Odd running (miss?)

Larry

Larry

True Classic
Hi,

I have a 1979 X1/9 with a 1984 FI engine. The car has an odd miss and I'm trying to track it down.

It only happens when the engine temperature is between the midway point to 190 on the temperature gauge and 190 and it seems to be the absolute worst a tick below 190. Below the midway point and the car is perfect.

It only happens between 3000-4000 rpm and can happen in any gear. The most common RPMs are 3200 and 3800 - which are usually the rev ranges when I'm driving in 3rd or 4th gear. But it'll happen in 1st gear coming off the line - sometimes but not always. Above 4,000 RPM - the car is perfect.

The car feels like it's misfiring, but there's no backfire or noise I can easily discern when it happens. Instead the car feels like I've hit a large bump in the road and the rear wheels are bouncing over it, although the car doesn't actually bounce. When it first happened I was on a crappy road and thought at first I'd gone over a bump I didn't see.

After the problem first occurred, I replaced the distributor cap, rotor, wires and plugs. It's happened with both NGK and Champion plugs and the timing is set correctly.

I've since replaced the AFM and the water temperature sensor (that goes into the side of the thermostat), but the problem still happens.

Looking for suggestions on what it might be or what things to try...

Thanks,

Larry
'79 X1/9
 
Almost sounds like a possible fuel pressure regulator or other fueling issue. I'd start with running a can of Seafoam through the intake and fuel system. Then you'll at least know nothing in the system is blocked/gummed up. Have you checked for any intake leaks?
 
When you did the AFM & CTS, did you check continuity in the harness from each connector to the ECU? It is conceivable that the terminals are not great & causing resistance variables.

Also if the ign brain is in the stock location, water can enter & cause connection issues. Worth looking for any evidence of oxidation on the aluminum casing. Same goes for trigger wheel and winding in the distributor, worth checking trigger wheel gap and winding resistance values & harness continuity.

If the injectors have never been out/flow tested, you may have irregular spray pattern, or air leaks around bases, but if the motor swap was done fairly recently that would seem less likely.
 
lookforjoe said:
When you did the AFM & CTS, did you check continuity in the harness from each connector to the ECU? It is conceivable that the terminals are not great & causing resistance variables.
Click to expand...

As Hussein knows, that's why the troubleshooter has us check values at the control unit end of the harness and not directly at the AFM and CTS---checking at the control unit also checks the harness, both by resistance and since you have to unlatch the plug to get to the contacts, visually as well.
 
lookforjoe said:
When you did the AFM & CTS, did you check continuity in the harness from each connector to the ECU? It is conceivable that the terminals are not great & causing resistance variables.
Click to expand...

I didn't, but I did pull the connection to make sure everything looked clean, dry and boring in there and it looked pretty much clean, dry and boring. But I can check, but silly question - you mean tap one lead on an ohm meter to a plug on the connector and then to its opposite number on the ECU?

lookforjoe said:
Also if the ign brain is in the stock location, water can enter & cause connection issues. Worth looking for any evidence of oxidation on the aluminum casing. Same goes for trigger wheel and winding in the distributor, worth checking trigger wheel gap and winding resistance values & harness continuity.
Click to expand...

I forgot to mention this - I have one of the rebuilt units there purchased from the person that was rebuilding them here on XWeb (but his name is escaping me right now).

I'll see about checking the trigger wheel and winding in the distributor. For the (somewhat) clueless shade tree mechanic, is there a writeup on the procedure to do this anywhere you could point me at?

lookforjoe said:
If the injectors have never been out/flow tested, you may have irregular spray pattern, or air leaks around bases, but if the motor swap was done fairly recently that would seem less likely.
Click to expand...

The motor swap was done over 20 years ago. I replaced the fuel lines about 3 years ago.

Hopefully this was a good thing - I ran a bottle of Techron Fuel System cleaner through the car about 2 months ago.

Thanks....
 
