General Information > Troubleshooting

Wondering why AAZ would spin up to 2200 rpm idle on 90 degree (F) days..

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Vandoka:
Hi All,

I have a 1987 Doka with a recent 1.9 AAZ rebuild. The truck had a great winter piling up 5000 miles in the mountains with no major issues...a few leaks around the oil filter manifold and oil feed line.

Recently on a few hot days I have noticed the truck starts fine and then after City driving for 20 minutes it will get what feels like a run-a-way idle. I take it out of gear and the rpm's linger at 2000-2200. At times they hang there for 10-20 seconds and descend, other times they stay high and I have to put the truck in gear to use the brake to slow the motor down.

On a cooler day, like this morning, the temps were in the 60's and the issue did not occur.

I have tested the throttle cable and it is not stuck. Wondering if others have seen this symptom before?

Thanks.

libbydiesel:
What rpm is your idle set to?  Lower it a little and it should fix it.

Vandoka:
The idle is set at 900 +/- rpm. It runs smoothly at this setting most days, I can adjust it to see if your solution changes anything.

Thanks!

libbydiesel:
Is your AAZ pump stock?  If so then it should have the slow/fast idle when the cold start lever is pulled.  If that is the case, then lower the 'residual fuel screw' which is the screw that the accelerator rests on when the pedal is fully released.  Just a small amount (e.g. 1/4 turn) should fix it.  If it does not have the fast/slow idle, then the same screw is the idle screw and the same fix is required.  What I am saying is not to mess with the slow/fast idle screws that are the stops for the little lever on the back of the top of the pump.

Post pics if in doubt.

Vandoka:
Hello Mr. Libby,

Thanks for the post..you may recall you helped me get my pump sorted out on thesamba after it imploded....Anyhow, I cannot figure out how to post a pic. The pump came off the original 1.6 td of the Doka. It has the idle screw on the drivers side of the pump, it intercepts the throttle lever/lobe piece.

There is a fuel adjustment screw with a lock collar on it located in the middle of the pump. Then there is another screw that seems to limit the extent of the throttle lever/lobe piece.

If there is an easy way to add pictures it would make my description more clear.

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