Yes a scanner would be handy, just trying to do the best I can without one at the moment. And in regards to the stop screw, not in this thread however, I read how the TPS would pick up the changes in position of the blades even when adjusted by the stop screw and the pcm would make corrections to settings. Which is why I kept tweaking it. I'll keep my hands off it now.

It seems my car is very cold natured. This morning, pretty cold out, started up and ran very rough for first 10 minutes until temps got up pretty good. Then, it started to run fine again.

 

It's not so much the TPS (as it has a wide range of values in determining what it sees as closed throttle), but the effect it has on the IAC. This can really screw with your idle speed. The PCM tries to compensate by adjusting the IAC steps. If the throttle stop is too far out of whack, it makes this more difficult and results may not be as expected. I think a stock TB would be better for you than a 58.

IMHO, a scanner is more than handy-it's mandatory. It will save you more time an money than it costs.

 

I agree the oversize TB could create problems, but it's what was installed when I got the car and can't change it anytime soon. I have freescan and datamaster already on my computer just needing a cable. Coming off an unpaid internship which required 40+ hrs a week and now still can't find a job, it limits me monetarily. :/

 

What could a faulty IAT sensor actually contribute to or effect?

What could a faulty or misreading MAF contribute to or effect?

Just a basic inquiry...

 

If you think about the function of those sensors you can pretty much figure this out yourself.

The IAT, or inlet air temperature, sensor helps the computer estimate the desity of the incoming air as density changes with temperature with cooler being denser. If this sensor is malfunctioning it'll cause the PCM to not calulate correctly. This will either enrich or lean the mixture improperly. I would think, if this was the only issue, that the feedback loop from the O2 sensors would be able to compensate for this but it wouldn't be optimum. All-in-all, I'd rate this one as a minor deal.
The MAF, or Mass Air Flow sensor, measures the amount of air flowing through it to help the PCM calculate the amount of fuel to add to it for optimum power and efficiency. If this sensor fails, the PCM can switch over to internal table and add fuel using other variables such as throttle position, manifold absolute pressure, inlet air temp and engine coolant temp. This won't be optimum on these cars as they aren't tuned to be speed density controlled...but can be. The real problem with the MAF occurs when it reports improperly. The PCM will add fuel to the incoming air at the amount it thinks is there. This leads to lean/rich problems that the O2 sensor data may not be able to overcome. Remember that the PCM can add or subtract injector duration to adjust the mixture, but only within a range. If the MAF data is outside the adjustable area the mixt \ure will be wrong a lot of the time....

I know, lots of words..

 

Thanks, the Haynes manual doesn't explain the possibilities on these sensors so thought I would ask here.

For the IAT, the manual says it should range around 240v resistance for 190 degrees temp. My engine temp was about 200 or so and the voltage read 1400v. Didn't check it cold though, I'll redo these checks later to make sure.

Haven't check the MAF doing that soon as well. Haven't had time being everyone's errand boy all day :/ but thanks for the response. I'll update later.

 

Good Luck with it!

 

Ok, car had been sitting since about 1:30 and I only moved it about 20ft. to the garage on ramps so it obviously didn't get the temp up.

Before even doing any checks I decided to clean up the wiring a little bit as there is lots of electrical tape on this engine and wiring. I took the tape off my IAT wires and they fell apart, the wires were just laying across each other and taped together, pathetic. I went and grabbed some butt connectors and clamped them together, solves that issue.

IAT checks: Taking the reading from earlier, when temps up to norm operating range the voltage was around 1400V. The manual says at 190 degrees temp it should be around 240V?!? Taking temps just now after it's been sitting, the lower the temp the higher the voltage, voltage is now 1,342V. The manual says it should be around 2,700V!?!? Uh problems!

MAF check: It says check SIGNAL voltage. I thought signal voltage was checked by having the sensor and connector plugged in or using clips to attach them and checking the volts that way? It has them checking signal V off the connector terminal, or at least that's how it looks in the pics they have?

Wire connector- I have around 5V on black and yellow wires where they say it should be between 4-6 for reference so I'm good there. And I also have the battery signal ref of 12V on the black and pink wires on the connector terminal so it's not my wiring.

