Minuit Posted November 14, 2013 Share Posted November 14, 2013 This may be a first or something, posting a help thread while your truck is MJOTM, but I have a little bit of a problem worrying me. Occasionally (every 5-10 startups) my truck makes some disconcerting noises while the engine is turning over before it catches. It almost sounds like detonation or a backfire to my inexperienced and quite stupid ear, but I want a second opinion. Normally it starts and runs fine with plenty of power and no other problems. It's been doing this for quite a while and doesn't seem like it's getting worse. It also sometimes sounds like the starter is bogging down, without the 'bang' noise accompanying it. Sometimes it does it several times in a row, and it won't start up until I give it some throttle (TPS?) Video of the noise: Any help will be greatly appreciated. I'm trying to fix some of the last problems it has and this is the worst of them. :thumbsup: Link to comment Share on other sites More sharing options...
Kkilmer87 Posted November 15, 2013 Share Posted November 15, 2013 maybe cps! or your starter could be getting ready to eat it..... good luck fixing it man trying to diagnose mine sometimes its impossible lol Link to comment Share on other sites More sharing options...
KSjeepguy88 Posted November 16, 2013 Share Posted November 16, 2013 If the CPS was bad it would not start at all! It would not send a signal to the ECM telling where the crank is at in its rotation, check all your vacuum lines and maybe your idle air control valve Link to comment Share on other sites More sharing options...
Eagle Posted November 16, 2013 Share Posted November 16, 2013 If the CPS was bad it would not start at all! I can attest from bitter experience that the above statement is nor correct. A failing CPS can (and often does) send a weak and erratic signal, resulting in a number of odd behaviors. Weird starting is one of them. Link to comment Share on other sites More sharing options...
carnuck Posted November 20, 2013 Share Posted November 20, 2013 Is the starter coming loose? (I mean the through bolts holding the body together) Link to comment Share on other sites More sharing options...
48MJ Posted November 20, 2013 Share Posted November 20, 2013 I second what Eagle said. My MJ would start with a bad cps and it was new (the cps). Went through and was checking everything else because it started but would not throttle up ( was told it would not start with a bad cps). Finally checked the cps (checked bad) and bought one from Napa, checked it and it showed good and installed and it fired and ran perfect. Will never buy a cps any where else again and will check them before installing. Bought the bad one from auto zone. Learned my lesson the az one was made in taiwan and the Napa one was made in Mexico, could be because they still drive old American cars down there? Otherwise MJ's rule I own a few lifted and stock, 2 and 4 wheel drive. Link to comment Share on other sites More sharing options...
Minuit Posted June 17, 2014 Author Share Posted June 17, 2014 This is a very very very VERY old thread but I fixed this a couple of months ago and forgot to update. Turned out the distributor was not indexed correctly. It has not done this since re-indexing it per the FSM. The 4.0 is a computer-timed motor folks, don't mess with the dizzy unless you have to. Link to comment Share on other sites More sharing options...
cruiser54 Posted June 17, 2014 Share Posted June 17, 2014 This is a very very very VERY old thread but I fixed this a couple of months ago and forgot to update. Turned out the distributor was not indexed correctly. It has not done this since re-indexing it per the FSM. The 4.0 is a computer-timed motor folks, don't mess with the dizzy unless you have to. And MANY of the Renix 4.0s had improperly indexed distributors. Even had a TSB on it. I just index them as a matter of course now. Click on my link and see post 13 for instructions and photos. Link to comment Share on other sites More sharing options...
91Pioneer Posted June 18, 2014 Share Posted June 18, 2014 As an aside, I've not indexed my distributor, I have no symptoms as far as I know. cruiser, what are the common symptoms of that? Link to comment Share on other sites More sharing options...
cruiser54 Posted June 18, 2014 Share Posted June 18, 2014 As an aside, I've not indexed my distributor, I have no symptoms as far as I know. cruiser, what are the common symptoms of that? Just do it. Bog, hesitation, jerking at highway speeds......... Link to comment Share on other sites More sharing options...
88whitemanche Posted June 18, 2014 Share Posted June 18, 2014 As an aside, I've not indexed my distributor, I have no symptoms as far as I know. cruiser, what are the common symptoms of that? Just do it. Bog, hesitation, jerking at highway speeds......... Does this also involve the 2.5s also cruiser? ...I'm having a similar issue? I have already done all your tips and added grounds.... Link to comment Share on other sites More sharing options...
cruiser54 Posted June 18, 2014 Share Posted June 18, 2014 As an aside, I've not indexed my distributor, I have no symptoms as far as I know. cruiser, what are the common symptoms of that?Just do it. Bog, hesitation, jerking at highway speeds......... Does this also involve the 2.5s also cruiser? ...I'm having a similar issue? I have already done all your tips and added grounds.... Not as far as I know. Would be interesting to check though, huh? Link to comment Share on other sites More sharing options...
BryceOJ Posted June 20, 2014 Share Posted June 20, 2014 I don't think you can index the 2.5 distributor? Link to comment Share on other sites More sharing options...
cruiser54 Posted June 20, 2014 Share Posted June 20, 2014 I don't think you can index the 2.5 distributor? Why not? Link to comment Share on other sites More sharing options...
BryceOJ Posted June 20, 2014 Share Posted June 20, 2014 Why not? actually I'm wrong, thought that indexing was meant by moving/rotating the distributor housing in order to adjust spark timing like older conventional distributors. when setting a distributor for a 2.5 i believe its similar where the oil pump gear is slightly past 3 o clock, and so then the rotor should be at 6 oclock i think. Link to comment Share on other sites More sharing options...
cruiser54 Posted June 21, 2014 Share Posted June 21, 2014 Why not? actually I'm wrong, thought that indexing was meant by moving/rotating the distributor housing in order to adjust spark timing like older conventional distributors. when setting a distributor for a 2.5 i believe its similar where the oil pump gear is slightly past 3 o clock, and so then the rotor should be at 6 oclock i think. More than likely. But, why couldn't the distributor be mis-indexed on a 4 cylinder just like the six cylinders were from the factory? Link to comment Share on other sites More sharing options...
BryceOJ Posted June 21, 2014 Share Posted June 21, 2014 More than likely. But, why couldn't the distributor be mis-indexed on a 4 cylinder just like the six cylinders were from the factory? I don't know, I guess that it could happen. With less cylinders would a 4 cylinder be able to run even if the distributor is mis-indexed by one gear on the shaft? I'm no mechanic nor good with cars or my 2.5. When I was trying to get mine running I took the distributor out and for got to mark it before I pulled it out. It took me several times to set it to get it correct. All the times that i set it incorrectly It never was able to run Link to comment Share on other sites More sharing options...
cruiser54 Posted June 21, 2014 Share Posted June 21, 2014 When you index the distributor, you're not going for a whole tooth, just somewhere in between. Link to comment Share on other sites More sharing options...
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