car wont exceed 2500 rpms
 

My 98 monte carlo ls 3.1L recently started having an issue while I was driving down the highway. It started to sputter and misfire badly, I managed to get the rest of the way home and park it in the driveway.

Now my car won't exceed 2500 RPM, if I try it just sputters and won't run any harder, sometimes it almost dies out when trying to get over 2500 rpms.

I've checked the EGR system, and my fuel pressure, which seems to be at about 41-47 PSI which is at spec, it drops slightly when under load and running because of the regulator.

Could it still be a problem with the fuel system even tho the fuel pressure seems to be fine?

WHat else should I check? is there a way to check to see if it is the catalytic converter?

It's not storing any codes but previously it stored an EGR insufficient flow code but i reset it because I was afraid the computer might be sending the wrong signals or somethi9ng.

Could it be the timing is off or something like that?

Have you changed your Cat? What about a coil pack? Fuel filter?

No i don't have money to just replace things with wild shots in the dark, I need to make sure the part I replace is the part I need.

I checked teh fuel pressure, if it was the fuel filter wouldn't that show up during fuel pressure tests? I have another fuel filter as soon as I manage to get the old filter off I'll replace it. But just replacing a cat for the sake of replacing a cat is quite expensive, I'm not made of money, times are tough.

How can I test to see if the cat is failing/clogged?
Autozone can test the coils, but wouldn't they cause misfiring at all rpms, not just high rpms? and these problems happen while the engine is cold as much as hot, well I think it gets slightly worse when the car is warm because it wouldn't even idle when it was warmed up.

i say it's your cat...your symptoms point me in that direction.

i can understand/appreciate you not wanting to shoot blindly at solving this issue, but such is the case when you don't know exactly what the issue is...

you can try cutting the cat off, and see if your issue goes away, and if is is still present you can just have the pipe welded back on and keep looking...

this is the cheapest route you can take to eliminate the cat... i had a buddy that changed his transmission 5 times each with the same shifting/power loss issue, i told him to cut his cat off, and it runs like a dream now...

there is no test to see if the cat is clogged? I read somewhere about disconnecting the o2 sensor and seeing if there is compression in the exhaust before the cat, like connecting a guage, said slight compression is ok where as much of it is bad, what if i unscrewed the o2 sensor allowing any compression to vent, but that would cause problems with the computer delivering fuel and air properly right?

with the EGR valve off so that the hole that comes up from the manifold is open to push out as much exhaust as it wants, it still misfires, I saw some liquid shooting up through the hole, not alot just a few drops. but the egr system is connected to the exhaust so any compression issues in the exhaust causing misfiring should be relieved in the same way as cutting off the cat right?

well I took the ignition coils and ICM off, borught them to autozone, the coils all measured 0 resistance between the bottom, and between the top. THe icm passes their scan test.

I finally got the fuel filter off, the old one was pretty grimy, thick black crap poored out of it then it went completely clogged, I put a new filter on but same symptoms.

i pulled a p1676 code off an OBDII scanner, any idea what this is?

I read somewhere someone mention about the brake booster, could my problems be from vacuum failure in teh brake booster? I noticed when i first started the car that my ABS would kick in when i hit the brakes coming to the end of my driveway at like 5 mph.

I jotted down some values from the freeze data, the car wasn't running when it threw the code, at least it said 0 rpms,

MAP sensor at 99 KPA

Short term fuel trim 1 0.8%
Long term fuel trim 1 0.8%
Short term fuel trim 3 -96.7% (is that normal?)
Long term fuel trim 3 8.5%

this is what i found.
P1676....Powertrain control module fault (quad driver 4), or EVAP canister vent valve

here is where i found it.
http://www.aa1car.com/trouble-codes/...1500-p1699.htm

I had the backpressure tested and it was ok, I changed the plugs and the wires and its still acting the same.

I brought it out on the road and I noticed if I try to floor it, it will misfire immediately and not seem to even fire off anything for a second, then itll cathc and run again, if I gradually press the pedal it drives normal(but doesn't exceed 3k rpm) and will get up quickly enough and shift fine. When in O/D it starts to miss when im going about 60 mph and it's at only about 2k rpm, but itll work through that and get up to about 65 but sttarts missing more.

when testing the MAF with a DVOM what exactly am i checking for? there are 3 wires to my MAF, a yellow one on the left, a black one witha white strip in the middle, and a red one on the right. Which one do I want to check? I tried myself and one of the wires read 4.53V at idle, and dropped down steadily to 4.0V when i increased teh throttle to about 2500 RPM. I didn't test the black wire witha white line in it, the other wire read 14V so im guessing that was the power feed.

