FlyingDog

I took the Shark for a test drive around the block earlier. When I got back to my lot and was about to put it in reverse I noticed the idle was bouncing up and down and would stumble a little like it was about too stall every few bounces. After sitting for 5-10 seconds the idle evened out. I put it in reverse and backed into a space. The bouncing and stumbling started again. After 5-10 seconds it went back to normal. I had to pull forward and back to straighten out and it all happened again.

This has been going on possibly since I owned the car but I never noticed the pronounced change before.

Is this a MAF problem?

John Speake

How many miles on the car ? Is the idle steadier when the engine is below normal running temperature ?

Does the car have an O2 sensor ?

Regards

Gretch

Does the 84 have an idle stabilizer valve.....if it does this is classic symptoms of one that is a bit gummed up......the WD40 flush technique should clear it up.....

the flyin' scotsman

Gretch............I too have an idle issue. The car starts well and when in park or neutral idles around 800rpm (GT mapped Eproms) but when any gear is engaged the idle drops to 600rpm. The engine performs well off idle at any other rpm so I also suspect the idle stabilizer valve and performed the WD40 flush which did not cure the issue. Is it possible if the valve is so gummed up it has to be fully removed, disassembled, cleaned and put back together or can you continue to flush until it is cured? Should the engine be running during the flush?..........I tried both methods blocking the vacuum line.

Red UFO

Matt I have the samething with my Euro.

Starts just fine. But after warming it up and 110 on the freeway, it does just what you described. It starts to stall.

Next day works fine, day after that, it goes back to crap idle. WTF? This is after I just paid to have it fixed so it works every other time. I pulled the spider and the MAF is filthy if that counts. WTF?

FlyingDog

I guess my last post didn't post...

The car has about 115,000 miles. I don't think I've driven it more than a mile or two at a time since october, so it probably hasn't reached normal running temp.

I don't think it has an O2 sensor.

I have no idea whether an 84 has an idle stabilizer.

Gretch

Malcolm, The "flush" is not a guaranteed technique. As I had it explained to me and others by Wally, you can load up the vaccum line going to the valve with WD40 or other solvents, (I use a graphite enhanced penetrating solvant called penephite) let it sit overnight, hook everything back up and run the car for a while. I even think it can be done a couple of times with no harm. The alternative is to replace the valve....which requires removal of the intake manifold.

John Speake

Flyingdog -
If that is the mileage on the MAF, then it is highly likely it is a problem. See my website...

The Euro 84 does not have an idle stabiliser system.

Malcolm,
The problem is that the GT cams do not match an auto. The GT cams do not correct the idle when you engage "D", the software is different.

Regards

Garth S

Malcolm,
Prior to stuffing the GT eprom in the LH, did the idle behave correctly? As you have a steady idle, even though it is lower when in gear, I would not suspect the ICV .... rather, the higher idle commanded by the GT chip is fine in a manual transmission car: with an auto, the torque convertor is asserting itself ....

FlyingDog

I guess I'll be running some tests on the MAF.

Gretch

That is what paying attention gets you.....a much better answer....I missed the GT mapped Eproms point......

the flyin' scotsman

Flying dog..........John Speake supplied me with a rebuilt MAF..........made a difference to the stability of the idle and the richness of the mixture. Also, didn't mean to hi-jack the trhread but perhaps we can all learn something.

Garth/John...........I believe i understand what you saying, the stock eproms compensate for the auto transmission when you drop the gbox into gear and the torque convertor applies pressure; the GT eproms do not have this mapping as they're all standard gbox's.

Gretch..........thanks for the input but given the above I'll leave well alone.........I don't drive much in towns or cities so the idle is not a big deal as compared to the on rush of power you get with the GT eproms at aprox 3800rpm..........they were also supplied by John.

John Speake

Flyingdog
You can't run any meaningful tests on a MAF, because the accuracy required is so tight - 1%.

The tests in the workshop manual are only for gross MAF failure. If you belive the problem is truly intermittant and random, rather than repeatable (e.g. always worse when engine hot) then you might look for a interemittant connection/ground point.

Drmark

John,
I am interested in your comments about idle in D - my 95 GTS has a rough idle (it is steady around 800 ish but feels like the car is missing and not firing on all cylinders) but only when in neutral. When I engage D it idles perfectly, and no problems when accelerating. But in neutral the missing is bad enough to make me and my passengers bounce up and down (albeit very sligtly!).
Any bright ideas why putting it in D and N should alter a misfire??
Cheers
Mark

John Speake

Hi Dr Mark,
Well, when in "D" the engine is under load... I can't think of an ECU problem that would cause a rough idle. Especially if the idle speed is around 675rpm under all conditions.

You could try an idle adaptation using a Spanner or Hammer...this sometimes helps, especially if you have done a battery disconnect and the MAF is aged. Because this sets everything back to the default settings, determined for all new components.