Runs like a mis while cold

by **TangoBravo** » Wed Apr 04, 2012 4:15 pm

Ok so I have developed a new issue. When my engine is not at operating temp it runs like it has a mis. Once it warms up it runs just fine. Any ideas? The plugs have 30k on em and the air, fuel, filters have been changed the Tbody has been cleaned. I think I have checked the easy things any suggestions would be great.

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by **DAKR** » Wed Apr 04, 2012 4:50 pm

Intake gasket?

by **TangoBravo** » Wed Apr 04, 2012 4:59 pm

I didnt even think of that. I guess its possible, if that was the case would it go away when warmed up?

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by **DAKR** » Wed Apr 04, 2012 5:25 pm

Maybe the metal expands enough to seal it...??? Just a wild guess, I didn't see anyone chiming in so I gave my uneducated guess.

YouTube Videos · by **Trail X** » Wed Apr 04, 2012 5:53 pm

Robert, might make sense to do a compression check cold vs hot and see if one cylinder has a big difference. Could be a valve or something not seating right. Wish I had a better answer though.

by **TangoBravo** » Wed Apr 04, 2012 7:37 pm

JamesDowning wrote:Robert, might make sense to do a compression check cold vs hot and see if one cylinder has a big difference. Could be a valve or something not seating right. Wish I had a better answer though.

Yeah I think I might do that this weekend. It just threw me because it goes away when warm. One of my friends said maybe carbon build up inside the cylinder but I dont know about that. What do you guys think?

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by **TangoBravo** » Thu May 17, 2012 3:51 pm

Turns out I need a new motor. Anyone know where I can get one cheap. Perhaps a salvage yard anyone know of?

YouTube Videos · by **Trail X** » Thu May 17, 2012 4:23 pm

What's the root issue?

by **TangoBravo** » Thu May 17, 2012 4:33 pm

From what I was told its the bearings.

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by **TangoBravo** » Thu May 17, 2012 4:35 pm

Even with that I am not too confident its the right diagnosis but im in a small town and its been looked at by 3 different mechanics and all came to roughly the same conclusion.

by **navigator** » Thu May 17, 2012 4:49 pm

I would think if it were bad bearings the engine would run rough all the time.
Did you tell each mechanic what the other mechanics said or did you just bring it to them and say "it misses when cold but runs good when warm".

Have you done the compression checks yet?

Would a bad bearing even cause a miss?

I would think a miss would be caused by not enough spark, not enough fuel or not enough compression.

If it only misses when warm, a lot of folks would get it warm and go trade it. Kudos to you for not sticking it to some sleazy dealer.

by **TangoBravo** » Thu May 17, 2012 5:14 pm

I let each tech figure it out on there own. The compression check was in spec on all cyls. It was explained to me that once the bearings heated up they expanded enough to make the issue go away. And its not actually missing thats just how it feels. A motor woth a 100k warrenty is about 2800-2900 which im not against doing since i have a new trans with the same warrenty. So I would have basically a 100k powertrain at that point. Idk I might just go used and same some cash since I can remove and replace on ny own as long as I get a long block I shouldnt have any issues transfer over.

by **Opeth** » Thu May 17, 2012 5:55 pm

Even after my new head was replaced I get one or two odd shakes on a cold start up. Once in a while It also cranks a couple times normally and then when it starts it almost falls on it face but then catches it self. It did this a couple times before the new head was installed. But if I let the fuel pump prime for a couple extra Seconds it seems to occur rarely.

Do the misses seem to go away after the air injector pump kicks on, or are they there till she's up to temp? Mine go away after the air injector kicks off, I'm stumped on that myself as I've double checked the manifold bolts already.

by **fishsticks** » Thu May 17, 2012 6:41 pm

Bearings will be NOISY if they are bad. Also, if you catch rod/crank bearings in time you can usually just replace them and be OK.

Do you hear metallic sounds?

Cold engine misses are usually a sensor problem. Your truck is in open loop for the first couple minutes that it runs.

Requesting video with good sound clip.

by **dvanbramer88** » Thu May 17, 2012 9:59 pm

I never like to trust a "It needs a motor" diagnostics, that's the idiot proof fail safe replacement part. I had a shop tell me i needed a new motor. It really needed a distributor cap...

by **TangoBravo** » Tue Jul 03, 2012 4:39 pm

Ok so I know it's been awhile since I posted, but due to the recent fires in colorado I have been pretty busy and haven't driven the truck much. Fishsticks I will post a video with audio as soon as I get back to Wyoming. It does not produce any sounds that would suggest bearings. The mechanics that looked at it said they tested both the cam and crank sensors and they passed so they said it isn't a sensor issue. Could it be possible to have one or both sensors fail intermitently and not be picked up while the mechanics were tasting them?

by **TangoBravo** » Tue Jul 03, 2012 5:24 pm

Also does anyone know if you can do a CASE relearn without a tech11, Im looking at trying to stay away from dealerships.

by **navigator** » Tue Jul 03, 2012 5:29 pm

why do you need to do a case relearn?
Are you throwing any codes?

by **TangoBravo** » Tue Jul 03, 2012 5:46 pm

Well Im thinking it might need to be done after I replace the cam and crank sensors.

by **navigator** » Tue Jul 03, 2012 10:58 pm

you don't have to do a relearn in order to replace the camshaft position sensor but you do for the crank sensor.
If your crank sensor is bad though, I would expect it to throw a code.
When my camshaft position sensor went out it threw a code.

Have you cleaned/replaced the camshaft position actuator? I understand it can contribute to a rough idle at times.

Offroad Trailblazers and Envoys

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