why is this happening - long

[jimmy hat]

long explanation and question here, but i am getting toward the end of my rope with this.
i THINK? i am fouling plugs. i put autolite platinum plugs in about 3 months ago. everything was fine until shortly after i switched to TFI w/ msd6a. i was told to re-gap the plugs with the msd so i pulled the plugs and they looked okay (a little black), i cleaned them off and re-gapped. shortly after i started to expereience some hesitation when accelerating. when the rpms get higher the hesitation would stop. addressed some easy fuel delivery problems to no avail. disconnected the msd box...no change. pulled the plugs this weekend thinking maybe i had misgapped one or two...regapped back down to .040 (msd still disconnected), cleaned plugs up in the process, the looked really sooty, i.e. rich. put them in and everything is honky dory...for about 4 days. same hesitation starts again yesterday, continues today etc.

questions:
1. obviously i am running rich but what about changing to tfi would effect how rich i am running.
2. could it just be coincidence. maybe the carb started going south the same time i did the tfi swap? although i am not sure how the carb can just start running rich either (but i am an amatuer)
3. do i need to re-time with the tfi? i noticed a wierd hard starting thing after i put it on.
4. if so, could the timing cause me to run rich-er?
5. i have heard that if your timing is way retarded your engine will run hot, mine runs really cold..again, could timing be part of my problem?
6. if so, i am in denver at about 5000 feet. if i follow the timing rule about 5 deg of advance per 1000 ft of elevation, that woudl put me an additional 25 degrees advanced...thats crazy! any guidline what i should set my timing at?

any help is appreciated. the cold is moving in and i need to get this thing running right for ski season!!! (not to mention i don't have any place to work on it in the winter)

thanks guys

[ October 29, 2003, 03:06 PM: Message edited by: jimmy hat ]

[FSJ Thing]

I highly recommend timing your ignition by ear. Idle the engine and move the ignition around between 6-10 degrees before TDC. Set it where the engine idles the fastest in that range. We are very high in elevation and I don't know much about what TFI you did, but if it has a good O2 sensor, it should be adjusting the fuel mixture itself. I think the running rich problem is in the ECM or O2 sensor. tell us more about your TFI setup and someone here might know more about it... But definitely fix the timing before you blow a hole in a piston or something!

Hope this helps!

Matt

[jimmy hat]

Matt, thank you. but I don't think I have an O2 sensor. I didn't mention mine was a 79 cherokee cause its in my sig file. I don't think I have an ECM either...but i could be wrong.
the tfi ignition is a really common ignition mod where the dizzy cap and rotor is replaced with a ford big cap and rotor and the can coil is replaced by a ford thick film coil. in general a nice swap, worked grat on my 85 waggy. theres a write up on ifsja.org in the tech section.

[Smooshy]

Timing can very easily be part of the problem, if it where mine, I would probably see how far I can advance the timing before the engine runs bad (pinging and flat spots), stock I think you can get around 12 at low altitudes when motor runs rich.

Also probably run it leaner... easy to do by ear, just turn the screw(s) in until the rpms drop then go out maybe half turn (mess with it to see how it runs...) Turning the screws in leans it out. I think on factory 4 barrely the right screw (as your facing) is the slow idle mixture, do that one first.

I test my adjustments by driving jeep down the road and accel at 1/4, half and full throttle to see if it runs correctly under all conditions.

[89grand]

Yeah, he said the TFI(ignition upgrade) not TBI(throttle body injection), there's no O2 sensor. The TFI and MSD should not and probably could not have caused your problems. I've got the TFI and MSD combo and my Grand has never ran better. You should not have to alter the timing either to get it to run right assuming it ran well before the upgrade, the plugs DO need to be re-gapped for maximum performance, mine are gapped at .045. The problems you describe sound like a bad carb, my 66 Dodge Monaco was doing the same thing several years ago as far as fouling plugs and I put on a new Carter AFB that I had for another project and the car ran great and has never fouled plugs again. Take a closer look at the carb, it is probably your problem.

[ October 29, 2003, 03:42 PM: Message edited by: 89grand ]

[Smooshy]

You should not have to alter the timing either to get it to run right assuming it ran well before the upgrade, the plugs DO need to be re-gapped for maximum performance Unless he bumped the dizzy by accident :D

[FSJ Thing]

Oh, when you said TFI I thought you meant throttle body fuel injection. I've seen it abreviated both TBI and TFI, so I wasn't sure if you meant TFI ignition or asperation. Bring down your mixture, since the air is so thin here, it may seem like you're setting it to run lean. Our engines don't have a whole lot of power up here at this altitude, running rich can make a little more power, but causes all the problems you're having and makes passing emissions dang near impossible. So you may notice a slight drop in power, but then you might notice an increase if your running too rich as well. set the idle at 600rpm, then set the timing where it idles the fastest between 6-10 deg BTDC. If it idles faster the farther you move it BTDC, you can keep going forward, but I wouldn't going any father than 12. You'll probably find it idles smoothest and fastest at right around 8 or 9. After you set the timing , bring the idle back to 600 rpm or however low the book says or you feel is right. If your TFI has vacuum advance, disconnect before setting the timing. I'm sorry if you already knew a bunch of this stuff and think I'm explaining this at a lower level than your mechanical experience warrants, I just wanted to make sure I got it all out of my head in the right order. Hope this helps some more!

