Fuel injection ?s !! TPS!! LEVE?? - Off-Road Forums & Discussion Groups
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post #1 of (permalink) Old 08-07-2001, 06:38 AM
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Fuel injection ?s !! TPS!! LEVE??

Well, the suburban has ANOTHER $200 stuffed into it and the problem still exists!! It now has a new CAT. and fuel pump..I need to know the perimeters of the tps. It starts at .565 or so ans at WOT. it only reads 3.6 somthin..Is that high enough or should it go to around 5.0..You can floor the thing on the highway and it'll step down into the next lowest gear and make all kinds of rpm but no speed..I think it's to lean on top to make power..The volts dont jump around like a bad one, but they dont go high enough from what I remember some other experiences being..

It's as close to a 1ton as it can get and still be a jeep!!! Gotta love it!!
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post #2 of (permalink) Old 08-07-2001, 07:56 AM
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Re: Fuel injection ?s !! TPS!! LEVE??

Leader, if I remember right the TPS voltage goes from about .8VDC to around 4.7VDC. To test the component remove it and test with an ANALOG Ohm meter. Connect the meter accross the wiper and one end of the Variable Resistor) VR. Then turn the VR slowly so you see a decrease or increase in the Ohm value (depending on how you hooked it up).

Turn slowly so if you see the needle Jump and can reconfirm by backing up over the same spot and doing it again... the TPS is bad. There's a bad spot in the VR. You're looking for a smooth transistion from low to high Ohms. Rapid needle fluction means you've come over a dirty spot in the TPS.

Once you've confirmed the TPS is good, look elsewhere. The voltage you quote does seem low, however if the voltage is 30% low at WOT, that's more than enough for the computer to signal a TPS code.


From the description the problem seems more akin to the following:

MAP/MAF sensor: Monitors Engine Load.

IAC motor: Controls Lean/Rich at idle, and can lean an engine out too much, even under load.

Fuel Regulator: Failing to deliver enough pressure under load to the fuel rail/injectors. This is confirmed by a pressure gauge on the schrader valve.

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post #3 of (permalink) Old 08-07-2001, 09:23 AM
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Re: Fuel injection ?s !! TPS!! LEVE??

I learned how to test it with it on the truck with a digital volt meter..(thanks to holley efi)...WHen it kicks down into a lower gear, it revs to no end but doesnt gane any speed till it shifts or you let off the throttle.Then it kinda chuggles like a dead cylinder that hits every now and then.I put a GOOD tbi on it that I had on my jeep , so I dont think it's the iac acting up but I had to use the same tps because the other tbi was of a different vintage.So far I have replaced the cap/rotor/coil/pickup coil/fuel filter/fuel pump/cat. converter/throttle body/ esc module, and it still does the same thing at WOT...Thats why I'm wondering about the tps not giving the computer a high enough voltage at wot..The only code it has given me is the one for the esc module..I havent replaced the knock sensor, but it test out just fine and it hasnt coded again.It takes off just fine, and runs ok till it gets under a good load or wot... I'm bout ready to put a carb on it!!!!

It's as close to a 1ton as it can get and still be a jeep!!! Gotta love it!!
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post #4 of (permalink) Old 08-07-2001, 10:02 AM
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Re: Fuel injection ?s !! TPS!! LEVE??

Humm... I gotta think about this one... I'll email you the results...

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post #5 of (permalink) Old 08-07-2001, 10:03 PM
 
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Re: Fuel injection ?s !! TPS!! LEVE??

Go to www.thirdgen.org in the tech section there is a very good article about adjust and fine tuning your tps and iac. You might want to adjust your timing. If your cranking on it and your timing is off you might be getting a little detonation, which the computer will sense (knock sensor) and it will retard your timing. You will notice bad gas mileage as well as the ses light come on. And if it is way off you will go into limp home mode and that sucks.

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post #6 of (permalink) Old 08-08-2001, 07:06 AM
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Re: Fuel injection ?s !! TPS!! LEVE??

I have the Holley Pro-jection manual, which is basically the same thing as the GM TBI. I can scan and email you copies of the manual if you would like. Email me at [email protected], if you would like the manual.

Jesse

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post #7 of (permalink) Old 08-08-2001, 09:03 AM
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Re: Fuel injection ?s !! TPS!! LEVE??

Yes, could you do that for me? I'd like to have those laying around for the fun of it.I replaced the chip back to the factory one, and the wife says it really runs like hell now.Dont know if I goofed it up putting it in or what, it drove good for me last night!! LEVE, I tested about 4 different tps units last night and all of them read more than the one that is on it, but they all had different values..I'm bout ready to burn the damn thing...I do have another question though...It seems to stutter when both ac's are on and it's pulling the amps way down.Could a weak alternator cause one to stutter at highway speeds? The guage shows about 9-10 volts running both fans on high at 55mph..This thing has a nasty ghost in it....any exorcists out there??????????

It's as close to a 1ton as it can get and still be a jeep!!! Gotta love it!!
post #8 of (permalink) Old 08-08-2001, 10:20 AM
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Re: Fuel injection ?s !! TPS!! LEVE??

The biggest cause I have found for these ghosts is low voltage and/or bad ground. The Holley TBI must have 8 volts to operate correctly. Make sure you have good ground. Send your email addess to [email protected], and I will get the manual scanned and send it out to you in .jpg format. It is only a few pages.

Jesse

<font color=red> I have a CJ... and I am current on my tetinus shots. </font color=red>
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post #9 of (permalink) Old 08-08-2001, 06:52 PM
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Re: Fuel injection ?s !! TPS!! LEVE??

Leader, you've got to get a known good TPS. My manuals indicate that the computer will fire a TPS code if the voltage is > 2.5 volts for 3 seconds at less than 1200 RPM, or a short to grund, or an open condtion will also set a cone in 3 seconds.

Does the vehicle have VSS sensor?

I'm beginning to think you may have a kick down problem or a transmission lock up problem.

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post #10 of (permalink) Old 08-09-2001, 06:40 AM
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Re: Fuel injection ?s !! TPS!! LEVE??

I was reading the shop manual last night (after new plugs and oxy. sensor) and was thinking the same thing about the vss. It does run better now, at least it will pull when it kicks down but it still surges like no fuel.It will run like hell at take off (ok, kinda sluggish but hey it's big!)then while at wot. it'll start to loose power then gain a little then do it again..It seems to me that the computer is having a migraine and cant make up it's mind. I dont know how to go about testing the vss,I was VERY disgusted and gave up last night!! I'm sure it tells me in there somwhere..Last week when I had it plugged up to the scan tool, the speedo and the mph on the scan were very close so that leeds me to believe that the vss works. Other wise it woulda shown different right? I'm going to pull the computer out of my jeep after this weekend and see if that is the problem...It has the same engine and electronics.

It's as close to a 1ton as it can get and still be a jeep!!! Gotta love it!!
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