'89 CRX, Cutting Out at Partial Throttle, Low RPM

[Mr_Incredible]

My 89 CRX DX is stumbling at low rpms, partial throttle conditions and I'm trying to think my way through it rather than throw money at it.

Symptoms are cutting out, cough & quit, and bucking/jerking. Symptoms occur at 1200 to 2300 rpms, but not unless I'm pushing down on the pedal. Slow rpm rise and steady speeds do not produce problems. Appears to happen mostly when pedal is past the first inch or two, but not when pushed very slowly through that rpm range. Still runs good. Still gets proper mpg. Still cruises at 80mph if asked. Symptoms started last Sep/Oct. At times it almost appears as if it has gone away, but it can be induced at will.

Maintenance History - Got it with 253k miles, have 270k miles now. Replaced plugs/wires/distr cap & rotors shortly after purchase. Adjusted the valves about 11k miles ago. Changed timing belt at that time, ran great afterwards. Two Italian tuneups with fuel system cleaner in quick succession might have helped a bit, but inconclusive.

I'm thinking there's something like a vacuum pot or a switch that engages at the part-throttle point where the trouble starts. I suppose it could be valve adjustment like the trouble-shooting pages say in the Chilton manual, but wouldn't that be constant?

If anyone has had this condition I would be grateful for some insight.

Thanks.

 

[ThirdeYe]

Have you changed the fuel filter? It might also be worth cleaning the IACV. This might be a stupid question, but have you changed the air filter, too?

 

[eljefino]

Don't a lot of honda from this error have bad distributors? Is there an ignitor pickup within the dizzy? I'd look there, sounds like a spark issue still.

 

[Cup of Joe]

No codes? You may want to verify there are no stored codes. Spray some starting fluid on your vacuum lines while the engine is running, if rpms increase you have a small leak. There are a few possibles like a throttle angle sensor or the map sensor which generates its input data from manifold vacuum.

 

[artificialist]

EGR?

Clean out the EGR passages, and check if the EGR is sticking by testing it with a vacuum pump.

All the other tests mentioned by other posters are good too.

 

[Mr_Incredible]

Fuel filter changed last weekend with no effect. Air filter not an issue.

Tried some flammable fluid around the vacuum lines, carb, etc. with no effect.

Codes are a difficult thing to get on this one. No plug in, have to take up the carpet and watch blinky lights on the computer...IIRC.

 

[ryan2022]

That sounds like a spark issue. Check your wires and dist cap with an ohm meter.

 

[eljefino]

Do these things still have vacuum distributors? That could be going berzerk somehow, either the advance weights are flaky/ gummed up or the vacuum mechanism leaking or otherwise variably effective.

 

[punisher]

Originally Posted By: ryan2022
That sounds like a spark issue. Check your wires and dist cap with an ohm meter.


Ditto. Part throttle with low/medium RPM miss is usually ignition related.
EDIT: I don't know about ohming the wires and dist cap. Sometimes you have tracks that won't throw resistance out of spec. Visual inspect wires and interior of dist cap for burns/carbon tracks, ck plug porcelain for tracks.

Quick test, get a spray bottle, fill it with water and with engine running, mist down the dist cap and wires to plugs to see if anything arcs.

 

[mechtech2]

Sure it could be ignition, but that 20+ year old carb is sure to have problems. Check the [censored] [accelerator pump] first.
Also, those carbs were not designed for alcohol fuels - just straight gas. They run lean, and they were already too lean.

 

[mechanicx]

I agree the symptoms sound like accelerator pump or just a dirty carb, transfer slot, bleeds etc. I'm not real familar with the older Hondas, but the symptoms sound like what a TPS would do on injected engines or the transition circuit and accelerator pump circuit would do on a carb.

 

[chrome]

Is the engine fuel injected? Does it have a throttle position sensor? Sometimes the TPS wears out at certain ranges (usually 0-40% throttle), and causes erratic timing and fuel injection behaviour.

 

[Cogito]

Originally Posted By: chrome
Is the engine fuel injected? Does it have a throttle position sensor? Sometimes the TPS wears out at certain ranges (usually 0-40% throttle), and causes erratic timing and fuel injection behaviour.

Hmm, I've got an 89 Civic that idles fine around 800rpm, but will jump up to about 1600rpm for a minute or so, while idling. It will do this every 5 minutes or so. Could this TPS thing be causing that kind of issue?

 

[chrome]

Originally Posted By: Cogito
Hmm, I've got an 89 Civic that idles fine around 800rpm, but will jump up to about 1600rpm for a minute or so, while idling. It will do this every 5 minutes or so. Could this TPS thing be causing that kind of issue?


That could be a faulty Idle Control valve... does it compensate idle properly when you turn on the AC?

 

[Mr_Incredible]

The distr cap/rotor/plugs/wires are less than 20k miles old. They aren't too dirty but I'll certainly check for arcing and reseat them carefully.

There isn't a carb. It has a main injector and a supplemental injector as an "accelerator pump." I'm thinking they aren't the main cause since everything works well if the revs are raised more slowly.

I haven't had time yet to study the book for TPS, vacuum swithes, etc. I do remember seeing a little vacuum thingy behind the "carb" that I could probably change out for cheap.

I always use regular fuel, and nobody could accuse me of not using enough fuel system cleaner. I still have to check the plugs themselves to see what's going on with them. I'll do that while I check the plug wires and related do-dads.

 

[mechtech2]

I am very surprised that there isn't a carb on there!
Your fuel pump or filter may be weak or plugged.
Or, simply a bottle of good cleaner in the gas tank will help.

 

[Cogito]

Originally Posted By: chrome
Originally Posted By: Cogito
Hmm, I've got an 89 Civic that idles fine around 800rpm, but will jump up to about 1600rpm for a minute or so, while idling. It will do this every 5 minutes or so. Could this TPS thing be causing that kind of issue?


That could be a faulty Idle Control valve... does it compensate idle properly when you turn on the AC?

Can't say, no A/C.

 

[artificialist]

Originally Posted By: mechtech2
Sure it could be ignition, but that 20+ year old carb is sure to have problems. Check the [censored] [accelerator pump] first.
Also, those carbs were not designed for alcohol fuels - just straight gas. They run lean, and they were already too lean.

1989 Hondas had oxygen sensors to keep the AFR at 14.7:1 at idle and crusing speed, and to compensate for E10 gasoline.

 

[gotnogunk]

The post about the EGR is a good one I spent a lot of money chasing a problem like this found ont EGR is a common problem .

 

[FusilliJerry82]

This is a common older Honda issue.

Find, remove and clean your Idle Air Control Valve.