Poor gas mileage, hesitation when cold and hot start issue

[Alex Proulx]

Hello all, this is my first post but I have been reading this forum for a few years now.

Our 1988 Vanagon GL full camper is suffering from the following 3 issues; it has poor gas mileage, it hesitates when cold and it is hard to start when hot. We own the van since 2009, the first 2 issues came with the van and the last one just started a few weeks ago after we tried to fix the first 2 issues (without much success).

Poor gas mileage: We can do 300km on one tank of gas, which is roughly 12.5 miles per gallon. The owners book says we should be doing 18 on the highway. I read all the time on this forum people doing 450km on one tank…

Hesitation when cold: If we get moving right away after the van is started, it does not accelerate smoothly, it hesitates, buckles, has little power unless we floor it. It is worst when moving from a complete stop, it is not so bad when we accelerate while already moving. On the other hand, It idles really well, steady at 900rpm and revs up and down no problem. When the van is hot, we have none of those problems what so ever, it is butter smooth.

Hot start issue: If we stop the van when it is hot and wait a few minutes before we re-start it, it cranks fast but when it gets going, it revs at 300rpm like it is starved of something (air or fuel?). To fix the problem we just rev it up a bit then it stabilises at 900rpm like nothing ever happened. It drives really well after that. If we restart immediately it does not happen, it must sit for 5-10 minutes for this thing to happen.

So far this spring we put a new Gowesty vacuum TPS, new leads, new sparkplugs, new distributor, new fuel filter, new fuel lines (engine compartment only), new pressure regulator, new temp 2 sensor, new O2 sensor and cleaned a bunch of grounds in the engine bay. The hesitation problem got a lot better but it is still there, the gas mileage did not get better and the hot start issue started to happen. We don’t have access to a good Westy mechanic in town so I try to do a lot of stuff myself.

Any help or tips would be appreciated.

Thanks,

Alex[/img]
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Vanagon GL 1988 Full Camper, 4 speed manual, 2.1 stock engine
Audi A3 2.0T S-Line Quattro 2015

[funagon]

You replaced the temp II sensor and the OXS. Have you verified that the Oxygen sensor wiring is good? (Even with a new sensor, the wiring is notorious for shorting out and sending a bad signal to the ECU.) This last post on the page linked below (scroll to bottom of page) has good, detailed instructions for exactly how to check this out:

http://www.thesamba.com/vw/forum/viewtopic.php?p=3444744
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1990 GL 7-passenger
2.2 liter WBX

[Alex Proulx]

Thank you funagon,

I tried the second test with the engine running and got no change in rpm or exhaust smell, it was rich the whole time, but the engine was cold so I will try again later with the engine hot and see if I get a different result.

I was going to try the first test with the meter but got confused by the coax cable description. My new O2 sensor has only 2 wires, one is a blade connector going to a normal green wire (no sheathing braid, but I think its the one called the green coax in the procedure), the other connector is the large type with the metal retaining clip, the sensor grounds directly on the exhaust metal I was told. Is it possible that I dont have a coax cable but a normal wire instead?
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Vanagon GL 1988 Full Camper, 4 speed manual, 2.1 stock engine
Audi A3 2.0T S-Line Quattro 2015

[funagon]

Look at the green wire. That should be the coaxial cable. The inside is a strand of wire, and the outer sheath of the green wire has what looks like little filaments, or little strands of wire. Those cannot touch the inner wire, or it will mess up your O2 sensor signal. This commonly happens at the end where the wire is cut and clamped (you may be able to fix by trimming back the green sheath a bit), or possibly the wire has been pinched somewhere else.

On a 1988 vanagon I would expect to see that the other OXS wire is a two-pin connection, actually two wires. Right?
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1990 GL 7-passenger
2.2 liter WBX

[T3 Pilot]

Good advice so far......

If you haven't done so already, download and print out a copy of the Protraining manual. I find it really helps in diagnosing these types of problems by keeping things in a logical order. Once you have confirmed proper function of a component by testing, I find that you really have to get up close and personal with the wiring. Clean and inspect every inch. Lots of connections appear good, but upon close inspection you might discover corrosion inside the crimped end for example.

One recent example that I can think of was the hall sender connection that appeared good but under the rubber boot, all three wires had cracked insulation and some level of green oxidation at each crack.

Good Luck.
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1988 Vanagon

The most important part in every vehicle is the nut behind the wheel......

[Ahwahnee]

[Alex Proulx]

Thanks everybody, I was hoping for a magic pill but I guess there are none. I will get started with the testing as soon we get back from this trip. I find that changing a part is often easier then testing it, but with the most expensive ones now left on my list it is indeed going to be cheaper to be smarter, especially if it is a bad connection
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Vanagon GL 1988 Full Camper, 4 speed manual, 2.1 stock engine
Audi A3 2.0T S-Line Quattro 2015

[Randy in Maine]

WE NEVER REPLACE ANY FUEL INJECTION PART UNTIL IT IS PROVEN TO BE FAULTY. NEVER.

