Yes it was doing this when I got it back but I just thought that I did something wrong when I put it back in. But after driving it 1500 miles and going back over everything I can't find anything that doesn't look right. I know that the place that rebuilt it for me normally does an excellent job. The motor is under warranty so I guess I'll give them a call and see what happens.

 

Honestly did you try replacing your throttle position sensor? This sensor tells the IAC when to operate and gives the computer a refference for how much fuel to give the engine at a given throttle position. In some cases it will make the rpms go up or down by 2-300 rpms while driving even!

If the motor runs good & consistent even at 1100 Rpm, I would not suspect a blown plenum gasket on a rebuilt engine, my sisters had a blow out in 4 places and that never ran over 800rpm at idle ever. Pretty much it was 800 at first start up then dropped to about 550-650rpm. Every plenum job I've done has had minor leaks that cause other problems and never once was the high rpm idle one of those problems.

So my point is, if theres even somewhat of a gasket on that plenum, the engine should idle down normal.

I would just for piece of mind, spray some starting fluid around the plenum where it meets the heads and see if the rpms change at all, if so try re-torquing the intake in the correct order and then After checking the throttle body for vacuum leaks and all vacuum hoses, I'll throw a good chunk of change bet on your Throttle position sensor being bad replace is my best advice! which even without doing the rest of the above I'd change anyway.

The only worry on the engine itself I'd have is if they used intake gaskets that have the front & back cork seals, sometimes they can slide even when you use permatex to help keep them in place and when you set the intake on you can move them, along with the intake not being torqued properly in the correct sequence which I suspect was most likely done which brings me back to the TPS replacement and making sure no leaks are coming from the throttle body to intake seal.. If they screwed this up, confiscate their tools and call a lawyer.

My Neon engine swap I did 2 weeks ago was pretty scary! my parts motor I put in had been sitting behind my dads garage in the elements for 3 years and on its first start up it shot up to 8,000 Rpm before we could react to turn it off. That ended up being due to me assembling the plastic intake manifold on the engine in 5 degree weather and the flange became a banana from sitting outside and then assembling it.

 

Ya I might as well go ahead and replace that tps. If a $30 part will make my expensive motor run right it will be well worth it. The only thing is the truck always idled fine before the motor swap. I guess the sensor could have gotten water or oil or something in it while the throttle body was off the motor and that could be causing it.

 

If they took the tps off the throttle body for any reason it could have not been put back on properly & set. Sometimes from old age they can wear and not read the same, and if not set back on the exact way it was taken off & tested with a multi meter to ensure a good reading you could encounter good or bad results. Even though there is no official way to set it, the slop in the bolts can be enough to throw off an old sensors throttle mapping ability, which is why some people will drill those holes out on the sensor itself bigger to get some adjustability out of an old sensor thats wearing out. I do warn that this is not the only issue that can go bad with a bad TPS, it can be just crap with no saving.

I think a new TPS should be in the $25-$30 range.

 

I guess I'll just have to pick one up and see if that does anything. I know that this high idle is putting extra strain on my transmission and putting more wear on my brakes so it needs to be fixed pretty soon.

 

You can replace all the parts you want, but so long as you do not address THIS issue, you aren't going to solve your problem.

 

I didn't read the whole thread completely but after reading Heyyous post above it Almost sounds as if the intake gaskets are leaking or were damaged somehow, crap makes you wonder if they even put a gasket on the plenum?. Probablem definitely sounds like its in the Keg intake for sure.

My previous post was assuming the build was done half way decent, but it appears there is something wrong with gaskets that its sucking in that much air and creating that kind of a vacuum.

 

I have had 2 other motors done by this shop and they are the best running engines I have ever seen but he has a bunch of kids working for him and I bet one of them didn't put it back together right. I got a check engine light on my way to work today and it's p1294: target idle not reached. I don't know why it just now came on. It's been idling this way for 1700 miles now. I guess it just now figured out that there was a problem.

 

How is the engines vacuum when you take off the oil fill and put your hand over it without blocking anything off? I remember vaguely you said you blocked ports off before and it wanted to suck your hand in, how about without blocking the other vacuum ports off how does it suck?.

If you lived near me we'd get it figured out in a day!

This is more involved cuz you have to jump inside your engine bay, but take your air cleaner off and open up the throttle body and shine a flash light into the throttle body to view the plenum pan and see if you can see any gasket around the bottom of the plenum edges. This is often times how you can check for a blown plenum gasket, but I'm curious to know if there is even any gasket in there or if it was even changed. If the gasket looks new and is not inflamed assume that is not the problem. You will only be able to see a little bit of the gasket because of the casting of the keg intake but if it looks like its cruddy or pulled in theres a possibility they never changed that gasket then and its causing that.

Also might be a good idea to listen for any air leaks that may come from the front or back of the intake just incase cork gaskets were used on the front & back and they slipped out which can happen easily if they did not pay attention when building the engine.

Heres what the bottom of the intake looks like so you know what to look for...the side toward us is facing the engine (of course) but where that gasket goes on you should be able to see part of the new gasket from the top/inside of plenum or if one was even installed. Look for the gasket to be uniform in its fit and if it looks all black and old looking then look for certain sections to be pulled into the plenum pan like a banana.

 

It still has a very strong vacuum with everything hooked up like it's supposed to be. I'm going to put a vacuum gauge on the intake manifold tomorrow. I called the shop that rebuilt the motor and they said that if the vacuum is less than 16 then a seal is not in there right. They also said that there should be a very small amount of vacuum in the valve covers due to the pcv system. It makes me mad because they said that they would provide me with new gaskets for free but I would have to change them out. We'll see about that. I think that they should put everything in for me since it was their fault.