I have had a HUGE drop in fuel economy and power lately. I was getting over 30 MPG and suddnely I am getting 16 or 17 maybe 20 if lucky. Also I have a HUGE power loss. When I first got my car several years ago I could just give it ¼ throttle from a complete stop on asphalt and it would really burn rubber, but now I cant even spin a tire on GRAVEL at FULL throttle!

I dont know what is going on. However I have recently heard that a knock sensor can cause big fuel economy losses. But I am not sure about power losses, especially not this big!

I know that I have a very minor knocking problem with regular 87 fuel but I have always used 87 fuel and I always thought this faint noise I was hearing going up hills was fuel injectors opening, but after putting some 89 in it just yesterday I stopped hearing this sound so I have confirmed this is a fuel detonation I am hearing.

I have always used regular 87 till just now but for years I got 30 MPG and suddenly I can not even touch 25! Also I have always had plenty of horsepower, until just the past few months.

Does anyone have any ideas?

 

any codes?
probably the KS

 

No, I dont have any codes besides this:

1st gear signal fault (shifter)

 

your ks is prob bad. It will not throw a cel. You can look at the stickys and see how to test it.

 

Dang that is very hard to replace! I will test it and I will get back with you after I test it.

 

actually no. its pretty easy. there is a thread on the quick way to do it.

 

do u guys use Oem or autozone knock sensors?

 

i use oem

 

OEM knock sensors are under $60 dollars shipped on eBay. Unless you are a 99 cali-spec, the knock sensor shouldn't be a hard task. The only way to test it properly is by removing it and testing it with a multimeter.

 

this isn't regarding the original post, but i envy your 4th gen.

 

I have a very bad feeling about this.

Yesterday after I got out of my computer programming class at Davidson County Community College, I talked to the Automotive Mechanics teacher about this problem, unfortunately, he told me that the only common factor of all the problems I have described to him is a seized torque converter stator clutch! I really hope its not that because I cant afford alot of downtime with this car as it is currently my ONLY source of transportation!

Is there any possible way for me to test the Torque Converter to see if that is the problem?

I have done the stall test and the result is about 2100 RPM, but I am not sure if this is good or bad or even if it has anything to do with the stator at all.

Any ideas?

 

does it feel like the car is holding its self back? kinda like a seized caliper or like the tranny is slipping, if not than its probably not the TC.

 

well it dont feel like a seized caliper, HOWEVER, the reason that I have to believe this may be the case (unfortunately) is I recently had a brake problem with both front brake calipers, somehow some dirt got into the lines or something and BOTH front brake calipers seized, and it was so bad that when I parked I would have orange brake rotors. As I said this is my only transportation I have right now so I dont get many chances to work on it, so it was a while before I fixed the brake problem, I was eventually forced to fix it due to a cracked rotor. THIS is the reason that I think maybe the torque converter may be damaged, especially since I was near full throttle just going 45 MPH while I had this brake problem! That was REALLY putting ALOT of stress on the whole drivetrain! The torque converter NEVER locked up when I had this problem and I NEVER got past 2nd gear, NOT EVEN at Highway speeds!

This is the reason I think I might have torque converter problems.

(yes I know I will probably get flamed for being stupid and driving with such a terrible brake problem, but I cant help it, I just dont have so much time to fix things like this due to school (and during that time period, work too))

By the way, when I type words in all caps this is NOT to yell or express anger, its just to express the important words that I think are the most important words people should notice.

 

oem

 

You already answered your own question.
1st gear signal fault (shifter)
You probably don't have 1st gear and from a dead stop your starting out in 2nd gear. At highway speeds does your car have power?

 

I know what this signal fault is. It just means this shift lever position sensor has a bad 1st gear switch which means that it cannot see if I have MANUALLY shifted into 1st. I KNOW that it has 1st gear from a dead stop because if I put it into 2nd gear, it starts out, revs up and then shifts, but does not go past 2nd. Its just if I put it in 1st MANUAL selected, it either does the same as MANUAL 2 or does the same as when its in D. It HAS 1st gear from a dead stop, its just that the MANUAL 1st gear selector does not work properly.

 

Ah HA! New symptom now. I have a clicking Idle Air Control Valve for some reason and NOW my car is running terribly rough, even while driving. Sometimes it even backfires!

Now what?

Could this have anything to do with my drop in HP and MPG?

 

have you checked your ECU codes? If you leave your ECU in diagnostic mode, your IACV will click.

Its probably your knock sensor. If you havent done it, you probably should anyways.

 

Sounds like the knock sensor, since it limits the engine after detecting a knock, also wouldnt hurt to check the air/fuel filter and such

 

Another new symptom

I ran down to about 1/4 tank of gasoline
and when it gets below that it runs like crap, wont go faster than about 30 MPH

Also it was missing alot and backfiring some.

