Engine will not rev, no power?

I have a 94 civic lx with 128, xxx miles. I recently did a tune up with new plugs, wires, distributor cap, rotor, air filter, oil change. Have a fuel filter to put on still, but anyways. When I start my car up in the morning it overides a little bit to about 1200 rpms. It stops after I begin to drive the car awhile. While I am driving the car has a hard time accelerating and seems like it almost has a dead spot where I cannot make the car go forward. I feel like I have to make sure the car gets going enough because sometimes when I got into second the car does not have enough power to keep going, esp on inclines.

I was thinking that maybe I should get the timing checked out. I've never done timing before so I guess I should just pay to have it done?

I was also thinking
PCV Valve
Oxygen Sensors
Fuel Pressure
Fuel Injectors

Any input would really help if you think I am on the right track or not. Thanks.

Thanks for the help, i'm going to try that tomorrow after work. Anyone else have an idea or suggestion of what it could possible be. I think i'm going to try all the cost free methods first, and hopefully it will be one of them.

Thank you for your time. My Civic has 178K miles on it. When the engine is cold, especially in the mornings, it has plenty of power and response. On a hot afternoon, after sitting in the sun, it's a little less power. The main symptom is almost exactly 8 minutes into my drive, the idle goes down (from 800 to 550 roughly), the engine gets noisier (valve sounding, I think), and I lose a significant amount of power. The idle change is well past the FITV stage, and a good 5 minutes past the engine being brought up to operating temperature. Based on my fuel gauge being much higher (2/3 full) than it usually is after 160miles on this tank, I'm guessing it's running lean, or that the timing is off. If I stop the car, wait five minutes, and start it again, the problem persists. So, the power loss is clearly a matter of temperature. If I wait 3 hours, I have power again, for 8 minutes. I'm going to test the fuel pressure, check timing, and replace the oxygen sensor this weekend. I don't want to throw 20 parts at it, so I'm hoping you can help me prioritize things. Cooling system works great, timing belt/water pump are new, throttle body is clean, TPS tests perfectly. After turning off my car, CAT is 280 degrees before and 380 degrees aft. Vacuum stabalizes at 18 pretty responsively. My car doesn't have an EGR. Not likely main relay, because it seems more engine temp dependent, than cabin temp dependent. PCV is new. Oil is GTX 5W30 and is in good shape. Fuel pump primes. Coil meets Haynes resistance specs. Distributor is only two years old. Disconnecting MAP stalls engine. Spark plugs have gas carbon on ring, white ceramic looks great, tip looks a bit on the white side. The valves were adjusted recently. Air filter looks great.

Another note. The idle seems to stabalize at a different level every time. The RPMs drop, hang a little at 900, then continue to 700, or 800, or 600, depending on the mood of the car. I noticed that when the car has power this idle tends to settle more in the 800 or 900 and when it's lost power it settles in the 600 area.

The power loss can be described as similar to the loss you get when turning on the AC, only double that. It isn't jerking, or stalling, it just feels light on the pedal. An inch of accelerator movement, might only slightly, slowly, begin to think putting some torque on the wheels. Golf carts have more power.

So, I'm thinking Knock Sensor, replace all vacuum lines, Ignitor, Improper timing belt installation, ECT sensor, or Crank Sensor. As a novice, I'd love to have an expert help me. I have a feeling the symptom of having power when cold, but not when hot can narrow the sensor/timing troubleshooting down.

THANKS AGAIN for your time.

Robert Jason

Fuel filter is new also. Injectors were cleaned with B-12 in the tank. Combustion chambers were cleaned with water sprayed into the brake line vacuum.

I also ran a compression test. Compression is a bit higher than the 185 spec in the manual, more around 205, but all cylinders had close readings +/- 7 psi.

For good measure I made sure the valve cover GND wire, and the sensors GND wire on the thermostat had a solid connection. Battery tests good cold and running.

Okay, I have more info.

It's a D15B7 1.5L 16V SOHC engine.

In case you forgot by now, my problem is, major power loss is accompanied by a some pinging engine when warmed up. It is running VERY LEAN.

Tested the ECT, it was about 240 ohms with the engine hot (approx. 180 degrees). It was about 1400 ohms with the engine cold (approx 85 degrees). These seem a little on the low side. I might just replace it for good measure, it's only $20. Supply wire got good voltage. One thing to note, I found oil in the connector because the valve cover had been leaking for a while. I cleaned it out, the problem hasn't gone away. I wish it was that easy.

Tested the Air Intake temp sensor. Hot engine the resistance was 650 ohms, cold engine it was 1950 ohms, seems within spec. Power was a solid 5V.

Replaced the O2 sensor.

Looking through the manual. The only sensors my car has are TPS, O2, Air Intake Temp, Atmospheric Pressure, MAP, ECT, Crank/TDS/CYL sensors (all in distributor). There is no knock sensor that I know of. I've tested or ruled out most of these sensors.

On a cold engine I put soapy (leak detector) water on the exhaust manifold and saw no bubbling.

I thought I'd double check for a vacuum leak with propane gas, with IACV unplugged. The propane did not affect the RPMs. So, I could not find a vacuum leak.

Installed a permanent fuel pressure gauge. 44 lbs of pressure not counting the FPR, 34 lbs when the vacuum line to the FPR is connected. Turning off the engine the fuel pressure drops very slowly, so there is no leak.

