RJason1111

Sorry for the long winded description, but I have a real mystery that I've already put weeks of time into and need a honda genius to help me. I've stumped two mechanics, and a few autozone employees with this question. I've even stumped the guys on the carpros website.

Symptoms: Intermittent and temperature related -

1) Severe loss of power - feels like retarded timing. The base timing is exactly 16°. I would describe the power loss as the equivalent of running three A/Cs. No, or very slow acceleration. Same power loss that running on 3 cylinders feels like, but without stuttering or stumbling. I want to mention that it's MAJOR, so that we rule out sensors or systems that only have a minor affect on horsepower. And Intermittent.

2) Idle becomes more unstable - Starts bogging down to 550 or so, but sometimes settles on 900, 800, etc. This might not be a symptom, as I do have a tiny brake booster vacuum leak that can cause this. I'm more concerned about symptom #1, which a small vacuum leak wouldn't do. When the idle is stable at 900 while the car is warming up, the car drives fine.

3) More engine noise - The engine becomes more noisy. Makes in-and-out grinding sounds. Like mwah-mwah-mwah at a frequency of about one second. Some clicking or pinging becomes noticeable.

4) Runs lean. My MPGs went from about 32 city, to about 37 city. The spark plugs are a bit on the white tip side, but mostly look normal.

** All of the above symptoms occur at the same time, the engine just goes into FREAK OUT mode. It seems temperature related. Letting the engine cool for 30 mins does not fix the problem. Letting the engine cool overnight fixes the problem temporarily. In the mornings, I get a perfectly working, powerful car. On my drive home I get a car that feels like a fuel pump is dying.

Spark and Ignition test okay: I hooked a tach to all four plug wires and none are missing. Spark tester shows I'm getting a spark. I did a resistance test on primary coil, secondary coil, and ICM. twice, once with engine cool, once at temps the engine acts up. Both time the components passed the books specs. 18K ohms primary, 0.7 ohms secondary, 2.2k ohms ICM. Wires get battery voltage.

Base Timing is correct: Took my car to the mechanic who did the timing belt and he double checked that the timing is 16°. I recently replaced a leaking valve cover gasket, it had leaked into the timing chamber, but oil didn't get on the belt.

Fuel delivery system tests okay: I installed a Fuel Pressure gauge and it reads 44 psi with FPR closed. 34 psi with FPR engaged. It holds pressure after the car has been turned off. I did a fuel volume test and got 27 ounces of fuel in 30 seconds. I pinched the FPR return line and the pressure went up to 78 psi. Injectors are clicking. I put injector cleaner in the tank once in a while. I haven't actually tested the injectors other than listening for the clicking. However, I've heard they do not fail intermittently, and would fail on my morning drives as well. I haven't cleaned them, but I use good fuel and put an FI additive in the tank once a year.

Vacuum System tests okay: I bought a vacuum gauge at harbor freight and am getting about 21 inHg. Stepping on the throttle, it kicks down to almost zero, releasing the throttle it jumps to about 25, then settles back at 21. The gauge does sort of sputter (up/down) about 0.5 inHg. I'm not sure if that's normal. I also tried the propane trick and no amount of propane anywhere around the gaskets caused the engine RPMs to go up.

Throttle Sytems test okay: I cleaned the TB and all of the passages. I hooked an ohm meter to the TPS and the needle moved smoothly as I opened and closed the throttle. I replaced the gasket and torqued the bolts to spec. I can't test the MAP, that I know of, but I heard they don't usually fail and if they do, you get a rich condition, not lean.

Oil systems test okay: I have proper oil level. No coolant leaking into my oil.

Cooling systems test okay: I recently replaced the radiator, hoses, and t-stat. I spent 45 mins burping the system, so there aren't any bubbles. The cooling fan comes on when it should. The radiator is not plugged, it gets good flow.

