oldrusty Posted December 15, 2008 Share Posted December 15, 2008 Ok I know troubleshooting like this is tough but I'm gonna throw this out there hoping someone else has had the same problem. My 89 has developed a case of the hiccups. Truck starts right up and idles fine. Around town it seems to run great but when I get it out on the highway it starts acting up. When I'm pulling a hill in 5th gear the engine will start to "hiccup". It feels like it shuts off for a split second then comes right back. If I down shift it will run a little rough 4 a second or two untill the rpms come back up then it smooths out and runs fine. So here's the list of whats been done so far ; a complete tune up ( new plugs wires cap and rotor), New air and fuel filters, New cps, Cat has been hollowed out, And new IAC solenoid along with a thorough throttle body cleaning........So.....has anyone had a problem like this with their mj. I'm looking for any and all advice. Sensors for the renix seem to be awfully expensive and I hate to buy ones I don't need. Link to comment Share on other sites More sharing options...
oldrusty Posted December 15, 2008 Author Share Posted December 15, 2008 Ok I know troubleshooting like this is tough but I'm gonna throw this out there hoping someone else has had the same problem. My 89 has developed a case of the hiccups. Truck starts right up and idles fine. Around town it seems to run great but when I get it out on the highway it starts acting up. When I'm pulling a hill in 5th gear the engine will start to "hiccup". It feels like it shuts off for a split second then comes right back. If I down shift it will run a little rough 4 a second or two untill the rpms come back up then it smooths out and runs fine. So here's the list of whats been done so far ; a complete tune up ( new plugs wires cap and rotor), New air and fuel filters, New cps, Cat has been hollowed out, And new IAC solenoid along with a thorough throttle body cleaning........So.....has anyone had a problem like this with their mj. I'm looking for any and all advice. Sensors for the renix seem to be awfully expensive and I hate to buy ones I don't need. Link to comment Share on other sites More sharing options...
HOrnbrod Posted December 15, 2008 Share Posted December 15, 2008 Try checking the fuel pressure readings at the rail with the vacuum line hooked up to the regulator and w/o the vacuum. I had an XJ that stumbled under load; turned out to be a bad f/p regulator. Link to comment Share on other sites More sharing options...
HOrnbrod Posted December 15, 2008 Share Posted December 15, 2008 Try checking the fuel pressure readings at the rail with the vacuum line hooked up to the regulator and w/o the vacuum. I had an XJ that stumbled under load; turned out to be a bad f/p regulator. Link to comment Share on other sites More sharing options...
Eagle Posted December 15, 2008 Share Posted December 15, 2008 Water in the gas? Link to comment Share on other sites More sharing options...
Eagle Posted December 15, 2008 Share Posted December 15, 2008 Water in the gas? Link to comment Share on other sites More sharing options...
oldrusty Posted December 15, 2008 Author Share Posted December 15, 2008 Ive been thinking it might be the fuel pump. It doesnt seem to be very loud even with the ballast resistor bypassed. Guess its about time to get myself a fuel pressure guage. Anybody know what the fuel pressure shoul read? Link to comment Share on other sites More sharing options...
oldrusty Posted December 15, 2008 Author Share Posted December 15, 2008 Ive been thinking it might be the fuel pump. It doesnt seem to be very loud even with the ballast resistor bypassed. Guess its about time to get myself a fuel pressure guage. Anybody know what the fuel pressure shoul read? Link to comment Share on other sites More sharing options...
Pete M Posted December 15, 2008 Share Posted December 15, 2008 off the top of my head, I think it's around 30 psi. Link to comment Share on other sites More sharing options...
Pete M Posted December 15, 2008 Share Posted December 15, 2008 off the top of my head, I think it's around 30 psi. Link to comment Share on other sites More sharing options...
BWMJ Posted December 15, 2008 Share Posted December 15, 2008 My truck does something similar. It starts and runs fine, but once in a while it will start to stumble just like described here. It doesn't always do it. It will last anywhere from a few seconds to 5 minutes, but always clears itself. Link to comment Share on other sites More sharing options...
BWMJ Posted December 15, 2008 Share Posted December 15, 2008 My truck does something similar. It starts and runs fine, but once in a while it will start to stumble just like described here. It doesn't always do it. It will last anywhere from a few seconds to 5 minutes, but always clears itself. Link to comment Share on other sites More sharing options...
oldrusty Posted December 16, 2008 Author Share Posted December 16, 2008 mine also doesnt do this all the time but it drives me crazy that it does it. Going to pick up a fuel presssure guage hopefully tomorrow and go from there. Link to comment Share on other sites More sharing options...
