bulletboy29

My Maro runs great at idle and great around town, but at WOT it loses power. Put it to the floor and it takes off strong and then starts fading out. It makes a low drone kinda noise until you let up on it. Then it kicks back in.

Here are the things I've done so far:
Replaced fuel pump and filter
Removed pump inside tank
Blew air thru fuel lines
replaced ECM
new ignition control module
new plug wires, cap, and rotor
adjusted timing
checked for vacuum leaks
plugs look normal and gapped at 45
installed a rebuilt carb

I'm lost...what could it be?
The EGR vacuum line is capped, but somebody said it could still cause problems. Wouldn't it mess up the idle though?
It has a cc quadrajet.

sellmanb

I'm guessing that this problem has been there since you bought the car.... well, it sounds like you're experiencing some of the normalities of 3rd gens ---- crappy exhaust!

You could just have a clogged, but I think that you are trying to compare your low - mid range torque/horsepower to your mid - high end torque/horsepower. Our cars stock are great low end city drivers, hella fun! But you might as well be driving a geo metro on the freeway (not that drastic, but you get the idea heh).

If you wish to ail this problem you'll have to really re-work the engine, but you can help it a ton by getting headers, and full 3" mandrel bent exhaust. Then something like a dual plane intake, a new cam, head work, new springs, probably new valves as well.

sellmanb

btw, your plugs should be gapped to .035 not .045

bulletboy29

Yeah....after I put them back in, I realized that the hood on the car is not original....it's from a V6. Would that 45 gap cause these symptoms?

This is not normal thirdgen stuff...this is a problem that has gotten progressively worse! It used to haul az!

sellmanb

ok... SC's came with V8's didnt they? Eh, regardless....

Sounds like you need to check and see if your cat is becoming clogged over time or something. Got a bit of a hunch that its' exhaust related. You've pretty much checked all the other stuff heh.

I dont know if gapping them to .045 would do that, but it's possible I think.

bulletboy29

No cat...and I even ran it without the muffler and still no change. I'm going to gap the plugs to 35 today and see if that helps. I doubt it will, but anything is worth a try now.

From a dead stop it will buck at WOT, but WOT rolling along it just fades out and then comes back if I let up. Why does the tach say the RPMs are up even though the motor sounds choked down and not making any power? I would think that the tach would go down too.

mnegovan

Is your EGR still connected? The EGR shouldn't activate until around 3000 RPM. At that point the exhaust gases should be recirculated back to the intake. I have read in these threads that the CC works best when your EGR is working as designed.

It could be that the EGR valve is faulty and allowing exhaust gas to continuously get recirculated. If it is not connected and you can determine that the EGR valve is opening at high RPM then you may want to block the port with some aluminum sheeting.

I am just guessing here. I have a similar problem where I lose power at high acceleration but it is probably due to a misadjusted carb. I haven't set the dwell on the M/C solenoid according to specs because I don't have a dwell meter.

bulletboy29

I installed brand new plugs today and gapped them to 35....No change!!! Although it is running great in the low RPM range with all the new parts I've installed, it's still screwin' up at WOT. Since the EGR is supposed to open at high RPM, wouldn't it be ruled out even though I have the vacuum line plugged. From what I've read on here, a malfunctioning EGR would cause stalling at low RPM and a terrible idle. I'm not throwing any codes and my idle is smooth and it runs great around town.

I feel like I'm so close to fixing this thing that I can't give up now!
If I sell it, someone will put $2.00 part on it and fix it. Then they'll drive by here everyday just to rub it in.

Any more ideas? Should I block off the EGR?

bulletboy29

I'm beginning to think that the new mechanical fuel pump isn't doing the job. I removed the pump in the tank, so maybe the fuel lines just aren't letting enough gas go thru at WOT. I might install a pusher back by the tank. I'm going insane......

Does this sound like a lack of pressure at WOT? It runs so good at other times that I can't imagine what else it could be.

89rsragtop

What kind of air cleaner do you have? is it getting enough air into the engine?

bulletboy29

Yeah...I ran it with no filter and didn't change anything.

bulletboy29

Could it be a problem with the rod going to the mechanical fuel pump maybe?

sellmanb

agreed with above post about the EGR valve. I also remember someone saying something about AIR diverter valve (i think that's what it's called?) if it malfunctions it could give you the same problems.

bulletboy29

So you think I should block off the EGR valve?


