My truck isn't running too good rough idle so i decided to check the timing just to make sure it was good but Its not. I jumped out E1 and TE1 to get to "base timing" but the timing mark is going around the pulley counter clock wise. I have tried two different timing lights, and same problem. They work on other trucks. I have a movie on YouTube. http://www.youtube.com/watch?v=ZENAceyqF34
I have checked the TPS but it seems good. any ideas? any solutions.

Also my truck CEL reads all good when at idle but If I rev the motor up it flashes code 51, is this normal???

Thanks

 

Check the tps again, 51 means

 

Tps or timing belt.

I changed the timing belt on my 94 3vze , when I put it back together the same thing happend to me with the mark jumping back and forth like yours.

I thought the belt jumped a tooth so I re did it and then re adjusted the tps , after that It was ok no more jumping of the timing mark.I really dont know which of the two fixed the problem but one did.

 

If you insert the jumper with the engine running, you should hear a noticible change in the idle speed, usually to a lower rpm. If you don't, the ECU isn't getting the IDL signal from the TPS, or the idle is too high. Considering the code 51 you're getting, even though you're not getting the CEL until you rev it, the TPS is probably the cause. It may simply be mis-adjusted, or may be faulty (most likely it's faulty if you or anyone else has ever used one of the engine cleaners on the engine). You could try loosening the TPS, with the jumper inserted and the engine runnign, and rotating it the same direction as the throttle opens, and see if you can find a spot where the idle suddenly changes, then lock it down, clear your code (disconnect the EFI fuse or battery for a minute or two) and try setting the timing again and check if the code comes back.

 

Ok, I'll Have a look at the TPS for the hundreth time. All the resistance values are always within spec. Could be that the resistance is fine with an ohm meter but it fails once you pass current through the resistive element but at 15mA max I doubt it.

The only thing Im not sure of is that it switchs from IDL @ >2300ohms to an open circuit at the correct time the physical throttle position seems to be more then .9 mm away from the throttle stopper. (I read somewhere the fact that it switchs is more important then where it switchs)

 

Another thing you might try is checking the TPS resistances at the connector to the ECU in order to rule out a wiring issue.
It is important that the TPS IDL / E2 resistance is correct (<2.3k ohm) when the throttle is closed. It should increase beyond that amount at the suggested opening. If it doesn't respond properly (i.e. resistance rises after the correct throttle opening angle), the ECU will think the throttle is not open as far is it really is and could throw the timing and fuel mixture off, but the O2 sensor feedback should bring the mixture into spec.

 

i'm having a similar issue. my timing mark moves counter clockwise. then you don't see it for a while (probably 10-15 seconds). then it comes back and moves from right to left and disappears again. my truck is running like crap. no power and starting yesterday it wont idle without my foot on the pedal. some times it has a little better getup than other times but still not right. and really really bad mpg. prolly around 10. i'm going to check the physical timing this week (po said the timing belt was done recently so maybe its off by a tooth) but i'm tryin to avoid tearing all that down if i don't have to. any ideas? i'll check the tps tomorrow.

 

checked tps idl/e2 resistance. absolutely no conductivity. moved the sensor both ways as far as it could go and still nothin. broke now so we'll see what happens after i replace it next week. maybe this is the source of all my problems (doubtful). could the tps cause a severe lack of power? maybe its reading too high. you can smell exhaust like its running rich but no smoke or anything. i guess i'll find out next week.