range of 'no power'

[Will89Lxi]

First let me say this is the best site I have seen yet when dealing with older Hondas! Thanks for the info I have gleaned so far!

My problem... hmmm... 89 Accord Lxi runs great cold. When warm the power is not there and the engine runs rough (like it's running waaaay too rich) until it surpasses the 3500 RPM mark, then all power is back full force. Two shops said it was a bad temp coolant sensor and replaced it both times... still no good though. However, you can disconnect the sensor and it runs great, if you can get it started, but it idles at about 200rpm without the sensor and the A/C will shake the steering wheel out of your hand at idle without the sensor connected.

I guess the computer might be malfunctioning.... I don't want to waste any more time with shops if they are only going to do whatever will get my car out of their shop. I'm considering cleaning/replacing the EGR unit to see if that will help since some posts point in that direction, but the computer keeps saying engine temp coolant sensor.

Any pointers will be greatly appreciated... my wife wants me to dump the car at this point but I want to keep it -- it's a great car but just has one little bug that's a serious pain! Help!

Thanks!
Will

[POS carb]

hmm do u have a check engine light comeing on (or PGM-FI light)??

[Will89Lxi]

The check engine light does occassionally come on after the engine warms up with the sensor connected. Sometimes, the light does not come on... however, when it does come on, the power comes back sporatically -- sometimes full power is restored, and sometimes it still runs very sluggish and rough.

[ACCORD EX]

i used not to have power below 3000 rpm ! and it was my ignition timing !

MIKE

[POS carb]

yea it could be that but he said it is temperature related. Next time the light comes on count the blinks of the LED on the ECU and it will tell you what it thinks has a problem. The ECU is under the driver's seat

[ACCORD EX]

Originally posted by POS carb
yea it could be that but he said it is temperature related. Next time the light comes on count the blinks of the LED on the ECU and it will tell you what it thinks has a problem. The ECU is under the driver's seat

oh me !


MIKE

[Will89Lxi]

From which viewpoint will I be able to see the LED on the ECU (as in from the front of the seat or back)? I will get to it this evening... my fear is that the ECU is going out... the consistency at which the problem occurs is almost perfect. I can't remember who said it, but:

"yea ur ECT sensor could be doing that....eventually its gonna get bad enuf to the point where the car wont start anymore after its warmed up. The problem is once the check engine light comes on for that sensor, the engine goes into limp mode, which is full rich and retards the ignition for safety. My car used to have that problem...it smoked a lot on hard acceleration (too much gas) backfired on shifts, or just letting up on the gas with it still in gear....once u change the sensor..the car will run like new....."

Problem is, mechanics have replaced the sensor twice, and I have replaced it twice... but the problem is still there. At least the car doesn't die at idle anymore. I'll get the code off the ECU this evening.

In the case that the ECU is bad, how much will a new or used one cost? Wait a tick... the wire going to the sensor is kind of hardened. Could that be a problem?

Thanks,
Will

[rocky2]

fuel injection is great if its working right , but when its not..................................... Check out all wiring to all sensers,injecters,grounds,ect. Pull all plug ins and look for corrosion.

[BoredRec]

Check the code (you see if from the back seat). The reason it runs better when the check engine light is on is cuz the computer goes to default parameters. If your car is running overly rich then the computer settings in default mode might be leaner than what the bad sensor is saying, thus why your car idles smoother.

Another thing, if it IS running rich, you might want to take out the spark plugs and make sure they aren't gas fouled. I'll bet that could be a big contributer to your problem. Either clean them, or replace them.

BoredRec

[Will89Lxi]

Ok, the computer says the error code is 6, which is supposed to be bad ECT sensor or circuit. Maybe I need to replace the portion of the wire harness going to the ECT sensor or replace the computer itself. The sensor has been replaced 4 times in an effort to fix this issue.

Where can I get the pigtail portion of the wire harness going to the ECT sensor? I've checked prices for used ECUs and it comes to about 130-145... definitely more reasonable than trying to let the shops hack around with my transportation for another day or two. Is it possible that the ECU is malfunctioning and thinks there is a bad ECT on the engine (code 6)?

Thanks,
Will

[Afrosheen]

Well it said bad sensor OR circuit. Since you've replaced the sensor a million times I'm betting it's the wiring that handles that sensor, something's gotta be loose.

[POS carb]

possibly corroded terminals. Since u said the problem worsens with heat I'd suspect a bad signal (heat = resistance) so try cleaning the prongs on the sensor/pigtail

[BoredRec]

Run a redundant wire (mechanical term). You can't just buy a new wire harness for that circuit...it's all one huge harness. So instead make a seperate harness out of wires you have around the home (or buy some) and cut the wires at the sensor and at the computer, run these new wires in their place. Just make sure you know what your doing before you start. Also get a manual so you know which wires to cut.

BoredRec

[Will89Lxi]

I think I am going to go with the redundant wiring plan (thanks for the idea)... I think for safety sake, I'll run the new wires from the ECT sensor to the firewall and stop there making sure that I don't get lost on tracing the wires... if that doesn't work, I'll try going all the way back to the computer. If I really screw things up in this process, does anyone know what a used 89Lxi (EFI) wire harness is going to cost me?

Will

[Will89Lxi]

Hmmm... Ok now this is wierd. I was checking resistance in the temp. coolant sensor wires running to the computer... one I could find by color and the resistance was 0 ohms The other wire is trouble... several wires at the computer responded to the ohm meter... I would think that there would only be one. Also, with the harness plugged into the computer, the ohm meter registers 0 ohms across the two wires that connect to the sensor I would love to have a 89 Lxi FI Wiring Harness Diagram if anyone would care to share One more thing -- the wiring harness junction under the hood in front of the master cylinder (round white harness junction)... I checked wires there as I did from the computer, and it seems that about 3 wires respond to the green/white wire at the sensor I am going to guess that several wires have melted and merged I'm really surprised at this point that I'm able to drive to work at all.

