2002 Gtx 4 tec rough idle

[Ussfsaleen]

Over the winter i rebuilt two 4 tec engines.
One was a 185HP and the other was a 155HP.
The 185HP runs great! But the 155HP runs very
Rough.

Sooooo, what i did was check timing again.
And it was correct. Cleaned out the oil pressure regulator
And pulled the fuel pump and installed new filter.
New sparks. Ignition coils are good( switched from other
4tec that runs great).

So my question is what am i missing that i can troubleshoot
Myself. I have the shop book, im mechanically inclinded hvac tech.
And it seems to not hold a steady idle 300 +/- rpm

 

[Ussfsaleen]

Well, i had this subject on my mind all
Day at work. Found 2 problems.

First: exhaust manifold clamp was too
wide( the inner channel), which i purchased
it from ebay. Bad move!

Second: top cylinder head cover gasket
wore funny(not so funny), caused a leak.

Engine doesnt vibrate, or have poor rpm's.

Hope this helps for someone else. Not much but
Something so little made such a big difference.

 

[Michael211_2000]

YES, every little bit helps somebody at some point in time. I take it you were able to resolve your own problem then? And in time for the 4th of July weekend too... WooHoo!

Head cover gasket? Is that the same as the head gasket that goes underneith the head? If so, those aren't re-usable you are supposed to replace them EVERY time you pull the head off for any reason whatsoever... when the head is torqued down, it compresses the head gasket and it will not seal correctly next time you try to use it after removing the head. Also, did you get all new stretch bolts? Those things stretch once the engine initially heats up after you have them torqued down... stretching them again, after re-using them, they can break when the engine heats up and expands. The stretch bolts include the crankshaft bolts, the connecting rod bolts, the head bolts, and the rocker arm bolts I think... all the bolts that appear to have rings all up and down their length (after the threads) are stretch bolts, and they should only be used once and then discarded.

Regards!

- Michael

 

[Ussfsaleen]

It happened to be the valve cover gasket, not the
Head gasket. Who would of thought the valve cover
Gasket wore down funny. Probally was over torqued
From previous owner. And yes mostly new stretch bolts.
Used my millimeter Gauge for the service factor as per
Spec's in the the shop manual. Sooooo my only bad part
About the new rebuild is the 10 hour break in time.
I guess its stay below 4,000 rpm's or just use
A learner key. Its gonna be a long 10 hours! Thanks for the
Reply mike, Sometimes i overlook stuff, and take things
For granite. Its usually the little s*it i forget lol. These forum
Are very helpful.

 

[Michael211_2000]

Taking things for rock is pretty bad my friend.... hehehe! I think you may have meant, "take things for granted".

Well I'm at 3.5 hrs and I've been up to almost 6K rpm a time or two now for 20 seconds or so each time, I didn't see where the service manual said to stay under 4K for the 1st 10 hrs of operation.... but I didn't do a full rebuild on my engine, just replaced a connecting rod. I don't know if it matters or not. I think I'll take it a bit easier for the next couple hours of operation however, just to be on the safe side. (sigh!)

So do tell, how was a leaking valve cover gasket causing the engine to not run smoothly? Or was it the exhaust leak that made it run badly? I don't understand what your solution turned out to be now.....

- Michael

 

[Michael211_2000]

NADA... my browser double-posted. Please disregard.

- Michael

 

[Ussfsaleen]

Hahaaha I am pretty solid! J/k. I use a program called dictation,
where i speak into my phone and it puts into words. 4 out of ten
tines im going back , cleaning up words. But anyways hahaha......

The exhaust clamp had a huge difference. The clamp i assumed
Was correct and wasnt. I think it was about 3/8"- to about 1/2" too big.
I didnt even notice till startup. As far as the valve cover gasket, i cant
see having a affect on idle. It would just not make sense. All i see it doing
is just loosing a tiny bit of oil. No high oil pressure in the upper head. So, yes
Your right it wouldnt make sense. As far as the break-in for the engine, its just
what i've been hearing people talking about. And after two engine rebuilds and
Pulling out the engine and installing the engine. Im not gonna screw it up by over
Heating the engine too fast.

 

[Michael211_2000]

Ok that makes sense then.

Hope you have a great 4th of July weekend! The winds here in Texas are finally supposed to relax later this week... assuming wildfires don't start breaking out everywhere here again, I'm looking forward to hitting the lake! :-D

- Michael

 

[Ussfsaleen]

Thank you! You do the same!