'85 vanagon dead spot in throttle after warmed up

[Schmid]

This is embarassing the amount of money I have spent trying to fix this annoying problem. lesson learned the hard way, this is my first vw.

it's a 1985 1.9l with digijet of course. Runs great. when cold, I can press the throttle and RPM's will increase smoothly. as an engine should operate. once warmed up, I press the throttle and nothing happens. once I press it far enough the van races. makes driving in a parking lot or campground difficult.

here's what I have done, as ashamed I am to admitt;

new air flow meter
new throttle pos. switch
plugs
wires
rubber intake boots
checked and replaced vacume hoses
temp 2 sensor
plugged a used ecu in

van runs great, but still has that acceleration problem.

that's my story, driving me nuts. very tempted to try the ztec or subaru swap but funds do not allow that.

any help or advice would be appreciated. I'll help out with anyone's vespa problems in exchange!

PS

[scottcollins72]

Doesn't neccesarily apply to your year of van but on my 81 I have a wide open throttle switch. If you have one you should check for proper operation. Do you have the bentley manual for your year? Personally I'd go through with my digital multimeter and test every component of the fuel system according to the bentley. It's pretty good for giving resistance values for things like injectors and all the other parts in there. First place I'd start is at the cold start injector and move on from there.
Also, did you check all of your injector O-Rings? Check your injectors as well for flow, resistance, etc. Barring all that I think you're on your own. Don't have enough knowledge on your year.

Scott
81 westy
88 jetta
91 passat (POS)
02 ford e-250 (best running vehicle in the house at the moment)

[syncromat]

Seems you are pulling too much air in . As long as its cold with extra fuel it works ok but as it warms and the fuel leans out you will get hesitation .


just a thought .

[Randy in Maine]

If it were me, I would take it to a shop and have them do a couple of things:

1) Confirm your ignition system is good (including the advance/retard of the distributor). It all needs to be ruled out as a possible problem.
2) Confirm your fuel delivery system is good including the injectors spray pattern, fuel pump pressure and the pressure regulator. No vacuum leaks are allowed. Inspect the AAR valve to ensure proper operation. That stuff needs to be checked to rule systems out.
3) Open up the top of the AFM and observe the copper AFM sweep needle moving along the black contact slide. Might need a bend.
4) Dial in the fuel:air mixture in the AFM with an exhaust gas analyzer.

It sounds to me that the engine is running lean or failing to advance and anyone of those could make it happen.

Let us know what happens.

[Schmid]

excellent advice - I'll find someone out here to take a look.

I'm going to wait on the adjusting the AFM until very last. The fuel pressure check is a good idea. makes some sense to me.

I'm thinking it could be electrical because the problem is so instant. I'll sit in my driveway playing with the throttle and it goes from perfect to problem in an instant.

also, I checked and cleaned all the ground connectors.

thanks again -

PS

[Randy in Maine]

You can buy a fuel pressure gauge at the local FLAPS and snip off the end so that it will fuel clamp to your fuel rail, 0-60psi is good. $40-50? It should look something like this http://www.germansupply.com/home/customer/product.php?productid=16610&cat=300&page=1

You can make one at Home Depot out of a water pressure gauge and a air compressor barbed fitting to fit your fuel hose if you are stuck in Stinkwater, Texas or someplace. Temp use only and the accuracy is just OK. A real gauge is better though. https://www.thesamba.com/vw/gallery/pix/189739.jpg

Do the Bentely diagostic to test the fuel pump and pressure regulator with and without the vacuum hose in the loop.

Speed shops and motocycle shops usually have a EGA to sniff the fuel:air mix for the good tuning.

If it were mine, I would diassemble the distributor, clean it out with Gum Out, relubricate it with Bosch distributor grease and then test the vacuum can to see if it is doing anything when you put a vacuum on it. A quick suck is OK to see if it moves any. Careful notes and a digital photo on the placement of the washers and stuff is handy. Impossible to do if there is a 2 year old "helping".

Even if you do not adjust the AFM, pop the top off that and have a look at what it is doing as the engine goes from cold to warm. Observe the operation as the throttle changes. Sometimes the needle needs to be bent a squeak to keep it on the track. If the tack is dirty, contact cleaner and "computer air" can clean it but make sure the contact cleaner doesn't eat plastic.

If you put your volt ohm meter on the temp sensor (where it plugs into the wiring harness), see what kind of change it is reading from cold to warm. Maybe it does not have a good connection or somebody used anti-sieze on it. About 2300 ohms cold going to 450 ohms or less when warm. Look for the change. That takes just a minute to test.


Give you self an afternoon to play with it yourself and see if you come up with anything.

[bljones]

I'm thinking distributor. Like randy said, it may be an advance issue.
_________________
OG JHC
Author of Original Rant #1
"It stingd itself to dead... now that is control on you"

2%

[r39o]

I had quite similiar issues with my 85 Digijet. In the end, the last thing we did was to adjust the AFM and it has been happy for the last 8 months or so.

My van had LOTS of deferred maintainance. It ran crappy cold, stalled and backfired every now and then. Those are ALL mixture related problems. BUT, because so much was screwy with my van, others had done things to it so it would sort of run. I fixed all that.

What you really have to do, is verify that every thing is as it should be. You can do that with a Bentley and an ohm meter for the most part. Prime candidates are: Sensor II, O2 sensor and throttle switch (total for all 3 can be as little as about $100. ($13 + $17 + $63)) Be sure you do all the simple checks first. I too thought I needed a new AFM, but I read and read and figured it all out, system by system. In the end, I really only replaced tuneup items and a scant few parts. Sensor II and the O2 sensor where the prime electrical parts I replaced besides the tune up parts. I also ended up fine tuning the throttle body and messing with the way the switch works. For grins, I also replaced the throttle cable, because it seemed a bit sluggish (didn't help much, but I know it is good.)

Of course, you have to check the operation of the distribitor with a timing light. Make sure the vacuum is working right. Check the fuel pressure and how it works with and without vacuum. All sorts of stuff, that you can read about here and in the Bentley. Basically you need to make sure you got spark and fuel in the correct timing and quantity.

Sorry for the long windedness, but I had such nagging issues for several months my self and I may have mentally blocked out all the things I did to fix this that or the other thing.

Good Luck,
Walt...
_________________
"Use the SEARCH, Luke" But first visit the Vanagon FAQ!

1990 Multivan EJ 22, Rancho trans 0.82 4th, Small Car front AC, CLKs w/ 215/65-16, homemade big brakes 303mm, Konis, Recaros, etc....

Click to see my ads for Cup holders, Subaru clutch fix and CLK wheels (no wheels currently)