Sputtering/Hesitation problem...
 

So, on the way to the race on sunday, I developed a sputtering problem under throttle in my 1984 944 N/A. The car is stock, minus a cherrybomb muffler. Also, the car spent the last month with the top of the filter box (with the element still sealed and in place) off. I put it back on that day for the racing sanctions rulebook.

The car would buck severely and hesitate. Even out of gear, revving it-- it would break up and not rev strongly.

Thinking it was a fuel delivery problem, and considering there was a intermittent whine from the fuel pump, I replaced the fuel pump and filter today, still there. So, I pulled the plugs to see what they look like. I took out the plugs and noticed #1(or the one closest to the front, not sure of the numbers) to have a little oil on it. The other three look fine, just used.

The wires and cap/rotor have been replaced less than a year ago. They look fine. I know the oily cylinder is firing because I pulled off the wire and it started to idle erratically, put it back and it idled fine.

I have pics, Ill put them up later. I'm at work.

Any ideas? Fuel injector? Computer?

Make sure the outer porcelan on the spark plugs are CLEAN. Happened to mine, sputtering, misfiring.....
just cleaned the outside porcelan really well. Fixed the problem ! Not saying this is your problem, but it's a starting point.

What kind of sputtering were you experiencing?

This is pretty violent, severe bucking. If I stay on the gas, It feels as if the throttle is being hammered, then let off. Repeatedly.

Ill throw plugs in it this afternoon. Suggestions? or just a set of Bosch?

Also, why would the outer porcelain affect anything? That's just an insulator, if its dirty it should still do its job....right?

Mine backfired and bucked, worse if I tried to accelerate. The porcelen was dirty and the spark was arcing across to the head. Same thing can happen if your plug wires start arcing to the motor, or each other. It fixed the problem on mine, but I was due for new plugs and wires anyway.

I just did the plugs/wires/cap a few months ago. But I threw new plugs in today, same problem. No backfiring or afterfiring, though.
I have:
Replaced the Fuel Pump
Replaced the Fuel Filter
Replaced the Spark Plugs (properly gapped 'em, too!)
Cleaned the Mass Air Flow Sensor (using CRC)
Cleaned the K&N Element

So after looking around, trying to get a hint to as what this motor is doing, I have discovered a few things. Some may be irrelevant to this particular issue. But...

I pulled out the plugs to see how they look and throw a new set in. Plugs #2,3,4 Looked normal with about ten grand on them. Plug #1 looked rough. It had been covered in oil.

Plug #2
http://i239.photobucket.com/albums/f...g/DSC01245.jpg

Plug #1
http://i239.photobucket.com/albums/f...g/DSC01248.jpg
http://i239.photobucket.com/albums/f...g/DSC01247.jpg

There was also a small amount of oil in the plug recess.
http://i239.photobucket.com/albums/f...g/DSC01251.jpg

A bit of fluid in the J-Boot, as well.
http://i239.photobucket.com/albums/f...g/DSC01253.jpg
http://i239.photobucket.com/albums/f...g/DSC01254.jpg

The 25 years of **** that accumulated in the Throttle Body.
http://i239.photobucket.com/albums/f...g/DSC01255.jpg

The Exit of the MAF. Cleaned, just stained.
http://i239.photobucket.com/albums/f...g/DSC01257.jpg

Breather hose off the J-Boot.
http://i239.photobucket.com/albums/f...g/DSC01261.jpg

Now, I'm not saying any of these are the cause of this, in fact I know they're not. But they have to be able to give someone a hint.

Tomorrow, I will be looking into the fuel injectors, perhaps some cheap gas killed one.

I can hold the car at a steady RPM and it will purr. If I fluctuate the Revs, it falls on its face, then bucks. It does this in and out of gear, so I eliminated a drivetrain problem. I don't think it's the DME because if it were, it'd be having the problem when I hold the Revs steady as well. Also, I dont think its a mechanical setting (Such as a timing belt), because, again, that would let the problem be seen when the car is iding, or under constant (not fluctuating) throttle.

Hmmm..

Any ideas? or any tests I can do to it to help you guys help me? I already missed last weekends race, I'm dying to get to this Sunday's event.

Vacuum leak?

I'll just throw some easy crap out there. Unplug the AFM when idling and see if it changes. Then if it doesn't change see if it drives the same.
Sounds like what happens to my car when I forget to plug the AFM back in.
BUT with no AFM the car usually stalls out eventually. So.... IDK.

Get new plugs! They are so cheap, i would just start there and see what happens.

I'll put my money on distributor - check the rotor is properly aligned and the contacts are good. Had a similar problem once.

Of course, might be wrong - but it sounds like a spark issue.

After taking those pics I threw new plugs in, checked the wires, and opened up the Distrib. to investigate. It looked brand new inside... No problems there..

You should check all your grounds. Its a pain but can usually be the problem in the 84's due to corrosion.

^ I heard that. Does anyone have a reference for all of them? or at least a few?

http://i239.photobucket.com/albums/f...0430091334.jpg
Well, using my billion dollar Snap-On scanner, I realized every part that said Bosch on the damn car was in spec. Pumps, Coil, MAF, fuel injectors. Everything. So I went back to basics...


After pulling the fuel hose off of the tank (the one leading into the pump) I noticed that it was not pouring out like it should be, something was clogging it.

After a quick shot of compressed air into the hose, the fuel now poured out of the tank. Good.
But whatever was clogging it is still in there, waiting to clog again. Bad.

Okay, how do I go about getting the crap (probably a cheap in-tank filter of sorts) out? Can I get a good look thru the top (where the sender for the gauge goes) hole, and perhaps throw a grabber down there to yank that garbage out? or does the bottom plug open more?

Purchase a fuel tank screen/gasket from Pelican $40. When I had the tank crack brazed, the fuel screen was removed. The old screen had tears.

It also looks like you should replace the AOS seals

GL
John_AZ
1988 924S + 1987 924S