Fuel Injection Problems Poll

compiled by Steve Blackham

I had over 50 listees respond to my request. Thank You all!

"Have you had any problems with your FI system this year?"

YES (21)
NO (25)
Other comments (6)

Temp Sensor #2 (7): "Intermittant Misfire, rough idle, richness"

AFM (mostly contact plate) (7): "Misfiring or cutout at a particular range"

Aux Air Valve (2): "idle and starting problems"

Connector problems (4): "intermittant cut out and starting"

Cold Start (1)

Fuel Pump (1)

Double Relay (1)

Altitude Switch Label (1) "backwards" created richness problem

The fact that the temp sensor #2 was a trouble spot didn't surprise me but I didn't expect to have this many AFM contact plate problems. I guess 20 years of friction of the control arm swinging over the contact plate is predictable to cause failure. If you haven't found a good spare for the AFM maybe its time to be putting away alittle to send to Bus Depot for a new one ($150 up).

Notice that no one mentioned a problem with the ECU!

Almost without exception, everyone voiced satisfaction with their Bosch FI System. With a simple multi meter test most problems can be easily diagnosed and corrected.

Karl von Salzen mentioned that he replaces his Temp sensor #2 every year.

Karl says: " I don't change it once a year just to change it. I change it once a year because that seems to be it's lifespan! I consider it a maintenance item. At first I thought it was a AFM problem. I would swap with another and all the problems would go away for a week. Then they would come back so I would put my original AFM back on. Problems gone again for a few days/week. Replace the #3 temp sensor and the problems were gone. I haven't been able to explain the one year life span. The one I have in now has lasted almost 2 years so far. This one I put in dry after I cleaned the threads of anti-seize. I believe the anti-seize was insulating the threads and causing the sensor to read 'open'. This one also hasn't had the problem of loosening up on it's own once a month where I have to retighten it. Seemed like it was 'check the oil, check the tightness'. Now it stays tight."

Steve says:

I personally would worry about stripping the threads on the head with this much replacement so I'd recommend just testing the sensor regularly:

Put ohm meter contact between #13 and #17 ground. This tests the Temperature sensor II. At 68 degrees it should be between 2000-2900 ohms. (700-1000 @122 degrees; 200-400 @ 176 degrees; and less than 200 at operating temp). Testing this at the Harness to ECU plug will test whether there is a problem in the harness too.

Back to Library Back to Fuel