Rough Idle - 1989 Ford Festiva L, Carbeurated

[westonganger]

I have a 1989 Ford Festiva L, Carbeurated Manual 4 Speed

It has a rough idle, I guess the best way to describe it is:

It idles inconsistently revving lower then higher, also runs rough when engine is cold for the first few minutes of driving

Check engine light turns on usually when engine is fully warmed up at high rev on the freeway

I have the engine codes: 70- Vacuum switch and 17-Feedback system

I have replaced all general tune-up items: spark plugs, cap, rotor, fuel filter
I have also replaced the O2 Sensor

Wondering if anyone knows what is wrong with it?

[WmWatt]

Sorry, don't know what's wrong with it.
You can check the vacuum hoses for loose connection, spits, and tears.
You can clean the carburettor with a spray can of carburettor cleaner (read instructions on can).
Sometimes the butterfly valves can get dirty and stick. Also clean the external linkages
(throttle and automatic choke)
Good luck.

[TheresGabe]

Sounds like a job for SEAFOAM! give it a whirl. Follow the directions exactly. Anger your neighbors with the terrible black smoke.

[georgeb]

So your code says "vacuum switch" and you replace everything but the vacuum switch! The closest thing by that name in my carb manual is vacuum switch valve, which "opens vacuum passage to #1 purge control valve and fast idle cam breaker according to engine coolant temp". It's located behind the distributor (picture is unclear). Disregard the other code which will correct when the primary issue is fixed. Good luck.

[zoe60]

I wonder if the code means the ABCV valve on the carb. Has 4 vac lines coming out of it and a plug for the wires. Might check all that.

[bravekozak]

I had a similar problem with my 89. I couldm't figure it out, so I ijust installed a Weber carb.

[WmWatt]

The vacuum switch is on the firewall at the extreme left (passenger side) of the engine compartment. Inside of it is the EGR solenoid #1, and inside of that is the High Altitude Compensation Valve (optional, I think). The vacuum switch is a horizontal plastic cyclinder-looking thing. I have no idea what it does.

The troubleshooting section of the Haynes manual does not have anything for "rough idle" but does have loping and eratic idling for which it suggests vacuum leakage, leaking EGR valve, clogged air filtre, faulty fuel pump, leaking head gasket, worn timing belt, pulleys, camshaft lobes. I'd add engine missing but you seem to have gone over the ignition components.

Good luck.

[WmWatt]

P.S. An inexpensive vacuum guage might show low or varying vaccum. I use mine when the engine sounds funny, mostly missign which is corrected by cleanign plaugs and wires. See permanent thread at the top of the repair forum page.

[Movin]

What does the Haynes manual show for a flow chart for code 17 ?

[WmWatt]

Movin: Do you mean a diagnostic flow chart? Haynes manual does not have diagnostic flow charts.
It has a troubleshooting section where it lists possible causes of some symptons.
It also lists check engine light codes and the part to check for each.

[blueoval]

i agree with brave,when i first bought my festiva it only had 106k onit but all the vacuum lines had been messed with i thought it was a carb problem so i bought a new feedback carb after i installed it it was still the same then by now i know i was in over a month or2 trying to straighten the car out.then i learned of the feedback carb and the webber swap,i sold my new feedbac carb on ebay and found a new webber that came with the adapter plate that was bolt on and go it was high but it cured all of my festiva's problems and been driving it ever since

[drumnerd33]

best fix would be the weber swap mine ran alot better with the weber only thing is gotta have an adapter made unless you buy the 700 some dollar one from Australia. if you would like to keep the carb you have now i would take out the vacuum switch and see if you can figure out whats wrong it is an electronic switch that has a vacuum line going to it on the far left of the fire wall, right next to the altitude compensator. the altitude compensator is just vacuum and has like 3 vacuum lines on it i think... i tore mine out so going by memory here. the vacuum switch has i think a bi pin connector on it. you can test it by applying power and ground to the appropriate connecctor just be sure to unplug the connector first so you dont fry the computer. I think you can open it up on the vacuum side and maybe clean it out but my guess if its throwing a code to the comouter is its bad because the computer only sees the electric side of it.

[drumnerd33]

another sensor to check that the computer relies on is the temp sensor located in the intake manifold on the bottom side... the computer uses this sensor to know when the engine is up to operating temp and will go into whats called closed loop, if this sensor is giving false readings it can cause some funky problems with the computer.

[drumnerd33]

Re: Rough Idle - 1989 Ford Festiva L, Carbeurated

Here's this from mitchell


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