Another interesting lesson learned worthy of a post on the forum...

Before I get started there was another very good thread on K&N filters on the forum at: https://www.fiero.nl/forum/A...021104-2-025021.html

After reading the thread above I broke down and spent the $$$ on a K&N filter a few weeks ago. Didn't really expect to see any significant performance or MPG increases; purchase was purely intended to save money in the long run. This was for my daily driver; an '86 GT, T-Tops, 5 spd, and modified 2.8. I'm very meticulous and keep everything up-to-date (e.g. annual tune ups regardless of mileage, replace sensors and parts often before they go bad, etc.). Overall the car has 145K miles on it...but motor only has 60k miles.

I recently experienced a rash of mechanical issues that started when pressed on oil pump pickup tube and strainer fell off in my oil pan while I was driving down the highway. Scared the crap out of me. Nothing like seeing 0 oil PSI and a blaring red light at night when driving 60+ MPH. Luckily shut it down, got it home, and fixed w/o any major damage to the internals. During that repair found the timing chain was uncomfortably loose....so went ahead and fixed that as well. When it was all put back together I experienced high idle and performance issues. Lots of trouble shooting later discovered the EGR tube was cracked....almost in half. My best guess it happened when I jacked the motor up to pull to remove the front engine mount in order to remove the oil pan. Lesson learned there, if you are dropping the oil pan always loosen the EGR tube. So I fixed that too.

After all that work the dang motor started running richer than hell. I know it was running rich b/c my chrome exhaust tips sooted up solid black after only 20 miles of driving, gas mileage went from a consistent 26 MPG to 18-19 MPG, overpowering smell from the cat converter, and the motor would buck and stumble at any steady engine RPM while under load. Acceleration and deceleration were fine, top end speed was fine, idle was smooth and steady...but trying to hold any steady speed was almost impossible. When this problem began, the ECM started throwing a code 44 on and off. After researching the issue on the forum I went ahead and replaced the O2 sensor, replaced the ECM temp sensor, replaced the temp sensor in the air canister, checked for vacuum leaks, new fuel filter, checked fuel psi, checked timing, replaced the ECM, checked all electrical plugs and connections, tried dry gas in the tank, and went through two bottles of fuel injector cleaner. None of these made a difference at all. Pull the spark plugs and found they were all equally black and sooted up. Very frustrated at this point, I went ahead and sent my extra set of fuel injectors to Cruzin Performance along w/ a cold start injector last week to have them cleaned. Figured I'd change everything out cause I simply didn't know what else to do at this point.

Well lo and behold, yesterday for some strange reason I went ahead and pulled the air filter. Don't know why, it was only in there maybe 2 months at this point. I live in the country, highway driving 90% of the time and in the past only changed air filters every six months. The filter didn't really appear all that dirty...but went ahead and cleaned it anyway. Used the recommended K&N cleaning kit, and followed all of the directions to the letter. When I rinsed it out, observed a reasonable amount of dirt and in the end the filter looked like new.

The very next time I drove the car after cleaning the air filter the stumble was gone, MPG went back up, no more soot at the exhaust, no more overpowering cat converter smell or nothing. This blew my mind. All that time and new parts b/c of a dirty air filter. Not only that....but a filter that clogged in only 2 months driving! Guess this is a testament to how much more efficient the K&N filters really are. Needless to say, cleaning my air filter is now going to be a monthly maintenance item, and I hope this thread helps prevent someone else go through what I did to fix the problem.

r/

Good post.

The location of your K&N makes a big difference. Where is it located? The oil impregnated filters do an excellent job regardless of the negative press generated by dry filter makers. I too am surprised by the dirt over a short period. Normally they don't need cleaning that often. Dusty conditions? Location under the vent?

Good questions

Arn

I dont think much of k&n filters, but they do last and are easier to clean , and so in the long run you save money. I actually heard a paper filter will out flow them, but for longevity the k&n was better since paper filter performance would quickly dwindle as it loaded up with dirt. If your filter is clogging that fast I would be worried about what is being sucked into the engine. Must be dusty where you live.

------------------
87 Fiero GT (3.2 Turbo)
E-mail: david88@peoplepc.com
www.angelfire.com/pa5/davidfiero/

"The location of your K&N makes a big difference. Where is it located? The oil impregnated filters do an excellent job regardless of the negative press generated by dry filter makers. I too am surprised by the dirt over a short period. Normally they don't need cleaning that often. Dusty conditions? Location under the vent? "

I have the stock filter canister and purchased the K&N filter that fit it. Thought, think I jinxed my self a little by posting a little soon. Put 100+ additional miles on the car this afternoon and it started acting up again toward the end of the trip. Not anywhere near what it was doing before....but still not 100% right. Still believe the dirty filter contributed to the problem. Will have to wait and see if a newly cleaned set of fuel injectors fixes things in Jan.