You will go broke and the thing will still not run well.

[Wildthings]

[Alex Proulx]

Did some testing as per pro training manual:

Page 107 Air Flow Sensor
Column A between 6 and 17 got 561 ohms
Column A between 6 and 9 got reading as per temperature chart
Column A between 17 and 21, got variable reading as expected except that instead of increasing gradually as I moved the flap, it went up to 800 then down a bit to 700 and up again and this was on a continuous motion of the flap. Is this normal? I am thinking it might explain the hesitation on acceleration?

Page 108 coolant temp sensor
Between 6 and 10 got reading as per temperature chart

Page 129 system check
ECU ground connection between 13 and ground got 1 ohm. Because the ground of the ECU was unreacheable under the water tank, I cut the brown ground cable as close as the cabinet as possible and made a new ground connection under the bench in the metal, got 1 ohm again. Is 1 close enough to 0?

Ok now the scary part, I thouroughly followed the tencent O2 sensor wiring testing and here what I got:
Between the green cable center wire and ECU #2 got 4 ohms ( supposed to be zero).
Between the green cable center wire and ECU #13 got infinty (not sure what I am supposed to get here nor if I have to test it but the procedure did not specify a number, instead it says signal pin).
Between green wire outside wire (finally found it by pulling hard on the connection rubber booth) and ground, got 1 ohm. Supposed to get zero.
So I am not sure if I passed this test or not?

One thing for sure is that the van smells rich all the time, something must be out of adjustment. Tommorow I will attempt to adjust the air flow meter with the O2 sensor voltage (saw a procedure on that somewhere).

Thanks in advance for the feedback.

Alex
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Vanagon GL 1988 Full Camper, 4 speed manual, 2.1 stock engine
Audi A3 2.0T S-Line Quattro 2015

[0to60in6min]

can you borrow an AFM from someone and try it?

[morymob]

Did u remove ecu plug and measure resistance between shield and center wire of oxy cable, can't see where u did this, should be infinite, also make sure plug connections to temp 2 making contact? What is your fuel press and does it increase when vac hose removed from reg? Did u remove injectors and check for any leaking under press, can just turn ign on to get press and the rubber seals at injectortips ok, i have been cutting off a section of good rubber hose and making my own, has worked for yrs.

[Alex Proulx]

I just recheck the resistance between center wire and outside wire with the ECU disconnected and got infinite, checked again outside wire to ground and got 1 ohm. Temp 2 sensor must be working because I get a reading and the ECU pin, tested cold last night and hot this morning and got reading matching the temp chart.

I did not do any fuel pressure testing so far, I don't have the tools but I will get them on Monday. One thing I noticed when I changed the fuel lines is the absence of residual pressure when I removed the bleed screw, nothing came out, the line only drained by gravity as I was removing them. Could my fuel pump be the problem?

Something else, I wanted to adjust the air mixture screw this morning as per the O2 voltage adjustment procedure I found on this forum and the screw was spinning freely without changing the mixture, I made 20 some turns just to be sure and no change on voltage.
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Vanagon GL 1988 Full Camper, 4 speed manual, 2.1 stock engine
Audi A3 2.0T S-Line Quattro 2015

[DirtyBlueVan]

Make sure your exhaust doesn't have any cracks.
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1989 Syncro Westfalia 2.5 smallcar subie

[randywebb]

[Bercilak]

Hit the protraining manual.

Start with baseline:

eliminate vacuum leaks

Verify the components are working

Set the timing

***********
I had all the problems you've mentioned, and found that my timing was way off. Gas mileage improved from 12.1 mpg to 16.5 or so. Eliminated a cold/hot starting issue, and improved the power through the range.

Make sure the basics are covered. Then hit the manual.

Best,

B

[morymob]

Fuel press bleeding off could be a leaking injector which could be flooding eng and cause hard starting. REmove injectors a side at a time havesome turn ket on NOT CRANK and check for leaks, if none u could check spray pattern at this time. Mak up a press tester with a dial tire press guage, 2 clamps & short fuel hose (keep intool box) cheap to do.

[Alex Proulx]

Injectors are not leaking. I installed a new fuel pump I had ordered a few days ago and that seems to have solve the hot start issue. YES!
Now I got a new AFM on the way, mine is shot anyway I can't adjust the mixture screw, let see what that does with the hesitation when cold problem.
I am getting close.
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Vanagon GL 1988 Full Camper, 4 speed manual, 2.1 stock engine
Audi A3 2.0T S-Line Quattro 2015

[Alex Proulx]

Well spoke too soon, I had not waited long enough, hot start is not cured, better but not perfect.
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Vanagon GL 1988 Full Camper, 4 speed manual, 2.1 stock engine
Audi A3 2.0T S-Line Quattro 2015

[MarkWard]