The air diverter valve isn't hooked up...that's the one on the exaust right?

bulletboy29

1st gear pulls really strong, but it usually hits the fan in 2nd, and even worse in 3rd.

(if it makes it to 3rd)

sellmanb

block off? no, I think you should reconnect it. If it's stuck open all the time there'll be problems, if it's stuck closed there'll be problems.

Yeah thats the one on the exhaust.

bulletboy29

If I hook it back up, I'll need to know how the vacuum lines run. There is a vacuum sensor/switch controlled by the computer, right? It looks like it has three vacuum line conections coming off of it. Two on one end and one on the other. Do you know how to hook this back up?:shrug:

bulletboy29

I think I'll puchase a fuel pressure gauge today, this thing acts like my old weed eater does when the fuel line gets pinched.

gmgod

Did you put a pickup out of a mechanical fuel pump car in the tank after taking out the electric? Souds fuel related to me, get the gauge and see what you have.

bulletboy29

I installed a piece of metal line the same length as the elec. pump.

bulletboy29

Alright....went to Autozone and the guy says they don't sell low pressure fuel gauges, they only sell the ones for fuel inj. vehicles. He goes on to say that putting it on there to where I can see what it's doing while driving won't work. He said that I will have to tee it in and that won't really be accurate. I wasn't in the mood to discuss with him so I came home! He gave me the name of a good mechanic that works at the car wash/quick lube. "If anybody can fix it, Cliff can" he says. I'm not ready to turn my car over to "Cliffy", so what should be my next move?
Surely one of the members of Thirdgen.org has had this problem.

It always pulls through first gear strong, but in second it either bucks if it's from a dead stop or it fades out if I'm rolling. Heat makes the problem worse, it's not as bad first thing in the morning.

mnegovan

I don't think the EGR valve is the problem. But It may need to be hooked up for optimum performance. There should be a vacuum line diagram near or on the radiator shroud. If not you can search here. It has been posted before.

Did you change your gasket on the carb when you put a new carb on? Maybe at WOT you are losing manifold vacuum because of a vacuum leak around the intake somewhere. The EGR valve could have a leak. It could be elsewhere.

A manifold vacuum gauge is only around $20 and can be hooked up easily for under the hood troubleshooting.

I think I would need someone to second this analysis though as I have never experience loss of manifold vacuum.

mnegovan

One additional thought. Since I am experiencing loss of power on acceleration and I think that it is due to carb adjustments, how did you verify proper adjustment of your rebuilt carb?

Since it is malfunctioning as it did before I would not think that the carb was the problem. But if it is different then maybe the carb is the problem.

Fuel pressure certaintly could be the problem. Measuring it on a CC 305 is tricky unless you have altered the stock fuel lines to include rubber sections. You may want to pay the big bucks and take it to a dealer for a diagnostic analysis. I would do this as a last resort however and plan on spending quite a bit for the work. I would trust the dealers more than others for a problem like this. The dealer service rep could assist with your decision.

But like you, I wouldn't give up yet.

DartByU

You didn't say anything about changing the coil, that can cause a high rpm bog, in addition to my Camaro I have a Dodge Dart and it had a problem like that, it would pretty much quit running at about 2000 RPM, after checking the whole fuel system it turned out to be the coil was going out, it ran perfect at low RPM but give it much gas and it would die. I put on a new one and it would pull to 6000 RPM again!!!

bulletboy29

Replaced coil and ignition control module.....still no change.

Thanks for all the suggestions!

Keep 'em comin'....I won't run off and leave this thread if I get it fixed.

I'll post the answer to this mystery for people that stay up late searching threads for similar car problems like I've been doing for the last few weeks.

bulletboy29

I FIXED IT!!!

The new mechanical pump that I had installed just wasn't enough. I put an electric pusher pump on it today and it now it shifts through all gears with no problem at WOT. I must have some kinda blockage somewhere in the line, but I'm gonna leave it alone for now.


So my stalling problem was a bad ECM(another problem that I had right before I fixed this) and the bucking at WOT was low fuel pressure.

New fuel pump doesn't always equal good fuel pressure.
LESSON LEARNED

Thanks for all the help guys! I would've sold this car the first month I got it if it weren't for this site!!!

mnegovan

Congratulations!