comanche1989 Posted September 19, 2017 Share Posted September 19, 2017 Hi Everyone, Recently I have been having hesitation issues with my truck. It is a 1989 Pioneer with a rebuilt '93 HO motor swapped in. However, it is still using all renix sensors. My issues began about a month ago, after I accelerated quickly from a stoplight. When I slowed back down, I noticed that when slowly accelerating between 1500 and 2300 RPM my engine would hesitate and backfire. If I accelerated quickly, this was not an issue. I suspected that the TPS was having issues after reading online, so I cleaned the throttle body and tried to adjust the TPS. I could not rotate the sensor enough to get it to my required voltage, which was .83 volts. I then bought a new TPS and am still having the same issue of being unable to get it to the required voltage. I have also cleaned the dipstick ground and crimped new eyes on. Would this cause my rough slow acceleration? Why can I not clock the TPS enough to get to the required voltage? Also, I attempted to get on the highway the other day and the engine stalled out once I got to about 60 mph. If anyone has any ideas about what could be causing this issue, I would appreciate it. I am near wits end with this truck. Link to comment Share on other sites More sharing options...
Ωhm Posted September 19, 2017 Share Posted September 19, 2017 Is TPS supply voltage at 5.1vdc? Is the idle set screw properly adjusted? Suspect MAP sensor. Link to comment Share on other sites More sharing options...
DirtyDeeds Posted September 19, 2017 Share Posted September 19, 2017 you can try the crank position sensor, I had the same problem last year. It controls timing so that might be it. It will also cause no starts Link to comment Share on other sites More sharing options...
comanche1989 Posted September 19, 2017 Author Share Posted September 19, 2017 Thanks for the replies. My TPS voltage from back-probing was 4.87. From what I understand this is within a reasonable limit. I have not adjusted the Idle Set Screw, however the butterfly opens and closes no problem. Is there a procedure for testing the MAP sensor? I don't recall seeing one. When it comes to the CPS, I have not had any issues when no start at all. However, I will test it when I have a chance. To me it seems like a fuel issue, due to the backfiring and popping I hear at the problem RPM range. Link to comment Share on other sites More sharing options...
87MJTIM Posted September 19, 2017 Share Posted September 19, 2017 Is the catalytic converter clogged? I had similar symptoms with poor acceleration and backfiring. Link to comment Share on other sites More sharing options...
Ωhm Posted September 19, 2017 Share Posted September 19, 2017 4.87vdc is a good reading when connected to TPS (back-probing). If its a stock renix TB, use cruiser Tip #14 . Easiest way to check MAP is with a known good one. Check MAP vacuum line. Link to comment Share on other sites More sharing options...
ParadiseMJ Posted September 19, 2017 Share Posted September 19, 2017 I know you said all Renix sensors, but if it is a 93 engine, how is the TPS mounted? On the front or on the side? Is it a 93 TPS? Link to comment Share on other sites More sharing options...
comanche1989 Posted September 19, 2017 Author Share Posted September 19, 2017 20 minutes ago, ParadiseMJ said: I know you said all Renix sensors, but if it is a 93 engine, how is the TPS mounted? On the front or on the side? Is it a 93 TPS? It is an 89 TPS with the HO throttle body. Adapted using the method in the link. Link to comment Share on other sites More sharing options...
comanche1989 Posted September 19, 2017 Author Share Posted September 19, 2017 27 minutes ago, 87MJTIM said: Is the catalytic converter clogged? I had similar symptoms with poor acceleration and backfiring. Catalytic converter was gutted by PO. 28 minutes ago, Ωhm said: 4.87vdc is a good reading when connected to TPS (back-probing). If its a stock renix TB, use cruiser Tip #14 . Easiest way to check MAP is with a known good one. Check MAP vacuum line. H.O. throttle body. I will check MAP vacuum line in a few minutes. I will keep everyone updated. Link to comment Share on other sites More sharing options...
comanche1989 Posted September 19, 2017 Author Share Posted September 19, 2017 Just took another look at my truck. Found about 2 ohms of resistance between back-probed TPS and negative battery terminal. Re-cleaned the dipstick ground thoroughly and that reduced resistance to the point where my cheap multimeter is not reading any. This brought my voltage on the TPS when adjusting up to .81 v. My voltage I need to be able to adjust to is .83v. Is that much of a difference negligible, or will it cause my issue? I can not clock the TPS any more. Line between manifold and MAP is in good condition. Is the MAP sensor responsible for fuel/air mixture along with the 02 sensor? If I remember correctly backfiring means that the mix is too lean. Link to comment Share on other sites More sharing options...
