Z28_1991_Camaro

I did an engine swap from a 305 to a 350 back in 2007 if my memory is correct. (Car is a 91 Z28 TPI)
Ever since the swap on every single emissions test I've had to do I either fail or borderline pass the HC category. It is not the curb idle test but the other one that is failing.
I need to bring my car in for another emissions test this week and would like to try and get to the bottom of the problem.
I checked for vacuum leaks this after noon but I couldn't find any.
The car seems to run fine, the only thing it does that it shouldn't is it changes into gear from park hard. It's just initially when I go from park to drive there is like a hard shift and then after it's in gear it changes gears fine.
When I did the swap I had to set the base idle and I think I am idling too fast still, not sure if that has anything to do with anything I'm experiencing. The other day I was reading whenever you change the base idle you should also adjust the TPS. So today I attempted to see what kind of readings it was giving. I don't know much about electricity so my bro gave me a hand and when he was using the volt meter attaching it to the a and b terminals the volt meter was reading 0. He tried a second volt meter and it too read 0. He tried both of them on the battery and they each read around 14v so it appears as though the volt meters were working fine. Also, when trying different terminals he was getting a reading, I don't remember what the # was but under no circumstance when the volt meter was touching and I increased the throttle did the volt meter change it's reading.
Did we do something wrong or could it be that the TPS needs to be replaced. It is still the original one that was on the old engine so its 20+ years old.
Which terminals should I be checking? Is the top one in fact A, the middle one B and bottom one C?
Any help would be greatly appreciated.

eseibel67

Stick the black lead of the DVOM on the black wire of the TPS. With the key on, probe the grey wire on the TPS with the red lead of the DVOM, and you should get 5v. Then, probe the blue wire on the TPS with the red lead, and at closed throttle you should get .54v. With the probes in this position, you should see a gradual increase to 4.5 v as the throttle is slowly swept to WOT.

Z28_1991_Camaro

Thanks, it seems to be working. I think my bro must have had the voltmeter on the wrong setting

Z28_1991_Camaro

Anyone have any thoughts as to why my hydrocarbon reading is so high?

neilcase

I just know this is a stupid question, but.... Can this test be done just in KEY ON position or does the car have to be running?

vetteoz

iTrader: (13)

Only the ECM needs to be powered up , not engine running

neilcase

Thank You Vetteoz. By the way I think you responded to my thread entitled barn find help me. I went through nearly everything and it finally turned out to be a bad ignition switch. Wasn't letting any voltage through at start position and was intermittent at run position. But I got it running today! Ten years sitting under a big redwood tree but I got her going. Thanks to a lot of great help from guys like you.

neilcase

Vetteoz can you help? I just measured my TPS and it starts at .72 and goes to 4.25 at WOT. Doesn't seem to jump around wildly at all while I slowly open the throttle. Is that within range? Just got this car running after 10 years of sitting. Seems to idle pretty good but stumbles for half second at throttle increase. I'm suspecting a timing adjustment needed but any other ideas? Noting what I said above about the TPS.