TheSamba.com :: View topic

Fri Apr 17, 2009 10:22 pm

Here's the scoop:

She's getting 9-10 mpg at 55 mph confirmed by gps on virtually flat roads. A fill only takes me about 220kms.

At highway speeds it intermittently feels as though one or more cylinders ether become weak or miss altogether, at first I thought it was soft spots on the gravel road but then I hit the pavement and I thought it might be the wind so I came to a stop and OOPS no wind to speak of.

Things I have replaced recently:

Air filter
Spark plugs
Wires
Cap
Rotor
Fuel tank and seal kit
Fuel filter
Ignition control module
Ignition coil
Front and rear brakes (they aren't dragging)

Thing I have checked or had checked recently

Timing
MAF adjusted
O2 switching
Fuel leaks (my nose doesn't work well so I looked to be sure)

I'm not sure where to start looking, any suggestions are greatly appreciated.

Fri Apr 17, 2009 10:53 pm

Digifant, Digijet?

Fri Apr 17, 2009 10:53 pm

I had the same problem when I had a major vacuum leak. Also idled high.

Fri Apr 17, 2009 11:03 pm

Quote: Digifant, Digijet?

not sure, it's a 84 westy, 1.9.

Is there a simple way to tell the difference?

Fri Apr 17, 2009 11:52 pm

iambeeman wrote: not sure, it's a 84 westy, 1.9.

That should make it a Digijet. Have you tried driving it with the Digital Idle Stablizer taken out of the system? Have you check the output of the coolant temperature sensor (TSII)?

Sat Apr 18, 2009 6:11 am

I had mileage that bad when my exhaust fell apart before the catalytic converter, and more importantly the oxygen sensor. The oxygen sensor was seeing no fuel so the computer kept trying to flood the engine. luckily I only had to go about 65 miles to get home.

Sat Apr 18, 2009 6:37 am

Quote: That should make it a Digijet. Have you tried driving it with the Digital Idle Stablizer taken out of the system? Have you check the output of the coolant temperature sensor (TSII)?

I was under the impression that the Idle Stabilizer only did anything at idle when the TPS low speed switch was activated. But I'll try it, have to use it tomorrow any way.

I plan on checking the TSII signal soon in a more controlled condition like on the stove with a thermometer. I checked the signal twice in the van and it seemed right according to my bently manual but it was not a proper test.

Sat Apr 18, 2009 6:45 am

Quote: I had mileage that bad when my exhaust fell apart before the catalytic converter, and more importantly the oxygen sensor. The oxygen sensor was seeing no fuel so the computer kept trying to flood the engine. luckily I only had to go about 65 miles to get home.

The exhaust is in leak free condition, but I do plan on checking the O2 wiring for a short to ground, disconnecting it seemed to have no effect on idle. According to the snap-on tool it was switching properly but if that signal doesn't get to the brain it won't help now will it?

Sat Apr 18, 2009 6:57 am

iambeeman wrote: Quote: That should make it a Digijet. Have you tried driving it with the Digital Idle Stablizer taken out of the system? Have you check the output of the coolant temperature sensor (TSII)?

I was under the impression that the Idle Stabilizer only did anything at idle when the TPS low speed switch was activated. But I'll try it, have to use it tomorrow any way.

The DIS is supposed to cut on only below 1100 rpm's IIRC and is not in anyway dependent on the throttle position switch. But in failure mode it may do as it pleases at any speed though.

If the cat has failed internally then the exhaust will tend to be quiet without the usual pulsations. So long as the engine is running and the gases are passing through the exhaust, the O2 sensor is still going to appear to work normally. For delta-vanagon the oxygen sensor should never see fuel and couldn't read it if it did. As its name implies it reads oxygen only.

Sat Apr 18, 2009 7:10 am

The exhaust seems to be free flowing certainly pulses the way I would expect any other car to

Sat Apr 18, 2009 8:06 pm

Just a note I own a '71 Ford F700 with a 361ci industrial 4bbl and a 14' cube van and it gets 12mpg, how can a 1.9L use more fuel and still run?!?!?!?!

