Head scratching 3100

[lumination]

Ok I will try to be brief I swapped the 3100 in my 97 lumina bout a month ago for one I found at the sy and for the first 2 weeks after it was in all was well back like new. Then periodicly it would fall on its face at 1/4 to 1/2 throttle cruising was out of the question. If you put your foot in it everything runs normal but set the cruise and the car kinda jerks to keep speed it idles great, if you floor it its all there but theres just this part throttle issue. I would greatly appreciate any help. Thanks JON

[Doubt_Incarnate]

sounds like a dead spot in the tps, just need a replacement.

[imported_germ]

did you replace anything on the newer engine?

like the plugs and wires?

sounds like you have some sort of misfire or vacume leak.

[lumination]

[did you replace anything on the newer engine]
I replaced lower and upper intake gasket, wires, plugs, and accidentally had to replace the powersteering pump. (plastic crap) I also replaced some hard brittle vacuum lines, One was to I think the cruise control tiny one on back of intake that runs across entire engine bay, the other was to the small black module on rear of intake I think its maf but not sure

Is there a way to test the tps? ohm meter scanner?

[lumination]

tps

Doubt_Incarnate

is the tps problem common?

[imported_germ]

which fuel injectors did you use? the stock ones or the ones that came on the used engine?

and yes, you use a mulitmeter to check the TPS. i know the procedure is in the haynes manual for your car (i have a 96 monte), but my book is at home and i am at work, or i would tell you how to check it.

right off the top of my head, i dont know what the values should be.

also check your IAC valve while your testing stuff.


when was the last time you changed your fuel filter?

[lumination]

I used the top end of the old motor the sy one had cobwebs in the fuel line and since i was changing the gasket figured id put the one i knew worked back on. I have only owned the car 6 months so the fuel filter is going to get changed but the fuel filter would make it cut at full throttle 2 wouldnt it? which one is the iac

[imported_germ]

the iac is on the throttle body, just above the TPS


and no, a clogged fuel filter wont always cause fuel throttle issues (not in every scenerio, in some yes, but all no)



you could also have some build up on your injectors as well and a bad injector(s) can cause the symptoms your having.

[Doubt_Incarnate]

i dont know which wires are specific to your car, but one is +5V one is grnd, and one is the signal. you need to check the values between the +5 and the signal through the sweep of the sensor. idle should be about .5V, and about 4.5V at WOT. if it doesnt climb steadily, or drops to 0, as the tps is swept then it is bad. and dont get one from advance or autozone, cuz you'll change it next year.

[lumination]

ill try the filter and run fi cleaner through her then get back with you I appreciate the help

[Doubt_Incarnate]

if you have the tb and sensors from the other motor, you can swap that on to see if the problem is fixed. slim chance both sensors are bad.

[3100 MPFI]

That one plastic vacuum line that goes across the back of the engine, and across the engine bay.

The one that is plugged into the back of the plenum right in front of the alternator. That is the vacuum feed for the interior of your car. If that was not plugged in, then your airvents would not work. Stuff like that.

I agree with the TPS. Mine was doing that not too long ago. Put a spare one on, and problem solved.

On the throttle body, the TPS is the FLAT SENSOR that has 3 wires going into it. The IAC is the FAT ROUND one that has like 5 wires going into it.

Also, that black sensor on the back of the plenum that has the green connector with 3 wires..... that is the MAP, not the MAF.

the MAF is the sensor on the intake duct between the airbox, and the throttle body.

MAF is MASS AIR FLOW
MAP is MANIFOLD ABSOLUTE PRESSURE (I think the A is for ABSOLUTE). Not really looked into the enunciations yet.

[lumination]

thanks

thanks for all the help guys I changed the tps yesterday and so far its running fine