84 Toyota celica misfiring between 1.5-2Krpm

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  #1  
Old 01-19-04, 05:00 PM
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84 Toyota celica misfiring between 1.5-2Krpm

I have an 84 toyota celica, 22RE engine, 186K miles.

It misfires only when accelerating hard from 1500-2000rpm in 2nd gear, for example, right after I've up shifted and the rpm is increasing. If I let off on the gas when it begins to misfire, misfiring goes away. If I jam on it again after it revs up past 2Krpm, it'll rev straight up thereafter with no problems. If I accelerate moderately, there's no problems across rpm range.

That would seem to mean my fuel delivery and ignition path are OK. Distributor appears OK. Didn't feel anything stiff or sticking.

I've already put in new cap/rotor, wires, plugs, and the routine stuff...EGR path appears to work OK. I also drove around with it unplugged--no difference.

I just put in a new vacuum advance diaphram since it was leaky, but that only fixed some funny idling I had. Other vacuum lines appear to be non-leaky.

I think my coil 'measures' within spec. The secondary sits at the high end of the spec. I measured about 12Kohms (if I remember correctly) given a spec range of 8K-12Kohms on the secondary winding. The primary side was about 1ohm which is ok.

What's the best way to test a coil? I really hate to blow $200+ on a new one if I don't really need it. But if it was my coil, I'd expect to have similar problems at any rpm. (??) Plugs are clean, so there's nothing funny going on that i can see.

Battery voltage appears to be ok and not fluctuating based on the voltmeter in the dash. I should check it at the coil and computer though.

No engine codes :-(

Any ideas? I'm a bit stumped..

thanks!
 
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  #2  
Old 01-19-04, 05:56 PM
Join Date: Jun 2002
Location: Long Island, NY
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Could be a lot of things, Start with the basics:

Fuel pressure, ignition timing , air gap on pick-up coil, TPS adjustment, Etc

Hope you used OEM wires and cap.
Try disconnecting all vac lines to dist and drive it and see what happens( looking for broken wires on pick-up coil).

Back probe coolant temp sensor( looking for .3-.5 volts)

Check O2 sensor for switching between .2-.8 volt about every sec or two.

Possible clogged injectors?
 
  #3  
Old 01-19-04, 06:10 PM
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I would have voted for the dirty fuel injectors also. Especially with that mileage. Have the professionally pressure cleaned. It has to be some help with that mileage.
 
  #4  
Old 01-27-04, 10:50 AM
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misfiring at 1500-2Krpm and O2 sensors

I've measuring my O2 sensor output. It oscillates between 200-500mV at approx 1.5second intervals. Seems low.
It peaks at 0.5V, but average DC level sits in the 300mV region. The output isn't a square wave like textbooks show, instead, it's a slow rising and falling sinusoidal-looking signal. It looks the same at idle as when the rpms up around 2K

If I jerk the throttle and then release it quickly, output drops to near zero and then gradually recovers over a second or two.

Is this expected?

I've dumped in a bottle of fuel system cleaner this morning--supposedly the potent stuff, not the watered-down every-tankful injector cleaner. Let's see if it isn't carbon buildup. Then I think I'll swap out the O2 sensor after this tank is used up since I have 80K miles on the sensor already.

thanks
 
  #5  
Old 01-27-04, 03:16 PM
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The wave pattern is OK, but the voltage is low. Could be that the sensor is good but reading a lean mixture. Or could just be a bad sensor.

Try "driving" the sensor by richening the mixture say by blocking the PCV or crimping the fuel return line and see if the voltage increases.
 
  #6  
Old 03-24-04, 10:38 PM
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thrashed driveshaft u-joint

Looks like I've found the culprit. I don't have misfiring. It's my driveshaft u-joint just behind the tranny.

The joint is completely thrashed. The joint has been worn down a good 1/8" into the U-part of the joint. It looks like the joint has been catching on itself and hence giving me the misfiring sensation. Holy smokes!

Now the challenge is finding a replacement driveshaft since the joint is not replaceable. Toyota has discontinued the darn thing. I've checked one junkyard so far, no luck. Of one I found from an automatic tranny, it looks like its joints are starting to get loose since I can hear some clicking if I twist the thing back and forth. I assume this'll be somewhat common given the age of the car.

Unfortunately, I have a manual tranny. and the shaft from an automatic is shorter in length.

Can the joints be rebuilt? Toyota manuals say replace the whole thing.


BTW--on the O2 sensor-- I opened up my propane torch (unlit of course) and shoved it into my air intake. O2 sensor output didn't jump much above 600mV or so. I assume it's almost time for a new one?
 
  #7  
Old 03-24-04, 11:58 PM
Join Date: Jun 2002
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Glad you found it, I'm suprised you didn't have a vibration around 50-60 mph with a bad joint.

Have you gone to parts store for the joint? If they can't help you find a shop that specializes in repair and rebuilding of drive shafts. I'm sure they can help you.
 
  #8  
Old 03-25-04, 05:45 PM
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celica O2 sensor

A properly operating O2 sensor should range between 125-800 mV and cross the 450mV threshold about 6-8 times per second.

If you've got access to a graphing multimeter, you should see a waveform with a "tight" or "close" pattern filling up most of the window.

Matt
 
  #9  
Old 03-27-04, 05:23 PM
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Hi Toyotaman--
No vibrations whatsoever. Just a lot of rattling right behind the tranny at low speeds! It was getting progressively worse. Needless to say, I'm not driving it now until I find a new driveshaft. The thing makes me nervous.

Driveline shop wants $160 to rebuild it, but not sure if they can reuse the piece that fits in the tranny--it's gouged.

Found a dismantler with one in the next town over. I might make a trip out there in the next couple of weeks if I don't find one locally any sooner . He wants $75 for it.


Hi Matt,
here's a quick and dirty scope shot of me running at idle (top) and approx 2Krpm (bottom). Maximum levels look a bit low... definitely not 6-8 transitions per second. Don't only newer cars run that quickly?

200mV/div vertical scale and 1 second/div horiz scale

sorry--Had to compress and resize the heck out of it to fit within the 10KB limit, so it's a bit hard to read..

thanks folks!
 
  #10  
Old 04-07-04, 03:22 PM
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it's the driveshaft

Hmm, not sure why my .jpg doesn't show up even though I supposedly attached it... oh well


So it looks like a new [junkyard] driveshaft fixes it. I picked it up this morning for $30 at a serve-yourself yard. We'll see how it goes in the next few days. So far so good.

Only concern is every junkyard car's driveshaft is somewhat dented from the forklift tines that were used to move the car around. I couldn't tell if the shaft was bent by eyeballing it--it appears ok, but the shaft has a few minor dings in a couple of spots.

Since this is a 2-piece driveshaft, I'm tempted to swap out the banged up back half with my original one which is in good shape. Are shafts balanced as a whole, or are they balanced in pieces? I naively assume I can swap out the back half and not have to rebalance anything? Maybe I'll just leave it as is.

Also, is it normal to grease the u-joint? I can't see how I can force any grease into the joint since it's pretty tight.

thanks again everyone!
 
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