Rough idle...Need HELP!!
10-30-2012, 08:02 AM
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Rough idle...Need HELP!!
So my truck idles rough and only during low rpm's. Usually right after it starts up or after it sits and idles for several minutes. It starts no problem. Most of the time, ill crank it up to leave and by the time i get stopped at the end of the neighborhood(bout 1/2 mile) itll idle rough on me. Then when im ready to take off, it hesitates and struggles to get going, but if its WOT, itll take right off like it should. When the engine gets warmed up it doesnt do this as often. I have a new fuel pump/strainer, new fuel filter, new coil, new distributor cap and rotor, and fairly new wires. this has been happening pretty much since i bought the truck in may. Im leaning towards a bad TPS or AFM but i dont want to just throw parts at it. Is replacing the TPS as easy as removing the old one and installing a new one, or does the new one have to be adjusted? I CANT FIGURE THIS OUT!!
10-30-2012, 10:00 AM
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I recently replaced and adjusted my TPS, following the link that ksti posted.
- Follow the instructions to test it while on the truck. It's pretty easy to tell if it is out of adjustment just by reading your voltage meter and using a feeler gauge.
- Another way to check to see if your TPS is bad or needs adjustment: If you have the tools, jump the terminal that you would use to perform the timing. Put the timing light on the timing belt. Remove the jumper from the terminal while watching the timing light. The timing should jump. If it is timed correctly it would most likely jump from 5* (22re) to 8* or 10*. If it does not move at all, adjust or replace TPS.
- If you have to replace or adjust it, buy the screws that the aforementioned link says to. It makes things easier in the long run.
- Remove the throttle body (TB) from the plenum. (Three bolts, one nut, two collant hoses and some vacuum hoses IIRC). Use golf tees to plug the two radiator lines that connected to the bottom of the TB.
- Unscrew the TPS (2 screws) from the TB.
- Now is your time to clean the inners of the TB. Use TB cleaner. It is not as corrosive as brake or carburetor cleaner. Make sure not to get too much gunk into the opening for the IACV. The IACV is what the two coolant lines attached to. Put some duct tape over the whole inside the TB and clean the heck out of it. Then remove the tape and clean what you missed carefully. I used a q-tip with some oil and lightly lubricated where the butterfly connects to the TB from the recommendation of someone on here once it was clean.
- Make sure you scrape and clean the surface of where the TB meets the plenum of any gasket or RTV. Ensure both the TB and plenum surfaces are clean.
- Once clean and dry, put the TPS back on with the two new allen head screws and line it up somewhere in the middle. Start with putting the .57mm feeler gauge between where the throttle lever and throttle stop screw are. If positioned close to being correct, it should give you some reading less than 2.3K. I worked up from there in small increments by using gauges .64, .76, .81 until i got to .85mm. Your reading should be infinite once you stick the .85mm feeler gauge in. I was happy when it was infinite at .76mm or .81mm. If you have to adjust the TPS, rotate it in extremely minute turns. It is amazing how finicky it is.
- Once you are happy with this measurement, check the other measurements with your voltmeter (throttle fully open and fully closed). If the feeler gauge measurement is correct, then these should also be correct. Tighten down the screws really well and do one final check to see if you still have the TPS to spec.
- Finally, make sure you have the right gasket. There are two types, one is square on all four sides and one is square on three sides with the fourth side jutting out at an angle (http://www.lceperformance.com/Gasket...-p/1061000.htm).
- Install the TB and hook everything back up and it should be fine. If it is running horribly, spray some TB cleaner over the TB. If the idle smoothes out, you have a vacuum leak somewhere (either vacuum hose or gasket not quite right).
- If your timing didnt move earlier, it should move now.
- Big thanks to 4crawler. Could not have done it without his write up.
- Follow the instructions to test it while on the truck. It's pretty easy to tell if it is out of adjustment just by reading your voltage meter and using a feeler gauge.
- Another way to check to see if your TPS is bad or needs adjustment: If you have the tools, jump the terminal that you would use to perform the timing. Put the timing light on the timing belt. Remove the jumper from the terminal while watching the timing light. The timing should jump. If it is timed correctly it would most likely jump from 5* (22re) to 8* or 10*. If it does not move at all, adjust or replace TPS.
- If you have to replace or adjust it, buy the screws that the aforementioned link says to. It makes things easier in the long run.
- Remove the throttle body (TB) from the plenum. (Three bolts, one nut, two collant hoses and some vacuum hoses IIRC). Use golf tees to plug the two radiator lines that connected to the bottom of the TB.
- Unscrew the TPS (2 screws) from the TB.
- Now is your time to clean the inners of the TB. Use TB cleaner. It is not as corrosive as brake or carburetor cleaner. Make sure not to get too much gunk into the opening for the IACV. The IACV is what the two coolant lines attached to. Put some duct tape over the whole inside the TB and clean the heck out of it. Then remove the tape and clean what you missed carefully. I used a q-tip with some oil and lightly lubricated where the butterfly connects to the TB from the recommendation of someone on here once it was clean.
- Make sure you scrape and clean the surface of where the TB meets the plenum of any gasket or RTV. Ensure both the TB and plenum surfaces are clean.
- Once clean and dry, put the TPS back on with the two new allen head screws and line it up somewhere in the middle. Start with putting the .57mm feeler gauge between where the throttle lever and throttle stop screw are. If positioned close to being correct, it should give you some reading less than 2.3K. I worked up from there in small increments by using gauges .64, .76, .81 until i got to .85mm. Your reading should be infinite once you stick the .85mm feeler gauge in. I was happy when it was infinite at .76mm or .81mm. If you have to adjust the TPS, rotate it in extremely minute turns. It is amazing how finicky it is.
- Once you are happy with this measurement, check the other measurements with your voltmeter (throttle fully open and fully closed). If the feeler gauge measurement is correct, then these should also be correct. Tighten down the screws really well and do one final check to see if you still have the TPS to spec.
- Finally, make sure you have the right gasket. There are two types, one is square on all four sides and one is square on three sides with the fourth side jutting out at an angle (http://www.lceperformance.com/Gasket...-p/1061000.htm).
- Install the TB and hook everything back up and it should be fine. If it is running horribly, spray some TB cleaner over the TB. If the idle smoothes out, you have a vacuum leak somewhere (either vacuum hose or gasket not quite right).
- If your timing didnt move earlier, it should move now.
- Big thanks to 4crawler. Could not have done it without his write up.
Last edited by 87redtruck; 10-30-2012 at 10:03 AM.
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