Engine Problem
 

About 4 to 6 weeks ago my engine started acting a little funny after it was completely warmed up. When I would accellerate from low rpms up to about 4500 rmps, the engine would kind of hessitate 3 or 4 times along the way. I don't know if hessitate is the right word to describe it. The engine will just kind of stop just for an instant a few times as I accellerated hard. At high rpms it is fine, and just cruisin at constant speeds it is fine. At this time I also would have a slight loss in power when the engine was warmed up. My exhaust manifolds had also started to leak at this same time.

I should also state that back in june I took my heads off and had a valve job done, for which I have to thank this forum for all the great threads that helped me on that (mainly I couldn't figure out how to get the freakin camshaft sprocket bolts out!)

I thought that I needed a new catalytic convertor so I spent $160 and had Meineke do that for me. When I got back in the car I noticed an immediate difference. The engine was quiet, it ran great, much more responsive. I could tell it was breathing much more free. But then after the engine was warmed up again the exhaust manifolds started leaking again. After I got off the freeway and started accellerating from stop lights I noticed the engine hesitations. But they were worse now. Instead of doing a slight choke 3 or 4 times, it now will do it 6 or 7 times from stop to 4500 rpms. It seems though that it would have normal power if it wasn't for the slight hesitations. For some reason with the exhaust flowin more freely its hesitating more.

I should also say that I have changed the air filter and fuel filter within the last couple months. I don't know if I did a very good job explaining my problem, but if anyone has any suggestions, I would appreciate it very much.

Thanks,

Will

Plugs/wires/cap/rotor.. fuel injector cleaner?

and ouch on the cat... you can buy them at summit for 60 bucks and install yourself...

Exhaust manifolds leaking may screw up 02 sensor signals and result in what you describe.

It happens after warm up because the motor is in closed loop and using the 02 sensor.

I am not really a motor guy but the symptoms you describe could also possibly be a fuel pump that is getting sluggish or a partially clogged fuel filter. I had to replace my fuel pump the symptoms were very similar to what you describe, the truck ran fine at idle and cruising speed but when I tried to give it gas it was sort of like it was starving for fuel and not getting enough. I would think the new cat would make this problem worse because the engine is breathing better, it is trying to respond faster to your pedal. At least it should be but the exhaust has me baffled I would look into that first I think. I would think that a code would set if it were the O2 sensor problem but you never know. Computers act funny sometimes. I also never got any codes or check engine light for my fuel pump problem.

If the exhaust leak is only noticeable when hot, I would guess that you have a crack somewhere in the system pre cat. Maybe even on the manifold. I don't know as much about the 3.0 but every 22re I ever owned or worked on had an exhaust leak right where the pipe and manifold connect. A cracked exhaust will show itself when hot because the metal expands and lets the crack open up more.

Keeping all that in mind, if you recently had the exhaust system off for any reason that would be where I would start looking for the problem. Remember, sometimes free advice can cost you a lot of money and time but the guys on here seem to really know what they are talking about.

Thanks for the responses. Im going to dive into the engine a little bit to tighten up the exhaust manifolds and fix an oil leak from my valve covers. I hope fixing the exhaust leak fixes the problem.

Go to any auto zone and buy a volt meter that tell you that if your battery and alternator is good or bad, and test it with the heater on, full blast and test the battery and alternator with engine running. Tell me what did it read? low input on both? I'll check back here when I have the time to use the computer.