Mad at my 98 civic LX! Sudden power loss / hesitation is making me nuts!
 

I've got a 98 Civc LX, and recently it has developed a very strange problem - for the first couple of minutes after start up, the car has abrupt and intermittent power loss... I'll be driving, and all of the sudden the power just cuts out completely (no matter how much gas I give it, the car keeps slowing down), and then, just as soon as it started, the power snaps right back... it'll do this several times. If I come to a complete stop when the power loss occurs, the car will idle very low and rough.

So far, I've changed the fuel pump and filter, and the distributor cap, rotor, and spark plugs... no effect whatsoever. Anyone know what could be causing this?!?!

Does it only do this when it's cold, or after it warms up as well?

It does it with the motor hot or cold after start up... I *think* that it happens more when the engine is cold, but I'm not sure.

Umm...

this is just a shot in the dark, but you might want to take a look at your O2 sensor...?

when you first start your car up, do you start driving right away.. or do you let it sit for a second to warm up? like nothing too long.. even like 20 seconds.. ?

Haven't touched the O2 sensor yet - not sure how it would cause the problems I'm having, but I'm definitly open to ideas. I guess I could unplug the O2 sensor and force open loop mode... if that eliminates the problem, then I'll go grab a new o2 sensor and see what gives.

My wife and I usually start driving pretty soon after the car turns over... definitely don't wait as long as 20 seconds to drive it.

I was thinking more along the lines of Idle Air Control motor. Sometimes if they get carboned up, you can get some really goofy idle conditions. It could be EGR as well. Have you tried running some fuel injector cleaner through it?

Also, is your check engine light coming on during any of this?

i dont think its your o2...if it was your secondary one would signal you that it was bad.... you only have a 5 year old car with i am guessing around 60,000 miles.. it seems like a throttle body sensor problem, did you check your distributor cap.. wires may be loose,,

i have a 98 ex with 164,000 miles on it, never changed anything major, solid compression, now i just want to see how far i can go before it dies...

It's got a little over 70k miles... I installed a new distributor cap and rotor yesterday, and put the fuel pump/fuel filter in last weekend. Might pull off the EGR valve and see if there is a problem there... after that, I really don't know where to look next. You think the TPS sensor might be the problem? Any way to check it? I wish I had some data logging or diagnostic software so I could figure out what exactly is going on

Don't think it is a problem with the IAC motor - the problem car happen when the engine is at speed (3k rpm, for example), not just at idle. I'll get some injector cleaner next time I'm at the parts store, and I'll definitely check the EGR valve the next chance I get. Never had the check engine light come on - almost wish that it did, as I could have the code scanned and know where to look for the problem.

well if no check light comes on, it shouldnt be any of the engine sensors then. (at least thats how it works?)

it might be clogged injectors, i always use fuel injector cleaner since new every other fill up.....0.99 cents at local 99cent stores!!!!

let us know whats up

Yes, you can check the TPS, basically all it is is a potentiometer. You can check it as follows:

1. Follow the wiring harness from the TPS to the back of the intake manifold and remove it from the firewall. This will give you more rrom to probe the electrical terminals. Check the electrical connector at the sensore for a sung fit. Check the terminals in the connector and the wires leading to it for looseness and breaks. Repair as required.

2. Using a voltmeter, check the reference voltage from the ECM/PCM. Chonnect the positive probe to the yellow/blue wire and the negative probe to ground. It should read approximately 5.0 volts.

3. Next, check the TPS signal voltage with the engine OFF, throttle fully closed and TPS electrical connector connected, connect the probes of the voltmeter to the red/black wire(positive probe) and ground(negative probe) (Note: use a straight pin to backprobe the connector terminal) Gradually open the throttle valve and observe the TPS voltage. With the throttle valve fully closed, the voltage should read approximately 0.5 volts. Slowly move the throttle valve and see if the voltage changes as the sensor travels from idle to full throttle. The voltage should increase smoothly to approximately 4.5 volts. If the readings are incorrect, replace the TPS.

4. A problem in any of the TPS circuits will set a code. Once a trouble code is set, the ECM/PCM will use an artificial default value for TPS and some vehicle performance will return.


REPLACEMENT OF TPS:

5. The TPS is an integral part of the throttle body and must be replaced with the throttle body as a unit.


This came out of my Haynes manual as procedure for TPS check and replacement.

Good luck. I would still check the EGR. Especially if you live in a big city and are required to burn the ozone friendly gas. That stuff seems to wreek havic on engines.

I had a similar problem, turned out to be a bad wire in the dizy going to the coil.

It could be a wire in the dizzy. The TPS can be replaced without the whole TB. You just have to know how to set the TPS the right way.

Check all you wires going into you distributer, and try checking all ur wires IN your distributer.
Loose wires suck!