1993 Mazda Truck Help!

Tiny
40CAL
  • MEMBER
  • 1993 MAZDA TRUCK
Computer problem
1993 Mazda Truck 4 cyl Two Wheel Drive Manual 130k miles

I have a 93 Mazda b2600i and have already had the computer rebuilt 1 time. Now, after turning in in to the shop (local shade tree mech) tp replace the coolant hoses under the fuel injectors and valve cover gasket, runs fine until it warms up then seems to want to rev up when stopped and can feel it surging (trying to speed up) in lower gears.

When I am stopped it revs up and down while brake is pushed in. If I leave it out of gear it stays idling between 1200 and 1600 rpms. Before last work was done, idled around 800 rpms.

At first thought it might be a loose vaccum line and even replaced pcv valve that seemed to help a little bit but did not come close to solving the problem. I thought maybe brake booster line but no luck there either.

I know I am not making a whole lot of sense but seems to me like the computer is telling it that it needs more fuel but the throttle linkage is slack and the auto choke? Or whatever it is called seems to be functioning properly.

Any help or input would greatlly appreciated. As I am sure you can tell, I know nothing about engines
Thanks
40Cal
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Tuesday, February 26th, 2008 AT 11:53 PM

3 Replies

Tiny
MERLIN2021
  • EXPERT
You may have a vacuum leak, get a can of spray gumout, spray the vac lines and maniflod area, when the idle changes, youve found the leak! You want the engine running and spray on the outside but do direct the stream onto the hoses, if it is a vacuum leak, the engine idle will change speed, then you have detected a leak, repair the vacuum leak and see how it runs! Pull the pcv out and block the line, put your finger in the hole for the pcv, is there a strong vacuum? If so the intake manifold is leaking. In the hole, not the hose!
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Wednesday, February 27th, 2008 AT 8:17 AM
Tiny
40CAL
  • MEMBER
[Hi Merlin
Thanks for the suggestons. Have had the flu and not able to respond before now.
Have tried with the pcv valve/hole and have a slight suction from valve end and slight pressure coming from manifold so that is ok, right?
Will get a can of gumout and try that suggestion and will reply and let you know. One fella said to try soapy water like for a leaky tire. I didnt do that by the way.
Thanks again and will donate cause I think it is a wonderful idea you fellas have with this website. Just reading the q's and a's have helped me understand more than I knew before!

Thanks,
40
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Sunday, March 2nd, 2008 AT 11:04 PM
Tiny
MERLIN2021
  • EXPERT
Take the PCV out of the hose you should have strong vacuum. Replace that PCV if you do! If you don't the hose may be leaking, or some othe part of the manifold.
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Monday, March 3rd, 2008 AT 2:29 AM

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