Alright guys here is my problem. This past weekend i replaced my lower intake manifold gasket on my beast (1994 ranger, 4.0, manual trans) Now it seems to be boggin down when i don't have it wide open. When I am not "on the pipes" as we say she wants to bogg until about 3k rmps then she gets with it. But I could be going down the road at say 30 miles an hour in 3rd gear and at about 1,500 RPMs and go to speed up and it will bogg all the way till about 3,000 RPM's then she will get on it. I was thinking maybe a vaccum leak since that is what the intake all deals with. I took it to auto zone and had them scan the codes. Then we looked them up and nothing outta the ordinary came up. I was looking for a MAP code to confirm a vaccum leak. But they said maybe a bad catalictic converter. What would be your thoughts. If it is a bad cat (not like any cats are good) i am going to just cut it off and run straight pipes with flow masters because 210.00 dollars for a cat is to much if ya ask me. Thanks Matt

 

Well you did change the manifold gasket, so if it isnt entirely sealed it will suck air from outside the motor. as for the cats you can remove them, but if you have fuel injection the engine light will most likely come on if there are two sensors on the exaust one on the exuast manifold or before the cat and one after the cat. This is becuase the comp. reads air fuel mix going in and coming out. Without a cat the outgoing reading will be wrong. This is ok it will not hurt anything. If you only have the one sensor then you shouldnt get the engine light, but all in all you will gain horsepower and torgue :-) so take em off.

 

Back in my younger days I had a beater of a car (I dare not mention the manufacturer on this website) and I had a problem similar to yours. It turns out that part the catylyst had broken off inside my cat and was clogging up my exhaust so it could be your cat. Id get rid of it whether or not it is the problem personally. Also, since you did replace the intake manifold gasket you could just be sucking some air in there. Good luck! : )

 

Most of the time when you change something on an engine (manifold gasket) and then the engine begins to do something strange (bog down) that is the first place you want to look. It would be a coincidence indeed if you changed the gasket and the cat converter failed right then. Not to say it can't happen, but my guess is a vacuum leak. Put a vacuum guage in the system and see what it says. If you don't have one or can't borrow one, go buy it. They are pretty cheap ($10-15) and will immediately solve that question. Or you could try spraying around the manifold with WD-40 while the engine is running to see if the rpm's change. If you remove the converter, the truck won't pass emission tests, if that is a concern. Try not to cut up things too much if you take the converter out of the system, just in case you (or the next owner) want to return it back to stock. Good luck.

 

Thanks you guys for your input. Now would it be a better chance of being on the upper intake rather than the lower intake? If and when i find the leak, is there anything i can put on it without changing all the gaskets AGAIN! Tomorrow I will pull the cats and take it for a spin and see if it is still boggin down. It is also seems to be running a little bit on the rich side (just a guess from the exhaust smell) What kinda pressure am I looking for at an idle speed and so on up at various RPM ranges. I know vaccum should decrease as i get on it but what would be a good baseline to start off with? Thanks Matt

 

Ok guys I found part of the problem but it is still boggin pretty bad. I found a vaccum line off of the fuel pressure regulator which would explain why it was running rich but it still is boggin. So i thought maybe with it running rich i fouled the plugs. So i pulled them and cleaned em with a torch and just burned the carbon off. Didn't do a bit of good. Got the codes read by a snap on scanner. It said that the Bank 2 O2 sensor was lean. Where would i go from here? Could it be an injector that is bad or clogged up? Thanks for your help again

 

Did you clear the codes after you fixed the vacuum line, that could be an old code.

 

Ok guys I have fixed my problem. It was both 02 sensors. I will tell you how i found out. I hooked up the scan tool and it said my EGO bank 1 and 2 were not switching which meant that my O2 sensors weren't swithing. So i unplugged them and it kicked the idle right back up to normal when it was running open loop. Then i tested them while the engine was running. I put a voltmeter and a scope on it and one was not sending a signal at all and the other one was reading rich. A little background info on testing 02 sensors. You look for voltage drop across it. You have 2 wires of the same color and it isn't those 2 you use. The voltage drop will somewhere between 0 and 1. The closer to 1 you get the richer the mixture and the more you get to 0 the leaner. Also the hottert he sensor gets the less resistance it has. A general rule of thumb is when you have been running the engine for a long time and you still have 3 M Ohm's of resistance that that is bad. After about that long you should have about a 100 ohm's of resistance. Thanks for all your help guys