I am now thinking that maybe the fuel filter was never replaced by any previous owner and maybe it is the original one and maybe it is COMPLETELY clogged, which is causing a lean burn under load when the gas tank is low and when it idles it richens it up becuase it has detected a lean burn, and maybe under load it is so lean that it cannot get enough fuel to even run properly/efficiently.

I can tell you that DEFINATELY the reason it was running crappy on a low tank was because of an extremely lean mixture, because the exhaust was so hot that the floorboard was very hot and the muffler was so hot that it melted some grocery store bags in my trunk!!!

Do you think it is a fuel filter?
I am almost certain thats a BIG part of the problem now, ESPECIALLY since when I have a full tank this is not a problem!

 

You're in safe mode.

Clean your IACV, MAF, TB. Replace your knock sensor, fuel filter, air filter, and run chevron techron injector cleaner in the gas. Also do a seafoam treatment.

Let us know if it improves any. What I mentioned above is relatively cheap (everything can be done for under $100 if you do it yourself).

 

AFAIK the A32 ECU does not have a 'safe mode' condition.

Fuel filter for me fixed running rough and hard starting with a low fuel level, and if you're not sure if it's ever been done, might as well.

Have you checked to make sure the injectors aren't leaking? That would certainly fit both of your MPG and HP losses.

 

Hmm...perhaps I'm confusing that with a 5th gen. I know I've read it somewhere a long time ago (before the 6th gen came out).

But yeah, definitely do what I suggested and what pmohr added.

 

Well my starter just failed on my the windings in the motor have obviously burnt up now because if I directly connect a battery to the starter with it removed it don't even turn at all, so now that i am down to this point I will go ahead and replace the fuel filter anyway and we will see what happens.

I will do this today and we will just see what it does for me.

I will keep you posted.

 

It won't trip the light but it is a silent code that will show if codes are retrieved..

 

No, there are no codes. I have just replaced my starter, air filter, and fuel filter. It seems to have a tad bit more power but still alot of hesitation still. Maybe its time to send off my injectors to have them cleaned. Well I can tell you that I cannot send off my injectors because this is my SOUL MEANS of transportation! I will try going to the local junkyard to get 6 fuel injectors, test them to make sure they work, and then send the used ones off to have them cleaned so that my car dont have any downtime, and then when I get them back, I can install those.

Also, I do know that my knock sensor is not completely bad because I have no codes, but I also know it is not up to par because I have a slight pinging under load or going up hills at a lower RPM.

 

The slight pinging is sign of a bad knock sensor and It also Is limited the peak power for your car and the acceleration and the MPG Is bad also. The CEL light will not come on at all times you might have a ghost code check that with the scanner. To check the injectors try taking the injectors out with the fuel rails on and turn the key to the ACC postion and It should spray out fuel.

 

coils? never gave me any codes and i had more then half or your problems....

 

My first attempt to change knock sensor was a failure. The swivile joint was the only part moving, it would have worked but the nut holding knock sensor was in tha wierd position lucky me. Next morning with lots of effort i noticed that my hand could actually fit in sensor vally. Slipped in a 3/8 ratchet with 12mm socket could not brake bolt with hand, so I took the handle to my 1/2 inch jack braced it against ratchet and engine head and carfully applied pressure and WALLA nut broke loose, gave a couple turns with ratchet did the rest with hand. Pulled out sensor and nut as one, sensor caseing was all cracked up def. BAD. Put in new ebay sensor hand tightened nut placed ratchet back in, gave it a couple turns and DONE, Also cleaned ground connection. Before sensor gas mileage was terrible trans shifting was bad thought it was going bad, and power was slugish. After install gas mileage is a lot better but I can't keep my foot off gas LOL, trans is back in sinc with engine {take note}, and boy is 0-60 asome!!!

 

I have no CEL and I have used my scan tool and it says under the DTC (Diagnostic Trouble Codes) menu that there are NO CODES. As far as coils, it might be, at night if I raise my hood, I can see blue flashes coming at random (but not so often) from behind my manifold. Heres the thing, I have NO missfiring, and it is running smoothe as silk, no misses, no surging (except on a low tank), no rough running, nothing like that, it runs FINE, but it has alot less power and it is really guzzling gasoline. I have calculated recently these calculations on fuel economy:
22 MPG
14 MPG
16 MPG
15 MPG
20 MPG
7 MPG (most recent)

Also I have hesitation when I hit the gas, and if I rev the engine in neutral, it is taking forever to rev up, instead of going waam, it goes waaaaaaaaaaaaaaaaaaaaaam.

This is the reason I am thinking maybe I need to have my fuel injectors cleaned.