Fernando87mj Posted December 8, 2014 Share Posted December 8, 2014 I need your guys's help , my 87 comanche 4.0 5 speed ba105 , has been having a quite a few issues lately and I need help narrowing them down and fixing it , I'm a high school student and I don't have money to be throwing parts at it and need my truck as my dd :/ Anyways my jeep is really hard to start , takes a long to crank and when it starts it runs really poor 100-400 rpm and either it's smooth out sometimes and go to normal idle or it'll die , if it dies it'll restart and will idle . Then when I let it warm up and I go for a drive it's seems like engine has no power at all , it bucks , backfires through the intake and then it'll pick up again and get power back but it's keep repeating those steps , seems like if I push the pedal all the way down to the floor it won't backfire but it still feels weakish :( , if I cycle the key a bunch a times like 10 times it improves the starting and it starts up faster I recently replaced the fuel filter to see if it helped and no diffrence . If you guys can help I would really appreciate it :) Link to comment Share on other sites More sharing options...
Knucklehead97 Posted December 8, 2014 Share Posted December 8, 2014 On the left of the throttle body theres a vacuum line that goes to a sensor on the firewall. This is the MAP sensor and if the line is cracked, loose, melted, clogged, in ANY way. It will make the vehicle do that stuff. Literally like the most important sensor when it comes down to these things running properly. Mine touched my intake manifold heat shield one time while driving and melted shut. Lets just say I've seen more torque come out of a hotwheels car. Link to comment Share on other sites More sharing options...
Fernando87mj Posted December 8, 2014 Author Share Posted December 8, 2014 thanks alot for your advice , but i had already checked it and it seemed good and i even swapped the one from 88 on this one to be sure and it made no diffrence :( Link to comment Share on other sites More sharing options...
mvusse Posted December 8, 2014 Share Posted December 8, 2014 Go to Autozone and get their fuel pressure test kit from the loan-a-tool program. It sounds more like a timing problem, but timing is not adjustable unless the sprockets are shot and the chain jumped a tooth or more. Before tearing into the engine to check/replace timing chain, it is easier to check (and rule out) fuel pressure regulator and fuel pump first. Link to comment Share on other sites More sharing options...
Brickmiata Posted December 8, 2014 Share Posted December 8, 2014 Sounds like the starting maybe be a fuel pressure issue. there is a one way valve somewhere that stops the fuel lines from draining back towards the tank while the vehicle isn't running. could also be a weak pump. the poor running could really be anything. vaccum leaks, electrical or spark problems, or fueling. I would start by checking for vac leaks, checking fuel pressure and cleaning grounds and contacts in the engine bay. At least that will rule out the easy things and maybe give you some leads as to what to check next. May also be worth checking the spark plugs. I recently had a poor running issue that I could not track down. Finally went to change the plugs after a few weeks and found the cylinder 1 plug arm to be almost touching the electrode. further inspection revealed nothing wrong in the cylinder (maybe some detonation or foreign object) other than that and new plugs solved the problem. Good luck. Link to comment Share on other sites More sharing options...
cruiser54 Posted December 8, 2014 Share Posted December 8, 2014 Click on the link below and do Tips 1 through 5. Link to comment Share on other sites More sharing options...
Fernando87mj Posted December 8, 2014 Author Share Posted December 8, 2014 It seems like a fuel issue , I hooked up a fuel pressure gauge , and while cranking it takes a while for the needle to finally move up and when it does the Truck starts and the fuel pressure is at 24 psi , would that cause all of these issues ?also when I turn the truck off the needle goes down to zero again . Link to comment Share on other sites More sharing options...
Fernando87mj Posted December 8, 2014 Author Share Posted December 8, 2014 And thanks cruiser I'll do those too Link to comment Share on other sites More sharing options...
Knucklehead97 Posted December 8, 2014 Share Posted December 8, 2014 Fuel pressure is supposed to be at 31 with the vacuum line connected and 39 without. Currently working on a fuel pressure problem myself. Link to comment Share on other sites More sharing options...
cruiser54 Posted December 8, 2014 Share Posted December 8, 2014 It seems like a fuel issue , I hooked up a fuel pressure gauge , and while cranking it takes a while for the needle to finally move up and when it does the Truck starts and the fuel pressure is at 24 psi , would that cause all of these issues ?also when I turn the truck off the needle goes down to zero again . Low fuel pressure causes all sorts of issues. Yes, do yourself a favor and do those Tips also. Link to comment Share on other sites More sharing options...
Fernando87mj Posted December 8, 2014 Author Share Posted December 8, 2014 I will and what brand pump do you recommend ? Link to comment Share on other sites More sharing options...
cruiser54 Posted December 8, 2014 Share Posted December 8, 2014 I will and what brand pump do you recommend ? NOT Airtex~~ Bosch is very good. Keep in mind your pump may be fine but the hose from it to the fuel gauge module may be damaged by these new fangled fuels and that's the whole issue. Link to comment Share on other sites More sharing options...
Fernando87mj Posted December 9, 2014 Author Share Posted December 9, 2014 Actually you have a point about the hose , about 3 years ago the jeep had been sitting for a while and when my dad finally went and tried to start it it wouldn't start and he thought it was the fuel pump and when he finally got the fuel pump assembly out it turns out the hose had been dry rotted and iirc it was bent or something and wouldn't let gas flow or something like that , he ended up replacing the hose and that fixed the no start issue and the truck ran great . Link to comment Share on other sites More sharing options...
cruiser54 Posted December 9, 2014 Share Posted December 9, 2014 You thinking history is repeating itself? Link to comment Share on other sites More sharing options...
Fernando87mj Posted December 9, 2014 Author Share Posted December 9, 2014 maybe , does the tank have to be completly empty to be dropped ? i have half a tank right now :doh: anyways thanks for all your help cruiser :thumbsup: Link to comment Share on other sites More sharing options...
cruiser54 Posted December 9, 2014 Share Posted December 9, 2014 Half is just fine. Link to comment Share on other sites More sharing options...
gogmorgo Posted December 9, 2014 Share Posted December 9, 2014 I dropped my tank when it was half full... then when I put it back I gave up after a half hour or so of swearing and drained it. Mind you, I had no help, it was around midnight on Christmas Day, and I was lying on my back on a concrete floor at -5°F. I just didn't have enough hands to hold the tank in the air and keep it level AND put the straps on with that much gas sloshing around. But with a half tank of gas, you should be fine to pull the pump/sender assembly. It does sit in the side of the tank, but it's the top half. And with a helper I don't see how you shouldn't be able to lift the tank back in place. Link to comment Share on other sites More sharing options...
mvusse Posted December 12, 2014 Share Posted December 12, 2014 Disconnect the fuel pressure hose, aim it at a bucket and short the fuel pump terminals on the diagnostic connectors under the hood. As long as it is pumping something it will pump out the tank for you. Link to comment Share on other sites More sharing options...
gogmorgo Posted December 12, 2014 Share Posted December 12, 2014 That's what I did, but I pulled the fuel pump relay and jumped the load terminals. Link to comment Share on other sites More sharing options...
fupduk2 Posted December 30, 2014 Share Posted December 30, 2014 Does it have an evaporation canister? When it gets saturated it can cause loss of power and lurching. Link to comment Share on other sites More sharing options...
Fernando87mj Posted December 31, 2014 Author Share Posted December 31, 2014 Yes , but I recently pulled the pump and the hose was split and was rotted so that's what caused the problem, decided to replace the fuel pump with a new Napa replacement while I was at it as "preventive maintenance " and all her powers back and she's running really good :) Link to comment Share on other sites More sharing options...
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