Larry said:
I didn't, but I did pull the connection to make sure everything looked clean, dry and boring in there and it looked pretty much clean, dry and boring. But I can check, but silly question - you mean tap one lead on an ohm meter to a plug on the connector and then to its opposite number on the ECU?
I forgot to mention this - I have one of the rebuilt units there purchased from the person that was rebuilding them here on XWeb (but his name is escaping me right now).
I'll see about checking the trigger wheel and winding in the distributor. For the (somewhat) clueless shade tree mechanic, is there a writeup on the procedure to do this anywhere you could point me at?
The motor swap was done over 20 years ago. I replaced the fuel lines about 3 years ago.

Hopefully this was a good thing - I ran a bottle of Techron Fuel System cleaner through the car about 2 months ago.

Thanks....
Click to expand...

The specs on the ignition parts should be in the manuals linked on the Wiki ("Home") link.

If the motor swap is that old, you really need to look at the injector holders (phenolic spacers) - there are at least two orings used to seal the injector to the intake runner. Possibly intake/exh gasket and/or plenum gaskets. Start by spraying carb clean around the runners/injector bases - if the idle alters, you know you're got a leak.
 
There has been some really good advice here. I was reluctant to jump in because I know these intermittent issues can be a real bear to solve. I've been noodling on the problem and think it might be a broken wire in either the ignition or fuel management harness. I believe it's making contact while cold but as the car warms up and vibration increases the conductivity drops and you get wonky engine management. Again, it's just a guess. One way you might test this and all the other possibilities suggested is to get the engine to start misfiring while its parked. I'd put it on jackstands and warm it up. Then put it in gear and go through the trouble zone rpm range. If you can get it to misfire while you are standing over the engine bay you can really start to troubleshoot. You can jiggle wiring to see if it stops. You can also spray carb cleaner looking for leaks too! Please keep us posted on any developments.

Always be careful working around a running car that is in gear!
 
Larry said:
I didn't, but I did pull the connection to make sure everything looked clean, dry and boring in there and it looked pretty much clean, dry and boring. But I can check, but silly question - you mean tap one lead on an ohm meter to a plug on the connector and then to its opposite number on the ECU?



I forgot to mention this - I have one of the rebuilt units there purchased from the person that was rebuilding them here on XWeb (but his name is escaping me right now).

I'll see about checking the trigger wheel and winding in the distributor. For the (somewhat) clueless shade tree mechanic, is there a writeup on the procedure to do this anywhere you could point me at?



The motor swap was done over 20 years ago. I replaced the fuel lines about 3 years ago.

Hopefully this was a good thing - I ran a bottle of Techron Fuel System cleaner through the car about 2 months ago.

Thanks....
Click to expand...

I wouldn't rule out the fuel lines and filter even if they are relatively new. I had some fuel line go bad in less than 2 years. It is even possible that the fuel system cleaner was incompatible with the fuel lines and accelerated their demise. Of course, this is all speculation. The other easy (potential) easy fix is a new set of ignition leads. These are very difficult to test as they may only exhibit issues at high voltages (you can't test them with a multi-meter).

Cheers,
Dom.
 
Thanks for the suggestions. Sorry I haven't been able to post back - things have gotten busy. The car's developed a fuel leak - it's under the fuel pump area - not quite sure where just yet - and I'm going to get that sorted out today. Then I'll be able to look into this more with the suggestions here.

Larry
 
I was almost right. The line between the tank and the fuel pump is leaking. I've checked the vendors' websites - Fiatplus and Midwest - but can't find the hose. I understand it's not a regular fuel hose and is something that has to be sourced from a Fiat parts vendor as it's 2 different ID on the ends. Did I miss it on those websites or does anyone have a recommendation/suggestion?

Thanks,

Larry
 
Larry said:
I was almost right. The line between the tank and the fuel pump is leaking. I've checked the vendors' websites - Fiatplus and Midwest - but can't find the hose. I understand it's not a regular fuel hose and is something that has to be sourced from a Fiat parts vendor as it's 2 different ID on the ends. Did I miss it on those websites or does anyone have a recommendation/suggestion?

