I can't speak much of the reliability of the Mopar kit. I know that they have worked out the problems they had with it earlier. It is claimed to be made mostly of late model (pre OBD II) parts and can be serviced and installed at your local Jeep dealer. (I wouldn't trust my local dealer to change my spark plugs.) But long term service and support should not be a problem. In addition, you can use a code scanner on it to diagnose any problems.
The Mopar system is available through any Jeep dealer. Mopar carries it in its performance catalog. If your dealer's parts man gives you a blank stare, smack him upside the head and contact Mopar direct.
As to cost, I paid $1660.00 for this kit in 1995.
I have had failures of the magnetic pickup for the crankshaft position sensor, which takes the place of the stock distributor. The magnetic pickup is the most trouble prone part of the system. I am on my fourth one now but they are easy to replace and relatively cheap ($40). You should keep a spare in your Jeep. I have had two other strange problems. First, the wiring that goes to the computer (the computer, combined with the ignition coils mounts to the valve cover) which is held in to connectors by set screws, had started to corrode and come loose after a year and a half. Electromotive advised me to apply solder to the wires and re-install them. Problem solved. Secondly, the system is not tolerant of less than 9V from the battery while cranking. I was finding on cold mornings that although the engine would crank easily, the engine would not start. The solution is a new, healthier battery, preferably one that is not as effected by low temps. (Gel cells, spiral cells such as the Optima and dry cells such as the Predator fit the bill). I installed an Optima. Problem solved. An advantage of the Electromotive unit is that the designers were nice enough to include a check engine light that will flash trouble codes when asked. No code scanner is necessary.
Overall, my opinion of the Electromotive unit is positive. Customer support was very friendly and helpful. The unit has functioned well too. But with either of these systems, it is important that your engine and exhaust systems be in top shape. My engine had 36,000 miles at installation and now sports a Borla exhaust. But keep in mind, unless your engine is running poorly to begin with, you will not see a dramatic increase in horsepower. The Mopar should give you a slight edge over the Electromotive unit, but most gains will show up in torque at low RPM's and mileage. My Jeep will get 18 MPG on the highway (highway speed means 70 MPH in my home state of Texas) and up to 20 MPG with a tailwind. My Jeep will now top 80 MPH without breaking a sweat.
The best way to get power out of a 4.2 is to swap camshafts and have some porting and polishing done on the head. Neither of these kits will work well with this type of performance tweaking if you overdo it. They are both designed to work with stock components and anything that greatly increases volumetric efficiency such as hi lift cams will screw things up. Additionally, this sort of work will move peak torque up on the power band, which is not good for off roading. However, Electromotive offers a version of their kit, which is not CARB certified that includes a programmable engine computer. With a bit of luck and expert help, it is possible to get that system to work with mods to the engine and even with a supercharger, but you would be charting unknown territory.
In addition, with the Electromotive unit, I can vouch for the fact that that it will run with quite a few sensors defeated. Before I soldered the connections, as mentioned earlier, I did not have a throttle position sensor or an O2 sensor and it still managed to run. It ran rich and stumbled when cold, but it didn't let me down. Evidently, the only two sensors that will kill the engine if they expire are the MAF and crankshaft position sensors. However, with only those two sensors and more than 9VDC power, it seems to get along just fine.
Even with major vacuum leaks downstream of the MAF it still runs. The smoothness of operation is, though, inversely proportional to size of the leak.
I've even heard of one ingesting water on a creek crossing. With water over the hood, the MAF took a gulp and the engine stopped quickly. It did not completely hydro (to hydro is to ingest water to the point that the engine locks and bends all manner of internal components such as connecting rods.) With the Jeep out of the water, and the plugs out of the head, cranking the engine pumped out the H20. A little drying time for the plugs and MAF and off it went. Keep in mind that the computer and almost everything else on the Jeep was under water for quite some time. Electromotive claims the computer and coils are waterproof. I estimate that on my Jeep you could run it up to the headlights before water hits the MAF. The computer would still be dry. I have yet to try that.
When there is a problem, the computer stores trouble codes and will alert you with a check engine light. This can be wired into your existing check engine circuit after you rip the pathetic OEM computers out and forward them, along with the Carter carb, pulse tubes and 9/10's of the wiring and vacuum lines, to the home of the director of the California Air Resources Board (Send them COD).
The JFI is not nearly a sophisticated as a newish OBDII system, or even as the Mopar system, but its simplicity makes it easy to understand and work with.
