When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
This will be rather lengthy, but I am deep into an issue that I do not have the solution to and am lost after doing so much; therefore I will give the full story to my situation as it may help for context. RHD 1997 RX7 Power FC TT 13B-REW bought in Japan sat for a while. Drove fine after sitting for like 6 months. Gunned it one day and immediately after it would not go past around 4-5k without bucking/jerking bad and backfiring. It has gotten worse. It now will not respond to the throttle at all ( loss of all power) after about 10% throttle and if I get up to it like 2.5k then no acceleration again. Therefore, I cant go past 10 mph or any grade of incline. Will backfire occasionally when this happens. Car only smokes on startup for a few seconds then good (read this was normal). Has been ran with only premium gas. Did attempt to premix recently in case OMP was bad. From what I've read, the Power FC will not go limp mode if this is bad? So, I was mixing to see if it would help and if it had helped I would have thought to block it off. But it did not. Will idle perfectly with just a few misfires very seldom. Revving when cold in neutral will go all the way through the rpm range, however after hot and driven will not. At this point it will stop like a rev limiter/governor almost at around 2.5/3k.
As a means to fix for the past 6months-year I have... new vacuum line to boost sensor, installed IGN-1A distributor-less coils, new spark plug wires, new spark plugs, new fuel pump (it is the cheaper MasterPro fuel pump from Advanced Auto Parts), new fuel filter, checked fuel relay, EVAP Purge Solenoid had 0 ohms replaced with new, all other Solenoids in vacuum chamber read 30-38 ohms, boost sensor when unplugged obviously car will die after chugging bad, removed catalytic converter to see if backpressure maybe was plugged? but no difference-reinstalled, and adjusted the TPS.
Final Questions: I read with a piston compression checker warm engine full throttle 60 psi at each bump for front rotor and back rotor consistent (however, if I kept the schrader valve in the tester it read 90 psi, don't think this matters from what I've read). I know this compression is low but it shouldn't run this bad right? It just means it is weak compression and sealing therefore eventually soon I could blow it correct? Power FC shouldnt have a limp mode but it is acting like a limp mode? PowerFC is on Normal PIM. PowerFC only has base map. Don't think I had one to begin with but maybe I deleted it? Don't think so though because the problem was instantaneous after gunning it that one time then got progressively worse. No blacked out sensor readings.
I know this was alot but hope you understand my situation. Any solutions or ideas would be of great help as you can tell I am lost. I was leaning toward maybe OMP or just need to rebuild. If rebuild is necessary, please send suggestions for cheap/good rebuild kits as I would be doing it myself to save money.
If you have a 1997 RHD, be aware the coil positioning was changed on and after 1996. If you use the uSDM FSM as a guide to hooking up the coil leads you may have it wrong. This is very dangerous, especially if you have leading coils hooked up to trailing plugs
If you have a 1997 RHD, be aware the coil positioning was changed on and after 1996. If you use the uSDM FSM as a guide to hooking up the coil leads you may have it wrong. This is very dangerous, especially if you have leading coils hooked up to trailing plugs
As the Japanese magazines article indicates tis emerged as a notable problem for many..
The mix up can happen easily. For me it happened when I had a local garage change the spark plugs.
I drove around for about six months (including stalling in front of a train at a crossing) with the car seemingly going into limp mode.
Finally blew out a corner seal when taking the car over 6000 RPM a few times in succession.
Shops used to the USDM set -up will just reattach the leads as they have always done. Maybe even by feel.
Redbul,
Yes, I checked the coils and wiring and they are all correct. I have rerouted the coils to the frame near the passenger wheel well as this was needed for the IGN-1A from Sakebomb when I installed them. However, thank you for the additional information about the coils, I did not know that. And I understand the need for the proper compression checker, however I had borrowed the conventional from Advanced Auto to save money. I could try again for consistency? I know it is not 100% accurate but shouldn't it be close? If not, where could I borrow the rotary compression tester or just bite the bullet? Thanks.
I trade a carton of cigarettes to the local shop owner to do mine once every three months or so (using my tester).
My engine was rebuilt in October 2016, now has 47,000 km on it.
Readings can vary from session to session, but gives you a good feel of state of the motor. My goal is to reach 100,000 km. But i am building a second motor just in case.
The November reading might explain the slight lumpiness at idle is not just the Power FC doing its thing. But the variance can be attributed to a number of things.
I tested my compression this weekend. I am getting 90+ish on each face of each rotor. Therefore, my previous compression tester being a conventional rental and used quite often must have been losing pressure giving faulty readings. This is good news, showing a healthier motor than originally thought! With that being said, I bought a OMP block-off plate and am waiting on it in the mail. The next thing I have thought might be faulty is the OMP causing a limp mode type effect/ complete fuel cutoff? I do understand I will have to pre-mix after this is done. Any other suggestions?
I'd put more money on an internal issue with the PFC or an engine wiring loom issue than chasing bad parts. There is a gentleman in Canada who services Power FC's and has a complete test setup that might be able to help you out, you can find him in some of the RX-7 facebook groups, his name is Michael Gagne.
I tested my compression this weekend. I am getting 90+ish on each face of each rotor. Therefore, my previous compression tester being a conventional rental and used quite often must have been losing pressure giving faulty readings. This is good news, showing a healthier motor than originally thought! With that being said, I bought a OMP block-off plate and am waiting on it in the mail. The next thing I have thought might be faulty is the OMP causing a limp mode type effect/ complete fuel cutoff? I do understand I will have to pre-mix after this is done. Any other suggestions?
