1991 Mazda B2600i. 96,000 miles.

New to Mazda truck. Truck will not start when it's cold unless I mess with timing. Once I get it started, it will idle decent except for a spit here and there. If I snap the throttle quickly, it will die. If I gradually press the throttle, it will rev but not smoothly. Once high rpm's are reached, it will smooth out. Truck starts until it cools then will not until I again mess with timing. Please help!!!!

I would check the valve timing, pull the top of the timing belt cover off, put crankshaft at the TDC mark, and make sure the cam pulley timing mark is alligned with the A on the pulley, if it is off 180

Doesn't the bot have a cold start circuit, based on what sensor tell it about the temp of the engine?
Ecu may be going bad, ask Scotch.

Does the 2.6 have a timing belt? Thought it was chain. Also ECM rebuilt by avpro

Have you changed the fuel filter?
Have you pulled the plugs to check their condition?
Check the compression, looking for better than 130 p.s.i.g.



It has a timing chain, well, I think a pair. But the directions are good, pull valve cover, bring crankshaft mark to TDC, cam mark should be straight up. If not visible, turn the crank one revolution (crankshaft turns two revolution to one of cam, "four cycle").
That said, pull the distributor cap, if rotor button in the distributor is pointing in the general area (because the computer can stagger timing some) of number one plug location in the cap, timing for the cam probably is right.
The cam chain rarely jumps a tooth. If the tensioner were shot, the engine would probably sound like a cloths dry running with nothing in it but silverware! And the cam chain has jumped off or a tooth every time it decides to.

Ask around here, rebuilt or new ECU's flunk out too.

Compression is good. If I unplug the oxygen sensor, it will run better for 30 seconds or so.

Guess I should say the about everything has been replaced. Distributor, injectors and harness. Plugs, wires, distributor cap, rotor. New fuel pressure regulator and filter. This thing is driving me crazy!!!

Patience, some one will direct you to the answer, continue trolling the water, ha. Bot is beyond my depth.
Give Scotch a shout.

I would check the engine ecm. I found corrosion in mine and mine only has 120000 miles. Computer was already repaired once. It's behind the pass kick panel on the floor. Ecm corrosion us pretty common on these due to location.