TPS or bad injector

paintedshrub · 09-16-2007, 07:49 AM

hey. after running through my jeep i think i have narrowed my problems to either a bad injector or a improperly adjusted TPS.

I tested my TPS using the FSM directions involving checking two voltages and comparing them to get a ratio. they say i should come out with .83 or 83%. well, i came out with .8237 or 82%.

Is that one percentage point enough to make the motor buck like its backfiring, and have a pretty bad skip somewhere in mid-throttle. it sounds alright at idle, and when i press on the gas to go, if i stay in that spot where you keep the pedal to maintain speed when you're cruising (just down a little bit) thats where it does bad nowhere else

CharBroiled · 09-16-2007, 08:36 AM

0.8% off is fine, thats pretty much within a test instruments margin of error.

but it does sound like theres a dead spot on it. Im not sure how the fsm tells you to test it but if its just hooking an ohm or volt meter up to it make sure its smooth over the whole range of travel and doesnt jump around. it should gradually change with with throttle position with no jumpiness or dead spots. analog meters may be better at seeing that.

dyna · 09-16-2007, 10:07 AM

In the various 4.0`s Ive had TPS settings prior to adjusting have been anywhere from .7 to .95, after adjusting them I didnt even notice any difference, still ran great. I cant see that be the cause of your issues.

tangofox007 · 09-16-2007, 10:16 AM

Quote:

Originally Posted by CharBroiled

but it does sound like theres a dead spot on it. Im not sure how the fsm tells you to test it but if its just hooking an ohm or volt meter up to it make sure its smooth over the whole range of travel and doesnt jump around. it should gradually change with with throttle position with no jumpiness or dead spots. analog meters may be better at seeing that.

Spot on. Just because the ratio is nearly correct at closed throttle says nothing about how it works across the full range. From your description, your TPS has a glitch at a throttle position above idle. If your TPS is original, replace it and don't look back!!!

paintedshrub · 09-16-2007, 10:49 AM

well, i might end up replacing it, but right now i have a problem that needs to be addressed before i can even fix that.

i took the intake hose off the throttle body and found another problem.

my butterfly valve is sticking...

its like it wont stay centered and the play it has is letting the valve stick on the firewall side of the opening
at the center it has a scrape that when i hold the valve up, means that the valve is scraping from close to 1/3 or a little more throttle. scraping and possibly sticking.

anyone know what to do with this without taking the throttle body off? i lack torx bits big enough

paintedshrub · 09-16-2007, 10:51 AM

yeah, and i have checked the TPS with an analog meter, and it does move smoothly. i tried moving it pretty slow, and it looked good.

CharBroiled · 09-16-2007, 12:03 PM

Id of bet money that the TPS has a bad spot. I would double check that the voltage (or resistance) is smooth over its range paying particular attention to the throttle position that causes the stutter. it could be smooth over 99% of its travel with only a smallish glitch on the bad spot. thats all it would need to mislead the computer.

as for the butterfly valve sticking you would definitely know if it actually sticking as its mechanically linked to your gas pedal and it would stick in position too. its a pretty strong spring so personally I wouldnt worry about it if the scrape looks very minor unless it seems like its really sticking bad, but thats just me.

has it ever actually stuck or caught? engine always drops right to idle when your foot is off the gas? can you post a picture of the scrape?

paintedshrub · 09-16-2007, 01:11 PM

yeah, it was definitely sticking. when i had the motor running, it would not always drop down to idle, and i checked the mechanical linkage and sure enough the stop plate was falling to about 3/16 to 1/4 inch away from the set screw. so i opened it up, sprayed everything down with carb cleaner and worked it in really good
it seemed like its fixed it for now. ill take it out for a drive in a bit to see if anythings better.

right now im trying to get the drivers side of the axle shifted forward by means of moving that control arm behind the tire that goes to the axle. im hoping that will stop my front driveshaft from knocking on my exhaust

tangofox007 · 09-16-2007, 01:52 PM

Quote:

Originally Posted by CharBroiled

Id of bet money that the TPS has a bad spot. I would double check that the voltage (or resistance) is smooth over its range paying particular attention to the throttle position that causes the stutter. it could be smooth over 99% of its travel with only a smallish glitch on the bad spot. thats all it would need to mislead the computer.

Agree. Often, a TPS glitch will be temperature related. It might work fine when cold, then act up when hot. Or vice versa.

paintedshrub · 09-16-2007, 02:13 PM

yeah... i was trying to do everything to avoid something more than 10 bucks, but i guess it can't be helped.

i rode it around the block after my latest series of adjustments, and it improved, though not as much as i had hoped. its still stumbling, and it had a few backfires, though not as many.

so i took it for a ride with the TPS unplugged. It rode smoother if anything. only one backfire, and about the same amount of stumbling. i reckon this means my TPS is bad, right?

thanks for all the help so far

illsnow · 09-17-2007, 10:18 AM

sounds like the same situation i dealt with when i had a bad tps. its only like 25 dollars tho, no big thing.

tangofox007 · 09-17-2007, 10:27 AM

Quote:

Originally Posted by illsnow

sounds like the same situation i dealt with when i had a bad tps. its only like 25 dollars tho, no big thing.

Unfortunately, the Renix version is about three times that.

illsnow · 09-17-2007, 10:32 AM

oh i suppose it is a 89, it would be renix huh. sorry.

danielhays_98xj · 09-17-2007, 10:33 AM

So i the mechanic insisted that he change the alternator thinking that it was the reason for the squeak/knocking sound.

Well, it wasn't the problem, it still knocks and I'm stuck with a $250 bill and a louder diesel sound knock.

And its not the serpentine belt, changed it three times.

I still think its the rocker arms.

Thanks

paintedshrub · 09-17-2007, 05:06 PM

so i have now replaced the TPS.

no change

changed an injector that was giving me problems. the new one is a GP Sorensen from autozone.

now i have a high idle. i crank the truck up and it just sits there at 1500, and it still skips when i rev it

but, never say die. anybody got a clue why after changing the injector i would have a problem like this?

09-16-2007, 10:07 AM	#3
dyna Senior Member Join Date: Oct 2006 Location: Kalifornia Posts: 840 Profile Gallery Classifieds My Jeeps	In the various 4.0`s Ive had TPS settings prior to adjusting have been anywhere from .7 to .95, after adjusting them I didnt even notice any difference, still ran great. I cant see that be the cause of your issues.