Ford Guy

Good day Moses, Thanks for the comments and suggestions. I too like to work from a known baseline, like the factory settings. I learned a long time ago those factory engineers are paid the big money for a reason. I rarely try to second guess them. I didn't get back to the Jeep until early this week. I started by identifying what I could, checking routing of wiring, vacuum and vent lines and checking the operation of the components. Starting with the original problem of the timing changing, I took a close look at the distributor and found what I thought was excessive lateral movement in the distributor shaft. Closer inspection showed there to be slight contact between the reluctor and the magnetic pickup. So, in went a new (not rebuilt) distributor, rotor and cap. The timing had been a bit erratic, but with the new distributor is now steady. The Jeep sounds better, Hard to quantify, but I am sure you know what I mean. The base timing (vacuum disconnected) still will vary about 8* up or down when the engine is dry revved to about 2,500 rpm and let return to idle. That is, with base timing set at 6* BTDC (vac disconnected) and the engine dry revved and returned to idle, a follow up timing check may show the timing at 12-16* BTDC or it might be 2-6* ATDC. This timing change can be duplicated at will in the shop. Idle speed will vary 200-300 rpm with these changes, from a curb idle of about 750 rpm. Returning the idle to 750 rpm in Park doesn't affect the timing. I set the base timing at 10* and let the owner have his rig back. It still has the non stepper carb but everything else appears factory. The owner took the Jeep through an State emissions testing station the following day. The Jeep passed on all accounts, visual and tailpipe. The HC and CO readings were both about 25% of what was allowed. These were the only measurements the test station took. It appears the erratic timing was causing the test failures. So...The jeep is licensed for another two years and the owner is happy. But...I still want to identify the reason for and correct the changes in base timing, if that is a problem. I am supposed to get the Jeep back next week and I will continue with the identify and confirm part of the task. Pretty sure I will have more questions. Ford Guy

Moses, Thanks for the comments and the additional thoughts. You touch on a number of points, that I while agree with most, I feel are best left for another thread. The LS /TJ swap was interesting, but it looks to be a bit more work than my friend is interested in. I was supposed to see the YJ back in the shop this week, but that was pushed to next week, so...The YJ's owner is concerned with getting his rig to pass the sniffer test, though his tags don't expire until November. Given that and based on your last post, I plan to give the Nutter Bypass a try, as a test. Then we can run the Jeep through the sniffer test and check the results. If it passes, great, and if not we are back at square one. Either way I will begin digging into and confirming the operation of the emission system components. I will get back in contact once we have done the test bypass and run the rig through the test station. Question. Do you think that with all other emission related components functioning properly and the ECU not receiving errant throttle position signals, the use of a non stepper carb should allow the rig to pass the basic tailpipe sniffer tests? Moses, your thoughts, comments and insight are valued. Thank you. Ford Guy

Moses, I appreciate you thoughts. From what I have found regarding the Nutter Bypass, it will most likely pass the visual inspection part of the smog test, providing everything appears original. Put the bypass wiring in the loom and make the vacuum lines appear untouched. Typically the visual part is nothing more than a quick glance under the hood to see if the major components are in place and appear to be functioning. As long as there is still a maze of hoses and wiring, the vehicle will usually pass the visual. The inspectors typically don't spend the time to check for every component, wire and hose. The non stepper carb would most likely go unnoticed, as long as the disconnected stepper wiring wasn't visible. The tail pipe sniffer on these older rigs is the big item the local inspection stations will fail a rig for. The rig is first checked at idle, then revved to a fast idle for a few seconds and allowed to return to a normal idle and checked again. This second reading is the "official" test reading. The allowable emission limits are a bit more lax than original limits, but there is no grey area. over the limit, even by .01% and you fail. After reading more on the Nutter Bypass this past weekend, I am less opposed to it than I was originally. Please correct me if I don't have a good understanding of the change. Simplified, it appears the Bypass removes the ECM from the ignition system and changes the advance vacuum from manifold to ported.This allows the ignition to work as a typical early Duraspark system with vacuum advance. When coupled with the non-stepper carb conversion already on the Jeep, this bypass returns the Jeep's ignition and carb systems to a mid 1970 norm. Again, any input would be appreciated. Ford Guy

Moses, Thanks for the link. I'm going to have to read it over more than once, that's for sure! The owner has been talking about the Nutter Bypass. I tend to try to keep things as originally designed and am not sold on this modification, though from the positive comments it seems to be something worth looking at. I would appreciate your comments on the Nutter Bypass. I won't have the Jeep back in the shop until mid next week. I will do the checks and verifications at that time and report the results. Ford Guy

Mr. Ludel, Thanks for the prompt reply and the schematics. I will check out the systems mentioned. Being unfamiliar with and not having solid information about this rig has been a large part of the problems I have encountered. The information you supplied will help me immensely. According to the owner the non stepper BBD has been on the Jeep for 4-5 years and has passed the state emission testing twice before, but not without difficulty. It was installed by a local shop because the stepper BBD was not "working properly". The owner is a long time friend and I have been aware of his problems with this Jeep, but not involved until now. I have often thought there was more going on than just a timing or carb issue. Did the original stepper BBD send inputs to the MCU or did the BBD just receive outputs from the MCU? With the non-stepper BBD in the system will all other functions work as designed? Again, thank you for you help. Ford Guy

Hello all. Newby on this forum. I'm dealing with a '89 Wrangler with the 4.2 and an auto trans. The rig has about 165,000 miles and I don't believe there has been any work done to the 4.2. The original BBD stepper carburetor has been replaced with a non-stepper BBD, but all else appears factory. The owner has not been able to get the rig through emissions testing and has asked me to help. I am not overly familiar with the 4.2 and much of the information I have seen seems contradictory, so...Here is where I ask for your help. The base timing will change by merely revving the engine and letting it return to it's normal idle. In one instance the base timing was set at 6*BTDC, vacuum disconnected, and after reconnecting the vacuum and revving the engine the base timing had dropped to 2*ATDC, vacuum disconnected. The base timing has also advanced 8*-10* in a similar test. A static check shows the distributor and vacuum advance assemblies working as they should and the distributor is firmly clamped. The idle speed remains reasonably constant and the carb linkage is resting on the curb idle screw. I have not checked for timing chain wear and suspect this may be part of the problem. I also plan to remove the distributor and check the internals for wear etc. This rig has manifold vacuum to the distributor at all times. I have read where it should have ported vacuum. I have studied vacuum diagrams for this rig and haven't been able to positively identify the vacuum source. Any help or comments would be most appreciated. Thanks in advance. Ford Guy