Idle adjustment how to minimise difference under load

[mcfly94 169]

Hi guys, really trying to figure out why my car idles at 1200rpm in park/neutral yet only 650/700 in drive, only happened since c4 went in.

Could it be vacuum line arrangement, because I cant seem to find any leaks.

I know I shouldn't worry but I have had enough of the car jolting into reverse, its pretty harsh on the trans, and im about to have it rebuilt.

What else can cause it?

[gerg 10,871]

Very much sounds like a vacuum leak. Check every single line coming off the manifold, check for splits at the end of every hose (very common) and check PCV valve by putting your finger over it. Squeeze the brake booster line shut with pliers. Leave no stone unturned... Crimp every hose coming off to see if it's the culprit. Spray the shit out of every joint, throttle shaft, gasket flange with WD40 when running and listen for change in RPM.

[mcfly94 169]

Will do, already tried pcv valve, Ill give every single one ago tomorrow. Cross fingers I find something, I hope I find something wrong better than not knowing.

[xeeclipse 37]

It must be something other then a vacuum leak mcfly due to the the rpm difference. Even if there was a vacuum leak the differential between park and drive would remain the same......250-300rpm

[mcfly94 169]

that's what I thought but what could it be?

[xr6tjet 98]

I would love the answer to this as well, my EFi has been jolting into reverse since I got it and I still can't find the issue. I actually blew my first transmission reverse gear because of it. Any ideas?? My vacume hoses seem fine but I really can't see anything there

[mcfly94 169]

Its worse when mine warms up cold morning isnt so bad

[xeeclipse 37]

_{How does the vacuum modulator on the trans work? try changing that maybe?}

[PSI_LTD 37]

i found that mixtures and timing can affect this to an extent.

when the auto's in gear its under load (small, but a load nonetheless).

 

i found reducing the idle speed adjustment but ramping up ignition advance and richening the mixture (on lpg) would reduce the idle speed difference.

[mcfly94 169]

Did a bit of fiddling with the idle speed and mixture.

Timing set at 10 degrees at about 900rpm.

Idling at about 900rpm in neutral and drops around to 650-675 in gear now. only around 200rpm drop which is much better.

Checked brake booster line, and its A okay.

 

Needs more fine tuning, thinking about setting up an Inno AFR.

[xr6tjet 98]

Is yours EFI mcfly94 or carby ?

[mcfly94 169]

Is yours EFI mcfly94 or carby ?

Carby mate, still a bit to sort with my carb, idle cut solenoid is a bit iffy sometimes and the idle circuit play us, plan is to run a 465 holley on a 4 barrel soon, got to sort my ignition first.

[xr6tjet 98]

Ah okay mine is EFI and I would love to stop the 'thump' in reverse or atleast lower it. My XE has a really nice soft clunk into reverse and it is also EFi. Must be something I can do!

[PSI_LTD 37]

another thing can be related to auto / converter.

 

i had my converter / auto replaced, and the clunks were much less severe...

 

currently has relatively fresh C4 and tight converter, and you just feel and gentle but positive click when gear is engaged.

[mcfly94 169]

Yeah trans is need of a rebuild and don't know about the converter

[xr6tjet 98]

I put a reco'd trans in it after the first one blew, what would it need to stop the "thump" its not actually a noise it just doesn't seem to have a drop when it goes into gear!

[gerg 10,871]

I put a reco'd trans in it after the first one blew, what would it need to stop the "thump" its not actually a noise it just doesn't seem to have a drop when it goes into gear!

Try some auto transmission conditioner. It makes your hard seals go all gooey again. Just don't expect to get it back together if you dismantle the box, as the seals swell up that much that you can't get the pistons back in.

 

Also, how often do you give your tranny a flush/oil change/filter? The fluid makes a massive difference to the way an auto shifts.

[Tyler06 266]

Never had that problem with that convertor but that said it did sit in the shed for 12-18mnths unused. Was a reco unit so unless the box has contaminated it maybe?

[mcfly94 169]

Nah not the converter mate, its all good rpm drop is only between 150-250 rpm now, my trans is getting old an tired however.

[mcfly94 169]

And now the idle cut solenoid is playing up -__-, need to source some more from upullit, also still needs a tune, such a prick to tune!, thinking about setting up an afr, would this allow me to get my mixture good? aatm tuning by ear does not seem to work! nor with a vac gauge.

[Clevo120Y 815]

Just put a Holley on it mate, easy to tune and rebuild. Download a tuning tips book from Holley and off you go. The webber is a good carb but once they get worn out they are useless plus all the extra emissions crap and idle solinoids etc etc they just have more parts to play up.

[xr6tjet 98]

Try some auto transmission conditioner. It makes your hard seals go all gooey again. Just don't expect to get it back together if you dismantle the box, as the seals swell up that much that you can't get the pistons back in.

 

Also, how often do you give your tranny a flush/oil change/filter? The fluid makes a massive difference to the way an auto shifts.

Before I put the trans in I gave it a service with a new filter and everything. not sure how the trans was before I bought it but its smooth on the gears just seems my car drops in gear too high in rpm.

[mcfly94 169]

Just put a Holley on it mate, easy to tune and rebuild. Download a tuning tips book from Holley and off you go. The webber is a good carb but once they get worn out they are useless plus all the extra emissions crap and idle solinoids etc etc they just have more parts to play up.

yeah had few people say that, ill look into to it, not going 4bbl, only 2bbl using adapter plate, too expensive otherwise.

[Clevo120Y 815]

Yeah just rebuild a 350 and go with that in my opinion.