Vellmen

Hello,
Thought I would post after reading all the post with the key word “bog”. I have read, checked item after item after post after post and I still am bumfuggled.

Ok here’s the history:

Purchased my 94’ Camaro Z28 LT1 with the 6 speed trans which is all stock except for the intake filters, exhaust and body stiffeners back in July 11’. The guys I bought it from “tried” to change the water pump but failed miserably and it shorted out the OPTI. I bought a new coil, ignition module, dist. cap, rotor button and OPTI installed them fixed the water pump and drove the car. Of course it was with a check engine light and I finally found someone who could pull the codes. He said it read “too many low res input signals or not enough high res signals”. Well I drove the car anyway. It was really slow to start every time but once it would crank it was a BEAST! I checked the forums back then and was told to check fuel pressure which I did. It was 30 psi not running and running however not running it would bleed down quickly. I changed the fuel pressure regulator which didn’t help to say the least.

Here’s the problem now:

Two weeks ago I was driving home from work and after about 3 miles it seemed as though I was losing power. It quickly got worse, I barely made it home and almost got rear-ended a couple times coming of stop lights. By the time I drove the additional 3 miles home with no power I noticed the engine was hot, climbing over 220 degrees. I haven’t ever seen the temperature over 180 and that’s with my foot in it.

I 1st tried this:

I thought fuel pump… figured since every time I tried to give it gas it bogged down and since it had to be running lean it was heating up. So I ordered a fuel pump and sending unit assembly when I could afford it, last Monday. Well it came in Thursday and of course I put it right in. Remember it was the whole assembly so I took it out of the box and installed it. (Yes, I cut a hole using instructions from these forums) I then installed a new inline fuel filter also. I then started the car and to my total dismay it is still doing the same thing!

What I tried next:

Well, since I had been getting codes from the OPTI and it was still under warranty and it was very slow to start (like 15 to 30 seconds of cranking) I decided to change it. So I pulled the old OPTI, got the new warranty replacement and while I was there changed the front crank seal to boot. After that I started the car again and OMG it started immediately and no check engine light! I then gave it some gas pedal and it bogged down again!

Finally:

Back to reading these forums! Well I’ve pulled the EGR it is fine. I’ve run down all my vacuum lines and changed any that were suspect. I’ve pulled all my plugs and did a compression test all cylinders are 160 to 180. I went and bought a fuel pressure gauge. My fuel pressure not running is 39 psi after the pump primes and it does not bleed off. While the pump is priming the pressure is at 43 psi. When the car cranks pressure holds at 43 psi. When I try to give it gas it starts to run up but bogs at 3000 rpm and fuel pressure also takes a small dive say 5 psi. It seems to idle fairly normal but doesn't sound right. And if you let it run long enough it will still over heat. I’ve searched all the way around the intake manifold and I don’t see or hear any leakage. The only thing I have found so far is my exhaust on the driver’s side at the firewall is leaking. It has leaked since I’ve bought the car, it now is possibly worse? Is this the culprit? Do you guys have any clue or suggestions on what the issue may be? While performing the compression test I did clean all my plugs and checked plug gaps. They were all at .050 and the Champion plugs appear to be in good condition. I plan on fixing the exhaust leak and installing a new set of plugs as a precautionary. Also, since I installed the OPTI I haven’t seen the check engine light on at all.

Thanks for taking the time to read this and any help will be appreciate.

bw_hunter

An exhaust leak can lead to a false lean condition...the O2 sensor gets some fresh air and sees the oxygen. The PCM adds fuel on that side trying to fix the lean condition but ends up overfueling. The result is a car than is sluggish....

shoebox

You beat all around your one known problem-the exhaust leak. That should have been addressed first. You gotta fix what you know is bad before going on to other things. You won't know if it is/is not an issue until you rule it out. BTW, 220° is not overheating.

divineprime

I guess there is a couple directions left.
Hey is the fuel still bleeding back? If so I think that is the first direction to look.

What you describe also reminds me of clogged cat converter. It can make the tell tale boggagagga... noise. Let off and its perfectly fine towards idle.
If you can disconnect part of the exhaust and test drive it then I would do so.

As others pointed toward o2 misreading, that could be. May or may not be because of exhaust leak but either way can do the same bog.

Vellmen

How true. I guess in my mind other things were more pertinent? Anyway, today I fixed the exhaust leak and still no dice. 220 is overheating to me because that's the hottest I have ever seen it get. Normally it runs around 165 to 170 and when I hot rod it, I've seen 180 to 185. So what is overheating on this engine?

Divineprime, you hit the nail square on the head. I enlisted some help and while I revved the engine up they checked the tail pipes to see how much difference there was and they said there really wasn't any difference. Like I posted earlier I don't have a CAT, so I looked under the car to see how it was all put together. My two exhaust pipes from the manifolds tie into one collector and the muffler is welded straight to it so at the seam closest to the muffler I hack sawed the pipe about half way thru.

Oh my sweet Jesus and you guys too! The engine actually tacked over 3k, of course it wasn't perfect since the pipe is still attached. I did drive the car around the block to see if I will be able to get to the muffler shop just down the road. So tomorrow I'm headed there.

Any suggestions on what muffler to install? I don't have a ton of bucks and I do like the rumble. My 22 year old son suggested just putting a pipe in place of the muffler, but I think I should install some type of muffler or I won't be able to hear myself sing while driving? lol

And if I haven't already said it thanks a million! I would have never thought to look for a plugged muffler. God I love this site and the support you guys provide us newbies.

divineprime

Awesome, hope you get going. The key word you emphasized, "bog" was a give away. Then along with the heat. It was old school my father taught me, and also we had a CAT do that on his 01 monte ss recently. Thanks

shoebox

4th Gen LT1 F-body Tech Articles
220 is not even to the threshold to turn on the fans.

A plugged cat is much more common than a plugged muffler. Yours might be the first I have heard of on these cars. The excess backpressure was likely coming out of your exhaust leak, too.

divineprime

Ya the amount of heat was not overheating to the point of damage, but he noticed it out of normal range. Good piece of into to help in diagnosis though. Not sure if the OP had the CAT done or what, but occasionally a piece can break off and end up downsteam, otherwise it's just rusty inside.

Vellmen

Color me an idiot, the item I thought was a muffler is in fact a CAT.... can I say DOH! Either way it's plugged and going away! Is there any reason other than it is illegal I shouldn't replace it with a straight pipe?

divineprime

In most states I believe it is legal to delete the CAT on 95 or before. Or you can clear the CAT out for a good visual inspection in certain states. It wont hurt the car, but it will increase performance.

EDIT DMV in Mississippi http://www.dmv.org/ms-mississippi/smog-check.php

Vellmen

Awesome! And thanks for the link. I will be deleting the CAT and enjoying the added performance, not to mention a "running" car lol.

Again thanks a bunch!

shoebox

You might not like the smell after deleting the cat. A good cat won't degrade performance.

bw_hunter

Gents, it is currently illegal to remove a catalytic converter from any car that originally came equipped, regardless of whether there is emissions testing in your state. There is no cut off date...even the majority of cars made in 1975 must have converters to be federal law compliant.

You may chose to remove it...just don't do it thinking you are allowed to do so because the car is old.