourne
Posts: 132
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Post by PeterSchurms on Oct 16, 2004 0:25:48 GMT 11
I am still working on this one....
Alan... is the relay your referring to mounted in the fuse box under the bonnet?
When I start the car cold, the engine speed is approx 500rpm. When she warms up, it rises. If I tap the accellerator the revs will return to normal.
I'll be looking into it some more on the weekend.
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Post by geeves on Oct 16, 2004 11:26:04 GMT 11
pass sorry dont know
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Post by Roger on Oct 19, 2004 18:42:01 GMT 11
I am still working on this one.... Alan... is the relay your referring to mounted in the fuse box under the bonnet? When I start the car cold, the engine speed is approx 500rpm. When she warms up, it rises. If I tap the accellerator the revs will return to normal. I'll be looking into it some more on the weekend. Be careful at start up- not enough revs restricts lubrication under the piston as oil doesn't spray out of the bearing to that region. (I'm pretty sure that's how it goes). My MU oscillates the rpm- but not so defined. Also noticed when driving, 60km/h- 4th gear; sometimes 2000rpm exactly, othertimes a bit less. (same road). Maybe a vacuum hose might be the prob- good luck |
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Post by geeves on Oct 19, 2004 20:05:16 GMT 11
interesting thought on the piston lube Ive always let it idle at whatever it starts at and runs smoothish untill oil presure comes up When very cold that is 500 but this climbs to a normal 750 after a minuit or 2.
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nig
Isuzu Junior
94 TD Rodeo
Posts: 123
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Post by nig on Oct 19, 2004 22:45:59 GMT 11
My MU oscillates the rpm- but not so defined. Also noticed when driving, 60km/h- 4th gear; sometimes 2000rpm exactly, othertimes a bit less. (same road). Assuming you have a manual transmission, the only way your revs can vary for a given road speed is if your clutch is slipping. Of course if you have an automatic it will vary all over the shop. |
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Post by Roger on Oct 20, 2004 21:00:12 GMT 11
It's not slipping, it's that auto rpm change that occurs. It maintains the rpm difference throughout the rev range.
Regarding start up rpm. The cold oil is resistant to flow and therefore won't lubricate certain areas as well as warm oil will. When I start up, I set it to 750 rpm, by the time I get back to the car it's around 900-1000.
Too low an rpm can also cause uneven heating of the components and therefore more wear in some areas. Not enough oil being sprayed under the piston is the main killer.
Note that when starting a piston aero engine, The very first thing to do is set rpm to 1000 and check oil pressure in the green. This is for the above reasons.
cheers
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PeterSchurms
Isuzu Junior
Black 95' 3.1 MU Auto in Melbourne
Posts: 132
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Post by PeterSchurms on Oct 25, 2004 16:05:22 GMT 11
Alan, I think you are on to something, last night I found the Aircon relay and module, it is located inside the LHS kick panel. At idle, If I turn the AC on RPM increases, when I turn AC off, the RPM does not drop until I tap the accellerator. My guess is a sticking solenoid, faulty relay or module. Just need to find another one to swap and test.
I have looked for cracked vac hoses but non so far...
At least I feel like I am closer to a solution
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MattMU
Isuzu Senior
Rodeo Now!
Posts: 206
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Post by MattMU on Oct 25, 2004 17:58:58 GMT 11
Well Pete maybe this will help.....
That relay ends up controlling a VSV (vacuum switching valve) in the LHS of your engine bay and that sends vacuum down to the little diaphragm on the side of your Fuel injection pump. Its the part with the little metal arm with a hook that can grab the throttle lever and pull it slightly.
I would switch on the aircon and then off and if the revs were still high, pull the vacuum line off that diaphragm to see if it is still sucking. If so the vsv hasnt let go, either due to mechanical fault in the valve or its signal current is still operating!!
Goodluck!
Matt.
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PeterSchurms
Isuzu Junior
Black 95' 3.1 MU Auto in Melbourne
Posts: 132
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Post by PeterSchurms on Oct 25, 2004 18:19:44 GMT 11
Good one.... I'll check it out. Thanks Matt
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Post by Roger on Nov 3, 2004 16:19:59 GMT 11
I have noticed recently that when I turn on air con, the rpm drops- not rises. When I touch the accelerator, the the rpm increases as it should and the pedal is now down that little bit- could that problem also be what MattMU is on about?
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PeterSchurms
Isuzu Junior
Black 95' 3.1 MU Auto in Melbourne
Posts: 132
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Post by PeterSchurms on Dec 11, 2004 17:36:51 GMT 11
The problem dissapeared then returned again, rather frustrating. Mat was right, the vsv is not switching off every time. It appears intermittant. I will have to try and find a spare. I have the switch disconnected for the time being and it appers to be running ok.
Thanks Mat!
Pete
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