i have been having horrible idle problems and throwing code 33 on a 92 model speed density model. I removed the TPS plug and it smoothed out. I then checked the voltage and it read negative .69 at idle and negative 4.4 at WOT. i am assuming that i had the leads reversed but that was what the fluke 187 was saying.

so are those aff far enough to make the idle CRAP?

How do i check the voltages to the IAC valve? I can hear a sucking though my K&N until it warms up then it goes away and the idle get better.

thanks for the help

 

https://www.thirdgen.org/tpimod2

I believe the speed density TPS sensor resets at 0 and goes up to almost 5 volts wot, and they are not adjustable.
at least mine isnt adjustable. Sounds more like you need to mess with the IAC instead of the tps.

 

thanks for the help. The engine has been transplanted into a 85 chevy truck and i am trying to work the bugs out. I modified the OEM harness but I am about ready to go buy the painless harness so i can rule my wiring out!!

 

Like MdFormula350 stated, the 90-92 TPS is not adjustable. Unlike the MAF TPI systems, the speed density ECM doesn't care too much what idle TPS voltage is at, it just looks at the % change over idle voltage.

.69 seems higher than I would expect, but I don't think thats a problem. So long as there aren't any sudden peaks, dips, or flat spots in output voltage while you move the TPS swingarm through its range, and it reaches over 4 volts at WOT (which yours does) it should be fine.

If you want to check your IAC, there is a simple resistance check you can do outlined in the GM service manual to check the condition of the two coils inside of it ( I don't recall what the resistance is supposed to be off the top of my head though). So long as you can verify that the IAC pintle can move in and out on its own, its fine. Also, verify the position of the four wires at the IAC and ECM to rule out a wiring error.

Code 33 means the MAP sensor is reporting low engine vacuum. I would suggest you focus on this, since this is more than enough to cause poor idle quality. Check spark advance, fuel pressure, check for vacuum leaks.... and hooking up a scanner or laptop will be quite helpful in diagnosing the problem as well.

 

Thanks for the help.

I have a few questions that may help me.

1. what should the vacuum be at an idle and which post should i measure it at?

2. Does anyone know what wire should read what on the TPS when it is disconnected?

3. what is code 42?


I have 40psi of fuel pressure and the timing is at 6* with the plug removed. The truck runs fine with the TPS plug removed but like total crap with it plugged up. The voltage is NEGATIVE and it is a sooth linear increase. I do not think the TPS is bad but the voltage is wrong.


anyone got a clue?

thanks
Chris

 

Stock cam should idle anywhere from 18-22psi vacuum. Check it at one of the ports on the passenger side rear of the plenum.

TPS has 3 wires, but I dont recall which is which. Black-ground, power lead 5V, sensor lead nothing with it disconnected.

Code 42 is because you pulled the plug and set the timing.

 

you are right on about the code 42. I just read up on it. thanks

this swap is SOOOOO close to being finished but it is driving me crazy.

I think i will buy a new intake gasket set and pull the intake off tomorrow. that way i can be sure they are all sealed up. I pulled the runners when i put the engine in a reused the old gaskets. then i will clean the IAC and measure the vacuum.

One more thing i noticed is that the previous owner installed some ford mustang injectors. will this cause any issues?

 

Unlikely unless the flow rate is wrong.

 

they are the stock ford 19 pounders. so they are fine. I will update more tomorrow after the regasket the runners and plenum.

 

The cam and the heads in a 1985 305 truck are going to be ALOT different than the stock TPI components of the 1990-1992 Camaro. The ECM is speed density. You did not state whether you have a 305 or 350 ECM. If you have a 350 ECM, the tables will be even more off. 19# ford injectors flow about 21# in a GM TPI setup. Stock fuel pressure should be up around 46 psi.

 

i bought the complete engine, computer, and harness from a 60,000 mile firbird. the previous owner is a member here. I think his name is Shroom. anyway it is a nice set up, I just have to get the bugs worked out.

 

all fixed

I should have looked a little harder into the code 33. I had left the vacuum line off of the MAP sensor.

so to all that helped me. now I am off the exhaust shop for some true duals with long tubes on my TPI