1998 mazda b2500 2.5 put a scaner on the truck and when under a load the timing was retarding to -6 any help guys

 

So I assume you are losing power more than expected under load?

So not just a data error, there are real time symptoms.
What is the timing at idle and at 2,500rpm with no load?

'98 has the ICM(ignition control module) in the Computer
ICM uses CKP(crank position) sensor to set base spark timing.
Computer uses CPS(cam position sensor) to set fuel injector timing, but also uses this signal for spark advance.

I don't think the 2.5l had a Knock Sensor in '98, didn't see one listed, but if so equipped this will retard spark if pinging is detected, reducing power, you wouldn't hear the pinging.
If you have ever heard the engine ping under load, which the 2.3l/2.5l is known for, then you do not have a Knock Sensor.

 

at 1000 rpm its +12 as soon as give it gas it starts retarding

 

I would say your scanner is just reversing the signs, + and - , as you interpret them
10-12 deg BTDC is common idle timing for Fords, and as RPMs increase it should get closer to 0 then change signs as it gets more advanced with higher RPMs.

Technically speaking, if you delay the spark you are retarding it, if you want the spark earlier you are advancing it, which is confusing but correct.
So if TDC = 0, then a spark 12 deg BTDC is +12 deg, spark is happening in advance of TDC.
-6 deg would be spark being delayed and happening 6deg after TDC


What are the symptoms if there is a problem?

 

no the timing should advance at high rpm but its not and it runs like crap

 

Advance on your scanner is a "-" number, retard is a "+" number, from what you have said.

It reads like it is advancing, going from +12 at 1,000rmm to -6 at 2,500rpm?, but I would expect higher "-" number based on +12 at idle, but the -6 might be OK depending on RPM at that time.


Runs like crap covers alot of ground, lol.
If it idles OK and lower RPMs seem OK but it "craps" out at higher RPMs or under load then I would look at fuel filter or fuel pressure.

If you are certain it is spark related then I would get a couple of coils from the wrecking yard.
The ICM(in the computer) does get a "firing" feedback from the coil wires so might be reducing advance because of a coil problem.
You can test Ford Coil Packs with an OHM meter but it is not a definitive test, it will for sure show a bad coil, but passing the test doesn't mean coil is good.

 

i put new plugs and wires. fuel filter ,coils, mass air, cam sonsor, and it still runs like crap

 

I would stop changing things, an engine is still just an engine no matter how many fancy do-dads they add to it.

Computer, sensors and controls just make make it more reliable, probably not your point of view right now, the "good ol' days" of carbs and distributors sucked, you had to adjust stuff all the time to keep engine running right.
I think the main issue these days is that people don't have to mess with the engine, so when there is a problem they haven't been practicing one or twice a month, like we had to in "the good ol' days", lol.

I would invest in a $25 Vacuum gauge, and read up here on some test results: Technical Articles: Engine testing with a Vacuum Gauge - at Greg's Engine & Machine


Low vacuum could mean timing belt has slipped, or a vacuum leak
Slow vacuum return could mean clogged exhaust


How many miles on the engine?
Does it run better cold than warm or visa versa?
Does it run better at high or low RPMs?


Any gas engine is still ruled by the big 3
Fuel, in right mix with air
Spark, at the right time and intensity
Compression, above 120psi, 2.5l should be 150+ psi

 

my 94 2.3 is doing the same thing. did you figure out what was causing yours???

 

OK guys.... I have searched for a repair to this very problem (timing retarding to -8 on accel) and I have found no other information as how to repair this issue. Has any body found the problem??

Thanks,
Tod