Engine Trouble Codes

BosnianLanos · Post by **BosnianLanos** » Sat Jun 18, 2005 4:02 am

Well, regardless of the car running well, I went to get my CELS scanned at Advance Auto Parts and came up with the following: DTC P0420 "Catalyst System Low Efficiency", and DTC P0301 "Cylinder 1 Misfire".

Since the plugs/wires/coil are new I have narrowed the misfire DTC to a bad injector and will get that taken care of tomorrow.

The other DTC puzzles me, I have researched and it could be anything from a vaccum leak, to bad O2 sensors, to an exhaust leak, to a shot catalytic converter. Since the car runs fairly well, I would rule out the possibility of an exhaust, catalytic or O2 problem, so I think it might be something to do with a vacuum leak.

Question 1: Can a plugged vacuum hose affect car performance, I mean, it would seal the vacuum and the car should run OK?

Question 2: Can a faulty EGR valve be read as a vacuum leak? I assume that if it is stuck open that a lot of exhaust gas would be getting sucked into the engine to heat the air, and in turn could be causing the catalytic DTC?

My car acclerates well, but it doesn't feel "right". It gets really loud (Might be CAI), it gains speed, but not with the vigor it used to a month or two ago. It idles OK, maybe a little high but I don't have a tach to test, and the noise from the CAI might be distracting and making it seem like a high idle. Otherwise, cruising is totally normal.

My goals for tomorrow to get this problem sorted out are to; make sure all my vacuum hoses are free of all the Carbon buildup from over the years and that the pins where they attach to the manifold are also clean. Then I plan to plug the EGR tube where it attaches to the manifold right after the throttle body to see if performance improves. I don't think blocking the EGR should be any kind of an issue, because when I was cleaning the intake manifold, I found that the EGR was fully blocked anyway and the car ran fine, I think after the cleaning, my problems began. Then I plan to take off the fuel rail and clean the #1 injector to insure proper sealing and that it isn't dripping fuel into my engine.

What do you guys think? Do you think that the EGR could be the source of the problems, would it be safe to block it off? It is a comman mod so I don't think there would be a problem.

Thanks for the help.

MMamdouh · Post by **MMamdouh** » Sat Jun 18, 2005 1:07 pm

a vacuum line is always a vacuum line... i mean it is not passing arround air at all so a blocked vacuum line is as good as a vacuum line if you are considering this from the engine side.

the device on the other side of the vacuum will be the one to be affected, as in a MAP sensor or an EGR valve the problem can be not working properly to not working at all depending on how much blocking we are talking here.

the leaky vacuum line can affect the engine performance as you have introduced an extra passage for air... in my messing arround with the engine i managed to make it idle a bit higher by unplugging a vacuum line... the engine did not sputter but revved a bit higher than usual so i would say this depends on how much air you leak.

an open EGR will cause crappy idle, i once forced the valve open with my hand and every mm the diaphragm moved the idle became worse and worse till the engine stalled with the diaphragm just half way up. if yours is stuck open it would make your idle bad as hell.

maybe it is nor fully closed (5% open or so) and some exhaust is going to your intake... try to take off the EGR and make sure its mechanism is moving freely.

as for blocking the EGR, i suppose blocking its vacuum line is a much easyer way to reach the same effect... at least you can have it back on whenever you want in a matter of seconds rather than blocking the exhaust passage in the exhaust manifold or blocking the exhaust pipe.

MMamdouh

BosnianLanos · Post by **BosnianLanos** » Sat Jun 18, 2005 6:42 pm

OK, I checked the vacuum lines and all the pins and hoses are clear, even though to the vacuum hoses are really restrictive, they all allow air to pass. I took off the TB to clean it and the idle air sensor, and it turns out they were really dirty from all the crapy air the EGR vavle was sending in. So, I fabbed up a piece of soft metal to replace the EGR tube gasket and blocked it, now the TB is in a bucket of degreaser and the sensors are being cleaned. I hope everything works OK.

So you guys are sure it is OK to block the EGR vavle? It was blocked before and I didn't notice an issue, but I just want to make sure.

Audacity Racing · Post by **Audacity Racing** » Sat Jun 18, 2005 6:59 pm

if you block it, make sure to reset and re-learn your ecu. otherwise you'll be getting codes out the butt for O2 sensors...

BosnianLanos · Post by **BosnianLanos** » Sat Jun 18, 2005 7:58 pm

Ok, reset is next.

Results:

1. Noticeably more vacuum, so much so that it makes the throttle body a little harder to open when the car is on. IDK why a blocked EGR would create more vacuum if it wasn't killed to begin with.

2. Calmer idle, even though not fully warmed up, the car idles a lot quieter, to the point that if the music is up just a bit you can't tell that its on.

3. Better throttle response and quieter acceleration, my basic goals.

I'll see what happens tonight, but overall I think it is an improvement.

MMamdouh · Post by **MMamdouh** » Sat Jun 18, 2005 11:54 pm

the crap you found in your TB and IAC is not from the EGR gases but from your crank case breather.

the EGR pipe is right behind the TB and with the normal air flow the gases goes into the intake and cyilenders but they never reach the TB or AIC.

the crank case breather constantly throws in oil vapors which condense on the TB and IAC tip and the very small dust particles that passes the air filter stick onto the oily surfaces and given enought time they form all the crap you found which block some of the TB passages and could cause your AIC to be sluggish and affect how your engine idles.

resetting your ECU for the blocked EGR valve was not necessary but it will certainly help with the cleaned up TB and IAC.

blocking the EGR won't hurt the engine... the valve was designed to reduse NO gases which develop under very high temps so all what you are going to get is more NO gases in your exhaust.

personally my EGR don't kick in unless the ambient temp. is some 40C and i am going at 120 Kms and trying to accelerate hard (full throttle) in 5th gear with a passenger along side... i don't think this is your daily drive conditions so you got nothing to worry about (hell you even got the valve's passage blocked before and you noticed nothing... right?)

MMamdouh

BosnianLanos · Post by **BosnianLanos** » Sun Jun 19, 2005 12:25 am

You, are right, it was blocked before and all ran fine, and all runs fine now, I think I found my vacuum leak in that it was the EGR valve.

The gunk was from the EGR because I haven't had a breather connected to the intake for over a year, I simply took it off when I installed my CAI. It was dirtier before, but it was pretty bad now, so it must have been either the EGR throwing up stuff from my exhaust or oil cycling through my intake manifold, however, all runs fine now.

In other news, I think my transmission fluid is low, cause a week ago I changed it and replaced my dented pan with a like new pan from the junkyard. The only thing was that there was a rubber plug in the new pan probabally from when someone got a transmission flush. So I put it on anyway. Well, after an hour of driving, the plug broke and all my fluid leaked out, I don't think I put enough back because it is kinda hesitant to downshift during hard acceleration. That will receive attention tomorrow.