bucking bronco

[davy83]

i have what looks to me like TB problems all of a sudden after a reasonably quick drive after discovering my son had been rushed to hospital, i parked up without any real cool down. now it revs like a mad man on start up and idles at 1500rpm hunting about 200 rpm. I checked for air leaks, with a smoke test, i have tested the pedal sensor and all appears ok. Strange thing is no error codes? My TB was upgraded by Xemodex less than 2 years ago so i would be surprised if its that, but struggling to think of what else can cause this sort of behavior. is there an air flow sensor and can it cause this too? I presume there is some where. I am thinking of jsut sending the TB back to Xemodex for testing to see if thats it. Any suggestions gratefully received.

 

[Parisien]

MAF does give bother its been referred to on here a number of times....maybe do a search for a more detailed response


P

 

[2b1ask1]

Hope the lads alright Davy?

Try a battery reset & see if it clears itself?

 

[ledlights]

Hi Davy,

Despite the smoke test, it sounds like it could also be the plenum chamber plate or a split hose on the inlet which I think you'd suspected. Mine did exactly the same thing after a drive. Only strange thing is that I think you'd hear it.

My TB symptoms were the hunting and the error light but no fast idle.

Hope you get it sorted soon.

Regards,

Steve

 

[davy83]

Hi Newton, he got his appendix out and seems to be fine now, bit of a panic though since he graduated the day after! seems the 3200 does not have and air flow meter, just searched the workshop manual and no sign of it. I presume they calculate the air flow rate from the two pressure sensors? any one know how this is done?
And Steve yes i just don't believe the Xemodex part has gone south less than 2 years old, i would have to be desperately unlucky but hey its a Maserati. i thought if there was an air leak i would have heard it or seen some signs with the smoke test, so am a bit confused. I guess it does not cost any thing to strip the plenum chamber apart and have a look. The seriously fast idle on start up bothers me as i would not expect an air leak to cause that, its more like a sensor reading wrong and causing the TB to aim for the wrong place.

 

[bill]

Davy
I would check if the throttlebody butterfly is sticking. With the engine OFF AND KEYS REMOVED, take the big pipe going into the throttlebody. Using your fingers move the butterfly. You should feel resistance but is should return from both fully open and fully closed, to the idle partly open position.

Good luck!
Bill

 

[davy83]

Hi Bill, sorry should have mentioned i did that almost first test and the butterfly is moving very smoothly and the ODBII reader says it returns to 6.7% open which i think is about right. I also got some 0% readings out of the ODBII reader for the butterfly position which is either a sign that some thing is amiss with the TB or the ODB is a bit flakey, either is possible at this point. MY plan is to remove the plenum chamber and if every thing looks ok i will return the TB to Xemodex and see what they say. Although i will need to organise the shipping myself as Zemodex said they would look at the unit but wanted $195 for shipping! yeah right, I will be agreeing to that.

 

[bill]

Davy
If you want you can send it to me and I ll check it over FOC. Carriage would be cheaper.....!

 

[ledlights]

Hi Davy,

When the plate under the plenum chamber came loose on my car it caused a high and unsteady idle, actually more unsteady when coasting on a bumpy road -probably due to the plate moving about. When it first happened, I didn't notice the noise but it got worse the longer I left it. When the bolts come loose the boost in the plenum usually spits a piece of the molded O-ring out causing the problem. I could well be wrong but I think the plenum would be where I would start to look. There's a guide on how to remove it to get to the starter motor on this site somewhere.

Good luck with the problem solving.

Regards,

Steve

 

[Danny]

A leaky Kayser valve would also result in hunting for revs (but it would reduce braking power at the same time). Worth a check though: http://www.eurospares.co.uk/searchResult_one.asp?S=377493347&TM=3&TMo=698&TA=1&TB=41514

 

[NickP]

Have you performed a throttle reset? You need to put the car in neutral for 2 mins with ignition turned on. Then turn off ignition, turn back on with pedal down for 10 seconds then switch off the ignition.

 

[davy83]

Hi Nick, did several throttle resets, not the problem. as far as the plenum chamber leaking, the kaiser valve is a good suggestion i will have a look. I have been round all the plenum bolts with my ear to them and a smoke test, and there are no loose bolts, I also replaced the seals 6 months ago when i was in there replacing the knock sensors. I will probably strip the plenum chamber any way just in case, its not that much work. i will check all the little vacuum hoses first i think.

 

[davy83]

an easy one for once

it looks like it was the plenum plate, several loose screws and the seals was blown out in one place so easy fix for a change!! will get a new seal and see how it goes!

 

[bill]

That's great news! I would add a bit of thread lock just to make sure...

 

[davy83]

already planning threadlock for sure