85 Jetta pings

[Jetta 85]

I'm trying to track down the cause of pinging in my 85 Jetta. It's a GL, with 1.8 8V engine, auto, AC, ~150,000 miles. It has CIS-E, not Motronic Fuel Injection.

I've replaced the transfer pump (it was missing!?) and the fuel filter, adjusted the idle to 900 rpm, set the timing, and run all the Bentley checks that involve the current going to the distributor valve thing on side of the fuel distributor (e.g., oxygen sensor, cold enrichment, airflow sensor). All current readings were within spec.

The idle was up about 1100 rpm and the timing was a little advanced. I followed the Bentley procedure of pinching off the one hose that comes out of the air distributor and disconnecting both hoses going to the EGR valve (and there's a fourth step I did, but can't remember what it is--the Bentley's at home) before adjusting the idle screw. It settled right down at 900 rpm, and then I set the timing to the zero mark.

Vacuum is rock steady at 20 in. at idle. There's a little bit of cam follower noise, but not very loud. I'm running 20W-50 oil per the Bentley recommendation. The coolant is full, and the injection coolant temperature sender shows 625 ohms at 185 degrees Fahrenheit coolant temperature, which meets the spec. Disconnecting it nearly kills the car, which would indicate to me it's working.

I'm using 91 RON gas, from Costco here in Anchorage. Don't know who supplies them, but most gas comes from either Tesoro's Fairbanks refinery or the refinery in Soldotna.

The car idles quietly if it's out of gear, but when you put it in drive at a stop, it feels like it's lugging down. Until it gets fully warmed up, I hear a thumping sound like a loose exhaust that stops if I put the transmission in park or neutral. I checked the exhaust system, replaced the torn rubber doughnut next to the fuel pump, but everything else looked fine.

As soon as the engine warms up to operating temperature, the car sounds like a metallic popcorn popper under any amount of acceleration. It really gets wild going up a hill.

I can wiggle all four cylinder injectors just a little bit, but none of them is backed out of the cylinder like my daughter's 85 Jetta car in Montana.

Any ideas what I should look for next?

mailto[email protected]

[Jetta 85]

Originally Posted by Jetta 85

I'm trying to track down the cause of pinging in my 85 Jetta. It's a GL, with 1.8 8V engine, auto, AC, ~150,000 miles. It has CIS-E, not Motronic Fuel Injection.

I've replaced the transfer pump (it was missing!?) and the fuel filter, adjusted the idle to 900 rpm, set the timing, and run all the Bentley checks that involve the current going to the distributor valve thing on side of the fuel distributor (e.g., oxygen sensor, cold enrichment, airflow sensor). All current readings were within spec.

The idle was up about 1100 rpm and the timing was a little advanced. I followed the Bentley procedure of pinching off the one hose that comes out of the air distributor and disconnecting both hoses going to the EGR valve (and there's a fourth step I did, but can't remember what it is--the Bentley's at home) before adjusting the idle screw. It settled right down at 900 rpm, and then I set the timing to the zero mark.

Vacuum is rock steady at 20 in. at idle. There's a little bit of cam follower noise, but not very loud. I'm running 20W-50 oil per the Bentley recommendation. The coolant is full, and the injection coolant temperature sender shows 625 ohms at 185 degrees Fahrenheit coolant temperature, which meets the spec. Disconnecting it nearly kills the car, which would indicate to me it's working.

I'm using 91 RON gas, from Costco here in Anchorage. Don't know who supplies them, but most gas comes from either Tesoro's Fairbanks refinery or the refinery in Soldotna.

The car idles quietly if it's out of gear, but when you put it in drive at a stop, it feels like it's lugging down. Until it gets fully warmed up, I hear a thumping sound like a loose exhaust that stops if I put the transmission in park or neutral. I checked the exhaust system, replaced the torn rubber doughnut next to the fuel pump, but everything else looked fine.

As soon as the engine warms up to operating temperature, the car sounds like a metallic popcorn popper under any amount of acceleration. It really gets wild going up a hill.

I can wiggle all four cylinder injectors just a little bit, but none of them is backed out of the cylinder like my daughter's 85 Jetta car in Montana.

Any ideas what I should look for next?

mailto[email protected]

A little more information. I thought the timing advance might be broken, so went through the sequence in the Bentley manual and discovered that both the mechanical and vacuum advance are working just as ordered (I don't have an adjustable timing light, so can't actually measure the degree of advance, but the diaphragm holds, vacuum advances the timing, and speeding up the engine advances the timing with the vacuum hose disconnected and plugged.

Also, the fourth thing before adjusting the idle is to turn the little 90 degree elbow so it plugs the hole in the side of the rubber cover, and i had done that when I adjusted the idle.

At this point, I'm pretty sure it's not timing and not fuel flow and not air flow, and I think, from the way the car runs ok except for the ping, it's not the computer. So what's next?

Jetta 85
mailto[email protected]

[asskickingdominato]

NOrmal pinging is rare. Use Regane to to clean out your engine. Build up on the cylinders may have happened that glow red hot and ignite the gas before proper combustion. Sometimes, with all mechanical engines (old) the engine will not stop and take awhile to cool.