Does anyone have any pointers? Are these wires supposed to have crosstalk in them? Should I just replace the underhood portion of the FI wiring harness?

Thanks,
Will

Please share a wiring harness diagram if you can the two wires connected to the coolant temp sensor are dark green with white stripe and yellow with light green stripe.

[monsonhonda]

dude, i got the same problem right now, my check engine light doesnt come on, but thats cause the led's dead, doesnt come on in the beginning, but i get a code 6, i got an 88 lxi. i changed the sensor and i still get the error code, and it runs rich as hell, i mean it f*cking stinks behind the car.
so yeah, whats the procedure for checking the wires.

thanks

fussell

[jteuton]

Thinking out loud on a few posts back....when the engine is in closed loop and looking at stored parameters...it doesn't retard the timing does it...i mean how can it....we have a mechanical distributor with weight and vacuum advance...it doesn't have a magnetic pickup..

[monsonhonda]

couldnt it retard the timing if one of the parts in the vacuum system screwed up, causing vaccuum to be applied incorrectly. or the rotor could be badly worn.

[jteuton]

how would it know....sure your car would run rough cause of the vacuum problem....but the distributor is mechanical and as far as i can see it in no way monitored by the computer. That's why reprogammable cpu's are hard to find for our car...you would have to customize a magnetic pickup lead. The only tuning you can do with a computer is the air and fuel curves and shift points....Thank god i'm getting rid of my auto...Somebody correct me if i'm wrong

[jteuton]

Maybe it can control it through the solenoids in the vacuum control box but that has to be about it and i'm not even sure about that theory.

[88LXi/87CRXSi]

Will, after reading your last post, I think I can answer a few of your questions, I hope! 1st about the ohm reading between the other wires, is it between the dark green with white stripe wire and other wires? if so that would be normal, cause the dark green with white stripe wire is a 5 volt dc constant voltage signal to the sensor and a couple other sensors. So you're reading the resitance values of those sensors & would be expected. 2nd, what's really unusual is

the ohm meter registers 0 ohms across the two wires that connect to the sensor

. I went and measured the resistance on my 88 lxi and the resiatnce was 1710 ohms. Big difference!! check the resistance with the ecu unplugged, hopefully it's not in the ecu! Also you should get about 5 vdc at the two wires that go to the sensor with the key in the on position. also the resitance of the temp sensor should be about 1.4k - 2k ohms at about 75°, and about 200 - 400 ohms@ normal operating temp! Good luck with getting it running good again.
- Steve

[Einstein]

Mine has a similar "problem" when it's almost completely warmed up. I pull out into traffic at 1/2 throttle and the car accelerates lazy. All of the sudden (I'm not sure what RPM) It lets go and acceleration is what it should be. After the first time it does this, and I get out on the highway, it never does it again that trip. This confuses me!

[Will89Lxi]

I haven't had the chance to check the wires again with a meter, but I plan on pulling the seat again tonight. According to the service manual I found -- thanks to Paul/Aerodeck -- the voltage at the computer between the two wires should be .5v to .9v when the engine is warm -- I plan on checking that tonight. If the voltage is correct, that suggest the ECU is faulty oh well. If not, then the wiring harness has issues. One would think a car mechanic would follow the service manual (shops have replaced the sensor twice)... when all else fails....

Steve, the wires at the TC sensor ohms read 0 ohms when plugged in at the ECU and read infinite ohms (open circuit) when not plugged into the ECU. Thanks for the info about 5v at the sensor with key on -- I'll check that. The wiring harness diagram found in the service manual indicated that there was a common ground wire going to the computer and that the temp coolant sensor shared it -- that makes me feel a little better, but I'm torn between having to replace a faulty ECU or having to track down where a wire has melted amongst other wires under the hood -- one of which I'm pretty sure is the problem doh!

[monsonhonda]

alright, jteuton, i am thinking along the same lines as you, i know there is a wiring harness that goes to the solonoid box, but i do not know if the vacuum advance is controlled by the computer or not. anyway

my car is still giving error code # 6, and the electric cooling fan rarely comes on. so i took off the plug on the temp sensor and jumped it with a paper clip and it turned the fan on..... fancy that. so anyway, i had swapped the sensor out of my 89 lxi into my 88 thinking the 89's was ok, apparently not. this would lead me to believe that the ecu and harness are ok and i just need a new sensor. so tomorrow i will be getting a new sensor, but after i put in a sensor that works, will the ecu code dissapear, or do i need to pull the fuse. i cant remember.

peace

fussell

[88LXi/87CRXSi]

Will, don't think you'll get the 5V with a dead short across the terminals. And since there's no continuity in the wires when unplugged, I would guess the circuit somehow shorted in the ecu. That's just my take on what you've found, I could be wrong, but you seem to be homing in on the actual cause of the problem.

Monson, if your cooling fan came on when you shorted the terminals, I think the sensor you're checking is the radiator fan timer/temperature switch. Green connecter? Your cooling fan will run more often, and will run for 15 minutes after you shut the car off, if coolant temp has exceeded 226°F. It's probably bad, but you'll have to lay out more cash to also replace the ect sensor right next to it, smaller sensor, white connecter, to get rid of that error code #6 when you reset the ecu.

-Steve