New owner intro; engine bucking issues (possibly ignition or vacuum?)

[Shin Hayata]

I'll probably install a new distributor cap and rotor after Christmas, also. I just installed new Autolite plugs. The plug wires on the car at the time of sale looked to be of very recent vintage, so I'm not worried about them at this time.

The stumbling only occurs after the car is warmed up and the emissions are [presumably] in closed loop.

I'm hoping moisture isn't the cause of the stumbling/bucking. PA winters are cold and damp and the car is parked in the driveway at night. I could put the Festiva in the garage, but then my sano Honda Ridgeline would have to sit outside and I'm pretty fussy about that vehicle.

[TominMO]

The bucking returned this morning. Odd, because I went for a prolonged drive last evening, and the engine ran as well as I'd want it to.
The next thing I'll do is examine the filter sock in the fuel tank, as suggested, and take a closer look at the many vacuum lines.

Also look for a kink in the fuel line, where it goes into the fuel pump on the head. This fuel line collapsing on carby cars is a known issue. One fix would be to put a longer line there, with a more gradual bend. With the hood up, try working the throttle directly so you can observe if the line collapses at higher RPMs or vacuum, causing stumbling.

You might also try some fuel anti-freeze to get water out. Iso-HEET, red bottle.

[WmWatt]

Yes, carb'd cars have the pump in the engine compartment and suck gas out of the tank -> low pressure in the line -> weak line can collapse.
Fuel injected cars have the pump in the gas tank -> high pressure in the line -> line doesn't collapse but can spray gas.

[Shin Hayata]

Thanks. You guys are reading my mind.

Iso-HEET hasn't escaped my attention. It's not an additive that I've ever used; your recommendation suggests that it's generally safe?

The fuel hose is date stamped 2010 and looks to be in good condition. I know this because I examined it when I recently changed the fuel filter. I'll perform the throttle-by-hand test, as suggested, and examine the hose again. I'll buy some spare 5/16" fuel line to keep on hand.

[zoe60]

You might want to replace the O2 sensor. I think that the signal from it controls the feedback carb mixture. If it is reading wrong it can cause it to run lean. When I first got my '89 it did the same thing. Tune up and rebuilding the carb helped, but the problem never went away entirely until I replaced the oxygen sensor. I ran mine for years with the original carb and it ran fine. I finally replaced it first with a Weber 32/36 and then with an '83 Escort carb. I love the Escort carb and if you do it you will be amazed at the increase in power!

[TominMO]

Look at the hose while you are performing the throttle test. It won't stay collapsed when you let off; you have to catch it in the act. Not sure if that was clear.

You might also try replacing the carby fuel line with EFI-rated fuel line. More expensive, but I think it would be less prone to collapsing.

Good point about the O2 sensor. Get the Denso 234-1019, available at Rock Auto, $23. Or the 234-1000 universal one, where you will have to splice the connector on, $11. You can do a part# search at the top of the page; leave out the dash.

[Shin Hayata]

I'll add the O2 sensor to the list, but I want to see what improvement, if any, is provided by a new distributor cap and rotor. Both parts will require 2-3 days to obtain, since they aren't stocked at the local Autozone or Advance Auto stores.

Seems I'll need a slotted socket for the O2 sensor, also. What size(s) will I need in order to remove the OEM fitment and install the Denso part? 7/8" for both?

It's my preference to keep the Festiva as stock as possible, but I'll put a pin in the idea of an Escort carburetor. I had Webers on my sports cars, and they were the bee's knees, but using an Escort carb keeps it in the family.

Edit: Is there a part # for the small PCV filter that sits in the circular air filter housing? It's absent on my car.

[TominMO]

All O2 sensors for our cars use the same slotted socket, 7/8". About $10 at McParts stores. If the old sensor is rusted in there, tap the socket with a hammer to set up vibration to help loosen the sensor.

[Shin Hayata]

Thanks, Tom. The 3 small bolts on the exhaust manifold exhaust shield are very rusty, so they'll receive some percussive maintenance also.

A search on this forum revealed the suggested distributor cap as Standard Motor Products #JH133. The part is available on Amazon, but the site's Vehicle Compatibility tool states that JH133 won't fit on a 1988 Festiva. Conversely, the Denso O2 sensor #234-1019, recommended in this particular thread and also sold on Amazon, is noted to be compatible with the 88 Festiva.

I've never put much stock in Amazon's vehicle match tool, so: can anyone confirm that the JH133 distributor cap is a confirmed fit on the carbureted 88 L? It does appear very similar to the cap presently on the car. I'll also need brand and part number recommendations for a rotor. Might as well suggest a brand and part # for a coil, too, just in case.

I received some Amazon gift cards for Christmas, and would like to use them to fund parts purchases to the extent possible. No worries if I have to go for Advance Auto, etc. for anything. Thanks again.

[Shin Hayata]

Just ordered the SMP JH144 cap and JR163 rotor, as well as the Denso 2341019 O2 sensor. All are confirmed fits for the 1988 1.3L via multiple vendor site searches.

[TominMO]

Cool, keep us posted.

[zoe60]

Good luck! It took me a while to get mine running right 10 years ago, but I finally did. It was a combination of things but the O2 had a heck of a lot to do with it. If you end up having to rebuild the carb, take some extra time to label all the hoses carefully.

[WmWatt]

With respect to labelling hoses, you may notice that the hoses to the three coloured solenoids mounted on the firewall bear the same colour as the devices.

[bravekozak]

Feedback carbs have partial actuator control of the throttle.
Oxygen sensor expense is best applied to an Escort carb conversion.
Use the search engine to see how much spaghetti can be removed.
drddan hasn't been here since December 10. I was hoping he would be able to give you some advice. See if you can find an old Mazda 323 carb manifold and find someone who can do some aluminum welding to help you with the boss relocation.

[bravekozak]

The front one is what I suggest.
The runners are a little bigger and have a shorter distance.