Thanks,

Larry
Click to expand...
IIRC it is 12mm ID on both ends. 1/2" is 12.7mm so depending on the actual hose sourced, 1/2" might fit nicely or it might be too loose. This is not a "high pressure" hose and it's not in a premolded special shape or anything. No harm in running to the parts store, buying 2 feet of what they have on the reel (you have to think any store stocking fuel hose today would have the stuff rated for today's harsher fuel), and see how it fits. Use quality clamps (I like stainless Oetiker clamps for this spot).
 
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Dan Sarandrea (Phila) said:
IIRC it is 12mm ID on both ends. 1/2" is 12.7mm so depending on the actual hose sourced, 1/2" might fit nicely or it might be too loose. This is not a "high pressure" hose and it's not in a premolded special shape or anything. No harm in running to the parts store, buying a foot of what they have on the reel (you have to think any store stocking fuel hose today would have the stuff rated for today's harsher fuel), and see how it fits. Use quality clamps (I like stainless Oetiker clamps for this spot).
Click to expand...

Thanks. I'd heard it was a special line, but it's good to hear that's not the case.

I assume when I remove the line from the tank, the gas I recently put into the tank will attempt to pour out of the tank and onto my driveway.

I'm looking for recommendations on how to swap on the new line for the old and not lose the contents of the tank.

I know this is mostly theoretical discussion as the hoses likely haven't been touched for 30 or so years. I'm sort of assuming they've become practically welded onto their respective connections, so a good yank likely will result in the hose not budging or budging just enough to open the floodgates to having the tank begin to pour out. Or, the hose will tear thus allowing gas to come pouring out while I try to get the rest of the hose off.

If all goes well, can I get a plug for the tank where the fuel line attaches - so pull the hose off, shove the plug into place, get the hose replaced on the fuel pump and then connect it to the tank.

Larry
 
You could use the fuel pump to pump the fuel out into a proper fuel can. I wouldn’t do this.

I would suggest just letting it drain into a container directly.

I lifted the car high enough to get a 10 gallon Rubbermaid tub under there, removed the end from the fuel pump and let it all go into the bin. The dimensions of the bin is large enough that you can loosen the two clamps, pull the hose end off the fuel pump and rotate the hose to point down into the bin and not have too much spray all over. Judicious use of your thumb over the end of the hose is warranted.

The high speed flow out of the tank carried all the minor detritus out of the tank leaving a lot of fine (and some not so fine) grit in the bin. If you used the pump to do this, the particles would need to be processed through the pump and the fuel filter, thus why I wouldn’t run the fuel through the pump.

I would change to a new fuel filter along with replacing all the high pressure hoses in the system as part of this activity.

Some folks put a fuel filter in front of the fuel pump to keep all the large grit out of it in the future. I believe MWB offers a filter to do this. You can likely find one at an auto parts store but you will have to riffle through and measure the inlets and outlets of multiple filters. Assuming they let you.
 
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If you are doing this at a shop on a lift, you probably have what is needed to do the "yank and replace."

But I'll assume since you asked, you're doing this not in a shop and haven't done this job on a X before.

Precaution 1. Raise the car in the rear safely and put on jackstands. Use wheelchocks.
Precaution 2. You're working on the fuel system while lying under the car so take precautions: eye protection, no ignition sources, fire ext handy, ventilation, etc.

