all of a sudden the truck acted like the engine shut off?

NorthportMazda · 2019-03-04T08:46:12+00:00

I have a the truck listed above b2600i model that has been running like a dream until recently. I was driving down the road and all of a sudden the truck acted like the engine shut off. It was idling but as soon as I would give it gas it would want to shut off and the engine did not have enough power to move the truck. The issue I am having is that a idles high, 1,500 to 2,000 rpm's, and as soon as you give it gas it wants to shut off, though you can vary slowly give it a little bit of gas but eventually it will bog down and indicator . If you shake the wiring harness underneath the intake manifold sometimes it will all of a sudden drop down to the normal 750 idle speed and you can give it all the throttle you want and drive it just fine. Then all of a sudden it'll jump back up to a high idle speed and if you give it throttle it'll want to indicator . I have a 1,300 page mechanics repair manual for a 1992 b2600i and I have been going through it. I haven't checked the circuit board down near the feet of the passenger side (as I just found out about it a moment ago on this site) but I have checked for water in the fuel line, fuel filter, fuel pressure, every sensor that has anything to do with the control system and they all seem to be good. I pretty much determined it's the wiring harness under the intake manifold, which I'm not sure of because I do not understand how that can go bad. The other strange thing is that while it is idling at the high speed and regular engine temperature you can disconnect (all at the same time) the throttle sensor, the solenoid that coolant runs in and out of by the throttle sensor, idle switch/sensor, water thermosensor, temperature sensor, intake air thermosensor, oxygen sensor, a give it gas and the engine keeps running. The only thing that seems to affect it is when you unplug the idle switch the RPM's will go up a little bit. When you plug it back in it drops back down a bit. But from my understanding if you unplug the throttle sensor as soon as the idle switch is released something should happen because the computer then does not know how much gas to give the engine with the throttle sensor disconnected. So my best guess so far is that I need to replace the short wiring harness that is located under the intake manifold and connects the main harness to the fuel injectors, throttle sensor, etc. What is this short wiring harness called and where can I find it/purchase it? Any other suggestions would be great!

1991 MAZDA B2600

137,000 MILES • 2.6L • 4 CYL • 4WD • MANUAL

Repair Safety Notice: This information is for general instructional purposes only. Vehicle repair can be dangerous. Verify all information, follow manufacturer service procedures, use proper tools and safety equipment, and consult a qualified repair shop when needed.

WAYNE PEDERSEN

MEMBER
4 POSTS

The fuel pump seems to be pumping good pressure.Where exactly would I find the relay and how do I check injector pulse?