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.