MAF sensor- 12V between black and pink wire for battery signal. 5V on black and yellow wires for reference sig. So my sensor is good as well.

There went the thought of bad MAF. Oh well, on to the next solution attempt which is still attempting to get a scan tool!

However the IAT readings are still puzzling and off! Input?

 

Some good news out of the ordeal; grandfather came by and assisted again. He made a call to a friend of his who owns a shop and he's willing to allow me to bring it in as a favor....gotta love grandfather's with connections!

So I'll be getting scans and some data and maybe I can get the data file to bring back and share. IDK when this will be, whenever we all three have time.

 

No Data or scans yet. But did fuel pressure testing and would like to share and get some feedback.

Turned ignition key on and pump ran, did this a few times to charge the lines. Fuel pressure with engine off was 42psi, which falls between the 41-47psi range so that was good. Next I ran the engine and it dropped to 39psi, which the range of expected drop is 3-10psi and I dropped 4 so I was good there as well. Now when turning off the engine is where I encountered the problem. I read the pressure is NOT suppose to drop off when the engine turns off..? My pressure reading fell from 39psi to 30 immediately upon shut down. Yet is gradually worked it's way back up to about 39psi over a few minutes.

So going with what info I've looked up on fuel pressure, I checked the vacuum to the valve and it is present, although I don't have a gauge to see the pressure fluctuate. I pulled the vacuum line and smelled gas but did not see any fluid in the line. So the options I have left to check from my understanding are: clogged or pinched return line, faulty regulater, or leaking lines at the pump. It has new fuel filter so that shouldn't be the problem. And we can hear the pump and it sounds to be working well as it should. INPUT?

 

The one you missed is the most likely of all....a bad, or going bad, check ball in the fuel pump. The lines could be leaking in tHe tank but you're not having an issue building pressure. A clogged return line would increase pressure, not cause a bleed down.

Frankly speaking, this really isn't an issue. It might lead to a slightly longer crank time but mine bleeds down the same way and starts right up and runs and idles fine. I'd bet many of the cars on here do the same thing....

 

Yea it takes slightly longer to start up, just one of the things I was told to go ahead and check then post info. Why would it have a sudden drop of 10psi on shut down and slowly build back up with engine off though?

 

You need to read more carefully, or type more carefully. From Shoebox's guide, you can see that at 194*F the RESISTANCE of the sensor would be 241 OHMS (not volts). Are you saying when you measured the resistance of the sensor it was 1400 OHMS? That would correspond to about 105*F.

http://shbox.com/1/4th_gen_tech2.html#ect

Were you measuring the sensor resistance with the harness connector off the sensor? Were you measuring the sensor in the water pump? How do you know the coolant was at 200*F? Are you sure you have the meter set on the correct OHMS scale?

In your later post you indicate that the resistance of the sensor is not changing much, even though the temperature dropped significantly?

The only voltage you would check on the MAF senosr would be the voltage between the pink wire and the black/white wire in the harness connector. That should read 12V. That is what powers the MAF sensor electronics. The sensor ouput signal is not a voltage, its a variable frequency. You would have to set your meter to "frequency" if it has that capability.

 

Yes, I should recheck what I type I meant ohms. And yes, all the numbers of what I said before were accurate with the exception of using V instead of ohms.

I took the harness off the sensor to get my number readings. I was not measuring the ect sensor on the WP I was working with IAT sensor and it says nothing of coolant temp relating to this sensor so I just took an estimation based off the temp gauge for the hot temp and came out later when it was all cool, several hours. I had my meter set on 2k I believe. The readings didn't change much as I said even though the temps did, which is why I was confused.

 

IAT... yes, and I need to read more carefully. How would the IAT sensor get to 200*F? It's measuring ambient air temperatures. With no air flow to the engine, it might possibly heat soak to 100*F, but no way it would read 200*F. Take it out of the elbow, and do the test as suggested by Shoebox. In boiling water it will be about 212*F (depending on the elevation where you live) and in a glass of ice mixed with water it will be 32*F.

Why are you focusing on the IAT (don't want to read through 7 pages of posts).