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-   -   Still have engine running problems (https://forums.off-road.com/jeep-short-wheelbase/203071-still-have-engine-running-problems.html)

ricochet 01-03-2005 08:23 AM

Still have engine running problems
 
Well for those not familiar with my situation here is a rundown. I used to have a cj-5 with a 304 and a tbi. That always ran like crap. I built a wrangler with a 360 and took my whole ignition, tbi and everything else off my 304 and put it on the new 360. While on the 304, I never could get it to run correctly. Always sputtered under pressure. When I put it in the 360, I totally rebuilt my tbi (injectors, gaskets, pressure regulator, fuel pump) There was a big vaccuum leak comming from the base. Fixed the leak and hooked it up to my laptop. It was throwing a o2 rich code. Replaced my o2 sensor (had put on a heated one that it didn't like so put the factory one on) shortened my map sensor vaccuum hose. Got rid of all error codes and set the timing with a standard light. I had the warm fuzzy feeling that everything has fallen into place and i'd actually be able to drive the jeep around the streets (its run like garbage for years and only drove it on the trails) Well I went wheeling on New Years Day and to my dismay, it still ran like crap. If I was going down a dirt road, 1st and 2nd would be ok, but once shifted into 3rd it would buck and backfire until a certain sweet spot on the throttle then it would be ok unless I moved from the sweet spot then it would act up again. While running everything that i've changed and fixed in the past years with this system through my head, it dawns on me that I am currently running the TR TFI upgrade with a msd 6a box. I've had this box long before the fuel injection. I had problems very similar to this when I initially installed a new quadrajet carb. I had everyone and the brother try and tune the carb, but it would act the same. So What are the chances that this whole time the problem could have been the damn msd box all along???? And since I already have the coil and the rest of the TFI upgrade, how hard would it be to just yank the msd box in place of the hei upgrade? Sorry for the long post but it looks like i'm going to have to put my tire money into this rather then my new 39" iroks which is really bumming me out.

ricochet 01-04-2005 10:05 AM

Re: Still have engine running problems
 
Anyone, Will was nice enough to send me the hei link, but I just want to make sure my reasoning is good before i make anymore changes. I'm tired of wasting money (even though the hei is cheap) Thanks

RRich 01-04-2005 11:36 AM

Re: Still have engine running problems
 
If you think it's fuel, try the "propane trick." It'll tell you right away - do a search. You might spend $10? max if you don't already have a propane torch and a hunk of hose.

If you suspect timing advance, disconnect the vacuum advance line and try it. Cost = 0. It must be PORTED vacuum.

Converting over from the MSD to HEI is just the cost of the module, a hunk of wire, and a couple of spade terminals -- $30?

Symptoms do sound like a defective coil wire though - you tried a different one?

MSD -- make sure the wires from the pick-up coil to the box are NOT running close to the high tension - coil wire, coil, plug wires. The magnetic induction will drive the box crazy! All sorts of problems.

ricochet 01-04-2005 11:42 AM

Re: Still have engine running problems
 
I did the propane trick before and fixed all vaccuum leaks, the vaccuum IS connected to ported vaccuum

I haven't tried a different coil wire

If you are refering to the wires coming from the dizzy, then yes they are run in the same bundle as the rest of the msd wires. I guess the first thing i'll try is to seperate all the wires and replace the wires going to the coil. If that doesn't fix it, then i'll take the msd box out and install the hei module.

Thanks...

RRich 01-04-2005 01:44 PM

Re: Still have engine running problems
 
I wasn't thinking vacuum leak when I suggested the propane trick. A vacuum leak won't cause your symptoms.

Read down farther down on that post to see you how to check running condition - checking to see whether or not it's rich or lean at speed.

Run the propane line into the air intake, bottle and valve in the cab in your hand.
Drive it -- make it stumble or run bad.
Open the propane valve slowly.

If it runs BETTER you were too lean to begin with.
If it gets WORSE it's rich.

All the propane does is add more fuel to what you have already.

Great way to determine fuel vs ignition troubles.

And, it's great way to determine carb jetting and power valve needs. Once you get a feel for it, you can get rid of your $50,000 dyno, and exhaust analyzer.

Possibly the handiest diagnostic tool you can own.

ricochet 01-04-2005 03:44 PM

Re: Still have engine running problems
 
This may be a stupid question, but isn't that what the o2 sensor is for? If it's running lean or rich, it would throw a code causing the idiot light to go off. It has in the past. I'm currently not getting any codes.

RRich 01-04-2005 04:11 PM

Re: Still have engine running problems
 
Maybe, maybe not.

Sometimes the "condition" has to last for quite awhile before a code sets.

Even if it was ignition, a code would set because the O2 level would be too high - misleading you if it was fuel.

Obviously you aren't holding it stumbling, backfiring, popping, running terrible long enough to set a code. As soon as it happens you back off. If you hold it stumbling and popping till a code sets, you may have enough damage to the engine that problem becomes the least of your worries.


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