racing engine

I've put this is a couple of other places, started as a vacuum diagram request, and with a lot of help, I've gotten that straightened out. Still racing.

Put a Clifford header on my 2.5L, and after I replaced everything but the EGR tube (which I had to modify), it raced like mad on startup (I have no tach, but I'm guessing 2500-3000rpm). I've since replaced the EGR tube, and same problem. I'm still running the open header, because I haven't gotten it to the local exhaust shop to weld up some pipe to the header, because it's racing!

It seems a really remote possiblity that running lean with an open header would cause the engine to race like that on startup. The intake appears to be on properly, I'm 95% sure the vacuum lines are on correctly now. Anyone have any ideas?

it may be the IAC setting it self wrong. does it go back down?

It never comes out at all. There is no throttle component to this racing, I disconnected the IAC just to test.

misunderstanding. does the idle ever go back down?

Well, the most I've let it run is maybe 2-2.5 minutes for fear of a fan blade flying off or doing damage to my 180K+ engine. Doesn't show any signs of slowing down in that time, though.

is the throttle plate fully closing? or do you have an enormous vacuum leak. hows the brakes. the booster may have failed. though i don't believe it would rev it that high. surprised no one else popped in with a solution.

Throttle plate closes, I pumped the brakes during racing and it felt like I had good boost, but did not change the idle speed. I thought the enormous vacuum leak might have been the EGR tube, but that's now hooked up, but the header isn't connected to the rest of the system. Would that cause a vacuum leak??

are all the vac lines hooked up. enough leaks and it will signify an open throttle. if you have pics post.

They're all hooked up...I'm pretty sure they are hooked up CORRECTLY, I even switched a couple around while it was racing, to no avail. Anyone????

Sounds like what the commanche did until I found the intake nuts finger tight. Sure it dosent have a massive vacume leak?

would no O2 sensor cause this? since the manifold isn't hooked up the O2 sensor thinks the engine is pumping out fresh air. just a thought...

Hey,
I just replaced the exhaust manifold, so I tightened it and the exhaust manifold in the order required by the FSM. I'm sure it's all tightned up. As for the 02 sensor, yes it's in the header, and I was wondering too if the open header was the cause...

MjTjNJ said:

Hey,
I just replaced the exhaust manifold, so I tightened it and the exhaust manifold in the order required by the FSM. I'm sure it's all tightned up. As for the 02 sensor, yes it's in the header, and I was wondering too if the open header was the cause...

Click to expand...

i dind't know it was built into the header. i think some have 2 O2 sensors, but i would guess you would have seen the other one removing the exahaust... keep us posted. i think mine has a cracked manifold, so i might go to a header.

how is the quality of your new header?

Tom,
The more air you let get into the cylinders, the faster the engine will run. Think of the throttle plate as nothing more than an air regulator...the more open it is, the more air it lets past into the engine, and the faster the engine runs. If you're sure the plate is closing, then that engine is pulling air from somewhere else, where it's not supposed to be:roll:

Likely suspects would be the EGR tube (but now that it's hooked up it shouldn't be an issue)...you do have it connected at both ends, right? Other than that, I can't think of anything else but the intake manifold bolts being loose. You sure the two lower ones (the PITA ones to reach) in the center are tight?
Also, did you remove the TB from the intake? There's a paper gasket inbetween the TB and the mating surface on the manifold that you may have forgotten to replace, or it may have ripped.

Somewhere, there's air getting into that engine that shouldn't be....

Jeff

Mine only has one 02 sensor -- it's an 87. I like the quality of the header, and it fit up nicely. I wasn't happy that I had to fab the steel EGR line; since they put the flange there, it should have fit up, IMHO. I'm sure I did something wrong to cause this racing, but I'm not sure what. Could crossing up the vacuum lines do this? I don't have any pictures, but the two TBI ports run to the MAP sensor and the valve cover. The manifold port runs to the EGR solenoid, and a line from the solenoid goes directly to the EGR. I disconnected the thermac unit long ago, so that's not the issue. Thanks, guys.

Hey Jeff! Thanks for chiming in. I did take the TB off, scraped off the old gasket and replaced it! Those PITA bolts definitely got tightened, but I'm going to take another look at them tonight. I thought it was the EGR tube, too, but now that it's hooked up, I don't know. Seems that it's pretty open to air anyway, being connected to an open header.

my father once showed me a little trick to find an intake leak. he would spray apparent trouble areas with carb cleaner, and when it found its way into the engine it would cause the engine to idle differently, and they you know where to find your leak. i'm sure this isn't the *safest* route, since your spraying a flammible liquid around the engine compartment, but it always worked for him.... don't blow yourself up.