Matt

[jimmy hat]

Originally posted by Smooshy:
Also probably run it leaner... easy to do by ear, just turn the screw(s) in until the rpms drop then go out maybe half turn (mess with it to see how it runs...) Turning the screws in leans it out. Icorrectly under all conditions.thanks smooshy. not to start another thread here (or to sound ungrateful) but i thought the screws only adjusted the idle mixture? when i open the throttle won't the jets determine how much fuel is added to the mix? just thinking out loud, i am in all sorts of need for help smile.gif

[FSJ Thing]

Wut carb you got? 2150?

[jimmy hat]

Originally posted by Wago Thing:
Wut carb you got? 2150?i think so. i am not 100% certain. i thought i read that the 2100 (very similar) was used up until and including 79...but i have got differnt info from differnt people.

[FSJ Thing]

You've been PMed!

[marcd]

Just speculating here . . .
Since the only thing you changed was the TFI, I wonder if you disconnected a vac line, i.e. the vac advance line (I assume it had vac advance). Or if it's mechanical, maybe that got messed up with the cap change. That's the only thing that I could think that correlates between the two. Maybe a gearhead can chime in and verify whether that would cause your symptoms.

[jode]

2 things

If you are not very carful when re-gapping plugs, you can ruin them. Did you pry against the electrode when re-gapping? If so, I would toss all the plugs and install new (or at least double check that they still function)

Watch out messing with your mixture screws on the carb...if you don't know what you are doing, you can not only spoil any remaining performance you may have, but you can end up burning holes in your pistons or something. (not saying don't adjust mixture - just saying not to do it if you don't know what you are doing). Vacuum guages are useful in mixture screw adjustments.

Carry on :D

[jimmy hat]

there is both vac and mech advance and i have the vac advanced hooked up and working. didn't screw with the mech advance springs in this one. i took the advice to heart though an went through and verified and checked the vac line tonight (not to bad).

i have screwed up plugs in the past, but i went out and got me a decent gapping tool a few months ago...where prying on the electorde isn't necessary. i think new plugs are in order too.
*btw, i mis-wrote, they are not platinum plugs, just standard autolites*
i am pretty comfortable adjusting mixture screws, at least i understand the principle. i have done it many times on the weber carb in my cj, just not too familiar with the carb on the chero. i think i am looking at a rebuild for this carb in the next couple days so i am sure i feel better aboiut adjusting it by then.

thanks for the good thoughts and input guys, keep it coming.

[jode]

If you have the stock 4v carb (Motorcraft 4350) I would think 2X about that rebuild - that particular carb is notorious for warping upon dissasembly (never to be gas-tight again). If it is the MC 4350 - I would have a spare vehicle to drvie in the meantime and a spare few hunert $$ to be ready to buy a new intake manifold and carb if the rebuild fails.

PS - this is experience talking :(

If you can post a pic of the carb, I am 99% sure somebody here can identify it for you. (How you gunna get a rebuild kit for it if'n you don't know what it is?)

[Gargel-orum]

id start first and formost with ditching those plantum plugs for some autolites... when i put platum in mine, i continued to fould them up and thought i had some major problem going on.. then tryed the plane ol $0.59 kind and never had that problem agian.

[andy d]

ive noticed that about 1/2 of the guys who do the tfi upgrade post back with problems. the same with the msd thing. the rich running may be caused by a weak spark. i wouldnt touch the carb. i would look at the tfi stuff and the msd components. if the carb was fine before the tfi, why is it at fault now? when ever i have trouble, i return to the last thing i was working on. i know me :D

[jimmy hat]

Originally posted by jode:
If you have the stock 4v carb (Motorcraft 4350) I would think 2X about that rebuild - that particular carb is notorious for warping upon dissasemblyits definately a 2100 or a 2150, i just haven't looked real close yet. thanks for the advice.

Originally posted by Gargel-orum:
id start first and formost with ditching those plantum plugs for some autolites... when i put platum in minein an earlier post i explained that i was mistaken about the plugs...they are not platinum, just autolites....i had some platinums autolites in my zj and just got it mixed up for some reason.
thanks, i will stay away from platinum in the future (lots of others have said the the same thing to me)

[ October 30, 2003, 08:42 AM: Message edited by: jimmy hat ]

[Smooshy]

Dont forget to give it a good kick :D

[Smooshy]

Oh yeah, to answer your question, yes the jets do take over, mostly, but you can be fowling plugs at low rpms...

[will e]

Yeah, don't mess with the carb yet. I like the idea of trying different plugs. If it doesn't fix your problem you haven't spent much money and you have a spare set of plugs for the next tune up.