Before you add variables to the equation, you need to accurately diagnose what is happening first. Version 4 (96-98) works slightly different than Version 1-3 (92-95), but the overall "logic" is the same. If it is hesitating/bucking, it sounds like the fuel/air mixture is being thrown off by one or more sensor/device readings being skewed electrically. The most common cause is additional resistance caused by failing grounds.In short, everything is ground-referenced. So if a poor ground is in the equation on, for example, the Coolant Temperature Sensor, the ECU will think that it is either warmer or colder (I forget which, consult the USDM manual for the graphs) than it is, and either add extra fuel or pull back fuel incorrectly because of it. The result is that the engine falls on its face or starts bucking because the air/fuel mixture is incorrect for the conditions.
On items like the Throttle Position Sensor and OMP Position Sensor, extra resistance on their grounds pushes their voltages HIGHER, making the ECU think you're planting your right foot when you barely feathered the throttle. So it dumps in fuel when it shouldn't, and then faceplants/bucks accordingly.
ECU uses both Ground Point #11 and #12. #11 is by the Oil filter, #12 is near the O2 sensor connector and rear secondary fuel injector.
Redbul mentioned my thread about Japanese Manuals. I'm in the final phases of the project, adding connector images and text back in, then assembling the whole thing.
Please note that the compression test levels in the original USDM FSM were changed in the follow up version of the USDM FSM. They were changed to match the JDM FSM. (and other in period manuals)..
In the JDM FSM, it is stated that anything below 100 PSI at 250 rpm sea level, should trigger possible remedial actions.
Please note that on my rotary compression tester the first readings are raw figures. The tester will then show a set of corrected figures.
Please check if your readings in the "90s" were the corrected figures.
If you corrected figures are indeed in the low 90s, the car may run fine provided all the "faces" are within range of each other.
This is the recent reading on my back rotor. You can see the "Cor." reading. The variance between faces may be a cause for concern for my car, but this reading was done cold after a severe "flooding" event where we also had sprayed in "engine starter". We have corrected the flooding issue * and I plan to do another compression test this week (fingers crossed).. (* after doing various deflood procedures 15 times, we finally got the car to run, after we swapped out the gas - Chevron 94 - for Shell 93, but not before I had the shop replace the spark plugs - twice, the O2 sensor, MAP sensor, ISC, coils and TPS, and test injector connectivity. In the process we found a broken vacuum line to the oil injectors that had been driving my power FC nuts. The result of all that is that my car now runs super nice.)
Probably a lot of possible options, but my car did very similar and my fuel pump was bad. It worked enough to run off boost, but couldn't supply pressure with any boost and would drop down to 10psi. then would start bucking and jerking and almost no throttle response. I'm running a power FC also. If you have a fuel pressure gauge, its an easy check to see if that is working properly or not.
Before you add variables to the equation, you need to accurately diagnose what is happening first. Version 4 (96-98) works slightly different than Version 1-3 (92-95), but the overall "logic" is the same. If it is hesitating/bucking, it sounds like the fuel/air mixture is being thrown off by one or more sensor/device readings being skewed electrically. The most common cause is additional resistance caused by failing grounds.In short, everything is ground-referenced. So if a poor ground is in the equation on, for example, the Coolant Temperature Sensor, the ECU will think that it is either warmer or colder (I forget which, consult the USDM manual for the graphs) than it is, and either add extra fuel or pull back fuel incorrectly because of it. The result is that the engine falls on its face or starts bucking because the air/fuel mixture is incorrect for the conditions.
On items like the Throttle Position Sensor and OMP Position Sensor, extra resistance on their grounds pushes their voltages HIGHER, making the ECU think you're planting your right foot when you barely feathered the throttle. So it dumps in fuel when it shouldn't, and then faceplants/bucks accordingly.
ECU uses both Ground Point #11 and #12. #11 is by the Oil filter, #12 is near the O2 sensor connector and rear secondary fuel injector.
Redbul mentioned my thread about Japanese Manuals. I'm in the final phases of the project, adding connector images and text back in, then assembling the whole thing.
I was just about to say that he should make sure his grounds were clean and tight.
My FD was basically an early stage parts car that had sat for several years, and when I finally got it running, it sounded like a lawnmower and wouldn't rev.
It turns out one of the large grounds on the engine block was loose. Tightening that one bolt fixed it.
Gentlemen the problem has been solved. I diligently worked and applied all the helpful information you all gave. However, after I got no results I decided to go back to my first assumption, the fuel pump. I replaced with an aeromotive 340 this time instead of a garbage autozone one. Nothing.... however the wiring from fuel pump to the adapter on the fuel sender unit was bad at the adapter. Multimeter read 0.2 ish ohms however I replaced anyways because it looked awfully messed up. That was it! I no longer have any acceleration issues! I am now only working on cosmetics and currently chasing a boost leak; im getting like 0.36 on the power fc I believe mmhg and a notable air leak noise entirety of time im building boost. I am so happy to have fixed the original issue now though. Thank you all.
Perhaps run a smoke test to help identify the boost leak. They pump smoke into your system and hopefully any leaks may become obvious with smoke wafting out.
Anyone with a smoke test kit might do the test fairly inexpensively.
Perhaps run a smoke test to help identify the boost leak. They pump smoke into your system and hopefully any leaks may become obvious with smoke wafting out.
Anyone with a smoke test kit might do the test fairly inexpensively.
Smoke testers are overkill… clamp a plastic bag over the intake and apply compressed air to a nipple. Use soapy water if necessary.
11-22-23, 10:12 AM
Compressed