The only times it has quit cold on me has been:
(Since this was written, I have gone through two more sensors. The one I replaced after Colorado died of natural causes. It started exhibiting problems by causing the engine to miss occasionally. It eventually would not let the engine start. The next one I killed. When I installed it, I did not tighten it up enough and it slipped into the teeth on the sensor wheel. It worked for a while after I fixed it but it eventually quit for good while on a highway exit ramp. When these sensors die, the tach reads zero no matter what. It's rather odd going down the highway with the Jeep in gear and the tach reading zero.)
One more cool thing about the JFI. It has an electronic output for a tach. It'll drive any newer tach although a factory tach takes a little more work. I installed a tiny SunPro tach a'la hot rod style on my steering column. It's a must for a manual transmission yoked to an engine that will probably grenade if taken over five grand. (Although I think I was told that the JFI incorporates a rev limiter, I have yet to test it.)
When there have been problems, Electromotive has been helpful and knowledgeable. In addition they have a web site at www.electromotive-inc.com. The JFI is not mentioned by name, but follow the links to the TEC-II section.
Parts not included:
Installation is quite straight forward with half a dozen connections into the Jeep wiring harness. Fuses and relays mount up high next to the battery and the fuel pump mounts on the frame rail next to the tank. The computer goes behind the glove box under the dash.
Among the recommendations are sealant between the TBI, gasket and manifold. This limits vacuum leaks. Also replace the plugs at the time of installation. The old ones living downstream of the BBD are going to be fouled out anyway.
Mileage gains are in line with the other units (18-20) MPG, power is probably a little less because of the stock distributor.
As the system uses proven parts, reliability should be no problem. Trouble can be tracked down with a GM code scanner. Unique to the Howell unit are the wiring harness and E-prom for the computer. Howell can do custom E-proms as well.
The system is 49 state legal and should be CARB certified by the end of summer.
I have been told that customer service at Howell is top notch with helpful and courteous people.
The cost is around $1000.00.
Since this writing I have found that some Howell owners were experiencing these problems:
Dave C wrote:
I have to say, about this whole thing, Howell has been an excellent company to work with. They are polite and always willing to help. I would give them an overall rating of 7. The problem is in the particular chip or prom they are using. It has some kind of known defect, according to every GM mechanic I've spoken to. When the system is put on the computer it reads all wrong. The engine is doing one thing but the ECM ignores this and tells the TBI to do another. I am getting it back tomorrow and will drive it for 400 - 500 miles then have the system checked again. Howell is working with me on possible credit for the work related to their systems failure.
C B Wrote:
Howell has been very good to me they even sent out some replacement wiring at no cost because the system was reporting bad O2 wiring (it didn't fix the problem). They are good guys. It sounds like this is a GM problem not Howell. Keep up informed as to your problems / solutions.
What are your symptoms? Both Bill and I are looking at several hundred dollar repairs if the Howell system is not causing our problems. I am having the following problems ....
1. Cold missing / rare stalling. Mixture seems overly lean.
2. Flat spots in acceleration at times (overly lean again it seems)
3. Shortened plug life because of excessive temperature (too lean)
4. Random error 13 code (O2 wiring bad) after warm restart, sometimes with a code 15. Field test shows system working normally (lean flashes and rich flashes and closed loop indications at the right times). I ignore the code 13 errors now. A shutdown / restart clears the error and it doesn't reoccur until the next warm restart.
Other than #4 it seems like all these problems could be the result of a bad intake manifold / gasket or some other kind of intake leak. It would be nice to know if this is the case or if the Howell kit is to blame.
Vacuum leaks become a much more important issue. All of these systems rely on some sensor to measure the amount of air being pulled into the engine. Any leak down stream of the sensor will result in a rich mixture. This includes leaks in the vacuum advance system, EGR system, EVS system and especially at the manifold. The Electromotive kit also requires a good seal at the valve cover.
If your Jeep doesn't have an O2 sensor, all these kits require the addition of one. This means removing and welding one on to the exhaust. This is not a fun task.
If your Jeep has pulse air tubes, they will no longer be needed. If you strip out all the tubing, you will be left with a stub on the downpipe and at the catalytic converter. These can be plugged, but if you replace the exhaust, you can order replacements without these stubs.
If you do purchase one of these kits, or already have one, keep me informed on you experiences. As you can tell, the only system that I have any long-term experiences with is the Electromotive unit. As these kits start becoming more common, I would like to keep up with them. Also feel free to e-mail me corrections on any errors or omissions.
Keep Jeepin', -Mark '85 CJ-7 -- Mark Shipman President, EndoImage 1602 Rock Prairie Road, Suite 140 College Station, Texas 77840 1-800-347-9949 fax 409-731-8048 firstname.lastname@example.org