da_cain

So I managed to obtain an online manual, and thanks to links given to me by members on many different ways of adjusting TPS and testing, managed to get it adjusted correctly (it seemed).

When I tested the resistance of the TPS with my DMM, it read about 1200 ohms at idle, and 6000 ohms at WOT. So I assumed that the TPS was ok. But....I continued to adjust the tps with the 2 light system, Turned screw one way till no lights came on, back the other way till 1 light came on, paying attention to the location of the screw head at each turn, and set it inbetween with one light on. Then I went ahead and Tested my BAC valve with my DMM and it read a perfect 12.3 ohms. Detached the hose goin into it and gave a puff to see if it was stuck open and it was not.

Start my car up, starts up fairly nicely, as nice as it can ( I have a toggle switch under my dash that jumps the ignition and fuel injection because it is a pain to start) and idles fine, not that I been having an idle problem anyways, my problem is with lost of power on acceleration and random backfiring in between gears, and at times (very rarely) total loss of pedal with backfires when I give it gas. Back to the point, car is idleing fine, so I pull it out on the street and was gonna rip down the freeway and back and see how the pedal feels, when I notice that upon giving it slight gas, it surges, and once I put it in gear and maintain a constant slow speed it bucks.

Am I to beleive that the test I took on my TPS was just accurate at the 1k ohm side and at the WOT side @ 6000 ohms and my problem lies somewhere inbetween which is hard to find with a Digital MM and not an analog that might detect the problem in between?

None of my local parts dealers seem to stock the TPS, and the cheapest Ive found is about 160 dollars, and cant seem to find one online that is any cheaper, only actually found one sight with one. And am sketchy about pulling one out of the junkyard.

My question is: Is my problem the TPS, or am I barking up the wrong tree?

Turbonut

iTrader: (1)

Did you check the "lights" after you returned to see if still in adjustment?

da_cain

Yes lights were still in adjustment, and even out of curiosity held the throttle open while it surged and turned adjustment screw till it smoothed out, at which time both lights were on, but Im sure I was back to the crappy acceleration and backfires although I didnt bother to test it again, just adjusted it back correctly and came in here to post. Right now Im am debating on goin down to the Junkyard where I know there are a few 7's @ and picking up the TPS and possible the hole throttle body because I notice a little slop in the Rod that runs thru the throttle body which the the throttle is attached, and a couple other problems I noticed that just may cosmetic but I feel uncomfortable about.

Turbonut

iTrader: (1)

If the sweep of the TPS indicated no spikes or dips, can't see installing another. Some times it takes a few "tweaks" to get the TPS set correctly. As you did, make certain car fully warmed up. Could be another problem, eg plugs, wires, vac leak. They all been checked out?

da_cain

Prior to adjusting TPS:

1. Changed Plugs

2. Changed Wires

3. Cleaned Injectors

4. Went around motor with can of Carb Cleaner looking for VAC leaks

5. Made sure car was fully warmed up.

But as I was saying, my test only accurately tested the Min and Max ohm, I didnt accurately test for spikes in between as I have a digital meater, and they 90 percent of the time spike for any reason at all, they are very touchy. So I am leading to beleive that yes, my TPS has a bad spot or several in between idle and WOT.

WAYNE88N/A

The ultimate way to test your TPS is to read out the input pin at the ECU- this verifies not only that the ECU is seeing the signal, but you can leave the meter hooked up while driving, to see if any changes occur during different driving conditions. It's also neat to watch what the TPS is actually doing during all driving conditions (for instance, you'll realize that at anything above what seems to be about 1/4 throttle, the TPS is maxed out and the ECU senses a WOT signal the whole time)...

With this setup, you can also just turn the key on (hot or cold engine) and slowly push the gas down while watching the TPS sweep for any abnormalities...

da_cain

I verified ECU is getting the signal by simply holding the throttle at about 2k rpm, and moving the TPS in with my finger listening for changes in RPM.

da_cain

I just ran another sweep on TPS, and am noticing that @ WOT Im actually at 6250 ohms everytime, and I read somewhere on the forums that you should replace if it exceeds 6000 ohms.

da_cain

/bump 8)

WAYNE88N/A

Dude, I think you need to look in another direction. Your TPS sounds good...

If you have the 1v at 750 rpm from the TPS to the ECU, and you have a good sweep during the resistance checks, quit worrying about it...

da_cain

Figured I would post my solutions for those who are having similar problems. After coming up with pretty much nothing for a couple days and having to go out of town for work soon, I decided to throw a new o2 sensor in. Was easy as pie, got a Bosch single wire o2, injured the back side of my hand on the engine block which I still have a nice battle wound at the moment from pryting the old one off. Also replaced most the wire going up to the harness, lots of exposed wire showing and was hard and brittle. Got it all together and fired her up, right off the start still had some surging, and everyime I gave it gas she would pop like a hand gun (backfire). Well, I was disapointed at that time and said oh well and proceeded to pull out of the driveway and park on the street so my roomates could have the driveway while I went to work in Seattle for a few days, and while I was moving it I notice my brake pedal was rock hard. Parked it and thought nothing of it, just that I didnt solve anything this day 8(. So, the first morning I get back I go outside to tackle the beast again, had previously ordered a complete used Throttle Body w/TPS sensor before leaving town and it had arrived. First things first, I pop the hood and look for the suspecting vaccum line that I must have disconnected that was creating the brake pedal problem and found it immediately. Fired her up, a small bit of surging at first, a couple small backfires and everything seemed ok, I was gonna drive to go pick up my throttle body. Got on the on ramp and she was running much better, still a slight bit of surging and hesitation but nothing like before.

To the end of the story, I swapped out the old throttle body with the one I pickedup, after some maticulous cleaning of parts, fired her up, warmed the engine up, and tweaked with the TPS and throttle adjustments, and drove home from my freinds shop, and she is running like a champ now, has a little low of an idle which I plan on goin out an fixing after I am done posting here.

My final conclusion is I had 1. a faulty o2 sensor and 2. a faulty throttle body. I beleive my throttle was sucking air on the back side when I was giving it pedal, there was a bit of slop in the throttle rod that runs threw the body on the backside, so when I was giving it gas by hand from the front I wasnt seeing the symptoms but if I reached back and gave it gas form the throttle cable they would appear. Hope these posts can help others with similar problesm, lord knows if you look these are some very common problems with the 7's. Good Luck!

GTUser

Thanks for posting your solution, most guys get their problems fixed and you never hear from them. Can always benfit from what others learn.

da_cain

Oh yes, another thing that might help, when I tested the used TPS that came with my new throttle body, which I might add I only payed 90 dollars for the whole set up, that it test 1k - about 5k max at WOT, compared to the 6250 I was getting on my original TPS.