I did the mod last night on my TPS. My start reading was 1.220 VDC. I managed to get to 1.025 VDC. My question is: What gains will I see if I get it to .999VDC as recommended on the other post here?

 

I think you only want to adjust down if you are having a rough idle. The adjustment is for those who have below 1 vdc, they should adjust up. This is suppose to improve throttle responce.

Any experts out there to verify this??

 

Okay, first of all, lets better explain the TPS. The ECM's primary use for the TPS is to understand what the driver wants to do. It uses other sensors to learn what the engine is doing, and the conditions and loads it's under, but until the TPS, it had no way of knowing what the driver really wanted. Now it does. One of the major differences is between idle and driving. An engine requires less fuel and different ignition timing/firing patterns at idle, and so when the ECM knows that idling is the drivers intent, it leans out the mixture and retards the timing. The way it knows this is when a predetermined reading is received from the TPS. On Ford vehicles equipped with the EECIV system, the factory specified TPS setting at idle varies between .45vdc and .85vdc (depending on the application), but the point where the ECM determines you are no longer idling is at 1.0vdc. Below 1 volt, you're at idle, and above 1 volt, you're driving. Some bright kid somewhere with far too much time on his hands came to the conclusion that the closer he could get his idle voltage to 1 volt, the quicker the ECM would go rich upon acceleration. This theory, while actually true, can not make a difference that is noticeable. Even the best computers can't determine any gain between an adjustment of .85vdc and .99vdc. BUT, by setting the TPS at .99, you have brought it dangerously close to the 1 volt point at which the ECM determines that the driver wants to drive. The end result is poor gas mileage, a rough, hunting idle, oil contamination, accelerated engine wear, and clogged catalytic convertors. What is sad is that this has turned into a pipe dream for many, who actually convince themselves that their vehicle runs better like this. I can 100% guarantee that they are clueless, and wrong. All they are doing is damaging their vehicle for no gain. I don't recommend changing the TPS beyond the factory range for any reason, and to those that are foolish enough to try, PLEASE don't go beyond .95 volts. At least there you will have a year, maybe, before the routine wear in the TPS allows the ECM to misunderstand your desires as a driver, and starts damaging your vehicle. Better yet, .85vdc.

Hope this helps.

Take care
~Chris

 

I have to agree, with one possible exception. I don't know if the specs have changed since my '95, but the reference voltage of .5 to 1 volt is considered OK, and they say to set it at 1 volt on the nose for a new TPS install.

I have experimented a little, and my truck runs fine up until approx 1.2 volts, and then has the idle hunt. I went down as far as .7 volts and back up to 1 volt with no difference that I could tell as far as throttle response or driveability.

The amount of throttle body movement between the two ranges aren't enough IMO, to change much of anything.

 

pkrrud---right on, excellent on the explanation...leave some room for change over time...

 

Signmaster-
You bring up a good point. You really should research your engines recommendations as far as the settings are concerned. They do vary. For years, the cut-off point for Ford was 1.0vdc, but it's not uniform accross the board anymore. Whatever you do, do not exceed the recommended maxximum adjustment, and ignore the posts that swear by adjusting the TPS to .999vdc. These are made by easily fooled individuals whith high hopes, and a more than likely crappy running vehicle.

Take care,
~Chris

 

Typical Diagnostic reference values for the TP is .53 to 1.27vDC at hot idle. The spark advance is between 11° & 20°. I guess in theory if the advance is at 20° at hot idle it will take less time to advance it that if it was at 11°. How much time I have no idea. So throttle response would be quicker if starting at 20° vs 11°. Weather changing the TPS to read .999 vs .53 will change the advance remains to be seen.

Regards

Jean Marc Chartier

 

I wish I had seen some of these posts before I spent time playing with the TPS.

If I had seen JMCs post, I could have broken out the timing light and checked out his part of the question/theory. My TPS is a pain in the butt to get to, so I'll have to leave this to someone else unless I have to replace the TPS for some reason.

 

I am yet to see any vehicle that became more responsive off idle by maxxing out the TPS, but if idle/drive was determined at 1.27vdc, and you set it at .999vdc, I couldn't say. The bottom line is to avoid getting too close to that point where idle/drive is determined.

~C

 

HI!... All I know is that I have done the TPS mod and have it set at .98. It's been like that for 3 years and I have had NO PROBLEMS what so ever because of it. Mine was set at .76 from the factory and I DID notice a slight difference in throttle responce when I tuned my TPS. In my opinion it works to a piont, a small one.

 

Neal, I knew that you would reply sooner or later! As I stated, I started w/ a reading of 1.225. I am currently at about .90 vdc. Thanks for the replies!! Keep the rubber side down!!!