The car starts running rough at steady RPM under load. Not backfiring or anything...just feels like a miss that causes the car to buck, even at highway speeds. While it is acting up, if I give a little gas or let off the pedal just a little it settles down for between 10 and 30 seconds before starting up again. If I simply stop the car or take it out of gear it idles fine. If I give it gas or floor it, the car accelerates fine as well. Frequently when it is running rough, the engine will settle down, and within 15-20 seconds the ECM throws a code 44. This gives me the impression the ECM is trying to compensate for the rich mixture and in doing so causes a lean condition. Just a thought. The pattern is very consistent. Run rough, smooths out w/ a slight increase in RPM, then throws a code 44. When the code 44 clears the car will run for an unpredictable period of time before this cycle repeats itself.

I'm leaning toward an injector issue....but interested in other opinions. The only reason I have a little doubt about a single injector is the fact all of the spark plugs are equally sooted up. The only other test I would like to run is taping a fuel psi gauge to back window to monitor PSI while running under load at hwy speeds. Fuel PSI is well within spec w/ the car standing still, reving under no load, etc.

quote Originally posted by RotrexFiero: I dont think much of k&n filters, but they do last and are easier to clean , and so in the long run you save money. I actually heard a paper filter will out flow them, but for longevity the k&n was better since paper filter performance would quickly dwindle as it loaded up with dirt. If your filter is clogging that fast I would be worried about what is being sucked into the engine. Must be dusty where you live.

I think I would agree. I had a K & N in my DOHC 3.4 and took it out after a few months. Put the stock paper back in. Could see little difference. Dirt sticks to oil no matter what the size of the holes in the filter.....at least common sense tells me that so no matter how dirty it gets and how quick are not a factor in effectiveness. I would be more concerned with the size of the holes by which I would not be aware of the rating but possibly micron?

A dyno run might be the real test but since I have a new crate motor I'd rather be safe than sorry and not run anymore dirt into it than need be.

stange I had a caviler do this with the 2.8 and it ended up being the thing under the distributor cap
(cant remember the name) thing is it would only surge at hyway speeds when the car would be warm.
when they would test it the thing was cold and worked fine. finally we figured out the heat was causing not to
work. and the fact that there was very little grease under it. just a thought

Currie....another good suggestion. I believe you are talking about the ignition module. Have three of them on hand at any given time and tested all three when this problem started. They all tested fine and I changed the old one out for a newer module....but it did not make a difference. Having said that though....I admit to not having anything w/ the coil in the distributor for a while. There must be 30-40K miles on that thing. That is not too expensive to replace, and I will pull the distributor when I do the injectors b/c I plan to install a new cold start injector as well. Perhaps I'll go ahead and change the coil in the distributor at the same time.

Thanks.

I dont drive many dusty roads, but my Ferrari kit had a K&N for 7 years, cleaned once in 100,000 miles. I use them because there waterproof. You get no performance or gas mileage gains that I ever noticed.

Finally got my spare set of fuel injectors (including a used Cold Start Injector) back from CruzinPerformance and installed them in the car along w/ a new OEM Fuel PSI regulator purchased from the Fiero Store.

When I pulled the plenum off everything from the throttle plate back was uber dirty and black. Flushed everything out w/ carb cleaner. When I pulled the old injectors they were equally sooted in a uniform circular pattern around the tip. Indicated to me that the spray patterns were all the same, and probably not bad. So didn't appear there was a problem w/ any of the injectors. When I pulled the Fuel PSI regulator it was intact, but appeared to be the original b/c the bladder material was black from ware and stretched at the base. Didn't find any problems w/ vacuum lines or loose connections anywhere else.

Put everything back together and immediately noticed a difference. Fuel PSI was previously running 36-39PSI, was now steady at 43PSI. For the first two runs the car threw code 44 again....so I replaced the O2 sensor and Spark Plugs b/c both were sooted up. The O2 sensor was purchased from the Fiero Store only 6 weeks ago...but it was different than the one I pulled from the car....never thought it was right. I made sure the new sensor was OEM Bosch version. Since I replaced those parts, the car has not thrown any more engine codes.

Keeping my fingers crossed that this does it. Car's been running like crap for a long time now; would feel much better if it were fixed. Hate it when my baby is sick.

Just a thought though....seems logical to me that we should replace the Fuel PSI Regulator when cleaning/replacing injectors. It was only $60 for the item and another $9 for the special tool torx socket to take the screws off. Heck, probably get it cheaper locally. The Fiero Store sold me a Standard PR10 Fuel Pressure Regulator (V07198). That's the only info on the box.

For a little more money you might want to try:

http://www.jegs.com/webapp/...10001_10002_24488_-1

Holley adjustable fuel pressure regulator. It's advertised to fit Camaro/Firebird TPI motors, but I had one on my 2.8 and it fit just fine.

[This message has been edited by Doc John (edited 01-13-2008).]