Throttle_Jockey Posted December 16, 2008 Share Posted December 16, 2008 My truck does something similar. It starts and runs fine, but once in a while it will start to stumble just like described here. It doesn't always do it. It will last anywhere from a few seconds to 5 minutes, but always clears itself. I had this problem with mine and the first thing I thought was fuel also but after alot of trouble shooting and some knowledge from a buddy it turned out to be throttle positioning sensor. Link to comment Share on other sites More sharing options...
oldrusty Posted December 16, 2008 Author Share Posted December 16, 2008 Funny you should mention that. I have tried to check and adjust my tps twice now according to the method described in the fsm and its WAY off. Ive been hesitant to replace it because of the cost but I may just have to suck it up and order one. Link to comment Share on other sites More sharing options...
Throttle_Jockey Posted December 16, 2008 Share Posted December 16, 2008 This is gonna make me sound like a tight wad but I have a buddy that's parent's own a JY and since I went through there they do not have 4.0 left in there with a IAC or a TPS,yeah granted its not the right way to fix things but opposed to parts store prices,there's nothing that beats free! Link to comment Share on other sites More sharing options...
jeeptruck86 Posted December 17, 2008 Share Posted December 17, 2008 My 86 2.5 TBI does pretty much the same thing. I always figured it was either the TPS or the big injector. Then I figured out that if I take a sharp turn it'll stumble. So I'm faced with dropping the tank to have a look at the pump/pickup. I may wait and see what turns up with yours... good luck. Link to comment Share on other sites More sharing options...
oldrusty Posted December 17, 2008 Author Share Posted December 17, 2008 I ordered a new throttle position center today. It should be here tomorrow morning so well see what happens. Link to comment Share on other sites More sharing options...
oldrusty Posted December 20, 2008 Author Share Posted December 20, 2008 Got my fuel pressure guage yesterday and checked the pressure in the fuel rail. 30 psi with the regulator vaccum line connected. 20 psi with it disconnected. So I guess now its on to the tps hope to swap it out this afternoon after work. Link to comment Share on other sites More sharing options...
junior88mj Posted December 31, 2008 Share Posted December 31, 2008 your fuel psi should be higher when vac line is disconnected about 39 psi Link to comment Share on other sites More sharing options...
BLHTAZ Posted December 31, 2008 Share Posted December 31, 2008 your fuel psi should be higher when vac line is disconnected about 39 psiCorrect. Here is a snip from the FSM... ---------------------------------------------------------------------------- 2) Start vehicle. Pressure should be approximately 31 psi (2.1 kg/cm) with vacuum hose connected to pressure regulator and 39 psi (2.6 kg/cm) with vacuum hose removed from pressure regulator. Link to comment Share on other sites More sharing options...
Ed in North Ga. Posted December 31, 2008 Share Posted December 31, 2008 " Cat has been hollowed out" :doh: check your o2 sensor- quicky test- put in nutrel, rev engine- revs fine? now put in gear and hold brake and rev her...cut out? only falters under load, and downshifting cures it for a few seconds....? man, this brings back some old memories.... I can't find my o2 sensor cheat sheet, but its testable with an ohms meter...."IF" you find your 02 sensor is burnt, get a new cat to go with it. The Jeep mechanic that solved mine problem yearrrsssss ago, said hollowing a cat causes the exhaust gas to pass the o2 sensor too fast and burns it- without the needed backpressure you tend to lose the lower end umph and gain high end- old Renix`s are like that. I hope thats what it be- cause the only other thing that comes to mind is a clogged sock filter in the fuel tank, or a weak pump in the tank. luck to ya! Link to comment Share on other sites More sharing options...
oldrusty Posted January 16, 2009 Author Share Posted January 16, 2009 Well here's an update on my sick renix. I rechecked the fuel preesuer and according to the fsm it was dead on. So I went ahead and ordered a new tps. Pulled the throttle body off and gave it and the iac a good scrubbing( truck had been having some erratic idle issues). I reinstalled the throttle body and adjusted the new tps and..................She runs great again!!!! :banana: :banana: :banana: Thanks for all the help guys. :bowdown: :bowdown: Link to comment Share on other sites More sharing options...
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