missing/rough engine

[Gliderfixer]

89 Festiva,150K miles,4 speed, owned for 15 yrs.
Hope this isnt a repeat? First request didnt show on website.
Missing badly when driving at normal speeds, runs fine under load on acceleration!
Starts good but idles rough. Has been getting worse past 3 months.
Plugs show lean burn(More white than normal) Good gas mileage.
Have removed top of carb and cleaned all ports/passages and jets with Gumout carb spray. Thought this would help as found a fair amount of gunk in a few passages. Carb had never been opened before.
Spark plugs all seem to be firing, I pull leads off while on idle and rpm drops approx 250 rpm per cylinder. Can a sensor that's hooked up via a vacuum hose be the problem? There's a bunch of them!! Ive also varied the distributor timing alittle without any results. Any ideas??

[PaulLehr]

Start with the simple stuff. Check your cap and rotor. Check the resistance on your plug wires. Run it in the dark and look for any spark arching from old or worn plug wires. Then check your electrical connections at the Dist. and the coil

[PaulLehr]

Oops almost forgot, don't forget to check and or replace the fuel filter

[Gliderfixer]

rough engine

Paul, Tnx for reply.
Yes, Ive tried ignition tests awhile back and didnt find anything! I also thought it was high voltage trouble!
Perhaps Ive missed something but your suggestions will make me retrace my troubleshooting. It's getting worse,perhaps when it quits completely I'll find it. Tnx again

[Gliderfixer]

rough engine

Paul,
rechecked all ignition stuff, everything as it should be.
Will try working with choke tomorrow, will adjust so with hot engine, plate will still be slightly in choke position. Will help determine if engine is running lean.

[David88]

Run some dry gas through it. If you think you may have a vacuum leak you can spray starting fluid in the area of the possible leak and if the RPM's go up, there is your leak.

[Gliderfixer]

Rough engine

Tnx Dave,
I was lookin for a vacuum leak when I removed carb. a few days ago.
I had done the spray test on the carb to manifold connection and yes I did get a nice rpm increase. Theirs a intake air heater installed between the the carb and intake manifold (At that time I thought it was just a insulation spacer) It was stuck down real good so I left it. I didnt have a new gasket and Ive heard the heaters get brittle and break easily so I cleaned the area and tried to slim coat with JB weld! I know it sounds pretty tacky but It was 10pm at night. Will tear it back down and fix right this time. The JB weld didnt help. Tnx for the input!

[zoe60]

Distributor vacuum advances go bad on carbed festivas. Causes big vac leak. Spray it with carb cleaner to find out.

[Guest]

Zoe... Please look at the last reply date before replying. This thread is 9 months dead!!