I did a fuel volume test. I got 27 oz of fuel in 30 seconds. Not quite a quart. Seems low to me, but I don't think it's low enough to cause the problem of severe power loss.

I pinched the fuel return line and the pressure went from 34 to about 78, so the pump seems strong.

I am now getting 38 MPGs city. I used to get 32. I'm worried I might be damaging the engine driving to work and back. I'm concerned about detonation, so I keep RPMs below 2500.

Based on my tests, I really think the only thing left is the ignitor or MAP. I don't think a MAP would only act up when the engine is warm. I was really thinking it was an ECU, sensor thing since it only happens on a warm engine. It feels like timing gets retarded at that point. I don't know if I should replace the coil for good measure, the resistances on the primary and secondary are within spec.

Would a faulty ingnitor cause MPGs to go up that much ( from 32 to 38 )? Or a faulty coil?

I can run all these tests, but I have little experience with these systems, so interpreting them is difficult.

Thanks Again, this is officially the toughest problem I've ever tried to find.

Robert

Hmmm, yes it's a mystery.

I'm still pretty sure it's not a vacuum leak. Covering the IACV hole in the throttle body causes the car to significantly bog down, although not die. Also, the power loss is throughout the RPM range, not just at idle.

I'm leaning away from ignition coil and ICM because it starts up nice an quickly. And as you mentioned, these fail rich, not lean. Although I have heard they are more likely to fail after warm up.

Here's another symptom. I noticed if I have the car in neutral, and rev up to, say 2000 RPMs, the RPMs start to decline, 1900, 1800, 1700. I have to press the gas more to get it to go back up to 2000. They won't keep declining, 2000 might go down to 1600 and stop there. Shouldn't the RPMs hold steady at a given opening of the throttle? I have a feeling this symptom might be more telling than previous symptoms.

I'm not sure if this matters, but the problem usually occurs when the engine is around 190 degrees. This might be why the engine runs great for 10 minutes.

I'll check the timing today and get back to you.

Also, when applying electrical load, the RPMs surge, or are SLOW to respond. Example, at 800 RPMs, turning on the headlights, half a second delay, then RPMs go up to 1000, then after a couple seconds settle back at 800. Weak IACV? Maybe this three second RPM jump and settle is normal.

- Intermitant loss of power
- High MPGs (lean running)
- erratic idle (settles anywhere from 600 to 1000 randomly)
- RPMs slowly lower at set throttle position

I've read that lean running can be Weak Coil, MAP, TPS, Air Intake Temp Sensor, Vacuum Leak and other stuff we've already ruled out.

Would a faulty IACV cause this problem?

Some notes on the brake booster. I am getting intermitant solid and soft pedal. This keeps pointing to a vacuum leak. When I tested the vacuum, previously, I hooked it to the brake vacuum line. So, I may have eliminated the source of the problem when I tested the pressure. I'll cover the IACV hole and try the propane technique one last time tonight.

Just for troubleshooting sake, what if we pretend the problems have nothing to do with the car warming up. As I'm noticing the cold performance seems to be getting worse as well.

Can I clean out the MAP sensor by soaking it in electrical cleaner?

Thanks again. I'm about to go parts shotgun on this because it's so frustrating.

Robert

Hello everyone this is a very hard question, I have a honda civic 1994 coupe 1.6 EX, manual transmition and everytime is in neutral or car stoped the RPMs go down close to 0 but the car doesn't turn off and you can hear a noise because is to low the rpms that the engine is shaking, I saw that when the car is cold there is not trouble at all the rpms are close to 1000 but when it gets the normal temperature it starts going down to 0 rpms.

What can I do, I checked the computer and it tells me that no sensor is bad what else can I do? Or what you think is not working here? The car runs great and hasn't a problem with rpm when is running on the freeway, and never gets overheating

Yes, it surge and go back close to the normal rpm and drop again close to 0 rpms

KHLow2008,

Thanks again for your help.

I was completely wrong about the situation. I have learned a lot from this. I did some extensive testing on my ECU, ran through all the voltages from the sensors. I learned how to read an oxygen sensor, which is easy, now that I understand it.

Last couple times it acted up (again after the car was hot), I pull the O2 sensor wire to see how lean it was running. Guess what? It's running RICH, when the problems occur. The O2 sensor is getting great readings, then when the loss of power occurs, I'm getting 0.8 to 0.9.

I promise I'll post the solution when I've figured it out.

On the ECU, the MAP was reading 0.97 volts at idle, so I don't think it's the map. The MAP sensor wire is getting 3.56V from the ECU. The other MAP power wire gets 5V. I'm told 5V and approx 3V is correct based on the manual. And approx 1V in idle.

TPS passed the voltage specs closed and WOT.

I've replaced the ECT and Air Intake Temp Sensor. They both pass resistances at the ECU.

Cam/CYL/TDC all pass.

Basically, ALL the sensors passed the ECU voltage and resistance tests.

FI's are all 4 clicking when the problem occurs.

I took off the timing belt cover and made sure the cam and crank were aligned, they were.

So, we're down to three options.

1. Electrical, short/open
2. Ignitor
3. Coil

Does the rich condition change things?

Thanks, Robert

This happend when is in normal temperature (all ready warm), and happend everytime.