engine spudering

Htownsvx · #1 12-08-2004, 06:45 PM

i have been having a spudering problem when the car is sitting at a stoplight. it is fine most of the time.but if im sitting there for awail the idle will drop like 100 rpms and give the car a little shake. and the check engine light never come on. i have replace the PVC valve and changed tthe plug and it still dose it. i have also check it in a dark street to see if the coils were arcing. dose anyone have any ideas

lee · #2 12-08-2004, 07:11 PM

some other things to check...

dirty air filter?

cracked or loose air duct between MAF and throttle bodies (check all around the throttle bores - after I bought mine I found the inner bottom edge of the left side air duct to the throttle body wasn't on correctly.

vacuum hoses cracked or loose

Chiketkd · #3 12-08-2004, 07:27 PM

One more thing I'll add - a sign that your fuel filter may need replacing.

-Chike

Htownsvx · #4 12-08-2004, 08:58 PM

i have checked the all the intake hoses and i just clean the k&n.

One more thing I'll add - a sign that your fuel filter may need replacing.

-Chike
i have done the fuel system cleaners but never checked the filter how much is a new one?????

SilverSpear · #5 12-09-2004, 12:10 AM

I had the exact same problem before in my car. when I was at a stoplight, suddenly the car's rpm go down and the whole car shakes !!! I went to Bosch service garage over here, they cleaned my car's injectors, and while checking the engine, the guy over there told me that I had a weak valve which is making this problem... after that the problem persisted... when about three months ago I did my engine overhaul (only gaskets, filters, hoses described thourouly in other thread) the problem is not happening anymore. but I doubt it is filter related problem of any kind... I am still convinced it is rather a valve problem...

#6 12-09-2004, 07:06 AM

Quote:

Originally posted by SilverSpear
but I doubt it is filter related problem of any kind... I am still convinced it is rather a valve problem...

A car with a valve problem would run like crap 24 hours a day....not just when sitting at stop lights. It's not a valve.

We recently had an older Legacy in here for the same problem. Turned out that one of the intake gaskets was leaking air. Car drove fine, but idled like crap.

Dave

SilverSpear · #7 12-09-2004, 07:14 AM

Quote:

Originally posted by red95svx

A car with a valve problem would run like crap 24 hours a day....not just when sitting at stop lights. It's not a valve.

Dave

how do you know that??? it's just one valve !! so where is the problem in your opinion?

#8 12-09-2004, 07:17 AM

Quote:

Originally posted by SilverSpear

how do you know that??? it's just one valve !! so where is the problem in your opinion?

Because we've had cars in here with valve problems. One valve is all it takes to disrupt an entire engine....and the higher the RPM's of that engine, the more obvious the problem is. This guy has the opposite problem...his car runs bad at low RPM's, but runs fine at speed.

Dave

SilverSpear · #9 12-09-2004, 07:20 AM

Quote:

Originally posted by red95svx

Because we've had cars in here with valve problems. One valve is all it takes to disrupt an entire engine....and the higher the RPM's of that engine, the more obvious the problem is. This guy has the opposite problem...his car runs bad at low RPM's, but runs fine at speed.

Dave

same thing as my car used to do... so why did the mechanical expert diagnosed that it was a "Weak Valve" ?? or better do you know the cause of this spudering?

#10 12-09-2004, 07:25 AM

Quote:

Originally posted by SilverSpear

same thing as my car used to do... so why did the mechanical expert diagnosed that it was a "Weak Valve" ?? or better do you know the cause of this spudering?

My guess is that he wasn't a "mechanical expert". You changed your engine gaskets and the problem went away, right? So your problem was gasket related, not valve related.

Dave

SilverSpear · #11 12-09-2004, 07:27 AM

Quote:

Originally posted by red95svx

My guess is that he wasn't a "mechanical expert". You changed your engine gaskets and the problem went away, right? So your problem was gasket related, not valve related.

Dave

it is not the same guy, he cleaned the injectors (around 3 yrs ago)... 3 months ago i changed everything... till now no sputtering.
lets consider the gaskets for a while, what effect they have on this phenomena?

#12 12-09-2004, 07:37 AM

A leaky intake gasket will allow extra air into the intake. This in turn will cause a leaning of the air/fuel mixture (since the air is coming in from a point that is beyond the Mass Air Flow sensor, the ECU doesn't "see" it and therefore doesn't compensate for it). This lean mixture causes roughness at low RPM. However, as the RPM's increase, the air/fuel mixture is enrichened to the point where the small intake leak is not enough to lean it out. So the engine runs smooth. That's my guess, anyway.

Dave

Chiketkd · #13 12-09-2004, 07:41 AM

Quote:

Originally posted by Htownsvx
-Chike
i have done the fuel system cleaners but never checked the filter how much is a new one?????

A replacement Purolator filter runs $15.48 at Advance Auto Parts while the OE filter costs around $20.00 from Subaruparts.com.

-Chike

SilverSpear · #14 12-09-2004, 07:42 AM

I doubt this is the problem... because even though I changed the gaskets, they were like brand new (the old ones)... my car has 58000 miles on it. when I bought it it had 10000 miles (4 years and a half ago), It never had mechanical problem other than knock sensors... the old timing belt is still new !!!

#15 12-09-2004, 07:46 AM

Quote:

Originally posted by SilverSpear
I doubt this is the problem... because even though I changed the gaskets, they were like brand new (the old ones)... my car has 58000 miles on it. when I bought it it had 10000 miles (4 years and a half ago), It never had mechanical problem other than knock sensors... the old timing belt is still new !!!

You can doubt all you want. I've seen it first hand. More often than not an engine that runs rough at low RPM AND has no check engine light on has some sort of intake/vaccuum leak.

Dave