Sensitive throttle, ad nauseum

T.Hanson · Post by **T.Hanson** » Wed Oct 15, 2014 2:15 am

My distributor post becoming lengthy, it happened, I got the summer suspension resto rust '79 528i project back on the ground, running today. All that's left is rolling the rear fenders, not trusting 3/8" is enough under all circumstances, sharp edge horizontal, etc.

The procrastination is off for trying to remedy the (ten year) sensitive throttle in the '81.

The off throttle switch works. So does disconnecting it, maybe two votes better to reduce the gas pedal sensitivity. I can't imagine swapping one," Up to spec," throttle body for another will be a magic fix. Same with swapping AFM's, although my knowledge of their exact function in the system is insufficient to know if a bad one, or slight difference in '79, '81 parts may cause the sensitivity problem. Being simple solution minded, if the gas pedal is connected to those two parts, plus the distributor (advance, retard), I pick the solution being in the distributor, from all I've kept of the replies.

Besides three in the cars, all '79 to '81, I submit these (stamped) part numbers on my three spares :

0 237 302 001 PGFUD 6 ( arrow pointing at the 6)
0 237 304 006 PGFU 6 (same arrow)
0 237 304 015 PGF4U 6 (same arrow)

Visually, without complete dis-assembly, one looks no different from another. Unless I'm blind, realoem.com lists no such Bosch stampings as part numbers for a hint to which is more '81 than '79, etc.

I admit I'm just whining, hoping somebody will say, "Try the PGFU 6, just the advance connected, plug the retard ports,...to spare me screwing around for a week swapping through three distributors, plug wire connecting, timing, trying vacuum port combos.

Lenny D. · Post by **Lenny D.** » Thu Oct 16, 2014 1:32 pm

First: Apologies for a misinterpreted condescending reply to your post. It is never intended. Your reply indicated a distinct frustration with my reply. I can only try to illuminate facts that may help anyone progress in solving a problem.

Disclaimer: No one can fix anyone's car over the internet. period. Lady luck might intervene but nothing trumps 'being there'. That's why every mechanic says 'bring it in'.

Onward: I strongly recommend your spending time educating yourself on how distributors work, and understanding why they are built with the components they possess. That will help you in deciding how to go about taking an action. Ultimately you are going to spend time either learning before acting or just throwing darts blindly by swapping components without any reason as to why. Either way involves time. Your choice.
I posted years ago about your problem and suggested possible remedies based on my experience. I invite you to search for and revisit them. It is tiring repeating typing the same things. I don't know any more than what I posted then.

Lastly: I am not a guru. I learned things one a time. That takes time.
At this point you obviously have an unusual problem. Or possibly not. But you will have to spend time to track down the issue. Or just have fun with the piñata. But have fun knowing you are blindly trying to solve your problem. And you might get lucky!
I spent ten years before finding the ground/corrosion//chop-the-wire/solder-a-new-connector problem associated with L-jet engine management before I posted about that here years ago. I hope it helped someone else.
So stop whining and get to work!

Best of luck

T.Hanson · Post by **T.Hanson** » Fri Oct 17, 2014 1:42 am

I only wish you were in the garage for the pleasure of venting your frustration with having to type, with the alternative of your foot kicking my butt.

Just my impression you're a gas to be around.

Falkenberg · Post by **Falkenberg** » Fri Oct 17, 2014 2:25 am

Could it not be a throttle linkage problem?
As in, the action of opening is way to fast in the first part of opening the butterfly?
There is a number of rods and mechanisms things in there. Or is it cable?

Lenny D. · Post by **Lenny D.** » Sat Oct 18, 2014 8:41 pm

Just my impression you're a gas to be around.

Would that be a 'gas' in the respect of a bunch of hot air!?

'member, I'm a musician, and we're full of 'it'!

And yes, I enjoy being around me...oh, wait...nevermind..

But seriously,

I invite you to drive your beast down to da Big Eazy and I bet I'll diagnose something in 15 min if'n you can hang onto the wheel long enough! Nothin' like bein' there. And I'm easy but I ain't cheep

And to Fberg's post, he has a good point. Have you eliminated that aspect of a sticky throttle plate? You should be able to (with the engine running at idle) slowly and s m o o t h l y bring up the rpms by minutely cracking the throttle via the little lever attached to the throttle plate, no sticky/jerky spots particularly right off idle. You should be able to evenly raise the RPMs to at least 2k (and of course, beyond). If not, there is your problem. But what is causing it is the $64k question. That still leaves a possible distributor problem in the mix.. Refresh my memory, is this a standard or auto.? You know a standard will make the problem more pronounced.

From your complaints I still put money on a faulty vacuum advance or broken/missing spring on the centrifugal advance weights. How fast (in rpms) is the engine running when this lurch occurs? If it's right off idle, likely the VA. If later possibly the CA although in the aircooled VW world the lack of a VA exhibited a stumble off idle until the weights kick in for advance. Now, see, you're learning 'how distributors work'!

And don't forget you have the luxury of having a nearly if not identical platform from which to compare. Use it !

There - I've typed too much again

whatevah. . .

T.Hanson · Post by **T.Hanson** » Sat Oct 18, 2014 11:33 pm

From your last, previous post, I am confident the answer has been listed, to make my next post on the subject only to announce which one solved the problem. Using tools and parts, not typing on a keyboard.

Saying that somewhat frightens me, having to contemplate the thickness of my forehead bone.