rough running

James Fowler · May 8, 2015

After replacing heads,new exhaust and driving for about two weeks was driving and motor started shaking my whole front end even shaking dash. Havent been harsh on it at all. First poped hood found top ground wire from hood to fire wall was broke and figured that was it also checked all spark plug boots both ends with none being detatched. Driving home it still had motor bouncing and vibrating everything not to mention looks like oil seeping from unknown source for now. This all started after cutting off catalitic coverters ,sheared off all bolts one side in heads so just replaced the heads, had 200000 on this 2007 chevy silverado 5.3l flex fuel 4+4 ex cab

BlackZ71Silverado · May 9, 2015

Who did the work for this job??

I would bet that the oil came from improperly installed heads and gaskets. I would take a look at the head gaskets for sure.

Couple of questions ;

Were the deck surfaces cleaned before installing the new heads and head gaskets?

What type of gaskets and sealer used?

Were the head bolts fitted for length and torqued in sequence properly when being installed?.....If not, that could cause the gaskets to fail and leak, this may be your issue.

Did you allow the engine to idle and reach normal temperature after install?

Did you recheck the head bolt torque?

No reason to think the oil is leaking from any other source since you didn't have the issue before replacing the heads.

It seems whoever attempted this job may not have known what they were doing, hence a ground wire was not properly reattached and is now broken.

You may have a headache on your hands, all over 'cutting off the cats." Don't you have to pass emissions?

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n5xl · May 9, 2015

If the original cats were plugged or damaged, you need to replace them with new. If you simply removed the converters in an effort to pick up performance, you need to re-install them. The days of significant gains in performance of stock vehiles realized by the removal of the converters went away back in the 90's. If you remove converters today, you need a custom tune to compensate for the different exhaust characteristics so that the computer can manage the fueling correctly, and, at a minimum, turn off the check engine light that will be illumiinated.

So....you need to pull the codes and see what the computer is upset about. You should have a handful of codes, with at least one or two of them being related to the removal of the converter.

BlackZ71Silverado · May 10, 2015

^^^^^^^

Good point about cat. removal. Good advise on a tune as well.

He has a lot more to worry about than checking for codes. Seems like parts were hacked off the truck and in the process, caused extra damage and now has an oil leak.

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