My car has been in the shop two days now, and they have NOT been able to determine why the car running so bad. The car was dynoed to verify the power loss, and it was down around 25 h.p!

The computer is not throwing any codes, and I was told the cat was fine. I mentioned the whole knock sensor issue, and they are supposed to run an ohm check on that. They asked if I had bad gas, but I used the same gas from the same station before and it ran great. Then I filled it up again and it ran fine, full tank, for about for the first 1/3 of a tank before I started to notice power loss. Now its like the car is in limp mode and the harder I push the gas, the slower it wants to go. At times I can also hear what sounds like pinging.

Anyone have any ideas before I lose my mind completely.

 

Change your knock sensor anyway. Sometimes the sensor is good when you check it bit it really not.

 

You say they said the cat was fine? Did they use a backpressure tester?

 

No they just took it off and looked through it.

 

you think the powerloss could be cuz the tranny is giving out?

i dunno. i mean. you did all you could for the engine/ecu.. maybe its the xfer of pwr to the rest of the wheels?

 

QUOTE:

Pinging, also called engine knock, has a sound often described as an unpleasant irregular metallic rattle, similar to shaking a coffee can full of marbles. Pinging is pronounced when the engine is under load, such as climbing a hill or rapid acceleration.

Causes of pinging include:
- fuel AKI too low
- ignition timing too far advanced
- lean mixture
- carbon deposits in combustion chambers
- EGR valve stuck closed
- EGR passages obstructed with soot
- EGR vacuum signal hose(s) split, broken, or disconnected
- engine running too hot

There are other vehicle sounds which are similar to pinging. The most common example is an exhaust system heat shield which has become loose and rattles or buzzes, especially at certain engine RPMs.

Your Maxima has a Knock Sensor which detects pinging and signals the Engine Control Module (the computer). The ECM responds by retarding the ignition timing to eliminate the pinging. For this reason... IF your Knock Sensor is working... you have never heard your Maxima engine pinging.

If the sound really is engine knock (pinging), I suspect it is caused by a momentarily lean mixture. Check your PCV valve, EGR valve, Power brake vacuum check valve, and Oxygen Sensors.

END OF QUOTE

With close to 130,000 miles, you need to check things like the pcv valve, and also you need to clean your throttle body and make sure that the EGR valve area is very clean inside the throttle body. Your oxygen sensors might be malfunctioning too. There are many little things that it could be, the simplest of which that you can hope for is bad gas. You might try draining it and trying some fresh gas just to make sure. I would try the simple things first, but it sure sounds like the knock sensor. Hope this helps.

 

My guess is your EGR valve is stuck closed, causing the car to ping, causing the knock sensor to retard timing causing your power loss!!!

You did say you hear a slight ping correct?

 

Get all the simple maintenance stuff out of the way 1st before you have someone do open heart surgery on your engine.

Check EGR (like the others said)
Feul filter (Maybe it got really really clogged with something)
Spark plugs?? Maybe they're just done. Were you using copper plugs maybe? They have the best spark but don't last at all.


DW

 

According to the Haynes manual, pinging or engine power loss is caused by;
ignition timing incorrect
Fuel injection system fault
Improper or damanged spark plugs, wires, or coils
Clogged fuel filter
Low or uneven cylinder compression pressures
Obstructed air intake or exhaust system.
EGR valve not functioning
Vacuum leak
Emmission Control system not working properly

Check the vacuum at the intake manifold. If the vacuum is low or if the readings are fluctuating that can help direct you to the source of the problem. Depending on the guage reading it could be leaking cylinder head or intake manifold gaskets, restricted exhaust, stuck or burned valves, weak valve springs, improper iginition or valve timing.

A fuel pressure check should be done. A fuel pressure gauge should be set up between the fuel filter and fuel rail. This can help identify a bad fuel filter, clogged line, a bad fuel pressure regulator, fuel pump, or leaking injector(s).

 

AHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHH!!!!!!!!!! !!!!!!!!!!!!

Now that I have vented, I will tell you guys that so far they have found absolutely nothing wrong with the car. The knock sensor ohm'ed out fine. The cat was fine. No codes at all, just a 25 h.p. loss!

They want to do an intake cleaning, which takes roughly an hour.

I asked about the egr valve, and the service tech wasn't sure if that had been checked, but thought it had. The service will also include a fuel system service.

Looks like I will be forced to have it done, I have no idea what else to check. I really find it odd that no codes are being thrown at all!!!!!!!!

I have already changed the spark plugs and the fuel filter.
I will let you know the results this evening when I get the car back.

 

Have you done a compression test?

 

Wow. This is a tough one. Normally by now since you have checked almost everything that would cause this therewould be some kind of remedy found. So how are they telling the power is still not back? Just by feel or another DYNO? When they mentioned the bad gas did they say anything about draining what ya got in there and replacing it with some other type of gas (different brand whatever...)