ECU / Emissions test okay: I replaced ECT and O2 sensor as a "shot in the dark" at this power/fuel problem. Everything seems up to spec. The air intake temp sensor tests good. I made sure the ground for all the sensors was clean (the one on the thermostat). The catalytic converter is about 230 degrees prior and 320 degrees aft. There is good flow coming out of the tailpipe. I would love to monitor the sensor data stream, but I'm not sure if Honda can do that on OBD-1 and how much they would charge. I don't get any check engine lights. The ECU works, I can make a CEL by unplugging a sensor. I made some leak detector from dish soap and put it all over the exhaust manifold on a cold engine, started it up, and found no leaks.

Battery / Charging systems test okay: Battery get 12.6V, 14.44V when started, 14.23V after warming up.

Engine Temps seem okay: infrared thermometer pointed at the "D15B7" stamp show 165-180 degrees depending. I think napa gave me a 172° thermostat, so I'm going to put an OEM one in tomorrow.

Compression: tests okay.

Main Relay looks okay: the contacts are still well soldered and not pulling away from the circuit board.

** Please note that although the problem seems to occur at certain engine temperatures. I think there's more to it than that. The problem starts about 20 mins into a cold morning drive, and about 5 minutes into a warm evening drive. At 5 mins into the evening drive the temps are around 175. At 20 mins into a cold morning drive the temps have been at 175 for a long time.

I recently had a mechanic (a very inexpensive mechanic) adjust the valves. Could that have messed something up that would cause my problems....?

As you can see, I've spent a few hours a night on this problem for a few weeks now. I'm overwhelmed with possibilities, but want to rule out things that would not have a MAJOR affect on power. Yes, I might have a small vacuum leak, but my tests reveal that I don't have one large enough to make the engine feel like I'm driving into 200MPH winds.

At this point my best guesses are...

- Mechanical engine failure, that acts up intermittently or with temperature.
- Ignition Control Module or Coil that test fine, but are still failing (don't these fail rich, not lean?)
- Faulty or plugged MAP (don't these fail rich, not lean?)
- Cam/Crank/CYL sensor
- Faulty ELD
- Fuel Injector Solenoid ... hmmm, got me wonderin'
- Close loop issue
- The valve adjustment my mechanic did was wrong. (wouldn't this affect both cold and warm engine the same way..?)

Although the engine gets very noisy, loses power, and bogs down. It does not overheat and headlights do not dim.

This weekend I'm installing an OEM thermostat, replacing some older battery cables, replacing the Air Intake Temp Sensor, and remaking the engine grounds, since the wires look bad. I don't expect any of this will fix my severe power loss problem though.

I would LOVE it if someone has experience with these exact symptoms and knows of an obscure thing I can test. The basics like fuel pressure, spark, cooling, and charging system I've already passed.

THANKS,

Robert

Former User

The lean condition seems to be the main clue. It sounds to me like the ECU may be the problem in that it is not properly receiving or processing information from the O2 sensor. Have you tested voltages and resistance on the O2 sensor wires? If they are fine, you might want to find someone who will let you swap in a compatible ECU to see whether the problem goes away.

RJason1111

Good idea, I'll test the resistances on all the wires tonight.

I just remembered another symptom.

5) When in idle. I open the throttle to 2000 RPMs. It climbs nicely, then as soon as I stop moving and it rests on 2000, it then starts to fall... 1900 rpms, 1800 rpms... keeps going down to 1400 rpms. This is with the throttle at a steady position, and vacuum not changing. Shouldn't an engine hold an RPM at a given throttle position...?

Ron, I'll get back to you on the wires. Thanks again.

Robert

Former User

I think that this symptom, as well as others, may be a response by the engine to the extremely lean conditions.

RJason1111

Well, it hasn't been acting up much the last couple days. Probably because the temperatures have been on the cold side around here.

I ran EXTENSIVE ECU tests. Man, that's hard work. Everything looked good.

To answer your question, the resistance on the wires between the O2 and the ECU are all 0.3 to 0.5 ohms.

