M R Posted January 17 Share Posted January 17 I recently started having a problem where my comanche won't stay idling and when I try to drive I have no power and tons of backfire. Here's the kicker if I unplug the map Sensor truck runs way better(it's a new sensor) any ideas I'm pretty new to all this Link to comment Share on other sites More sharing options...
cruiser54 Posted January 17 Share Posted January 17 When you unplug the MAP sensor, the ECU adds fuel. How does the vacuum line look going to the MAP? Are your intake manifold bolts loose causing a vacuum leak? Link to comment Share on other sites More sharing options...
cruiser54 Posted January 17 Share Posted January 17 Link to comment Share on other sites More sharing options...
M R Posted January 17 Author Share Posted January 17 1 hour ago, cruiser54 said: When you unplug the MAP sensor, the ECU adds fuel. How does the vacuum line look going to the MAP? Are your intake manifold bolts loose causing a vacuum leak? No leaks in the line and all my manifold bolts are tight Link to comment Share on other sites More sharing options...
schardein Posted January 17 Share Posted January 17 It might help if you posted some info about your truck (year, engine, trans) On my 91 with 4.0, I swapped to a 99+ intake manifold. At the same time, I switched to a 96+ throttle body, which has the MAP sensor mounted directly on the throttle body. There is a small rubber elbow that provides vacuum, so the vacuum line itself is eliminated. I feel like it cleans up the engine compartment and eliminates a potential vacuum leak. When I first did it, the truck developed some strange quirks, one of which was erratic shifting. I don't recall now my diagnosis steps, but I eventually replaced the MAP and all was well. I think I had one from the wrong year. Even though the electrical connector plugged in, it didn't work right. Perhaps you have the wrong sensor? Even if it was new in the box, it could be bad, or it could have had the wrong part put in the box. Link to comment Share on other sites More sharing options...
M R Posted January 17 Author Share Posted January 17 8 minutes ago, schardein said: It might help if you posted some info about your truck (year, engine, trans) On my 91 with 4.0, I swapped to a 99+ intake manifold. At the same time, I switched to a 96+ throttle body, which has the MAP sensor mounted directly on the throttle body. There is a small rubber elbow that provides vacuum, so the vacuum line itself is eliminated. I feel like it cleans up the engine compartment and eliminates a potential vacuum leak. When I first did it, the truck developed some strange quirks, one of which was erratic shifting. I don't recall now my diagnosis steps, but I eventually replaced the MAP and all was well. I think I had one from the wrong year. Even though the electrical connector plugged in, it didn't work right. Perhaps you have the wrong sensor? Even if it was new in the box, it could be bad, or it could have had the wrong part put in the box. It an 87 renix 4.0 and the auto trans. I did some basic maintenance on( replaced spark plugs and injectors). I took the Throttle body off to clean and replace the gasket just in case. I do have an 04 Throttle body but not sure if switching that would even do anything Link to comment Share on other sites More sharing options...
schardein Posted January 17 Share Posted January 17 Did the symptoms start after the spark plugs and injectors replacement? Link to comment Share on other sites More sharing options...
M R Posted January 17 Author Share Posted January 17 15 minutes ago, schardein said: Did the symptoms start after the spark plugs and injectors replacement? Yes but injectors were tested and spark is gapped correctly Link to comment Share on other sites More sharing options...
schardein Posted January 17 Share Posted January 17 Just now, M R said: Yes but injectors were tested and spark is gapped correctly Maybe verify correct spark plug wire routing? I know that doesn't explain why unplugging the MAP helps. Also the injectors have the correct electrical plugs, not mixed up? Link to comment Share on other sites More sharing options...
M R Posted January 17 Author Share Posted January 17 Just now, schardein said: Maybe verify correct spark plug wire routing? I know that doesn't explain why unplugging the MAP helps. Also the injectors have the correct electrical plugs, not mixed up? Yeah I did them one at time to make sure I didn't mix them up. Link to comment Share on other sites More sharing options...
Ωhm Posted January 17 Share Posted January 17 Look for fuel in the vacuum line between the Fuel Pressure Regulator (FPR) and the intake manifold. Checking for leaky FPR. Link to comment Share on other sites More sharing options...
M R Posted January 17 Author Share Posted January 17 3 minutes ago, Ωhm said: Look for fuel in the vacuum line between the Fuel Pressure Regulator (FPR) and the intake manifold. Checking for leaky FPR. That line is good. I'm searching the other line just incase and not finding any leaks Link to comment Share on other sites More sharing options...
cruiser54 Posted January 17 Share Posted January 17 Tested, but are they the correct flow rate? Which injectors did you get? Link to comment Share on other sites More sharing options...
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