Spitting / Sputtering / Backfiring

[ftpiercecracker1]

Here we go again :shake: . . .

 

Truck was running excellent as recently as a few weeks ago, but last week it started this spitting, sputtering, and what not.

 

It has been getting worse each day I drive it, so I am parking it as of today (5/26/14) 

 

 

 

Symptoms:

 

Just cruising down the road (60mph) it will begin to stumble, spit and sputter for no apparent reason. If I try to accelerate through, it will stumble worse and quietly backfire. In a 20 mile trip it may do it 5 - 8 times, otherwise it runs quite smooth.

 

Every once in a while it will run rough at idle as well, not stall, just miss and stumble and generally run like crap. It still starts and revs fine. 

 

There is also a noticeable loss in power.

 

When its cold, if I am not very gentle with the throttle and clutch it will stall out. Even when its good a warm if I get on it, it has a noticeable hesitation, be sluggish until it get higher in the rpms and back fire between shifts.

 

 

 

 

 

Here is what I have proactively checked:

 

Fuel pressure - perfect 31-32psi while running w/ vacuum, 40psi without, and jumps up to 35ish with the slightest blip of the throttle.

 

TPS - I originally thought it would be this, and I am still trying to get it dialed in perfectly, but from what I have seen so far it is not the problem. Yes Cruiser I am following your instructions.

 

Catalytic Converter - Pulled the exhaust off and checked it just a few hrs ago and much to my surprise found it to be completely and utterly hollow

 

Spark plugs - Slightly out of spec (.039) but very good color. I pulled the forward most, middle, and rear most.

 

TB - Thoroughly cleaned as little as a month ago

 

 

 

Plug wires are HD 8mm, I will check rotor and button.

 

Crank sensor, CTS, and O2 sensor are all within 1.5 years old

 

Fuel injectors are 4 hole orange tops out of a straight six ford, have zero leaks and have been in place well over 8,000 miles

 

 

 

Thanks for the help gents,

 

FPC.

 

 

EDIT: I have taken it in deep water recently (week ago, briefly over the hood) and nearly ran it out of gas on two occasions (also a week or so ago)

Edited May 26, 2014 by ftpiercecracker1

[Dillithium]

It kind of sounds like a fuel problem, even though you say it provides perfect pressure. How's the ballast resistor looking? Did you check the CPS for AC voltage?

Is the fuel pump any louder than usual?

[relyt120]

does it do it at idle? I had a similar issue a while back and it wouldn't do it at idle, ended up being the fpr despite it checking out good, something inside it would screw up with a bump and you can't really tell because you have to be under the hood to check the pressure. I have a spare if you want to swap it to see if it helps.

[ftpiercecracker1]

It kind of sounds like a fuel problem, even though you say it provides perfect pressure. How's the ballast resistor looking? Did you check the CPS for AC voltage?

Is the fuel pump any louder than usual?

 

Ballast resistor is in good shape, replaced it not to long ago. I have yet to check the CPS, but it is newer and i have done the 'upgrades' to it as outlined by Cruiser, plus i have zero problems starting. Fuel pump is as quiet as ever.

 

 

does it do it at idle? I had a similar issue a while back and it wouldn't do it at idle, ended up being the fpr despite it checking out good, something inside it would screw up with a bump and you can't really tell because you have to be under the hood to check the pressure. I have a spare if you want to swap it to see if it helps.

 

Every once in a while it will spit and sputter at a stop light, but the majority of the time it occurs while cruising with limited throttle application. I am pretty sure the FPR is not the issue, besides I have the newer fuel rail and intake manifold, so i don't know if yours would work if i even wanted to swap it out.

 

This is the style fuel rail i have now. Sorry for the large pic, not mine.

 

[Dillithium]

Does it only happen when in gear, or in neutral as well?

 

Manifold bolts are all tight?

 

How is the MAP sensor?

 

O2 sensor all check out fine?

 

Since it's intermittent, It has to be sensor related, but it might be worth checking the timing. 

[relyt120]

after I posted I thought yours might be different

 

It kind of sounds like a fuel problem, even though you say it provides perfect pressure. How's the ballast resistor looking? Did you check the CPS for AC voltage?

Is the fuel pump any louder than usual?

 

Ballast resistor is in good shape, replaced it not to long ago. I have yet to check the CPS, but it is newer and i have done the 'upgrades' to it as outlined by Cruiser, plus i have zero problems starting. Fuel pump is as quiet as ever.

 

 

does it do it at idle? I had a similar issue a while back and it wouldn't do it at idle, ended up being the fpr despite it checking out good, something inside it would screw up with a bump and you can't really tell because you have to be under the hood to check the pressure. I have a spare if you want to swap it to see if it helps.

