Starts up with full throttle.
 

Hi all, I'm new here.
I have a 2000 XJ 4L auto tranny. I had to replace the infamous 0331 head.
I took this apart around the first of May, and am in the process of reassembly this week. A lot of life happened between then and now. Apparently I messed something up. When I did the first start today, it went full throttle, got it shut off at 5K. :saddam: I've checked all the electrical connections, and they all seem OK. The vacuum lines are all connected. The throttle cable and pedal are functioning correctly. Don't have cruise control.

I'm thinking the throttle position sensor may be fubared, but I've been wrong a time or two before. Open to any suggestions as to where to start looking?
Thanks in advance,
Millwright74

Hmm, the odds of something electrical winding that high are, well, basically nothing. She's likely getting WAY too much air somewhere.

Throttle blade stuck, IAC stuck, wrong or wrongly installed intake gasket, huge vac leak, etc.

Intake not seated around guide dowels.

bingo!!!

i agree. vacuum leak.

Vacuum leak from the intake gasket not sealing up. Happened to mine when i changed my head gasket. Scary scary when it does that lol, Especially cold.

Reseated the intake.
 

Thanks Guys, that was the problem. Now that it runs at idle the header to pipe joint appears to be leaking. What pray tell are the conveniently located cans below the header flanges? Do I have to pull the intake again to get to the header flange bolts? I seem to be hampered by having only one wrist on each arm.:001_huh:

Thanks again, in advance,

Millwreight74 (retired)

Those are catalytic converters. You have the California emissions package. The EPA emissions package in 2000 had a single large catalytic converter in the back, with two O2 sensors. The CA version has two additional "pre-cats" in the downpipe under the exhaust manifold and four O2 sensors.

California Emissions Package
 

Oh joy.
I suppose deleting this package would be cost prohibitive. Would I have to change the ECU to accommodate a standard down pipe? I found a stainless steel exhaust header on Ebay for $100 with free shipping. There were no reviews of this item. Are their any known problems with this style of header?
All this started when my daughter was driving the Jeep and the lower radiator hose burst. This type of thing wasn't so bothersome before I turned 70.
Thanks again for all the help.

Isn't that a federal offense against the clean air act to tamper with emissions control equipment? You probably won't be able to discuss that here. I maybe wrong. A moderator will be able to answer this question.

The rule for that has changed. Delete at your own risk. Know your local law regarding emissions stuff.

IF it gets out of control we may delete as necessary.

:cheers:

Yes, tons. And... there are good ones, too. Do a search on "headers" here, and you'll find a bunch of info.