supercell

Thanks Jim, I will try checking those as well. Am I correct in assuming the plates (primary and secondary) should be closed completely with no clearance at idle? My primaries have a miniscule amount of clearance that I can pass some of my thinnest feeler gauges through. This may be part of the problem.

I took the car out today, and realized that I must have somehow put the car in limp mode when I took out the fuel jumper and put back in the relay - I got 5 psi of boost and then a sudden, violent, oh-****-I-just-blew-the-engine kind of engine braking feeling I have ever felt. After I cleared the ECU, everything was good again back in that department, 10 psi of beautiful boost on hand again. After I got that fixed, I jumped ten and gnd, idle did not go any lower. I then removed the jumper and unplugged the ISC. Still no difference. It looks like this is probably a mechanical problem of some sort. I think I'm going to go ahead and order my metal UIM gasket and the two that go to the AWS and ISC so I can pull the manifold. Is there anything else I should get/replace while I'm in there? (I'm not up to doing a complete and thorough vacuum line replacement at this time) Has anybody ever cleaned these valves before, and have any tips or tricks to getting them completely clean?

Eric Michel

Sometimes I get very busy with work and even have to jump on a plane at the last minute, but I really want to see you get this thing figured out, we have all been there. It could just be that your throttle plates are not adjusted properly as Cutaz35 mentioned. I have had strange idle problems before when these are not adjusted properly. If you think about it the computer has a default duty cycle for the ICS, with the throttle plates supplying to much air the default setting causes a high idle and who knows whats going through it little brain when it sees this. If you are concerned about causing more problems just record how many screw turns you adjust it so you can set it back if this doesnt help. As I already mentioned from what I have learned the upper plates should be completely closed, the air adjustment screw under the TB is usually closed but can be used for fine adjustment, start with it closed. How did you determine that the TPS was ok? Adjusting the lower single throttle plate will change the TPS idle position so keep that in mind when making adjustments. If this doesn't do it I will ask RP for a couple of suggestions, I will be visiting with them later this week.

Eric

Berserker

I was having the same problem with my car and my guess it was a grounding issue. It just so happened about that time my front headlight cover feel off and got stuck in the head light assembly (took two hours to get it out). Anyway, since the headlight would not retract it drained the battery. Once I fixed the head light issue I had to jump the car so I went ahead and cleaned the battery posts and decided to go ahead and reset my ECU. Ever since then the problem has been non existant. The car idles normal after it has warmed up for about 2-3 minutes, although lately it idles a little high I am thinking about cleaning out the gasket manifold as some people have posted that has fixed a high idle issue on a cold startup.

Hope this helps...

the_glass_man

iTrader: (2)

ttt

supercell

Update:

The limp mode is back - every time I start the car again after resetting the ECU. It looks like my ECU is now toast. When testing the fuel pump relay, I realized no that I put the jumper into the connectors toward the front instead of the back two, and I think this fried the ECU. I get a code 51 every time I reset the ECU. I tested the relay, and it is good. I tested the connector for the relay and it tests fine as well. I also tested the wiring from the relay connector up to terminal 1k at the ECU and it is good as well. With the key on, I get battery voltage at terminal 1k on the ECU - according to the book, this should be less than 1.0v unless the engine is running at idle and the PRC is not operating. I am not really that upset about this - I went ahead and dumped the cash on a new PFC, should be here by Friday. At least I will now be able to see what the sensors are really doing in real time instead of all the labor I have to go through now to test anything. Anything I should know about it before/after I hook this up? I don't plan on doing much modification of the fuel or timing maps, but I do want to monitor things and see what's really going on. This set me back a day or so, but I will get those gaskets ordered tomorrow - hopefully get them before the weekend to clean up the intake tract.

Eric - on a side note, since my fuel pump relay is always energized when the ignition is on, the pump stays in high output mode, and the idle and bucking were completely gone. Driveability is smooth and easy below 3k right now (I don't take it up any higher because of the limp mode) Frankly, I can't wait until I get the PFC in because I think once the mixture is right at low rpm again, it should run smoother around town.

