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Oscillating idle '89 Jetta...

So, the idle is still rough when cold; it oscillaties from 800-2000 RPM with an occasional shift of the entire range to higher numbers (e.g., 1000-2200). The car is an '89 Jetta (Mexico), 1.8, gas, ~270 K Km. The engine was setup last week after replacing plugs, cap, rotor, air filter:

Engine speed 853 RPM HC 9 ppm

02 0.92% CO 0.00% CO2 14.65%

Both coolant temperature sensors were replaced (blue and black) and wiring between temperature sender (black) and guage in dash was repaired. A new ignition coil was installed--when the engine was setup, diagnositics revealed that it was faulty.

I was pricing idle air stabilization valves a local shop and found out that the part number on my car (035 133 455 F) matches an '82-84 Quantum!? Now, the idle problem is new and I've owned the car for over 3 years, but was is this a common thing for VW to do? Or perhaps someone has done some work in the past? The factory part number is

037 906 457 D and I can pick one up for $60.

How do I troubleshoot the ISV? Check resistance in serial (?) with the car running? Can anyone comment on this?

Thanks for any suggestions.

Reply to
Darryl
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Reply to
Darryl

Ok, the Haynes manual (thanks Epi) indicates that the current to the ISV should be 420 +/- 30 mA and fluctuating at idle and the same mA but constant with the blue temperature sender disconnected. How do I check the ISV in series? Do I have to cut wires? Or disconnect the connector, bridge one side with a multimeter and the other with some wire???

Thanks, Darryl.

Reply to
Darryl

Yet another follow-up.

When checking the amperage (in series) at the ISV, I found the following:

Cold start (not operating temperature, idle is wild). fluctuates between 480 and 730 mA with blue sensor disconnected: 430 mA constant

At operating temperature: 450 mA constant with blue sensor disconnected: 430 mA constant.

The blue sensor is new within the last month or two.

Any ideas?

TIA! Darryl.

Reply to
Darryl

Most likely culprets of idle problems...

bad engine ground

bad ground at the driver's side rear of the head (the wires seem to tear here commonly)

vacuum leak--could be a small hose or could be the accordian pleated main intake hose.

bad sensor contact, for instance at the maf sensor in the air filter housing.

bad timing settings. Make sure the timing is set per special digifant instructions--at something like 2k RPM's rather than at idle like most other cars.

ignition system, check for arcing plug wires or fouled plugs.

Reply to
Bob Hetzel

New -ve terminal cable. Ignition coil and body to hood grounds are new.

All rewired to intake.

Can't find anything using ether.

Demated/mated everything.

Car was setup and is running mint when warm. Something isn't happy when cold.

from below:

Everything minus the wires is new.

Thanks! Darryl.

Reply to
Darryl

Check out

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and do a search on VW idlingproblems... there are enormously long discussions on the subject with lots ofgood info.

As a side note, make sure you have continuity in the terminals of the idle stabilizer valve, if not the valve is bad. Also the only way the valve works is if your idle switch is working. check for continuity at idle in the harness connector for the idle switch.

anyways, check the bentley site... lots of good stuff.

Reply to
osurferx

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