ComancheCrusher9800 Posted July 21, 2017 Share Posted July 21, 2017 My Comanche is a 2.5l. It surges and bucks at low speeds. To me it seems to be the ignition. But I don't know. I'm including a link to the video of it running at the bottom. But sometimes it will start up just fine and run good for a mile or two and then start acting up. Other times it will do it right away. Cold or hot. Sometimes I can turn it off and then back on and it fixes itself for a hundred yards and starts again. It'll make a quick tick (not like an engine knock) sound while driving and it's like a misfire to me. It bucks at low speaks and sometimes at stop signs it will shut off when I take off like in the video ( and I do know how to drive a standard so that's not it) I replaced the tps sometime ago and it fixed it for a day and went right back. I replaced the cps and it fixed it for a day and went right back. I stop turn it off and wait a minute and turn it back on and it fixes for a little while. I'm complete stumped on this. I have a new rotor, cap, wires and plugs also. The coil is newer. I have done some of c101 delete and it did it before and after. Refreshed grounds. Refreshed conections. I don't know what it could be. Sent from my SM-G900V using Tapatalk Link to comment Share on other sites More sharing options...
HOrnbrod Posted July 21, 2017 Share Posted July 21, 2017 Rent a test gauge from Autozone or similar and check the fuel pressure w. vacuum and w/o vacuum while running. Link to comment Share on other sites More sharing options...
ComancheCrusher9800 Posted July 21, 2017 Author Share Posted July 21, 2017 Which line is the vacuum one Sent from my SM-G900V using Tapatalk Link to comment Share on other sites More sharing options...
HOrnbrod Posted July 21, 2017 Share Posted July 21, 2017 Which line is the vacuum one Sent from my SM-G900V using Tapatalk The small black tube with the elbow on it that connects to the fuel pressure regulator on the fuel rail, below left side in the pic. Link to comment Share on other sites More sharing options...
ComancheCrusher9800 Posted July 21, 2017 Author Share Posted July 21, 2017 I have seriously never seen that before in my life. I don't have one Sent from my SM-G900V using Tapatalk Link to comment Share on other sites More sharing options...
HOrnbrod Posted July 21, 2017 Share Posted July 21, 2017 Crap - just noticed you have an 87 2.5. Probably a TBI (Throttle Body Injection) model? Or is it carbed? Someone else will have to chime in on how to check the fuel pressure on those........ Link to comment Share on other sites More sharing options...
ComancheCrusher9800 Posted July 22, 2017 Author Share Posted July 22, 2017 It's throttle body injection Sent from my SM-G900V using Tapatalk Link to comment Share on other sites More sharing options...
cruiser54 Posted July 22, 2017 Share Posted July 22, 2017 Link to comment Share on other sites More sharing options...
cruiser54 Posted July 22, 2017 Share Posted July 22, 2017 Along with inspecting those hoses, verify that your intake manifold bolts are snug. Link to comment Share on other sites More sharing options...
metrictonner Posted July 26, 2017 Share Posted July 26, 2017 Although I know absolutely nothing about the 2.5, TBI or otherwise, it sounds like you have distributor problems to me. Yank the cap and rotor and pull and push on the drive shaft to check end play. The 2.5 distributor has a shim in it to keep things tight that may have gone away over the years causing a lot of play that can cause a small amount of surging. I would also advise retiming of the distributor by yanking the distributor and doing a TDC #1 cylinder, both valves closed replacement of the distributor except for the fact that the 2.5l doesn't work that way. You actually have a TDC sensor that keeps everything timed. Have you checked that recently? I figure since you did a TPS replacement you can do a TDC replacement too. Of course, don't do the replacement first thing. Check the TDC connector for contact cleanness and tightness first. Oh...and...good luck because I know absolutely nothing about the 2.5l, TBI or otherwise. Link to comment Share on other sites More sharing options...
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