SuDZ

 

They did an induction system cleaning, which takes over an hour and costs $139. They thought that may fix the problem. Then they went, after running the gas down to nearly fumes, and filled it up with 93 Amoco.

On the way there the tech ran over a metal hitch pin, which gave the car a flat tire, ruining the tire. They temporarily patched the tire after getting the car back to the shop. I was told the car would be ready this evening. After arriving and getting the not so good news, the car was placed back on the dyno.

The tech came out with a long look, saying that the power was still down, and that the car is in limp mode for a reason they still can't locate.

He requested more time with the car, so after driving 45 minutes up there I ended up leaving the car. They are replacing the tire at no cost.

I am so frustrated now that I am getting fed up. What in the world is so hard to figure out! I will ask them about a compression test tomorrow, but honestly I doubt the compression is an issue. There is no miss when driving.

Its very obvious the ecu is backing off on the timing for whatever reason. Why is the question!?

 

swap knock sensors.. or swap ecu's with another 97 SE 5spd

 

Even though I'm no Nissan expert, I'll throw in my 2 cents. Since your car is OBDII (post-'96) the computer essentially tries to unlearn your mods so it can stay with its preprogrammed emmissions map. One the Prelude, we reset the ECU at least once a week to wipe out the ECU's memory weekly. Those who dont, with the typical mods of i/h/e, dont dynoe much over stock. While the loss is relatively small on the Prelude, around 5whp, the age of your cars ECU may have basically led to overloading it or something. Like others have mentioned, try an ECU swap. If you had a CAI, I would think you sucked up some water, but I dont think thats the case with your hot air intake. If the problem cant be corrected, sell the Max and run to your local Honda dealer for redemption

 

Didn't you put in a couple of gallons of 110 octane gas at the track one time? You could have possibly burned up your knock sensor or oxygen sensors. FYI, just because the ohms check out on the knock sensor doesn't mean it is in good shape, it might still be malfunctioning. You could also try swapping ecu's with somebody. Got one of those Atlanta boys to drive you to the shop tomorrow and swap in one of their ecu's and see if it helps.

 

I've had the EXACT same problem with my car for a good long while now....no codes...but a VERY noticable power loss. I am dynoing this saturday...and we'll see if my car is still slow. I have done EVERYTHING on my car....plugs, fuel filter, intake and fuel system cleaning, PCV valve, fuel pump (upgraded), adjustable FPR, relplaced stock cat with R/T cat..even did a compression test..and came back with GREAT numbers....and although I'm almost there...my car still isn't as quick as it used to be.....I'm now suspecting my number 1 fuel injector...and/or my knock sensor...even though the knock sensor hasn't thrown a code.

I know what you're going through...I'm as frusturated as you are

If the knock sensor does the trick...let me know....cuz I'll do the same...

 

I don't think so. My 98 has a CAI and Y pipe and RT cat. My friend's 97 has the stock intake and a stillen muffler. We exchanged rides to see how each other's car felt. He said mine kicked a$$ compared to his. He only needed 1st and 2nd gear to make that conclusion, too.

So, my OBDII ECU didn't un-learn nuthin

DW

 

Clogged cat? That would make a loss in power defintely.

 

Veetec your in AL right? i wish we (atl boys) were a little closer so we could help out. i know everybody has already mentioned it but the knock sensor is the only thing i can think of. swapping the ecu would also be a good idea since you said it is in limp mode. bags533 has a FSM for 97 maxes. PM me or him and we can see what is says that can help.

 

check your pm's

 

I am in Atlanta.

 

 

Well...I picked the car up about an hour ago. They are closed during the weekend, and I wasn't leaving it there.

The only thing they haven't checked, according to them, is a leak down test. But I don't believe that will reveal any problem. They tell me ALL of the sensors are ok, and that the knock sensor ohm'ed out fine. Also that if there was a problem the ecu would throw a code. They added a fuel system cleaner when they filled the tank up, before I picked up the car.

My first impression driving the car home was that it was running worse than ever before. It just didn't want to go at all, and it sounds like its straining at the slightest push of the throttle. It also pinged. About 5 miles away from home I noticed that the car started to run a little better, and ping less, and it continued to improve right up to when I arrived at home. Now its still running bad, but the improvement makes me wonder if it was/is a fuel system issue, and the cleaner is helping. Whatever the case, it has a long way to go to be normal again.

I will post an update, to tell if it continues to improve.

Basically they checked everything except the leak down test, so if this doesn't clear who knows whats next.

 

hey VeeTec any updates? how is the car running?

 

It's all fixed up. It was a clogged cat.

 

ness

 

Are you sure?