High/wavering idle - 3200gt

[Ben3200gt]

Morning all,

Took the 3200gt out for a 'good run' on Saturday, and towards the end of the run (and now permanently since) the car seems to idle noticably higher than normal. Not by a lot, but where as normal idle sits just over the 1000rpm mark, it now seems to be much more like 1250-1300rpm, which then requires a lot of brake riding when crawling in traffic. I let it go with no pedal contact whatsoever and it drove up to 30mph and switched up to 2nd (its an auto box) without any acceleration on my part. I also notice that when coming off the power and naturally decelerating, the car starts to kangaroo a little bit before settling.

Final symptom, when moving into either park or neutral, the revs climb even higher - maybe 1400rpm, which as nice as it sounds - its a bugger having to then put it into a drive car as its certainly not what would be considered a smooth change!!

My (VERY) limited technical knowledge- 97% of which was gained from these very forums, lead me to think throttle body - any more mechanically minded people care to share their thoughts? Been thinking about the contactless throttle body upgrade for a while so maybe this will be the final straw, but would appreciate any opinions before making the move.

Thanks in advance!

Ben

 

[NickP]

Hi Ben,

First off I would try a throttle reset, from memory I think this requires you to turn the ignition on for 2 minutes, turn off then turn back on again with the throttle fully depressed for 10 seconds, then turn off again. If I recall correctly the fbw throttle requires full travel pretty much every time you drive the car to learn the parameters, failure to do this will result in a gradual loss of response, odd tickover etc. If you keep having problems with your throttle and the check engine light comes on I would think about getting the contactless throttle body. It may also be worthwhile looking at the throttle pedal pot for which there is also a simple fix looked at.

Hope this helps.

Nick

 

[conaero]

Well, its one of a couple of things:

Main suspect is the fly by wire throttle system. Try doing a throttle reset:

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 this does not work I would still suspect the throttle system but worth a look. I would look at the pedal pot first.

The second thing that give high idle is an air leak. These mainly come from the underside of the plenum where it has a plate and the screws fall out into the V of the block and then the gasket gets sucked in and hence the high idle. I would also check all the other pipes do and listen out for a noticeable hissing.

Do you have an Error light on the dash?

 

[Ben3200gt]

Hi guys,

Thanks for your prompt responses!! No engine management light showing - just the idle issues, so will go give the reset procedure a go at lunchtime. Fingers crossed this will work it out; if not I will have my local trusted indie take a look at the possible air leak you mentioned. Will report back with my results this aft.

Never ceases to impress me how much knowledge can be found on these forums - Maserati owners that are not familiar with this forum must have significantly higher annual maintenance expenses than the forum readers!!

 

[conaero]

Cheers Ben for the compliment...you get out what you put in is the way we work.

Let us know your findings, my guess, pedal pot.

 

[Ben3200gt]

Ok, so; I followed both the procedures you kindly noted earlier (closed throttle resetting & full throttle resetting) - sadly not much change in the erratic revving.... On initial start up (in Park) the revs slowly climbed up to about 1800-2000rpm and settled there - after a gentle blip of the loud pedal, the revs dropped back down to around 1250rpm and chased a little, but not too badly. This is also evident in neutral; revs seem to climb somewhere between 1500-2000rpm and waver a little but again with a little persuasion on the accelerator, they seem to drop down to around 1250rpm (which is still higher than it normally sits, at around 1100rpm). It feels like my first car (a faded red/pink late 80s VW Polo) used to feel when the choke got stuck all the way out, but of course that didnt concern me quite so much!

In your opinions, does this sound pedal pot related? Any suggestions on ways of further exploring the issue? Still no warning lights gracing the dashboard, but it sounds/feels like the accelerator is stuck open a little bit which clearly isnt right. If it is pedal pot related, does it generally lead to spending an absolute fortune via Eurospares to replace?

Any further advice appreciated....

 

[dickygrace]

Ben, you're only in Leeds, pop over to Autoshield and they'll tell you within 2 minutes.

 

[Ben3200gt]

Hi Dicky, true enough - will have to fly over to Manchester this weekend time allowing; just in the process of moving over to York so free time seems to be something of a luxury at the minute!! Will give Marios a call and get myself booked in.

 

[boomerang]

Solid tips from Conaero.

You could check one thing yet before going to the dealer: delete the intake hose from the TB and try to move the throttle valve.
If you push it open, it schould immediately move back into its nearly closed position after you let it go.
If it does not come back immediately, your TB is shot.
Your info points into the direction of a desintegrating TB rotor.
In most cases there should occur the Check engine light though.
If everything looks ok, i would advise to visit a specialist indeed, to diagnose the problem with the SD2 tester.