1. While at the local parts store getting the 12mm hose***, pick up 3ft of 5/16 standard everyday fuel hose. You'll need one clamp for 5/16" hose. You're not using this hose to replace any of the small fuel lines, you are just using it as temporary emptying hose.
2. Start by removing the air cleaner can assy and the short elbow hose that connects it to the AFM (air flow meter). One 10mm mounting nut is somewhat hidden under the lip of the sheet metal piece that divides the engine compartment from the left side drain pod area. This gives you easy access to the top of the fuel pump and the AFM flap which you will use to empty the tank.
3. With extra rags under the work area and wrapped around the connection, disconnect the top (output) hose from the fuel pump. If the car has been run within the last 18 hours the system will still have some pressure---the longer it has not been running, the less pressure will remain in the fuel system. You will have the contents of the fuel filter and the upper fuel hose (about a pint) to catch in rags.
4. Plug the end of the pump to fuel filter line with something. Ensure all spilled fuel is clean up and dried.
5. Now connect the 5/16" hose and clamp to the upper nipple of the fuel pump and have it hang down to the ground.
6. Now raise the car and set up jackstands, chock front wheels. Go as high as you can safely get it. Good jackstand points are evident at the front outer bottom edge of the wheel house, you'll see sturdy flat pads with a hole.
7. Under the car, locate your 5/16" hose end and place in a suitable clean container to catch fuel--if necessary, fasten the end to the container to ensure it does not squirm out under pressure. You will need as many containers as needed to accept however much fuel you have in the tank. When full the tank is about 11 gallons.
8. Out from under the car. Remove gas filler cap.
9. Inside the car, place the ignition key in the RUN position (MARR). If your FI system is stock and working correctly, the fuel pump will NOT come on at this point. That is expected.
10. Using a clean wooden paint stirrer, or a pencil (eraser first), insert it slowly into the now-open left side of the AFM. Contact the flap inside and push slightly, this will engage the safety contacts for the fuel pump and should run the fuel pump.
11. Observe the output, changing containers as necessary. Stop-start fuel pump by operating the AFM flap.
12. When tank is empty, ignition key to stop.
13. Now you can replace the leaking 12mm hose***. There should be a plastic shield under the fuel pump that protects the main feed line from damage, if this is missing see if you can get one from one of our vendors or post in the For Sale/Wanted section.
14. Remove the 5/16" hose from the output nipple of the pump and return to original configuration.
15. Button it up and you're done.

***VERY user-friendly FI hose replacement kit is offered by Midwest-Bayless: https://www.midwest-bayless.com/Fia...el-hose-kit-fiat-bertone-x19-1980-88-new.aspx Although on my car for best results I trim down the rail-to-injector hoses to about 43mm in length from the supplied 45mm.
 
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Larry said:
I know this is mostly theoretical discussion as the hoses likely haven't been touched for 30 or so years.
Click to expand...

Hi Larry,

the fuel lines should be pretty standard (8mm) ones. Just a question, above you mention that they haven't been touched in 30 years although in your second post you had said:

Larry said:
I replaced the fuel lines about 3 years ago.
Click to expand...

Not trying to be pedantic here :rolleyes: but it does make a bit of a difference, especially in relation to the initial problems that you were experiencing. If the fuel lines are old and disintegrating than this would be a very likely cause of the poor running. As the lines break down, bits of rubber break off internally and lodge themselves in the injectors (or clog up the filter, if in the lines before the filter).

I'd be replacing all the lines and filter in this case.

Cheers,
Dom.
 
kmead said:
You could use the fuel pump to pump the fuel out into a proper fuel can. I wouldn’t do this.

I would suggest just letting it drain into a container directly.

I lifted the car high enough to get a 10 gallon Rubbermaid tub under there,
Click to expand...

After you get the gas into a 10 gallon tote, what do you do with it? Do you siphon it back into the tank or into jerry cans?
 
I got the line replaced yesterday but not without some fun. By fun, I mean being sprayed with cold gasoline but that helped me decide that the sweatshirt and jeans I pulled out of the "donate" pile really should have been put into the "throw away" pile.

I put an open top oil container on the ground under the car and a vise grip bill clamp onto the line. As I clamped it, fuel started coming out from the sides of the line upstream from the clamp. I got the hose end off the fuel pump, put the new hose onto the pump and tightened the clamp. I added another vise grip a little upstream from the clamp to slow the flow from the hose a bit.

I loosened the clamp on the hose at the tank, turned the hose left and right a little and saw the clamp moving which made me believe the hose was willing to cooperate. But when I twisted and yanked, the hose tore off at the end of the tank nipple, although I didn't realize it at first but did when the new line wouldn't fit onto the tank. I was amazed at how far a full tank of gasoline will make gas fly out of the tank as it completely overshot the oil drain pan. I was quick enough to dodge it so only the back of my head got hit by gasoline - the goggles I was wearing never even got a drop on them. I plugged the tank with a finger (I won't say which one) and was able to pick, peel the old hose off of the tank nipple. I then got the new hose onto the tank, put the hose clamp on as well, checked the connections and then proceeded to do clean up.