- MAP starts at 3.56V and goes down to 0.90V when I start the car.
- TDC/CRANK/CYL sensors all have 450 ohms resistance at the sensor and about 420 ohms at the ECU.
- ECT was about 250 ohms on a warm engine. The ECT circuit was reading about 0.97V on a warm engine.
- TPS was 0.48V closed, 4.56V WOT.
- Ignition output signal was about 11V
- ELD passed all tests. Ran about 1.5V while driving with headlights on. started at 3.5V with IGN ON.

- O2 sensor was all over the board. While driving it jumped around from 0.2V to 0.7V, seeming to average around 0.6. While idling it jumped from 0.2V to 0.5V.

Three things to note.

1) when stepping on the brake pedal, the O2 reading dropped below 0.1V. I have a vacuum leak in the brake booster, but I would think that would cause a lean reading, not rich.

2) The ECU seems 'off' a little on the A terminals. The O2 sensor heater is only being fed 11.8V, it's supposed to be 12.6V. This is due to the GND the ECU is sending, not the + the main relay is sending. Also, the Ignition output signal is sending 11V to the ignitor, it's supposed to be 10V. I don't know if these differences are negligible.

3) The MAP sensor is being fed a 3.5V signal on the Sensor wire, the manual says it's supposed to be 5V, but to be honest, I think the manual is wrong.

The best thing to come from this is I learned a bunch, and confirmed that the sensors are working, and I can "easily" test the O2 sensor when the car acts up again, now that I know how the circuit acts.

At this point, since things aren't acting up right now, I'm going to take a break. :-)

Thanks, Robert

MonkeyMagic

OP, i got you covered...

on the right track, but wrong train station, o2 sensor doesn't have enough say in injector operation and ignition timing to create these lean conditions.

i'd be willing to bet $100 USD currency that it is the OP's intake air temperature sensor or the associated circuitry. this can be checked with a multimeter.

other thing with that much power over engine operation is the barometric pressure sensor, but highly unlikely. and would throw a code sense it constantly compares values with the MAP sensor.

Former User

Edit: The MAP sensor reference voltage should be 5V. This voltage is supplied by the ECU. The lower than expected 3.5V reference voltage is possibly a hint that the ECU is faulty. I'll be interested to see whether this voltage and the output voltage drops further (=lean) when the problem resurfaces.

Just to verify, you measured 3.5V to body ground on the YEL/RED wire (+) of the MAP sensor connector, right? Did you also measure the same voltage from the YEL/RED wire (+) to the GRN/WHT wire (-)?

Former User

For my education, I wonder whether you could elaborate on this statement. The O2 sensor output tells the ECU to produce an air-fuel ratio that rapidly fluctuates between rich and lean. Please correct me if I'm wrong, but if the O2 sensor/circuit outputs an erroneous O2 value (low O2 levels) to the ECU or the ECU incorrectly processes good information, then an extremely lean condition could result.

Again, for my education, I wonder whether you could explain why you chose to focus your guess on the IAT. Have you seen or heard of a bad IAT that caused an extremely lean condition? I ask only because I haven't heard that a bad IAT could cause such a problem.

RJason1111

Hi Ron and MonkeyMagic,

I was wrong this whole time. Now that I've educated myself on quickly reading an O2 voltage, I've done so twice once the engine got hot and started acting up (10 mins into a drive), and each time it was reporting 0.8 to 0.9 volts. So, my LEAN condition is actually a RICH condition. I don't understand the increased MPGs, other than, I probably made a mistake in the calculation, or the mechanic who did my timing belt put some gas in...???

So, if I told you the problem is RICH running, power loss, after engine warms up... what would you say???

I'm really thinking Ignition Control Module or Coil now...? I'm going to replace the Engine ground just for fun...