 

[Ben3200gt]

Thanks Boomerang - will have a look at that this evening if I get home at a reasonable time - will report back with my findings later/tomorrow. Is a little weird that no CEL's have appeared though!

 

[ledlights]

Hi,
I had a similar problem on a manual car. Revs sitting at about 1800 rpm and loss of boost on acceleration. It was the plate on the back of the plenum chamber that had come loose and was allowing air to leak in and out. You could hear a slight hissing noise under the bonnet at idle.

On yours, it could possibly be that the revs drop when you slot it into gear because of the load created by the torque converter.

If so, it's not a big deal to sort out. About an hour's labour and a new gasket.

Hope this helps,

Steve

 

[Ben3200gt]

Cheers Steve - I like the sound of things being 'not a big deal to sort' Will hopefully get chance to take a look later this evening - otherwise tomorrow!! Fingers crossed its an easy fix.

 

[boomerang]

Indeed, a loose plenum bottom could also be your problem, good point from ledlight.
I even had that myselve when i drove a 3200gta
I have seen complaints about unstable idle after providing the contactless TB occasionally, caused by a loose plenum bottom. ( contactless TB's tend to respond faster and thus displaying this problem more pronounced)
In some cases even one or two bolts missed at the bottom of the plenum!
Worth checking out before doing anything else.
Good luck and hopefully it is just a matter of tightening some little bolts indeed.

 

[conaero]

The missing plenum bolts will be sitting in the V of the block as stated in post 3.

When you take the plenum off be careful not to drop anything down into the engine via the intakes. Plug them with tissue.

 

[BennyD]

Easy problem to cure; upgrade to a 4200!

 

[ledlights]

Yes, I missed that Conaero had suggested this when I scanned the post......

You could slip one of the small hoses off the front LH side of the intake with the engine running to see if this makes much difference to the idle and noise. When mine became loose, this didn't significantly change the idle speed and the hissing increase wasn't very marked. On a plenum that is not leaking, this test causes the revs to rise and the hissing noise is quite noticeable.

Steve

 

[Ben3200gt]

Morning all - thanks for your further advice! I was pretty late home last night so havent had chance to look anywhere, or at anything!! But, in typical Italian style, this morning I get in the 3200, turn her over and her idle sits perfectly at 1100rpm without missing a beat - regardless whether in neutral, park or drive!! Took a steady drive in to the office and could hear a faint whine (possible hiss) from somewhere front end - wonder if this is pointing towards the loose plenum as noted above - the other symptom; when arriving to the painful final 3 miles in to York City Centre, whilst sat in traffic on 1 occasion the oil pressure dropped a millimetre or 2 below the 2.5 mark momentarily, flashing the 'oil warning' error on the dash, but then the revs stabilised and it lifted back to somewhere between 2.5 and 5 and immediately the warning vanished. Had I not been staring at the oil pressure gauge at the time, I wouldnt have noticed as it was only for half a second or so - but still; would any of you suggest this points in a particular direction problem wise? Time allowing, I'm going to get over to Autoshield next week, but as the car is my every day motor, I dont want to drive it if it may lead to any further issues. As noted, bar the momentary oil pressure blip this morning, the car feels pretty much as it did prior to the recent issues - you think its one of those 'use it with caution and keep and eye/ear out for anything odd' issues, or would you suggest I park it and leave it until its had Marios & co look over it? Cheers for your comments - Ben

 

[conaero]

Morning Ben.

Based on what you have said, I would say the oil error light came on as the revs dropped to 500 and nearly stalled, so would not get over worried with that one as yet.

As the issue has disappeared this morning, I would say its electrical, more so the TB pedal pot has a worn contact disc.

The hissing would not be present if the idle was normal so I think you can probably dismiss this for now and concentrate on the pedal pot.

To remove the plenum is about an hour off, and no more than an hour back on again, just watch you dont break the injectors as you pull them out the head.

Obviously, if you do attempt it yourself, can you do a how to pictorial guide, thanks and good luck.

It might not be a bad idea to pull the plenum and make sure the belly plate is secure, then take it to the garage and have the TB looked at.

 

[Ben3200gt]

Thanks Conaero; I may have my trusted indie take a brief look this weekend, but think I may well get it over to the guys at Autoshield to ensure everything is as it should be! I agree with you reference the oil error light; it did appear as the idle dipped and as soon as it levelled out again it held firm where expected. Will update once the problem is resolved; if my indie does get involved I will happily get some pictures up as best I can. Thanks for the help.

 

[bill]

I wonder if it has something to do with the air con? I don't know about autos but on my manual revs do go up a bit when the air-con pump cuts in so if it doesn't activate the revs would be higher. Plenum bottom is a good shout as well as air leaks especially from the small pipes at the rear of the plenum. Keep us updated how you get on.