 

Every once in a while it will spit and sputter at a stop light, but the majority of the time it occurs while cruising with limited throttle application. I am pretty sure the FPR is not the issue, besides I have the newer fuel rail and intake manifold, so i don't know if yours would work if i even wanted to swap it out.

 

This is the style fuel rail i have now. Sorry for the large pic, not mine.

 

 

[ftpiercecracker1]

Does it only happen when in gear, or in neutral as well?

 

Manifold bolts are all tight?

 

How is the MAP sensor?

 

O2 sensor all check out fine?

 

Since it's intermittent, It has to be sensor related, but it might be worth checking the timing. 

 

 

Had to think about that for a second, but since i shift into neutral at stop lights i would say yes, yes it does do it in neutral as well. It does not matter what gear its in (5spd)

 

Manifold bolts are tight indeed, if they were loose it would cause a high idle or so i have been told/read. :hmm:

 

MAP sensor is original AFAIK, any way to check it?

 

O2 sensor is newer and appears to be in good shape, but i have no idea how to check/test it either. 

 

 

i am going to check the distributor index, cap, and rotor today.

 

keeping :crossfingers:

[ftpiercecracker1]

Think i found the problem brahs, pics soon.

[Dillithium]

MAP sensor testing: http://troubleshootmyvehicle.com/jeep/4.0L/how-to-test-the-map-sensor-1

 

The 02 sensor you test by checking the resistance in the unit itself, by measuring ohms between the two wires. I'm not sure how many ohms it should be at, though. I believe between 6 and 8 ohms is a good reading.

 

Please let us know what it is, I'm very curious. 

[ftpiercecracker1]

Large amounts of carbon build up on the dizzy cap contact points, its the higher quality cap with brass contacts instead of aluminum. Do they make caps with copper contacts? I think that would be even better.

 

ALL of the points looked like this, so i took my dremel and ground them down until shiny again. Going for a drive and shall report back.

 

 

 

 

Rotor button didnt look bad, but i still took it out and filed it down a little.

 

 

 

 

 

 

 

And since everybody loves pics, here is a shot of one of my spark plugs, right out of the engine, uncleaned. The gap is a little out, approx .038       The rest of the plugs all look about the same, pretty good color wouldnt ya say?

 

[Strokermjcomanche]

If that's the problem I would definetely replace atleast the cap and rotor, if not also the plugs and wires . I assume you cleaned them for diagnostic purposes ?

[ftpiercecracker1]

If that's the problem I would definetely replace atleast the cap and rotor, if not also the plugs and wires . I assume you cleaned them for diagnostic purposes ?

 

 

I havent gotten to drive it yet because i lost a vital part of my TB, but i will have it back together in the next day or so. Yes, i thoroughly cleaned both the dizzy cap contacts and the rotor button, but i think i will hold off on the plugs for a little while longer. The wires are newer HD 7mm, so unless i discover a massive problem with them between now and then i won't be replacing them, at least for now. 

[ftpiercecracker1]

Finally got around to putting the truck back together, boy how time gets the best of me. Unfortunately i don't think what i did helped, if anything it might be worse. I havent actually driven it yet, but just listening to her run i can tell somethings off. Under hard acceleration she sputters off the bottom and backfires like a cannon. If you raise the rpms slowly she is golden, but if you try and goose her she backfires pretty bad.

 

As of right now I have cleaned the terminals inside the distributor cap, the contact point of the rotor button, and reset my tps to perfection.       Input: 4.90v      Output: .83v      Ground: 0.7 ohms

 

 

Cat is completely hollow, so my exhaust is not the issue.

 

Fuel pressure is perfect, tested with gauge, 32 @ idle w/ vacuum, 39 without, and jumps up several psi according to throttle input. 

 

FYI distributor cap, plugs, and wires are all relatively new (about a year old) and of a higher quality.

 

 

 

The problem i am having just came out of the blue one day and progressively became worse, this is after the truck had been running flawlessly for several months prior.

 

 

Symptoms:

 

Slightly rough idle

Hesitation under moderate to hard acceleration

VERY loud backfire and mild bogging/hesitation under heavy acceleration

Intermittent stuttering and missing while at cruising speeds (60+ mph)

 

 

 

FPC,

[Dillithium]

I'm stumped, someone elss with a little more experience needs to chime in because right now all I can do is spitball.

 

But to be sure, have you verified your timing?

[ftpiercecracker1]

Well, i just got back from a short test drive and all seems well  :hmm:   I put the hammer down several times without any problem, hesitation, backfire, or otherwise. The only thing left to do is go for a cruise to town (20mi) and see if the stutter/miss at cruise is gone as well.