Thanks again, Robert

Former User

Your high gas mileage is completely inconsistent with the 0.8-0.9 volt reading (rich) from the O2 sensor, as is the color/condition of your spark plugs and your failure to mention any rich smell of unburnt gasoline or black smoke in the exhaust. Please clarify. Therefore, either your new O2 sensor voltage readings are wrong, the O2 sensor is malfunctioning, or the O2 sensor wiring is bad. Can you describe again how exactly you are measuring O2 sensor voltages.

Are the O2 sensor average voltages approximately 0.45 V when you are not experiencing a problem?

Did the reference voltage from the MAP sensor change when the problem resurfaced?

However, if you are indeed running rich when the problem occurs, then a faulty coil and igniter unit is a possible culprit.

RJason1111

Yeah, I'm at a loss. I'll have to get back to you. I am still getting overly great MPGs, but the Oxygen Sensor is reading rich on the meter. I tested it disconnected, with the meter in 2V mode, positive lead on the O2 blue wire, negative lead on the O2 white wire. After my last post, you had me wondering. I let the car sit for a couple hours, drove it to the nearest gas station, 38 MPGs. Pulled the car aside and tested the readings, 0.1V, 0.2V... Brought it up to temp by plugging the O2 back in and revving the engine at 2000 RPMS for a couple minutes. It started to make the "needs a tuneup" sound again. Stopped the engine, unplugged the sensor, and started the car... 0.8V, 0.9V...

Somehow it's reading RICH, and the car is running lean... It's a brand new DENSO O2 sensor, I guess it could be bad.

I need more info, I feel like I'm not telling you enough. I'll get back after I've had more time with it.

I'll test the MAP when it acts up also.

Thanks,
Robert Jason

Former User

One possibility is that the O2 sensor is falsely reading rich, thereby causing the ECU to respond with an extremely lean air-fuel ratio. This sounds like an O2 sensor/circuit problem.

I need to think more about how you are doing your O2 sensor voltage readings.

Former User

I read the conditions in which you are testing the O2 sensor. I think that you may have caused the engine to run rich temporarily by disconnecting the O2 sensor. When the O2 sensor is disconnected, the ECU will cause the engine to run in open-loop mode, which by default is rich. I think that this is the reason that you measured 0.8-0.9V at the O2 sensor. Nonetheless, I was unsure exactly when you connected and disconnected the O2 sensor in your tests. Was the O2 sensor also disconnected when you measured 0.1-0.2V?

civic_driver

Is this a D15B7 engine?

RJason1111

Thanks everyone for your help,

I have a feeling I've determined the problem, but only if you can answer one question...

Can a vacuum leak cause all this headache?

I hooked up two multimeters today at work, knowing that the problem occurs on a trafficy hot evening. I had one monitoring the MAP (at the ECU), and the other monitoring the O2 sensor (at the ECU).

When I started the O2 was jumping around like it should. For some reason it was still hot enough to be in closed loop, even though it had sat a couple hours.

Ron, you were correct about me testing the O2 wrong, I did unhook it and create a rich scenario.

So, the O2 seemed to want to be around 0.6 to 0.7 for most of my driving, it fluctuated a bit, but those numbers came up 80% of the time. I decided to take it on the freeway and get the thing really hot.

The map was around 0.9 at idle. moderate accelleration brought it up to 1.7, 1.8, 1.9, and over 2 volts. Once I was at a constant throttle it hovered around 1.2 to 1.5 volts. While on the freeway, the constant throttle hovered around 1.5 to 1.6 volts. Decellerating, brought it down to 0.8 then stabalized at 0.9 volts. It did NOT want to act up on the freeway, my power stayed good for 20 mins, I was almost out of town and decided to turn around. It was fun watching it on the freeway, keeping my speed going up hill the MAP was 1.9 + volts, keeping my speed going down a slight grade, it would be 0.8 volts. Kind of fun to see.

