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1995 FWB 124,*** miles
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Discussion Starter #1
How to check TPS for smooth and linear electrical response over the entire range of motion?

Thank you.
 

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1989 Brougham d'Elegance, 1985 Fleetwood Brougham *Coupe*
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4,256 Posts
To do it you need a CAT III Digital Volt OHM Meter (DVOM).

First you locate the TPS sensor and unplug it. Turn the ignition to the run position, but do not start the car. Go back to the sensor and the connector. Turn the DVOM to measure DC volts and probe the connector with the black DVOM lead at the connector ground (probably the black wire) and the red lead to connector positive. The meter reading should be a steady 5 volts.

To test the operation over the ranger, reconnect the connector. Turn off the ignition and insert needles into the back of the connector at negative and positive. Connect the DVOM to the pins with alligator clips. Turn the engine on. Manually open and close the throttle and observe the readings on the meter. It should smoothly increase from 1 volt to 5 and back down.

To test the sensor's resistance over the range, turn off the engine and the ignition. Disconnect the electrical connector and set yourDVOM to read OHM's. Connect the meter leads to the senor terminals, at their respective negative/positive. The resistance should gradually and smoothly change as the throttle is opened and closed. Different TP sensors have different resistance values and may have smooth changes but be out of specification, so it might be better to get a Factory Service Manual

Another possibility would be to purchase a very expensive DVOM or computer diagnostic tester, or something that has the ability to scope electronics. Scoping the sensor will give a more accurate description of possible flaws.
 

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Registered
1995 FWB 124,*** miles
Joined
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2,211 Posts
Discussion Starter #3
To do it you need a CAT III Digital Volt OHM Meter (DVOM).

First you locate the TPS sensor and unplug it. Turn the ignition to the run position, but do not start the car. Go back to the sensor and the connector. Turn the DVOM to measure DC volts and probe the connector with the black DVOM lead at the connector ground (probably the black wire) and the red lead to connector positive. The meter reading should be a steady 5 volts.

To test the operation over the ranger, reconnect the connector. Turn off the ignition and insert needles into the back of the connector at negative and positive. Connect the DVOM to the pins with alligator clips. Turn the engine on. Manually open and close the throttle and observe the readings on the meter. It should smoothly increase from 1 volt to 5 and back down.

To test the sensor's resistance over the range, turn off the engine and the ignition. Disconnect the electrical connector and set yourDVOM to read OHM's. Connect the meter leads to the senor terminals, at their respective negative/positive. The resistance should gradually and smoothly change as the throttle is opened and closed. Different TP sensors have different resistance values and may have smooth changes but be out of specification, so it might be better to get a Factory Service Manual

Another possibility would be to purchase a very expensive DVOM or computer diagnostic tester, or something that has the ability to scope electronics. Scoping the sensor will give a more accurate description of possible flaws.
Thanks Sven. I have encountered a few times shudder at very light throttle before 1-2 shift occurs, and the same shudder around 43 MPH while moving up a hill and adding some gas to keep the momentum. I want to exclude faulty TPS. What do you think is it transmission issue? Thanks.
 

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1989 Brougham d'Elegance, 1985 Fleetwood Brougham *Coupe*
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Thanks Sven. I have encountered a few times shudder at very light throttle before 1-2 shift occurs, and the same shudder around 43 MPH while moving up a hill and adding some gas to keep the momentum. I want to exclude faulty TPS. What do you think is it transmission issue? Thanks.
I would have the transmission flushed by a reputable transmission shop. Shutter is mostly caused by worn transmission parts, but it can also be caused by crud in the fluid and a gummed up torque converter, not allowing the clutch to release. I don't think 43 is a shift point (if it was it would be overdrive) so the TCC might be doing something and sticking, causing a vibration.
 

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2014 ELR
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shudder around 43 MPH while moving up a hill and adding some gas to keep the momentum
That sure sounds like the converter unlocking to me. You can confirm by calling up the tach feature on your climate control...
 