that is not normal...ill discuss it with some guys at work 2moro and c what they say (and im horrible at remembering to come back on here so hopefully i dont forget)

ok so I just figured out my s-10 has the same MAF sensor, So I took the sensor off my s-10, cleaned it, and put it on my monte carlo. I started it up, the injectors were pretty loud, but they usually are when I first crank it. Then I ran a bit, it misfired alittle but then it started making it to 4k rpm, and the rev limiter, So I took it on the road and punched it, it worked fine, I drove down the road with the occasional hiccup but it climbed to 6k RPM then cruised at 8- mph fine. I turned around to come back, and punched it again, and then it started missing again and I'm right back where I started. I don't know if it was working good because the engine was really cold or what, It threw no dcodes and now I'm back to where I started, I'm so confused and disapointed with the false hope I was given.

any ideas?

THank you kweef, please let me know what this means and how I can fix it.

Ok I ran it a bit more and got the original symtoms again, except worse. I went about 4 miles to the gas station, when I pulled in, it died. I put 5 bucks in the tank then I was gonna ride softly to autozone since at lower rpms it seems to be fine, well not now. I pulled out of the gas station and it started bucking at around 1500 rpm, the tach would drop and jump all over the place. So I turned around and drove home. Even with my foot off the gas and cruising it would want to die, the tach would drop 500-600 rpm and I still couldn't get it to go over 2500 rpm, also when I pressed the gas sometimes it would seem to do nothing, Obviously this problem gets worse the more warmed up the car is, and first thing in the morning with dew on the car it managed to get to 6k rpm. I read somecodes and got a new freeze frame data from when i unplugged the MAF I think tho I may be wrong, heres the info it put out tho.

MAybe its an electrical wiring problem? I don't know.

p0102

Load 1.1%

2610 RPM

MAP sensor 37 KPA

Air Flow Rate 1.90 GR/sec

Throttle position 16.4%

Coolant temp 197 degrees.

Fuel trim same as above

Fuel system open.

If I goto I/M monitor it says OK or N/A or INC, no fails.

It threw p1676 again as well I guess I need to check that wiring as well.

Hope some of this helps, and someoen can figure out what -96.7% short term 3 fuel trim is.

I got another p1676 code so I'm really starting to think this has something to do with fuel tank vapors constantly flowing into the vehicle maybe?

I noticed my fuel trim hasn't changed in this code, I read that the PCM doesn't adjust anything untill the engine goes into closed loop? So why would my engine not meet closed loop requirements?

Check to make sure there is nothing blocking your air filter. With that Short Term Fuel Trim it sounds like either excessive fuel or a restriction. How was your cat tested by the way?

Trust me i've had this thing apart all the way up to the throttle body and it still acts the same, nothing is blocking my air short of the intake. I tested my cat by relieveing any chance of backpressure and running the car to see the same symptoms. I did this by opening a hole in the exhaust before the cat, once by pulling the o2 sensor and running it, and also by pulling the egr valve and running it, I get the same symptoms either way.

I noticed every code for the past 3 days hads had the exact same fuel trim information, that means my computer hasn't tried to adjust the fuel trim, possibly I'm not going into closed loop at all? why would this be?

OK i Just took it out on the road, and got a p0401 code, EGR FLOW INSUFFICIENT.

I got this error a few times before, so I used carb cleaner and cleaned the EGR vacuum out best I could, and got a new EGR valve. Not sure what else I can clean out of it to improve flow?

Freeze Frame data:

------------------------------------------------------------

Throttle Position - 0.3%

Engine RPM - 1136

Air Flow Rate - 4.67GR/sec

MAP Sensor - 30 KPA

Coolant Temp - 177 degrees F

Short term fuel trim 1 - 0%

Long Term Fuel Trim 1 - negative 13.3%

Short Term Fuel Trim 3 - 50%

Long Term Fuel Trim 3 - negative 45.2%

Vehicle speed - 45mph

Fuel System 1 - closed

------------------------------------------------------------

So It finally went into closed loop and tried to adjust, but it was still misfiring. Note I took this drive with the evap purge valve unplugged. I was trying to go through the OBD II GM driving cycle I read but i didn't have enough space

I don't think pulling the O2 and EGR are very good ways to relieve pressure. Once my fathers T-bird died out. We couldn't get it started. I even went and loosened the exhaust flange just before the cat, there was about a half inch gap and it still wouldn't start. We replaced the cat anyway and when we cut out the old one you could see it was plugged. After the new one was on it took a couple tries but it fired up and ran like a champ.

Do you have a vacuum gauge? If so hook it to manifold vacumm. You should be around 12"-15" of vacuum. Take the throttle and rev it up to 2000-25000rpm. The vacuum should go up to about 20" of vacuum. Somewhere around there. But keep it revved up, the vacuum should stay up. If it starts to fall then you know you have a restriction.

