Runs rough and lacks power intermittently

[Rich06]

Here's my problem but it's not all the time. Rough idle, engine bogs on acceleration sometimes and hardly moves, rpms increase very slowly. strong smell from exhaust. The car always starts easily hot or cold. I had this problem but not nearly as bad last spring but it cleared up and ran fine until October. I have found that if I spray carb cleaner down the intake and rev the engine everything clears up and the car will run perfectly (smooth idle, great acceleration, etc.) until I've driven 15 or 20 miles, not necessarily all at once , then the problem comes slowly back. Sometimes it will start to hunt if I stop at a light or something but if I rev it a few times it stops. I did clean the WUR screen which wasn't at all dirty and also just replaced the fuel pump which I had planned on doing anyway. The frequency valve buzzes at first then sometimes after warmup a ticking that sounds almost like static. The car had a complete 30,000 mile service at DMCH at 8,000 miles , now has 23,000 on it. It seldom sits even 2 weeks without use. Any help or advice will be greatly appreciated. -Rich

[Bitsyncmaster]

Don't know why the carb cleaner would fix it unless your "plunger" on the FD is sticking. The FV should always buzz unless the mixture is to far off.

[DMCMW Dave]

Here's my problem but it's not all the time. Rough idle, engine bogs on acceleration sometimes and hardly moves, rpms increase very slowly. strong smell from exhaust. The car always starts easily hot or cold. I had this problem but not nearly as bad last spring but it cleared up and ran fine until October. I have found that if I spray carb cleaner down the intake and rev the engine everything clears up and the car will run perfectly (smooth idle, great acceleration, etc.) until I've driven 15 or 20 miles, not necessarily all at once , then the problem comes slowly back. Sometimes it will start to hunt if I stop at a light or something but if I rev it a few times it stops. I did clean the WUR screen which wasn't at all dirty and also just replaced the fuel pump which I had planned on doing anyway. The frequency valve buzzes at first then sometimes after warmup a ticking that sounds almost like static. The car had a complete 30,000 mile service at DMCH at 8,000 miles , now has 23,000 on it. It seldom sits even 2 weeks without use. Any help or advice will be greatly appreciated. -Rich

Check the connection ground wires at the back of the passenger intake runner, and then check and clean all the bulkhead connections. (you can try and figure out which is which but if some are dirty/corroded you need to clean them all anyway). This sounds to me like you are intermittenly losing Lambda control, i.e. either the signals to the frequency valve or the ground reference to the ECU which happens to be directly on the engine.

[David T]

What Dave said. I want to add that I have seen several cars where all I did was remove and reconnect the plug to the frequency valve several times to clean the contacts and it "fixed" the problem. Easy to try, low cost and fast.
David Teitelbaum

[Jonathan]

Is your car an auto or manual transmission? Not everything you described fits the bill, but some of those things you're saying that are happening could be related to an auto trans computer governor having given up the ghost. Mostly the no power, high revs type stuff. When my shift computer was shot, it kept each gear very late, so at times say if I was hovering between 1st and 2nd, when the car should have normally been comfortably in 3rd, I would get that no power, odd revs situation. Anyway, just a thought.

[Rich06]

Thanks for the replies. The car is a 5 speed. I have cleaned every connection I can find more than once already. I've also cleaned all the fuses and relays.
Rich


Don't know why the carb cleaner would fix it unless your "plunger" on the FD is sticking. The FV should always buzz unless the mixture is to far off.

So should the sound from the frequency valve always be the loud buzz? Or is the ticking kind of static interference sound okay. I've read elsewhere that the frequency valve should not buzz all the time once the engine is at temperature.
Thanks

I had a spare 02 sensor and rpm relay so tried changing both with no difference. I also cleaned and lubricated the idle speed motor. If I unplug the ECU the engine speeds up which I read indicates it's working. I read another thread where the WUR was causing a similar problem. Is that a possibility?

[Ron]

I go along with the advice above. It sounds like your FV may stop buzzing because it reaches its limit to adjust... Since you are confident in the connections, sensor,etc, I suggest you double check all of your basics (timing, plug gap-condition, vac leaks, ect) then check your CO (several post here on how to do it).

[Rich06]

Well I took apart the ECU today and one of the solder joints on the circuit board is loose where one of the connectors attaches. I'm charging the batteries for my microscope and will check the rest of the circuit board tomorrow and solder whatever needs it. This seems too easy to be the answer to my problem but I'll see what happens.
By the way, I drove the car today and it ran beautifully. -Rich

So I soldered the loose connection on the ECU today and went out for a ride. Had to stop and wait idling for 3 or 4 minutes at a construction site before the car had warmed up. Started back out and it started to bog down again. This time I put it in neutral and revved the engine a number of times. It revved slowly at first then got back to normal. It searched for a couple of minutes, then idle settled to normal and it was fine the rest of the way. I still haven't tested anything else that has been mentioned but will try next week. Just thought this might tell you something.
Thanks again, Rich