I decided while I have it set up, I'll do some traffic driving, stop and go.... I started seeing something new... When I would let off the gas, the O2 would drop down to 0.011 or so for two seconds, then go back to it's happy place of 0.6 to 0.7. Then if I brake, the same thing, it would drastically drop. My brake booster has a vacuum leak. and it's causing the O2 to read ZERO when I brake, or when I let off the accellerator. Probably why stop and go traffic would bring it on, but the freeway wouldn't. Also probably why on a cold morning it wouldn't act up much. 1. less traffic, 2. temps stay low.

I am curious why it was so happy about 0.6 and 0.7, I expected to see more 4's and 5's...?

The Map was also noticing a change. Instead of decellerating bringing it down to 0.8, it was dropping down to 0.6 (in city driving)...

I have a feeling the MAP and O2 are working, and that after the engine gets hot, the brake booster has a vacuum leak.

The only thing that still 'gets' me about this is that I thought vacuum leaks meant a surging 1000,500,100,500 every other second.

Could this cause my power loss...? or is it normal O2 sensor behavior...?

Someone else mentioned an exhaust leak.... I do smell funny things, but I have almost no sense of smell, so I couldn't tell you.

Thanks, Robert

JarvisW

Plug the brake booster, and check it again like that. (take hose off booster and plug it with a 3/8 extension, or whatever will get air tight)

Also you may want to hit the vacuum hoses with starter fluid, or carb cleaner and see if that effects anything besides the booster.

With the booster plugged, you should see a regular running engine, IF that is the only thing wrong. If not, then at least you can eliminate one source of problems.

Former User

No, unfortunately, a vacuum leak is unlikely to cause the low power problem that you are experiencing. It might instead cause the engine to run a bit rich, which might explain the somewhat high 0.6-0.7V from the O2 sensor during closed loop driving. However, the latter idea is inconsistent with your great gas mileage, so the voltage doesn't really seem to signify a rich condition.

In addition, the very low voltage from the O2 sensor when decelerating and braking is normal and reflects fuel-cut off by the ECU (see diagram below). Did the low power problem ever occur during this most recent test drive? I think you should look elsewhere for the cause of the problem. The key will be finding abnormal sensor readings specifically linked to the low power problem.

Former User

As asked by civic_driver, what year Civic and engine do you have? Is the engine a swap and does it match with the ECU?

Jimster480

do you have another ECU you can test with. After reading this thread, you have ruled out basically all the common problems. Have you tried driving the car with the O2 disconnected and seeing what happens?

RJason1111

Hi Everyone,

The engine is a D15B7, and the ECU is a P06.

I got it to act up last night, my car sounded like it has swine flu...

I ran tests on all the sensors again and they all checked out fine. During the problem (MAP 0.92V, Air Temp Sensor 0.94V (165°), ECT 0.78V (176°), TPS 0.49V, ELD 3.0V), with the O2 sensor jumping around a lot.

So, when the car is running great the O2 looks like this...

0.6, 0.7, 0.3, 0.6, 0.2, 0.5, 0.6, 0.7 (happy in the 0.6 to 0.7 range, a little rich)

When the car is NOT running great the O2 looks like this...

0.7, 0.8, 0.0, 0.1, 0.2, 0.9, 0.8, 0.8, 0.0, 0.2 (happy in the 0.7 to 0.8 range, AND happy in the 0.0 to 0.1 range, very schizophrenic)

So, I have a simultaneously RICH and LEAN condition, I don't know, maybe it balances out. I'm going to replace my leaking Brake MC and hope the new seal between that and the power booster fixes the vacuum leak, so that the real problem is easier to see.

I appreciate all the help, you are all awesome. I'm going to do some work over the next couple weeks and let you know what fixed it.

I "wish" I had an ECU to swap out, that would be a good test. But, let's face it, the only things left to replace are the ECU and Coil... :-)

Thanks, Robert Jason

Jimster480

it wouldnt be the coil, i dont think so. You can pick up an ECU on Ebay for $30 usually. I got my Auto P2P for $30. But manual ECU's are more and especially OBD-1 so idk. u could always get an external MSD blaster coil. I have one of those on my car cuz of turbo, but you dont have to be boosted to have one lol. And they are pretty cheap, like $60-70 on ebay for the whole setup (from MSD).

