fuel injetion woes

I'm finishing off an EFI conversion on my '88 jeep Cherokee (I dropped a carb'd 350 in it a few years ago, now installed a holley terminator EFI on it).

finished everything this weekend, did the initial software tuning, turned the key, and it started up almost immediately, but then raced up to about 4,500 rpm, and stays there.

I spoke with Holley tech support, and they went through all the software parameters and sensor readings with them, and they're convinced everything is connected ok (throttle position sensor is fine, iac is fine, fuel pressure is fine, a/f ratio is fine) they're convinced it's a vacuum leak.

Which makes sense to me, but I can't for the life of me track it down. I don't have a lot of vacuum connections on the motor --just timing advance, fuel pressure regulator, brakes, and pcv. brakes connect to the intake manifold, everything else to the TBI unit. I unplugged the timing connection, pcv, and fuel vacuum connections and blocked them off at the tbi just to eliminate them as leak sources... this did nothing. idle adjustment screw is almost completely out (though not all the way so as to create a leak), and at idle throttle plates are closed. no binding on the throttle cable.

any thoughts on this? any other likely leak candidates? I'm using a spacer plate between the intake manifold (edlebrock) and tbi, and I haven't changed the gaskets. I guess these could be a problem. I really would prefer to do whatever I can before sticking my head under the hood while this thing is racing at 4,500 rpm.

any thoughts would be greatly appreciated.

Classic symptoms of a incorrectly installed intake manifold.
Had this exact thing happen and found I had screwed up and had not evenly tightened the intake and exhaust manifold bolts.
The result was a slight hidden gap somewhere that allowed way too much air to sneak in. The second the engine fired, it would spin instantly to redline.
Attempting to retorque the manifolds in place didn't work.
My XJ is a 2001 and has the two mini-cats to complicate the assembly. It is almost impossible to get to a couple of the bottom bolts, when the engine is installed.

The fix, in my case, was to unbolt the head and redo the entire assembly on the the bench and then reinstalling it as a complete unit.
I found the gasket was slightly damage and probably would have never re-torqued correctly.
I had a spare gasket and the head was back on in about four hours.
An engine hoist simplifies this process.

At least it is easier to remove the manifold on a SBC than an XJ, when the engine is installed.

If the FI was screwed up, the IAC cannot dump in so much air that it will rev to the moon, assuming the throttle body blade was properly adjusted at the Factory.

ugh. I'm really hoping that's not the case --- I should also mention that the truck has been running for years with a carb with the same intake, and I didn't tough anything on the intake.

I'm going to redo the carb gaskets and try a new spacer, see if that does the trick.

I'm assuming the blade is also properly adjusted -- no idea how to check that, but will dive into it if changing the gaskets don't help.

I win the dumb azz of the year award.
The throttle plates were out of alignment, so even though the driver side looked like it was completely closed, the passenger side was open. The TPS was reading 0, but was still sucking in air through the "closed" throttle, and kept dumping more fuel in-- so there was my vacuum leak. A minor adjustment, and it runs almost perfectly.
only took me a week...

Consider the time spent as the cost of education.
It feels good to finally figure out problems like this and now you know a lot more how your new injection works.

How many of these damn treads you going to start? I know this has been talked about before.

wow.
call the admins bro. This is a terrible, terrible offense

You need to calm yourself. So many other things in life to get excited about, this isn't one of them.

lazyxj said:

Consider the time spent as the cost of education.
It feels good to finally figure out problems like this and now you know a lot more how your new injection works.

Click to expand...

Exactly. good point.

Thanks for the follow up.

jmg222 said:

wow.
call the admins bro. This is a terrible, terrible offense

You need to calm yourself. So many other things in life to get excited about, this isn't one of them.

Click to expand...

Im calm. People may as well start a new build thread for every piece of their lift kit that gets installed.

go1lum said:

Im calm. People may as well start a new build thread for every piece of their lift kit that gets installed.

Click to expand...

Or I guess just have a single thread for each vehicle they have. That makes sense.

Your opinion is noted. If I'm breaking any rules I'm sure the mods will tell me (which you are not). Stop trolling, get over it and move on.

jmg222 said:

Or I guess just have a single thread for each vehicle they have. That makes sense.

Your opinion is noted. If I'm breaking any rules I'm sure the mods will tell me (which you are not). Stop trolling, get over it and move on.

Click to expand...

You have some good tech. The next guy needing help with this may have problems finding answers in the many threads about it now. You have this one and the it lives, it may at least come up better in a search if the title is like "fuel injection woes holley kit 350" They could have been one, that is all.