3.2 hunting/misfire

[Robert Teague]

My 3.2 is hunting at less than 2000 rpm. The fault affects pulling away yet disappears above 2000 revs and did not occur during the recent warmer spell. air sensor of some kind affecting fuel mixture? any other ideas before I go chasing?

 

[GeoffB]

I had this on my old SC , check all your plug leads, mine was a loose connection

 

[Geoff_Fields]

Possible sticky action on Mas Air Flow. Often causes hunting when cold and stalling when returning to idle.

 

[nathan 1981 930 G50]

Air leak, bypassing the AFM? Check for split hoses or one popped off somewhere.

 

[BigAl1]

You are not alone. I have exactly the same symptons when starting if it is really cold> I assume it must be something to do with the air mass flow meter. For further information have a look at the latest edition of 911 & Porsche World, page 94, there is a very good article on this subject and if you have a spare 1500 dollars or so kicking about you could fit a Gekkatec hot-wire mass-airflow sensor!!
Alan

 

[nathan 1981 930 G50]

I like the thought of getting rid of the AFM, but, I have read where people didn't get the results they expected...

 

[3.2_fordy]

Don't blame the AMF I have the same fault on my car I thought it was the AMF or the idle speed adjuster but after changing said units problem still there have to investigate more

 

[Robert Teague]

Some good suggestions ta. I also got a comprehensive check list courtesy of 911 and PW contributor Peter Tognolia.
Thanks Peter. I will follow through on the suggestions and post what I find to assist all you others!

 

[Pete917]

it does sound like a sensor. Does the problem go away once the engine is up to operating temperature

 

[paul kelley]

Hi All

May sound too simple, but check that the oil filler cap is screwed down tight as this can cause an irregular running symptom.

Just a thought[8|]

Have fun

Paul Kelley

 

[Nick Shipman]

might seem stupid but my car was hunting and missing and tried everything even had the ecu out and got it tested , but the chap who tested sugested that i checked the crank sensor i sorted it in the end by re gaping the crank sensor i even set it a bit closer to the flywheel and it sorted it out .
nick

 

[Pete917]

Its a very good idea to check the crank sensor. As suggested the airgap is important. Slightly to big and you get problems. They are also prone to breaking down.....

 

[Robert Teague]

I found no leads or broken connections although a loose plug lead on the centre cylinder (left) was noted. Refitting caused no improvement. I also found a blown fuse in the engine compartment fuse box. The centre fuse of three was gone (8 amp).
Despite 30 minues googling I cannot find any info on what circuitry this covers. Any ideas?

 

[3.2_fordy]

Robert
fuses in the engine compartment should be heated rear screen 25amp, engine comp heater blower 25amp, and foot well heater blower 16amp according to my drivers manual I will look at my Bentley s manual when I get time if you like
Have you had a look at the distributor cap and rota arm for your problem just give the contacts a clean a 5min job and no cost

 

[Robert Teague]

Will do. Interesting point on the fuses. I took out an 8 and according to your recollection the heater blower needs a 25.
If you do get a chance to check the manual it would be welcomed.
Robert

 

[Pete917]

these problems take a while and are the often the simplist of things once found. Its the finding that hurts. I still think you should check the crank sensor. Do the dizzy cap and rotor arm first though as these are quick and easy to check!

 

[Geoff_Fields]

Graham's info regarding those fuses is correct. However the 8amp fuse you have installed probably will survive the load current of the fans.

 

[3.2_fordy]

Rob
Checked my Bentley Manual No1 16amp heater blower relay, No2 25amp heater blower, No3 25amp Defogger + rear window wiper