SVPete Posted September 20, 2017 Share Posted September 20, 2017 I experienced bucking (although I never heard a backfire explosion noise) and dying issues (driving along and the engine just stopped running, no rhyme or reason). The problem for me was between the EGR and transducer, coil (original at the time), distributor cap and rotor, plug wires, and plugs. I say between because: The spring in the EGR transducer was rusted to dust. The only way to get a new transducer is with a new EGR. While waiting for the EGR valve to come it, I broke a plug wire. So I had to wait for everything to come in and replaced all those items at one time. Problem was solved, although I really would have liked to know which was the culprit (it is possible I had a more than one issue). Upon visual inspection, I was pretty sure one of my plug wires was making poor contact with the plug. I checked, cleaned, tested as many things as I could according to Cruisers tips first. So that would be a good place to start if you haven't done so already. Link to comment Share on other sites More sharing options...
Ωhm Posted September 20, 2017 Share Posted September 20, 2017 5 hours ago, comanche1989 said: This brought my voltage on the TPS when adjusting up to .81 v. My voltage I need to be able to adjust to is .83v. Is that much of a difference negligible, or will it cause my issue? I can not clock the TPS any more. Line between manifold and MAP is in good condition. Is the MAP sensor responsible for fuel/air mixture along with the 02 sensor? If I remember correctly backfiring means that the mix is too lean. If you can reach .81vdc when swinging the TPS, you can set .83vdc for your closed throttle setting. MAP sensor play a major role in the fuel/air calculation, along with TPS and engine RPM's. Engine timing also uses these variables. O2 sensor controls the predetermined injector pulse width (mS) by either adding or subtracting time within its range of authority. Backfiring can be caused by many things. Link to comment Share on other sites More sharing options...
comanche1989 Posted September 20, 2017 Author Share Posted September 20, 2017 19 hours ago, SVPete said: I experienced bucking (although I never heard a backfire explosion noise) and dying issues (driving along and the engine just stopped running, no rhyme or reason). The problem for me was between the EGR and transducer, coil (original at the time), distributor cap and rotor, plug wires, and plugs. I say between because: The spring in the EGR transducer was rusted to dust. The only way to get a new transducer is with a new EGR. While waiting for the EGR valve to come it, I broke a plug wire. So I had to wait for everything to come in and replaced all those items at one time. Problem was solved, although I really would have liked to know which was the culprit (it is possible I had a more than one issue). Upon visual inspection, I was pretty sure one of my plug wires was making poor contact with the plug. I checked, cleaned, tested as many things as I could according to Cruisers tips first. So that would be a good place to start if you haven't done so already. EGR was deleted when I when to a H.O. motor. I have done most of the renix tips. I will however double check all wires. They are fairly new. 17 hours ago, Ωhm said: If you can reach .81vdc when swinging the TPS, you can set .83vdc for your closed throttle setting. MAP sensor play a major role in the fuel/air calculation, along with TPS and engine RPM's. Engine timing also uses these variables. O2 sensor controls the predetermined injector pulse width (mS) by either adding or subtracting time within its range of authority. Backfiring can be caused by many things. How would I set .83 for a closed throttle position when I can not get the TPS to clock any more? Adjust the idle set screw? I will be buying a new MAP sensor come payday to swap in. Link to comment Share on other sites More sharing options...
Ωhm Posted September 21, 2017 Share Posted September 21, 2017 On 9/19/2017 at 4:21 PM, comanche1989 said: Just took another look at my truck. Found about 2 ohms of resistance between back-probed TPS and negative battery terminal. Re-cleaned the dipstick ground thoroughly and that reduced resistance to the point where my cheap multimeter is not reading any. This brought my voltage on the TPS when adjusting up to .81 v. My voltage I need to be able to adjust to is .83v. Is that much of a difference negligible, or will it cause my issue? I can not clock the TPS any more. Line between manifold and MAP is in good condition. Is the MAP sensor responsible for fuel/air mixture along with the 02 sensor? If I remember correctly backfiring means that the mix is too lean. You mentioned that you could reach .81vdc. That's less than .83vdc. TPS output voltage should vary between .83vdc (CT) to 4.???vdc (WOT). Our you saying that .81vdc is the highest voltage you can read? Hold off on that MAP sensor till this is sorted out. Link to comment Share on other sites More sharing options...