Ok, here is a no BS diagnosis. Clogged CAT. How do I know? I had a 2001 Camaro that did this EXACT same thing. And I mean exact. I changed everything else first before I found it. I changed wires, plugs, coils, ignition plate, MAF and filter. Nothing fixed it. I was lucky and was under 80k miles so GM replaced it for free.

But, to check if the CAT is clogged you can try this. At night start the car outside and let it run for awhile, and I mean a long while. Crawl under the car and look at the CAT. If it's clogged it should be a slight red color, or maybe even glowing depending on the clog.

wouldn't taking the o2 sensor out alleviate any pressure on the cat when the exhaust escaped through that hole instead. As I suspected maybe the cat was bad, I removed the o2 sensor and it ran the same with that much less backpressure. I'll run it and see if the cat gets red

thats the same problems im having with my 01 monte, but in park it revs up fine as soon as i put it in drive it wont go over 2500 rpm i also changed wires,plugs and egr and still the same I also thoght it was my cat so ill have it remove today ill let u know if it fixes the problem so ill keep up with ur post

If your cars are under 80k miles take it to the dealer. I'm 95% possitive it's a clogged cat. If it is and the car is under 80k the dealer has to fix it because of it having a bad emission control system. It's 09 right now which makes an 01 8 years old. The emissions warranty is 80k or 8 years. Might wanna jump on it and see if they can do it.

i just had my cat removed and the car is running like a champ the guy said the reason for the codes is cus the heat is coming back up instead of out the back so try that and hopefully it runs better and thanks to everyone who posted it help me alot and saved me money too

I checked the possibility of a cat problem already and it's been ruled out.

Also my car doesn't rev past 2500 in park, let alone drive

I'm now more leaning towards bad fuel injectors or loss of compression.

The fuel trim readings on bank 1 are good almost 0% so they're running at near stock, while the fuel trim readings of bank 3 at at 50% on short term and long term since the most recent closed loop run.

This leans me towards a problem with 1 half the engine.

Ok the egr system is fixed, I ran a test drive and the I/M monitor says EGR system OK. On my test drive I had no codes but many symptoms. I got out on the road and took off gradually like the GM OBD II drive cycle says, Got up to 55mph and put on cruise control and drove 4 miles or so at 58 mph. I then gradually decellerated down to 20 mph, turned around and this time applied about 3/4 throttle and it was misfiring badly in the 2.5k-3k range, never got higher than that. I then got up to 55mph and re-equipped cruise control, it went a little bit, then it bucked alittle bit, kicking cruise control off. I traveled back to my house then cruised down to a stop at my driveway. It bucked a few more times on the way in.

I noticed that went it bucks the tachometer goes from liek 2.5k rpm down to 2k then flucuates some more before the car stops bucking and missing and settles down to slowly resume acceleration again. any of these driving symtpoms help anyone diagnosing the source of my problems?

I would just like to put my vote on the cat and if you can unbolt it or spend the 200 and get a aftermarket high flow (cheaper then stock) mine had a issue like this at 4500rpm's same throttle issues you describe. also i noticed alot of shifting issues when under heavy acceleration.

How did you rule out the cat? If you tried what I said, it's not really a test. Just something you can try. Mine was clogged really bad and it still never turned red at all.

Pulling out an O2 sensor might not be enough to diagnose a bad cat. Like I said before even when I unbolted the exhaust flange on my dads car still wouldn't start. We replaced the cat anyway and it was fine.

Loss of compression won't give the kind of symptoms your having. Bad injectors may.

Does the scan tool you have say "Bank" or just "Fuel Trim 1", with no "bank". If i remember correctly 1,2 and 3 refer to idle, under load and cruise. That -45% means it is running rich so the comp is reducing the amount of time the injector is open, it is trying to lean it out.

Have you checked the vacuum? Or did like someone else mentioned and look underneath at night? Even an infrared thermometer can diagnose a bad cat by measuring the difference in temp between the inlet and outlet of the cat.

Numerous people here have mentioned a cat. We may all be wrong but I wouldn't be satisfied until you really check that cat.

there was only fuel trim 1 and 3, no fuel trim 2. No bank, I dunno why it doesn't have fuel trim 2, thats when it has problems, under load.

I'm gonna keep saying it, over and over...IT'S YOU CAT!

a mouse always blames the cat lol but yea my uncles car was like that a few years ago and he replaced the cat

Oh hardy har har!

I'm just saying because he keeps describing EVERYTHING my Camaro did down to the T. Go buy a high flow cat and have it put in.

lol yea i know my uncle did the same thing but he had a crappy tempo that he put a bunch of money into before he finally changed the cat

love the orange strips by the way