Code 21, TPS Issue -1986 2.5 (Page 1/1) tbone42 SEP 19, 05:00 PM 1986 2.5 (4 cylinder) Base coupe, 5 speed Isuzu Hello again my brothers in mid engine madness. I have TPS questions and measurements and some history, I appreciate any help ir suggestions anyone might have. So about two months ago I had stuttering issues which seemingly cleared up after replacing my distributor cap a rotor. However, before I figured that out I had a code 21 and replaced the TPS thinking that might be it. Then came the cap rotor and it had been running pretty good for a while. Than a month back I had a no start issue. Banged on my starter and it started. So, nxt day I replace the starter. Goes good for a while, but then no start again. I check battery connections and they're good, but on a hunch I wiggled the pos cable and then the car started. Ok, so looks like I never needed the starter and it was the cable. So, I've been really broke (medical bills) and I had to wait a week for payday before I can get the cable. In the meantime, I get a few non starts, wiggle the cable and it starts. But I'm also getting stuttering again like before, and now day before yesterday it throws another code 21, high voltage to TPS. So I take this stuttering beast as it's the only car I got over to O'Reilly's and get a new positive cable and hook it up. No start issue has not come back, but still running terrible at times especially on startup...really high idle. Runs good for a while (usually) then I get stutters after 15-20 minutes of running. At idle it kinda goes up and down, can't give you the tach readings because I need a new tach board..one thing at a time since money is tight and proper tach reading is less important than running right...and a new tach filter didn't fix it. So here we go...I go out today and test my TPS. These are the readings at fully closed and open with the key on: Top Wire (Black) - .02v full open and closed no change. This concerns me a little, isn't this my ground? Why would it have any voltage at all? Does this mean I may have a short or is that ok? Middle Wire (Blue) - 4.78v full open, 1.18v full closed. Bottom Wire - (Gray) - 5.03v open and closed (does not change) I'm pretty sure those numbers indicate something is wrong..but like I said I just replaced this TPS maybe 2 months ago at the most...Did I fry it with the positive battery cable having issues? That's my best guess what happened. Let me know if you think so too. Other notes/questions: I've done so much with this car lately, all this has been replaced: Plugs, wires, coil, dist. Cap, rotor, Tach filter and harness, 3 fuel filters in the last 3 months. I was also thinking this was fuel before I got code 21, maybe my injector. The bowl in the intake is looking a bit yucky so I'm getting ready to clean that out after I post this... I had some bad gas a while back and it did gum stuff up a little before I emptied the tank out. Fuel pressure test (caused a fire long time readers may remember) was off the scale that topped at 10 PSI so I don't think thats the issue. TPS lever is correctly positioned to move it when throttle opens. I cleaned and tightened some of my grounds before checking voltage...at least the strap on the battery cable post and the secondary coming off the negative cable to the screw in the frame. (Both passenger side) I really don't know where the rest of the grounds that could effect this are, isn't there one on the transaxle case somewhere? Sorry it was so much info, I figured the more you know the more you can see I might have missed something. I believe it just needs another TPS because I fried it, let me know what you guys think and thank you in advance for any help! Tbone tbone42 SEP 19, 05:51 PM One last thing, since I thought it might be my injector, I was priming the fuel pump twice and it seemed when I did that it didn't give me high/low idle on startup. This may be a total fluke, but it ran like crap earlier and I just decided to start it with two primes just now and it started good and seems to be running normal at idle speed. Could a clogged injector/dirty intake give me a code 21? Just spitballing here. shemdogg SEP 19, 09:40 PM RWDPLZ SEP 20, 09:56 AM See if the resistance of the TPS has any breaks as you slowly move the TPS arm all the way through it's sweep. That would indicate a bad TPS. I had similar issues, it turned out the wires going to the TPS had an intermittent break, splices in a new connector with a few inches of wiring, no more issues. tbone42 SEP 24, 12:32 AM Replaced the TPS today, so far so good. Drove all day without it getting boggy, Skippy or high idle. Tentatively fixed, but if it returns I'm going to splice in a new connector like you did. Gotta a couple days of driving before I'm totally sure, it has gone away before but I'd have to say the battery cable shorting probably fried it. Good news it was a lifetime warranty part so it cost nothing but the gas to go get it Replacing the cable also cleared up the whine in the stereo when I used my Bluetooth fm transmitter...so bonus fix I was expecting to have to use a filter or something. 😊