So far, so good. No fuel leaks although it's raining today - it was earlier and is supposed to again, so I haven't been able to take it for a test drive to see if this leak was also sucking air in and causing my odd miss. But that also explains why the plastic cover under the fuel pump was very clean, but only under the hose. I assumed it was because the hose was gently rubbing against it.

Larry
 
Dan Sarandrea (Phila) said:
If you are doing this at a shop on a lift, you probably have what is needed to do the "yank and replace."

But I'll assume since you asked, you're doing this not in a shop and haven't done this job on a X before.

Precaution 1. Raise the car in the rear safely and put on jackstands. Use wheelchocks.
Precaution 2. You're working on the fuel system while lying under the car so take precautions: eye protection, no ignition sources, fire ext handy, ventilation, etc.

1. While at the local parts store getting the 12mm hose***, pick up 3ft of 5/16 standard everyday fuel hose. You'll need one clamp for 5/16" hose. You're not using this hose to replace any of the small fuel lines, you are just using it as temporary emptying hose.
2. Start by removing the air cleaner can assy and the short elbow hose that connects it to the AFM (air flow meter). One 10mm mounting nut is somewhat hidden under the lip of the sheet metal piece that divides the engine compartment from the left side drain pod area. This gives you easy access to the top of the fuel pump and the AFM flap which you will use to empty the tank.
3. With extra rags under the work area and wrapped around the connection, disconnect the top (output) hose from the fuel pump. If the car has been run within the last 18 hours the system will still have some pressure---the longer it has not been running, the less pressure will remain in the fuel system. You will have the contents of the fuel filter and the upper fuel hose (about a pint) to catch in rags.
4. Plug the end of the pump to fuel filter line with something. Ensure all spilled fuel is clean up and dried.
5. Now connect the 5/16" hose and clamp to the upper nipple of the fuel pump and have it hang down to the ground.
6. Now raise the car and set up jackstands, chock front wheels. Go as high as you can safely get it. Good jackstand points are evident at the front outer bottom edge of the wheel house, you'll see sturdy flat pads with a hole.
7. Under the car, locate your 5/16" hose end and place in a suitable clean container to catch fuel--if necessary, fasten the end to the container to ensure it does not squirm out under pressure. You will need as many containers as needed to accept however much fuel you have in the tank. When full the tank is about 11 gallons.
8. Out from under the car. Remove gas filler cap.
9. Inside the car, place the ignition key in the RUN position (MARR). If your FI system is stock and working correctly, the fuel pump will NOT come on at this point. That is expected.
10. Using a clean wooden paint stirrer, or a pencil (eraser first), insert it slowly into the now-open left side of the AFM. Contact the flap inside and push slightly, this will engage the safety contacts for the fuel pump and should run the fuel pump.
11. Observe the output, changing containers as necessary. Stop-start fuel pump by operating the AFM flap.
12. When tank is empty, ignition key to stop.
13. Now you can replace the leaking 12mm hose***. There should be a plastic shield under the fuel pump that protects the main feed line from damage, if this is missing see if you can get one from one of our vendors or post in the For Sale/Wanted section.
14. Remove the 5/16" hose from the output nipple of the pump and return to original configuration.
15. Button it up and you're done.

***VERY user-friendly FI hose replacement kit is offered by Midwest-Bayless: https://www.midwest-bayless.com/Fia...el-hose-kit-fiat-bertone-x19-1980-88-new.aspx Although on my car for best results I trim down the rail-to-injector hoses to about 43mm in length from the supplied 45mm.
Click to expand...

Thanks for this very thorough writeup. I chose not to go this route as I don't have enough containers for 10 gallons of gasoline. I'll probably install the pre-screen filter and when I do that, I'll drive the car until it's about empty.

I've bought the hose replacement kit from Midwest-Bayless before - actually for a friend's X1/9 that needed the lines replaced.
 
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