1989 dodge truck 318 TBI surging like crazy above idle, codes are 12,37,55. Fuel pressure is good ,timing is good, spark is good. its undriveable at this point. anyone have any ideas on what to check next? thanks.

12: battery recently disconnected

37: part throttle lock/unlock solenoid driver circuit (87-89)

55: end of test.


you have a lock up trans? sounds like it's locking and unlocking rapidly, causing the surge. i'd take of the air cleaner, and verify the injectors are both spraying also, and slowly rev the engine up, and verify a steady spray pattern, from both sides.

I dont think it has a lock up torque converter, it does it in park when you give it gas and hold a steady fast idle,surges between 1000 rpm and 2000 rpm ( guessing no tach hooked up).Injecter pattern looks good. Any more suggestions?

The Idle Air Control is hanging up in the bore, in the throttle body. Remove the IAC and clean out the carbon build up in the bore and on the valve. Also clean the throttle body with some carb cleaner and a toothbrush. Make sure and open the throttle blades and clean below them.

Try unhooking the alternator field wires and going for a short test drive. I have seen RFI interferace from the alternator play havoc on the PCM causing crazy drivability issues.

Anyone else have any suggestions? Im wondering if it could be the throttle position sensor, can it be bad without throwing a code? Thanks guys.

Sounds just like what my 88 van did awhile back,the idle surged up and down,would hardly take off from a stop sign. EGR valve fixed mine!

I removed the EGR valve today and it looked fine. Also replaced the ignition coil. Still surging really bad. Thanks for the suggestions.

If I remember correctly,I disconnected the EGR and it ran better. Try unplugging the vaccuum hose,or bypass the EGR just to see how it runs.It's easy to try.

Back on this problem again. I blocked the egr valve off, no difference.Today i hooked a dwell meter up,it shows about 20 degrees degrees.When i rev it up the dwell goes to about 40 degrees then goes back down and runs bad again.my question now is what controls dwell on TBI ignition system. Distributor pick up or computer?