cruiser54 Posted September 21, 2017 Share Posted September 21, 2017 On 9/19/2017 at 1:21 PM, comanche1989 said: Just took another look at my truck. Found about 2 ohms of resistance between back-probed TPS and negative battery terminal. Re-cleaned the dipstick ground thoroughly and that reduced resistance to the point where my cheap multimeter is not reading any. This brought my voltage on the TPS when adjusting up to .81 v. My voltage I need to be able to adjust to is .83v. Is that much of a difference negligible, or will it cause my issue? I can not clock the TPS any more. Line between manifold and MAP is in good condition. Is the MAP sensor responsible for fuel/air mixture along with the 02 sensor? If I remember correctly backfiring means that the mix is too lean. Okay, so one of the reasons you have trouble clocking the TPS is that it is a modified set-up. What is your vacuum source for the MAP? .81 volts should be fine. A bad TPS shouldn't cause acceleration issues though. Link to comment Share on other sites More sharing options...
comanche1989 Posted September 21, 2017 Author Share Posted September 21, 2017 7 hours ago, cruiser54 said: Okay, so one of the reasons you have trouble clocking the TPS is that it is a modified set-up. What is your vacuum source for the MAP? .81 volts should be fine. A bad TPS shouldn't cause acceleration issues though. MAP vacuum source is the closest nipple on the H.O. Intake. I’m fairly certain the location is not an issue, as I have put 10,000 or so miles on the engine since I put it in. Should I go ahead and spring the money for a new MAP? I hate throwing parts at a problem. 17 hours ago, Ωhm said: You mentioned that you could reach .81vdc. That's less than .83vdc. TPS output voltage should vary between .83vdc (CT) to 4.???vdc (WOT). Our you saying that .81vdc is the highest voltage you can read? Hold off on that MAP sensor till this is sorted out. The voltage swings up as the butterfly is opened. Link to comment Share on other sites More sharing options...
cruiser54 Posted September 21, 2017 Share Posted September 21, 2017 Unplug the TPS and see what happens. Link to comment Share on other sites More sharing options...
comanche1989 Posted September 21, 2017 Author Share Posted September 21, 2017 When I unplugged the TPS, it idled fine but when I pressed the gas it would stall. 21 minutes ago, cruiser54 said: Unplug the TPS and see what happens. Link to comment Share on other sites More sharing options...
comanche1989 Posted September 21, 2017 Author Share Posted September 21, 2017 I just went and bought a new MAP and installed it. No change at all in issues, still behaving the same. Link to comment Share on other sites More sharing options...
comanche1989 Posted October 15, 2017 Author Share Posted October 15, 2017 An update just incase people have a similar problem and are searching the forum. My distributor itself was bad. Now that the distributor is replaced (as well as nearly every sensor and ignition component) the Comanche is running smooth as can be! Link to comment Share on other sites More sharing options...
HOrnbrod Posted October 15, 2017 Share Posted October 15, 2017 1 hour ago, comanche1989 said: An update just incase people have a similar problem and are searching the forum. My distributor itself was bad. Now that the distributor is replaced (as well as nearly every sensor and ignition component) the Comanche is running smooth as can be! Do you know what the distributor problem was? Electrical, mechanical, ?? Might help someone else if you know the cause. Link to comment Share on other sites More sharing options...
comanche1989 Posted October 15, 2017 Author Share Posted October 15, 2017 As far as I understand, it was a mechanical issue causing an electrical issue. The distributor was worn out, causing oscillations effecting both the Cam position sensor ( I know the Jeep can run with it unplugged) and the rotor. I believe once the engine reached a certain rpm, it created an almost death wobble effect, where it oscillated at that certain rpm range. Certainly a strange problem. Link to comment Share on other sites More sharing options...
comanche1989 Posted October 15, 2017 Author Share Posted October 15, 2017 If someone has more knowledge of the inner workings of distributors and why it happened, I would be interested to hear and learn about it! Link to comment Share on other sites More sharing options...
Jeep Driver Posted October 16, 2017 Share Posted October 16, 2017 Like all things, they wear out, what you describe is what happens when a distributor wears out. Not unusual. Link to comment Share on other sites More sharing options...
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