Sun Apr 19, 2009 8:26 am

Has anyone ever considered the gas itself as being the culpert??
Who knows what kind of "stuff" is put into the gas now-a-days.
As a kid I remember that my 62 Rambler loved Texaco gas compared to the other brands.
Now...Madam Helga really likes Chevron, especially on a long trip.
Im squeezing about 20mpg outa Helga on the freeway and around 17mpg around town.

Mon Apr 20, 2009 6:43 am

Quote: Has anyone ever considered the gas itself as being the culpert??
Who knows what kind of "stuff" is put into the gas now-a-days

Tried a couple of different stations with no apparent difference, I don't really think that's the problem in my case anyway.

Yesterday I drove 120-130kms and use 1/2 tank approximately, and that was with the idle stabilizer by passed, the idle was higher than normal (I think since I don't have a tach.) so if my understanding is correct it is working properly.

The next thing I think I'll check is the temp. II sensor, unless some one has a better suggestion.

Mon Apr 20, 2009 7:07 am

Perhaps your rear brakes are dragging. Could be some of it.

Mon Apr 20, 2009 8:33 am

Quote: Perhaps your rear brakes are dragging. Could be some of it.

I just did the rear brakes and everything checks out plus i lubed all the movement points with raybestus brake lube after cleaning the backing plate and hardware (normal procedure at any good repair shop).

Mon Apr 20, 2009 8:59 am

iambeeman wrote:
Yesterday I drove 120-130kms and use 1/2 tank approximately, and that was with the idle stabilizer by passed, the idle was higher than normal (I think since I don't have a tach.) so if my understanding is correct it is working properly.

With the DIS disconnected your idle speed should have droppped and not increased. Don't know what that is indicative of though.

If with the engine hot you short out the TSII sensor and the engine runs different, the TSII sensor is likely your problem.

Mon Apr 20, 2009 9:29 am

My experience with poor fuel mileage is:

stuck fuel injectors
failed oxygen sensor
throttle position switch misalignment

Hope this helps.

dylan

Mon Apr 20, 2009 11:33 am

Quote: With the DIS disconnected your idle speed should have droppped and not increased. Don't know what that is indicative of though.

If with the engine hot you short out the TSII sensor and the engine runs different, the TSII sensor is likely your problem.

Like I say no tach. it may have been a mistaken impression.

for shorting out the TSII do I simply disconnect it to do so or do I run jumpers and short the 2 without removing the wires? I'm going to try both ways but if someone else needs the advice then it's here for them.

Mon Apr 20, 2009 11:45 am

Quote: My experience with poor fuel mileage is:

stuck fuel injectors
failed oxygen sensor
throttle position switch misalignment

The O2 checked out OK at a local shop that I worked for winter before last on a Snap-On tool I'm familiar with, it gives a very nice read out on a real time graph so you can actually watch when your mixture changes. I do also plan on checking the wiring leading up to the O2 to check for any opens or grounds.

A local fellow who specializes in German imports since '68 told me that these vans don't need the O2 sensor very much and that he would at times remove them completely because they ran better, is it just me or is there something wrong about that statement???

Mon Apr 20, 2009 6:19 pm

They can run fine with no O2 sensor, but then the mixture is more dependent on the AFM condition and adjustment. When the base idle CO is adjusted to the specs according to altitude, which is done "open loop", meaning without the O2 input, they will tend to run a little richer across the board than when closed-loop. That can be compensated for if you do decide to run sans O2, by making further AFM adjustments, but in that case it's best to have a wideband O2 monitor you can watch while actually driving so you can see that the mixture curves are working right overall under various actual driving conditions. Just checking CO at idle doesn't tell you that it's got a good mixture under load. But so long as these kinds of things are checked, you can get as good or better performance without the O2.

Your catalyst may have something to say about it over time, though; the whole reason the O2 is part of the system isn't for the engine, it's for the catalyst to work properly. The engine doesn't need it at all, and if you really know what you're doing it can be made t run both cleaner and more powerful without the constraints of a 14.7:1 AFR under so many conditions when that is not the ideal mixture.