Thread: 454 running bad

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I need some help. I have a mid 90's model fuel injected 454. It idles perfect. When I give it gas it looses vacuum and runs like crap. All the sensers seem to be good. the exhaust seems to be good and fuel pressure is good. Spark is good too. Any suggestions?

if you dont find anything with what denny said id look at the exhaust closer. a 1/2 stopped up conv. will do the same thing.

It's not throwing any codes. All the sensors have been checked and not problems. I have scanner for it and it not throwing codes. As for the exhaust we pulled the headers off and tried it that way and ran same way.

Originally posted by lt1s10
if you dont find anything with what denny said id look at the exhaust closer. a 1/2 stopped up conv. will do the same thing.

I would think if the converter or converters where plugged the 02 sensor would show a trouble code.Would'nt this cause an overly rich condition?

I think I will change the TPS and plug wires already changed plugs. I will post if there is any change.

Originally posted by erik erikson
I would think if the converter or converters where plugged the 02 sensor would show a trouble code.Would'nt this cause an overly rich condition?

not always

I don't have converters. Besides I pulled off headers and runs the same. The only code it has thrown is lean code on O2 sensor. Plugs say it's rich. Throttle control sensor is good. Doing another vacuum check. Then I guess it's off with the valve covers. Did I mention this motor is in an 83 Cherokee. Really tight fit. Don't pay attention if someone says " Can't put a 454 in there it won't fit". It did fit but bear to work on. Let you know how things progress and any more suggestions are appreciated.
Thanks

Originally posted by DennyW
I need some help. I have a mid 90's model fuel injected 454. It idles perfect. When I give it gas it looses vacuum and runs like crap. All the sensers seem to be good. the exhaust seems to be good and fuel pressure is good. Spark is good too. Any suggestions?

So, was this a test to see if we matched your code that you mentioned at the end ?

By your last post, I would look for a vac leak. And also, make sure your base timing is correct.

thats ok whats next?

Timing is good... Did change timing set, it was a little loose but nothing major. Was checking to see if it jumped timing. Didn't but changed it anyway.
Wasn't checking to see if you matched my code. Threw that code when it was still running only semi-bad. Doesn't give any problem codes at all now. Went from good to bad pretty fast. In a couple of days.
Doing another vac leak check today let you know how it goes.