 

keeping my  :crossfingers:

 

 

FPC

[88whitemanche]

Did you have any more luck figuring this out.

[benjy_26]

I'm curious too.

[oldseddie]

Have you checked the distributor indexing. I threw parts at and pulled my hair out trying to fix my 87 chief. Follow cruiser54's instructions. I can't believe how much better my mj runs with the injectors timed properly.

[yxmj]

Here we go again :shake: . . .

 

Truck was running excellent as recently as a few weeks ago, but last week it started this spitting, sputtering, and what not.

 

It has been getting worse each day I drive it, so I am parking it as of today (5/26/14) 

 

 

 

Symptoms:

 

Just cruising down the road (60mph) it will begin to stumble, spit and sputter for no apparent reason. If I try to accelerate through, it will stumble worse and quietly backfire. In a 20 mile trip it may do it 5 - 8 times, otherwise it runs quite smooth.

 

Every once in a while it will run rough at idle as well, not stall, just miss and stumble and generally run like crap. It still starts and revs fine. 

 

There is also a noticeable loss in power.

 

When its cold, if I am not very gentle with the throttle and clutch it will stall out. Even when its good a warm if I get on it, it has a noticeable hesitation, be sluggish until it get higher in the rpms and back fire between shifts.

 

 

 

 

 

Here is what I have proactively checked:

 

Fuel pressure - perfect 31-32psi while running w/ vacuum, 40psi without, and jumps up to 35ish with the slightest blip of the throttle.

 

TPS - I originally thought it would be this, and I am still trying to get it dialed in perfectly, but from what I have seen so far it is not the problem. Yes Cruiser I am following your instructions.

 

Catalytic Converter - Pulled the exhaust off and checked it just a few hrs ago and much to my surprise found it to be completely and utterly hollow

 

Spark plugs - Slightly out of spec (.039) but very good color. I pulled the forward most, middle, and rear most.

 

TB - Thoroughly cleaned as little as a month ago

 

 

 

Plug wires are HD 8mm, I will check rotor and button.

 

Crank sensor, CTS, and O2 sensor are all within 1.5 years old

 

Fuel injectors are 4 hole orange tops out of a straight six ford, have zero leaks and have been in place well over 8,000 miles

 

 

 

Thanks for the help gents,

 

FPC.

 

 

EDIT: I have taken it in deep water recently (week ago, briefly over the hood) and nearly ran it out of gas on two occasions (also a week or so ago)

 

Maybe it was just water in the fuel.....the reason it is running ok now is that it has finally worked its way out......Up hear we run Methyl Hydrate (google it) in the winter to control the water build up caused by condensation when it is really cold.....it should be available at a truck stop or truckers supply....they use it to clear the moister out of the air break lines.

 

Most gas stations around here have 150 ml bottles readily available to add to your tank. Try adding a bit….it there is water in there it will solve it.  :thumbsup:   . :MJ 1: . 

 

[ftpiercecracker1]

Well, TBH I still havent had the chance to take the truck on more than a 5 min drive, but the few times i have gotten to drive it hasnt had any problems to speak of, spitting/sputtering/backfiring or otherwise. One thing i have been wondering about is, why did the dizzy contacts get so corroded in such a short period of time? The coil, plugs, wires, cap and button are all newer and of higher quality than just bottom dollar, whats-the-cheapest-you-got parts.

 

 

 

 

On a side note, i have found a new love for totally WOT acceleration. I don't know if its because of my setup or what, but MAN and it sound freaking awesome when i mat in second gear. Really deep throaty sound as the engine gains rpm.  :drool:

[cruiser54]

Have you checked the distributor indexing. I threw parts at and pulled my hair out trying to fix my 87 chief. Follow cruiser54's instructions. I can't believe how much better my mj runs with the injectors timed properly.

Often overlooked. 

 

Not only does it affect the injector timing, but since the ECU tells the ICM when to fire, if the rotor is far from the dizzy terminal rather than where it's supposed to be, the spark is having to jump a rather wide gap.

 

Think that could lead to excessive build-up on nice new parts like cap and rotor?

 

Hmmmmmmm.

[ftpiercecracker1]

Not recently, but I have indexed the distributor at one time or another, but that is not to say it couldnt stand to be checked and redone again just to be sure. The next time i am out there i will look into it.

[cruiser54]

Not recently, but I have indexed the distributor at one time or another, but that is not to say it couldnt stand to be checked and redone again just to be sure. The next time i am out there i will look into it.

Sure couldn't hurt.