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79 coupe deville d'elegance (76k og), 84 coupe deville
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114 Posts
first i was getting code 30 but it went away and now im left with 27. all of this after changing the tps months ago, recently reseting distributor timing. car would start first crank every time without any codes. now i have to assit it to start. and seems to over rev mostly goin into 3rd with gas applied.

might try my oe tps or get a new one. any thoughts?
 

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1995 FWB 124,*** miles
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Discussion Starter #8
UPDATE: Finally had the time to run some tests. Did not measure the TPS voltage, but the resistance changed smoothly from 7.83 kOhm (closed) to 1.88 kOhm (WOT). The resistance data would obviously invert if I took another pair of pins. I will check voltage behavior later, but it will be most likely fine.

The transmission was serviced (ATF/filter changed) under the previous ownership 1.5 years ago at 78.500 miles. It is 86.150 now. The fluid is red and smells good.

The shutter usually occurs when I am moving up a hill at some 43 MPH and giving it a lil bit more throttle to keep the momentum. If I press the gas pedal more I will avoid that hiccup. Have not adjusted my driving manners yet, I guess. Do you think that "hiccup" is detrimental to the transmission? I have never experienced something like that with my 1991 Seville.
 

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84 Coupe w/500
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5,665 Posts
it really does sound converter related, bad spark(for whatever reason) can give the same issues also. Did you pull up the RPMs on the climate control?
 

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1995 FWB 124,*** miles
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Discussion Starter #10
it really does sound converter related, bad spark(for whatever reason) can give the same issues also. Did you pull up the RPMs on the climate control?
I know how to bring RPM to the climate control. But what is it going to tell? If it is not transmission-related but rather the engine, the RPM will jump too. Besides it takes only a second or so, hard to notice anything... The dealer I bought the car from believes it is a stuck open EGR valve. I do not think so though. If it is the EGR valve why I do not get the same shutter at the same throttle angle, but under different conditions?
 

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84 Coupe w/500
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I think that because its happening under a heavy load that the tranny/converter would be a likely cause, the fact that you have such low miles would point me to the ignition. I had an EGR valve issue at one time and the hiccup would happen at various speeds above 40, anywhere from 40 to 60 so I dought its the EGR.
 

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1995 FWB 124,*** miles
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Discussion Starter #12
I think that because its happening under a heavy load that the tranny/converter would be a likely cause, the fact that you have such low miles would point me to the ignition. I had an EGR valve issue at one time and the hiccup would happen at various speeds above 40, anywhere from 40 to 60 so I dought its the EGR.
Csbuckn,
Thanks for the input. Because replacing an EGR valve on this engine is not a big deal, my next step would be that. I'll report back. The car was owned by an elderly couple. I do not think they abused the tranny.
 

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Past: 95 Fleetwood, 91 Brougham. Now: 92 Lexus SC300
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5,418 Posts
I had a slight miss/shudder at 45-55mph going uphill in my 1991, with the 350 TBI in it. Changed the plugs, wires, and distributor cap. It runs better now that I did that, and that hesitation/shudder is completely gone now.
 

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1926 Model T street rod, 2000 Jaguar XJ8, 1999 Corvette.
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Simply disconnect the hose to the egr, plug the hose and drive it, is the shudder gone? If not then a new egr is a waste of money. My bet is on secondary ignition, cracked plug insulator or weak plug wires. A transmission problem is way down on the list.
 

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1995 FWB 124,*** miles
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Discussion Starter #15
Simply disconnect the hose to the egr, plug the hose and drive it, is the shudder gone? If not then a new egr is a waste of money. My bet is on secondary ignition, cracked plug insulator or weak plug wires. A transmission problem is way down on the list.
Carnut,

Thank you for the reply. I have got an extra EGR valve and a gasket. so it is like a 15 minute job for me. Besides, I believe if the EGR valve does not close properly ( a chunk of carbon stuck or something) disconnecting the vacuum line is not going to fix possible problem. Am I right?
Plugs and wires are the next on the list.
 
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