RJason1111

Is it normal to have an oil-like liquid on the ECU terminals? like an electrical contact spray or something?

I took the ECU out, to look for burnt spots or bad caps, and saw an oily fluid on the contacts...

Jimster480

thats some weird ****. have you ever taken the ECU out before?

jasonrazz

Yo RJason1111 You and I have exactly the same problem (and name, what a coincidence!) I have a 93 Integra GSR with a stock B17(and by stock I mean it looks like it barely came out of the dealer!) with exactly the smae problem. When I drive in the morning to school, which is about 25 miles away from my house, the car feels great, it responds great with nothing out of the ordinary but when Im driving home sometimes on a trafficky LA highway, the car feels like its always driving one gear up.

I'll be travelling and at around 3000 rpm the car feels like I just slammed into an invisible wall of thick air. Then it goes away for a second or two and comes back. I can hear the engine revving really fast but the car moving really slow. Its embarrassing cause last time, on one of the cars worst days, I was driving beside an old lady in a hyundai and I had to drive and shift as if I was drag racing her just so I can keep up with her! and she WASN"T EVEN TRYING TO RACE!! (neither was I but it illustates the point).

Anyways, I've also found this problem as more serious than just a little old vaccum leak. I've completely tested for any vacuum leaks and there are none. I've check timing, the fuel pressure and ignition equipment. I have lots of mechanic friends since I work next to a lot where there are like 6 shops all in the same center and they give their own conclusions. Perhaps they think Im stupid or something cause they don't really understand how bad it is. Some tell me that it is the Idle control valve and that I need to replace the temperature sensor and this stuff. Im not sure if the problem had anything to do with it but I recently had to change the headgasket cause it had warpped abit causing it to leak oil into the coolant and vice versa. but now Ive fix that and the car is still the same

I believe that I too am running lean cause my plugs are a bit white at the ends but at the base they are blacker than black. I've done a complete engine rebuild and I know exactly how everything is set up.

I recently took a look at my ECU and I tested the voltages, when I tested the Red wire with Green wire it was at 5V but the White wire showed around 3.46V. So because the service manual states specifically that they both should be 5V then I figured that that was the problem so I swapped in my PR4 I have laying around from an LS and the voltage on the white wire shows 3.5V exactly.

I was so confident that was the problem cause if the voltage only reached a maximum of 3.46V then there are still an extra 1.54V un accounted for.

Now Im stumpped cause one of my mechanic friends says that its the ICV that is causing it, probably due to te fact that my idle is sometimes at 700, then at 300, then on some not so rare accasions all the way at 1500, without me having touched the idle settings. But since the main problem is power wise I don't believe thats going to fix it

jasonrazz

Also something I forgot to mention, a while back ago the car made a faint ringing noise at idle and then left after a couple of weeks now the ringing is back, this happened I think when I changed the head gasket then went away and I think it came back when I unplugged the ECU. Im hoping that the problem will get settled soon cause it seems like Im narrowing down to the root of the problem. My mechanic friend said that he would get me a new temperature sensor and an ICV to test and check whether thats the problem.

Im starting to believe that it is probably the ECU cause I also seem to have some kind of ghost haunting my AC fan. When the car gets hot after an hour or so of driving, and I come and park the car the AC fan, not the engine fan, stays on. I used to think it was an automatic thing to cool the engine even while the cars sits there but I don't think its normal, especially since after a while it will start turning off and on like if theres a shorts in it. it will sputter on and off inconsistently and eventually it will turn off completely BUT if I put the key in the ignition and turn on the accessories it does it again and continues even after the key is out.Now Im not sure whether its a relay problem or an ECU problem but if it is ECU then maybe the fan problem is a sign that the ECU is either haunted, possesed, crazy or not working right.