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driftripper155 10-15-2004 09:56 AM

For Several months now, I have been experiencing a minor problem with my engine that is driving me up a wall. When I start my engine, it runs perfectly. However after the engine warms up it idles rough and actually runs a little rough throughout the entire driving range except at highway speeds. The roughness is characterized by a minor, but notable pop or put in an otherwise smooth running sound. It's not rhythmic but intermittent and it only occurs after the engine is warmed up. If I allow the engine to cool and start it up again, it's gone until the engine warms up. Right now I have several modifications to the engine. I have a performance ignition system with 10mm cables. Cold Air Intake. Street style exhaust header. 3 inch cat back system and 3 inch underdrive crank pully. At this point, I have had no check engine lights activate and the condition is not worstening. I have however heard what I think is a notable hissing sound from the rear of the engine compartment. It is noticeable over the normal engine noise and I'm not the only one who's heard it. Currently, I've replaced the O2 sensors, the pcv valve. I've pressure tested the pcv hoses and made sure there is a good seal on the nozzle where pcv hose connects to the manifold. I've also replaced the fuel filter. At this point I'm thinking my only option is to remove the intake manifold and check for cracks as well as replace the gasket as I'm convinced the piece of crap, PLASTIC intake manifold has cracked somewhere. I was wondering if anybody has experienced similar problems and what the hell was wrong. I need to know if I'm heading in the right direction with the leaking intake manifold theory.


soffiler 10-15-2004 02:25 PM

Matt -

The combination of the hissing sound, the fact that it only occurs after warmup, the rough idle - yes, it ceratinly sounds like it could be an air leak, and the manifold is one of a few likely candidates.

One thing bugs me, however. For a fairly large air leak (large, totally subjective term, but I mean it's large enough to HEAR above the engine noise!) I would expect a Check Engine light with a code P0171 (system too lean bank 1)

driftripper155 10-15-2004 05:40 PM

Hey, thanks for your reply. I should however, have mentioned that you can only really hear the hissing over the sound of the engine when you lean all the way in over the head cover and put your ear near the throttle body. If it makes more sense now let me know. But regardless, if there's a leak, I have to take the manifold off anyway in order to check for and fix it. I haven't gotten the time or the nerve to perform this surgury yet, but time time is drawing near. Anyway, it's still a myster and any more help anyone can offer would be greatly appreciate.


joshandlauri 10-15-2004 06:31 PM

if its an air leak and its doing it hot and idle you can pin point it be taking a soapy water solution in a spray bottle, spray it around the intake until it stops for a second, this is how i firgure it out in my shop, diagnose many-a leaks this way.

driftripper155 10-15-2004 09:08 PM

hey about the soap trick. Are you suggesting that the soap mixture will temporarily stop the problem, thus confirming my suspicions. Or do you mean that the soapy mixture will show where the leak is if there is one, because it's nearly impossible to see what's going on down behind the engine. You know I'm sure.

Thanks for you help

Tikinsin 10-15-2004 09:13 PM

you didnt mention having them, but ive heard that having engine mounts can cause rough idoling, not really much you can do about that though if thats what your problem is...

evnldr_Focus 10-16-2004 10:44 AM

Mine dose the same thing. I havenít pin pointed it to hot or cold operation but every few seconds it has like a miss it is random ... But cruzing at 50-60 it kind of sputters off and on a lil I can feel it but its not much...and I do not hear a air leak noise that im aware of . id like to know the outcome also

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