I have a 89 jeep with the 258 and put the Howell injection on it. It started out real good with more power and better gas mileage. In 6 months it started to go down hill bad. I have tried everything I can think of and is not helping. I am hoping someone out there can help. I read 20 plus mpg jeeps in the September 08 jp mag. and there was a problem with the power steering pump. What was wrong with it and how did you decide that was the problem with your mileage? I love my jeep but can not afford to drive it at 10 mpg. Help.  

What other symptoms are you seeing? Are there any fault codes? Have you checked vaccum lines. I believe there are wierd vaccum set ups on those motors.  

As o2 sensors age and wear out, the voltage that they generate decreases and this is interpreted by the computer as a lean condition. So, trying to make up for the so called lean condition, fuel economy suffers.

Also, lean conditions can be harmful to engine and exhaust components, so, as a safety feature when the computer is having trouble because of sensor inputs out of range, a rich override default fuel map is called for. This obviously would also affect mpg.

Since it's a MAP system, there is a good chance that the computer will compensate for a small vacuum leak. If there is a vacuum leak you might notice idle issues (hunting) and throttle response issues. I don't think you would notice a decrease in fuel economy.  

I had the fuel injection installed professionally and took it back to them. They checked all sensors and vacuum lines and everything is ok. They called Howell and went over everything again and it checks out ok. The jeep has lost power and gas mileage. The motor compression runs around 125 to 145, it has 200,000 miles on it. Is the engine just tired?  

8 years ago in upstate New YorkI had put that system on my 81 CJ-7 it only had 132.000 miles and 235's on it, I never got that mileage it was probably 15 at best, I'm sure they still use the same system today, I did see an increase in power and alot better cold starts. For the money I think I should of swapped in a 4.0 HO for a little more or go to the jeep MPI. I also had problems in getting the immsions test because most places are not used to see modifiesd vehicles I ended up having to contact the State to clear it up for the shop. Good Luck  

Ya might consider an ignition upgrade. By the way, your Howell EFI performs better than the Mopar MPI kit. We tested 'em head to head.  

What would you suggest for an ignition upgrade. I have put a new stock ignition module on it. Do I need a new distributor and if so should I go with stock?  

HERE

It's expensive but way worth it. It's tuned to your engine.

There are also less expensive versions out there that are not tuned to your application. But they work. Try Proform.
HERE  

Thank you very much JP Editor for the advice. I put a new distributor in the jeep today and it runs good. I will have to drive it a while to check the gas mileage but it don't smell gassy now.  Thanks  

I have a 1990 YJ that I put the Howell sys on and am experiencing some of the same problems. Will the same ingition sys work on my Jeep also? Should the plugs be changed to a different plug than whay is called for?

Thanks for any help.

BJ  

EODTmLdr:
I have a 1990 YJ that I put the Howell sys on and am experiencing some of the same problems. Will the same ingition sys work on my Jeep also? Should the plugs be changed to a different plug than whay is called for?

Thanks for any help.

BJ

Yes, it will. Stock plugs will work fine, but you will be able to open the gap a little more. Just follow the directions with the distributor.