Low RPM problem...

derangedsheep · Post by **derangedsheep** » Wed Oct 19, 2005 9:35 pm

First of all, I don't pay enough attention to remember if it does this cold and warm, but anyway.

For the past few days as I have been leaving school or leaving my house (or anywhere for that matter), driving with low throttle (parking lot speeds), the tach is bouncing up and down and the car seems to be bucking slightly. But only with the throttle at a certain range. If I go above that I don't have a problem. I also notice a slight hesitation if I punch it from a dead stop.

I am thinking TPS, but I wanted to double check before I spend $40-50 on a new one. If it is the TPS what brand should I get? GP Sorenson, Niehoff, Wells, GM?

p8ntman442 · Post by **p8ntman442** » Wed Oct 19, 2005 9:37 pm

sounds more like a bad spark to me, check out the coil and wires b4 the tps.

Shaun41178(2) · Post by **Shaun41178(2)** » Wed Oct 19, 2005 10:20 pm

find a women to grab your balls.

Taht should get those rpms back up.

This is what you are really asking right?

derangedsheep · Post by **derangedsheep** » Wed Oct 19, 2005 11:00 pm

p8ntman442 wrote:sounds more like a bad spark to me, check out the coil and wires b4 the tps.

The wires are Bosch with about 3000 miles on them and the coil is an OEM replacement with maybe 1000 on it. They shouldnt be bad yet.

Shaun - Maybe its because I'm really tired, or maybe because I'm feeling retarded tonight, but I have no idea what the hell you're talking about.

The Dark Side of Will · Wed Oct 19, 2005 11:18 pm

What Aaron was trying to say is that that sounds more like an ignition problem than TPS problem.

Put a scan tool on it and drive around for a while... see what it says about the TPS. The TPS is a variable resistor. They typically go bad by aquiring dead spots. If you spent much time at a dead spot, you ought to throw a TPS code...

Aaron · Post by **Aaron** » Wed Oct 19, 2005 11:56 pm

Aaron didn't say anything, he swears!

derangedsheep · Post by **derangedsheep** » Thu Oct 20, 2005 2:58 pm

Will- No codes. I dont have a scan tool. Is there anything that I can do with a multimeter? Maybe unhook the TPS, stick the probes in the pins and work the throttle? What pins would I use and what values should i be looking for?

derangedsheep · Post by **derangedsheep** » Fri Oct 28, 2005 8:37 pm

derangedsheep wrote:Will- No codes. I dont have a scan tool. Is there anything that I can do with a multimeter? Maybe unhook the TPS, stick the probes in the pins and work the throttle? What pins would I use and what values should i be looking for?

??

whipped · Post by **whipped** » Fri Oct 28, 2005 9:08 pm

derangedsheep wrote:
derangedsheep wrote:Will- No codes. I dont have a scan tool. Is there anything that I can do with a multimeter? Maybe unhook the TPS, stick the probes in the pins and work the throttle? What pins would I use and what values should i be looking for?
??

Yes, exactly. Use the pins that change in resistance when you move the throttle. If when you slowly open the throttle body (engine off of course) you see the reading go like

1000
1100
1200
1300
1400
80
1600
.
.
.
or something then you know it's bad

derangedsheep · Post by **derangedsheep** » Fri Oct 28, 2005 10:56 pm

whipped wrote:
derangedsheep wrote:
derangedsheep wrote:Will- No codes. I dont have a scan tool. Is there anything that I can do with a multimeter? Maybe unhook the TPS, stick the probes in the pins and work the throttle? What pins would I use and what values should i be looking for?
??
Yes, exactly. Use the pins that change in resistance when you move the throttle. If when you slowly open the throttle body (engine off of course) you see the reading go like

1000
1100
1200
1300
1400
80
1600
.
.
.
or something then you know it's bad

Which pins are the ones that change resistance? Actually, how many pins are on the TPS? If it's only like, 2 or 3 then ill just screw with it until I get them, but I don't want to be testing like, 6 pins.

whipped · Post by **whipped** » Fri Oct 28, 2005 11:58 pm

3.

There's only 3 ways to hook it up. 1 is wrong, so you have a 67% chance of success on your first try.

:la:

derangedsheep · Post by **derangedsheep** » Sun Oct 30, 2005 2:19 pm

I messed with it a bit today.

I have a spare TB with the IAC and TPS still attached. So I took the spare and hooked the multimeter up to it and with the throttle closed I was getting a reading of 1.6 (meter was set to 200k, whatever that means). At WOT it said about 4.6.

Hooked it up to the one in the car. Throttle closed it said 2.0. WOT said 5.something. So I switched the sensors.

I am assuming that the ECM needs to be reset. Can I just pull the ECM fuse or do I have to go unhook the battery? How long must the fuse or battery be unhooked? And is there anything special that I should do for the first while after driving with this new sensor?

Also, could the reading on the old sensor being so high contribute to that I get really shitty gas mileage? My semi-lead foot doesn't help my MPG but I was getting about 20mpg and that seemed low to me. I have a free flowing exhaust, no vaccum leaks, KN filter. Since I have an auto I figure I should have been getting around 25MPG (based on what people on OE get).

EDIT: The TPS mounting surface and screws on the old TPS looked crusty. I wirebrushed them clean. Does the TPS ground to the throttle body?

Shaun41178(2) · Post by **Shaun41178(2)** » Sun Oct 30, 2005 5:13 pm

seems like the reading on the current TPS sensor are bad and thats why you were having problems.

Replace it with the one that you tested as being good from the spare tb.

Yes you can get poor gas mileage from a bad tps sensor. When any sensor on a EFI car is not working as it should, mileage and power go down.

THe TPS does not ground to the tb.

Replace it and that should solve at least that problem. Who knows if you have others.

Ninja edit. Disco the battery for like 10 seconds. and hook it back up. That should clear the memory. If you want to leave it unhooked for a minute that is fine too. Hell if you want unhook it, go take a piss, come back out and hook it back up. More then enough time to wipe the computer of codes.

The Dark Side of Will · Sun Oct 30, 2005 9:28 pm

Multimeter only sort of tests the TPS. The computer looks at the voltage drop across the variable resistor portion of the TPS. That's why it has three wires. One is +5V supply, one is ground and the third is signal.

derangedsheep · Post by **derangedsheep** » Sun Oct 30, 2005 9:54 pm

Well, I drove about 15-20 miles tonight. Aside from the ignition module and the tach filter blowing out (that was a bitch to fix, the fucking dist cap screws stripped), it ran great. No more hesitation at part throttle coming away from a stop. I can actually cruise now too. It used to be almost impossible to get the throttle to where I would stay at one speed, I used to constantly have to be either accelerating or decelerating.

I'm going to pull the IAC next and clean it. Maybe I can fix my shitty idle. Is there any special procedure with putting it in? I.E. how tight should it be in its hole, etc.

Post by **admin** » Sun Oct 30, 2005 10:28 pm

I would fix your dist cap and the other small things first to make sure that is not what is causing the hunting idle.

To clean the IAC is not hard. I have been known to spray carb cleaner right into the tb. This will clean out the passages and the sensor itself.

Tightening it in is just guessing really what you think is tight enough. I usually tighten it to where the housing contacts the tb. Then go a bit more to where it "feels" tight enough. You dont' need to really tighten it down like 1000 foot lbs. It has a gasket so just enough to crush the gasket yet be tight enough to not allow air past.

Go finger tight, and then like maybe 1/4 to half turn more. But like I said I just go to where it feels tight enough.