When you own a 4Banger you are plagued with a very limited selection in aftermarket performance parts.
Recently, Chris Radoccia wondered if anyone made a throttle body spacer for the 2.5L's. Well, no one did and that's still the case. I told him how it was a old Hot Rod trick to raise the throttle body(well back then it was a carburetor.) Some were made from plastic, wood and other composite material. Chris being the smart guy went to a 4x4 shop and matched up a 2.5L throttle body gasket with the 4.0L Poweraid Throttle Body Spacer. Turns out they matched up perfectly. He soon posted that he had installed it.
"My throttle response lag was cut in half, it idles smoother, the somewhat flat spot at 4000 Rpm is gone, it pulls harder throughout the rpm range especially over 2500 Rpm. The only problem I have is I can feel it is starving for air, I still have the stock air intake on it. I hope to have that fixed this week. Now noting it pulls harder, I tested it getting on the freeway at my normal entrance. Making my entrance as normal it was only good for about and extra 3 mph at the actual merge point on the freeway. It seems to have an easier time to maintain freeway speeds of 75 mph. Which to me was unexpected as everyone said it would increase the torque more, therefore I would feel it more in the bottom end."
After hearing about this, I had to see for myself if the gains were really worth the cost. A quick call around got me a Poweraid Throttle Body Spacer shipped to me in 3 days. They only sell one spacer for Jeeps that works on 91-03 TJ/YJ's and 91-03 XJ/4.0L's, part number 310-510. The spacer comes with two gaskets, the TB spacer, 4 long throttle body screws, three smaller spacers and 3 screws for those. The Spacer has patent pending Helix bore. This is a course thread in the bore which causes the air to circulate as it goes into the intake manifold. For the TB spacer kit to work on a 2.5L, just remove the clamps that hold the air tube to the throttle body. Next snap off the throttle cable. This comes off with a twist. There are two connectors from the wire harness that need to be removed too. Then remove the 4 bolts that hold the throttle body to the intake manifold. This will require a torx. Now once you get the spacer in that's it. You won't be able to use the other spacers. 2.5L's have the linkage bracket in front of the fuel rail while 4.0L's have the bracket behind the fuel rail. The fuel rail makes it impossible to raise the linkage bracket but this will not be a problem. While the throttle body is off I recommend cleaning the bore out. There was a lot of build up around the valve since it had never been cleaned. Also scrape off any gasket that remained on the intake and bottom of the throttle body. Be sure not to let anything fall into the intake... that would be bad.
When re-installing the throttle body, the torx's are replaced with standard hex head bolts. Once the throttle body is on that's it. Ignore the rest of the instructions. The rest just shows you how to raise the linkage bracket which is not applicable to the 2.5L. Remember to re-install the throttle cable and in our case the hand throttle cable too. I ran into a few problems while trying to start the engine. I forgot to plug the wire harness back into the two sensors in the throttle body. The engine started but it sounded strange and the check engine light came on. One quick check and the throttle body was all set. Then another problem turned up. The engine wouldn't start unless the gas pedal was pushed some. Once the engine warmed up it would idle with the valve closed. So, the throttle body came off and the spacer came out. The engine still wouldn't start. Turns out while cleaning, gunk got into the air bypass passage and fouled it up the AIS motor. A quick tear down and cleaning of the motor got it working again. With the spacer back in we were ready for business.
Initial thoughts. The engine sounded slightly different when rev'ed. The biggest difference was in the lower Rpm range. The 4banger had enough torque that the clutch didn't need to be feathered anymore. This would really save the clutch from some unnecessary wear and tear. The torque band seemed to have moved down some so there is more torque available sooner. The engine still needs to be rev'ed some when going up steep grades but that is expected with a 4banger. The difference is that there was more torque so speed didn't drop as much as it usually did. The throttle body spacer is said to give the most increase in horsepower in the lower Rpm's and it does exactly that. It is also said that fuel economy will improve some. I have not noticed this yet. Now if you have already done everything else to increase power in your 4banger, then you might want to try this. Oh, and Poweraid now makes a spacer designed for the 2.5L, model number 310-511.
