An even more dumberer question about alternators

[Biernuts]

I searched but could not find a specific answer to this...

I've been restoring an XJ that had been stored outside for 2.5 years.
I finally got it to stay running (many new parts & procedures later)...

So I drive it around my property trying to get the new tank of gas and BG44K through the system. It still runs rough but at least it's running.
But after a couple of minutes of driving around in 1st gear, it'll stumble and miss when I give it gas, especially up a small hill. In fact it'll stall half the time.

Last night, as I was revving via the throttle cable, I noticed the old, cracked, serpentine belt would oscillate like Tony Iommi's E string between the PS pump and idle pully. It was obviously loose and was going to be changed this weekend...instead it decided to break on me....literally (ouch)

Before the belt broke, I checked the headlights to see if they worked. As soon as I turned them on, the engine started to struggle and almost died.

My question is, could the loose, worn serpentine belt affect the alternator enough to cause a weak spark under load thus causing a missfire?

Already done:
Cap/Rotor/plugs/air filter/oil&filter/fuel pump & filter/O2 Sensor, vac hoses, battery, new fuel & BG44K, EGR appears to funtion but I have a new one to put on (need to buy Torx), MAP appears to work...

 

[skierbri10]

Yes a loosse, worn serp belt can affect the alt. Then with slippage it will cause more problems. Put the new one on and tighten properly.

 

[Carzan]

An already loose alternator belt can be further overpowered by a reving engine and the alternator pulley won't significantly speed up and may even slow down from what it was at idle.
That said, with a good fully charged battery, it still shouldn't sputter just because the alternator isn't charging IMO. If the battery is weak, sure, that could make it run funny.
I can't help but think you have a bad connection somewhere...most likely a bad ground. Make sure you have good, heavy cable(s) from the battery negative post to the engine block to the chassis. They (battery neg post/engine/chassis) all need to be WELL grounded together.

 

[Biernuts]

...with a good fully charged battery, it still shouldn't sputter just because the alternator isn't charging IMO. If the battery is weak, sure, that could make it run funny...

This is thew answer I was looking for...The battery is new so my sputtering, misfiring during accellerationissue is probbaly something else I have not found or fixed. Possibly the TPS I am thinking.

I will check all the cables/connex this weekend as well...

Thanks.

 

[Matt S.]

Possibly the TPS I am thinking.
QUOTE]

What year?

why do you say that? There are quite a few sensors that COULD cause what your describing. My personal advice would be to get the known MECHANICAL issues taken care of, THEN work with a specific problem. It is to difficult and to straining (on you) to fight something that may not be there.

Take care of the alternator, belt, cracked vacuum hoses (if renix), air filter, fuel filter, etc.

Matt

 

[Biernuts]

Possibly the TPS I am thinking.
QUOTE]

What year?

why do you say that? There are quite a few sensors that COULD cause what your describing. My personal advice would be to get the known MECHANICAL issues taken care of, THEN work with a specific problem. It is to difficult and to straining (on you) to fight something that may not be there.

Take care of the alternator, belt, cracked vacuum hoses (if renix), air filter, fuel filter, etc.

Matt

Sorry. It's an 89, 4.0 manual trans.
It ran relatively well until it was parked when my father in law died (it was his) 2.5 yrs ago.

I say the TPS because of what I've read on this board. Just another thing to check to find the problem.
The EGR moves on it's own and I can move it so it appears to be functioning.
The MAP kills the engine if I unplug the vac line or power.
I replaced the O2 sensor last weekend.

It sounds like a loose belt won't cause misfiring so I am assming that putting a new belt on will get it running again but only just as bad as before the belt broke. ie;...Idles OK, stalls under load as soon as I drive it around for a few minutes or up a small hill...

Oh yeah, I also replaced the fuel filter & pump, Air filter, Oil/filter, plugs, cap/rotor, battery, checked for vac leaks...

 

[langer1]

Sorry. It's an 89, 4.0 manual trans.
It ran relatively well until it was parked when my father in law died (it was his) 2.5 yrs ago.

I say the TPS because of what I've read on this board. Just another thing to check to find the problem.
The EGR moves on it's own and I can move it so it appears to be functioning.
The MAP kills the engine if I unplug the vac line or power.
I replaced the O2 sensor last weekend.

It sounds like a loose belt won't cause misfiring so I am assming that putting a new belt on will get it running again but only just as bad as before the belt broke. ie;...Idles OK, stalls under load as soon as I drive it around for a few minutes or up a small hill...

Oh yeah, I also replaced the fuel filter & pump, Air filter, Oil/filter, plugs, cap/rotor, battery, checked for vac leaks...

It could if the voltage was low.

 

[Biernuts]

It could if the voltage was low.
--------------------------------------------------------------------
So even with a new battery, if the belts slippin' on the alt, my voltage could be low enough to cause misfire under load. That makes sense...especially since turning the lights on caused the engine to almost die.

Thanks Scrappy...

 

[langer1]

It could if the voltage was low.
--------------------------------------------------------------------
So even with a new battery, if the belts slippin' on the alt, my voltage could be low enough to cause misfire under load. That makes sense...especially since turning the lights on caused the engine to almost die.

Thanks Scrappy...

A new battery off the shelf is only partly charged.

 

[Carzan]

It could if the voltage was low.
--------------------------------------------------------------------
So even with a new battery, if the belts slippin' on the alt, my voltage could be low enough to cause misfire under load. That makes sense...especially since turning the lights on caused the engine to almost die.

Thanks Scrappy...

In my experience, if the battery is low enough to cause a weak spark, it is low enough that the engine will either crank over slowly or not at all. The headlights compounding the problem makes me think even more that it is a connector problem. Heck, turn everyting on...lights, heater/ac blower, radio, wipers and see what happens. You can have all the voltage in the world at the battery and alternator and it doesn't do you a bit of good if there is a bottleneck in a connector or cable that prevents current flow. Do you have a multimeter/voltmeter?
-Louis-

 

[davedanger]

My 88 had a similar problem, it was the ground connection at the ignition module.
START with the obvious. The simple things will bite you every time.
Charge voltage with a good battery should be around 14 volts at the battery.

 

[ren]

Maybe the injectors are partially gummed up? When I got my '88 Xj limtied, it had SAT in a barn for about 6 YEARS. It had alot of the stumble that you are describing, and I ended up letting it sit and idle for quite a long time, with the occasional whack on the gas pedal to try and help it clear out the injectors. I evenually figured out the injectors were gummed when I had to replace the "o-rings" on the fuel rail due to leaks. I figured that maybe I should look at the injectors, since I was already there, and gee, guess what I saw. I ended up using 2-3 cans of carb cleaner on the tips of the injectors to help clean them, put it back together, and let it rip. I also had to change the fuel pump, flush out the tank, change the filter, AND blow out the lines because this thing had been sitting with almost a full tank of gas.

 

[carnuck]

I'd do the fuel filter and get a can of electrical contact cleaner. Unplug and spray ALL underhood connectors and the TPS. They get corroded normally and sitting around all the time seems to attract even more than usual.