I am currently not driving the car until I get the PFC in. I don't even want to risk the damage that limp mode could cause to the engine.

Eric Michel

Jon,

I apologize, after reading your last message I realized that I made a mistake and told you to short the wrong two pins for that relay. I referred to my own car when I gave those pins but because of a custom air duct, I have modified this relay box on my car and the relays are in the opposite direction compared to a stock setup. I don't think I even referred to the correct page numbers in the manual, it was actually F110 & F111. I have a good stock computer collecting dust that you can have, let me know if you want it.
On the brighter side it sounds like that resistor may have been your problem afterall?

supercell

Eric -

Is the stock ECU a 93 model? if so, I would be interested in case I need to swap with the PFC for testing, etc. Thank you for the offer. I got the PFC today - I'll probably put it in tonight. Do you think maybe with the PFC (had it pre-programmed for my mods) the mixture will be better at idle than it was before, negating the need to do any further jumpering? I am hoping this will be the case. Right now I am just trying to figure out the best way to mount it!


Jon

Eric Michel

It is a 93, send me a PM with your address. I am trying to understand did jumpering the fuel pump resistor fix your problem and you just did not realize it right away because you were jumpering the wrong pins? If that is true you probably need to replace the resistor. I know almost nothing about the PFC so I couldn't tell you if it is using the two stage pump like the stock system.

supercell

Eric,

What happened is I jumpered the wrong terminals - this is when I told you that I didn't think it made any difference. Then, after I took out the jumper and reinstalled the relay, the ecu stayed in limp mode based on the fuel pump relay circuit being shorted. (I verified this tonight when I opened the ecu, and lo and behold, the transistor for that circuit was so crispy it crumbled when I touched it) Since the ecu was shorted to ground, this circuit always had the lowest resistance, bypassing the resistor and therefore preventing the pump from ever going into the lower power mode. The car's driveability below 3000 rpm was excellent after the ecu fried, but of course the limp mode prevented me from going any higher. The idle was still high, so I think that is an unrelated problem. So essentially, I did not short it properly myself, but the damage I did to the ecu tested the fuel pump high power mode for me....

By the way, I successfully installed the PFC tonight. Did not have a chance to start or drive it yet, but with the key on, I can immediately read the values of nearly every sensor that counts under the hood. (this thing is awesome!) When I had it tuned, I asked them to tune for my mods specifically so maybe this will bring the mixture back up to where it should be at idle...we'll see. If not, maybe I will need to replace that resistor (if the pfc even uses it). I'll let you know the latest after I take it out for a spin tomorrow.


Jon

suganuma

after all of your idle problems dont get freaked out when you start up the PFC for the first time. itll learn your car by doing a lot of crazy idle stuff taking it up and down around 2k and then revving it. just let it be and eventually it will settle around a 750rpm idle. you just have to trust it.....

supercell

Thanks for the advice suganuma - anything else I should know about this before I start it or drive it? Do you know if anyone has consolidated the PFC sensor monitors down to a chart for idle or with key on and engine off? I could track down every sensor in the manual, but this would be pretty time consuming!

supercell

Well, today I started it up for the first time with the PFC - the idle did a little bit of hunting and weird stuff like suganuma said, but idle evened out pretty quickly. It seems to need to 'relearn' idle every time a new accessory is turned on or used. The fans nearly killed the idle when they first came on, now the car idles up to handle the load after the PFC learned how. I still think I'll need to find that post someone did a while back on 'teaching' the PFC how to manage idle with the A/C on. The idle was still at ~1200 rpm when the PFC got itself dtraight, so I went ahead and adjusted the throttle stop down some and voila- the idle is now at around 820-840 after the engine settles down. It seems to take the PFC 30-45 secs after stopping to bring the idle down, but it works now. (probably still a function of learning) I think maybe this whole episode was brought on by the throttle plates being gunked up, and the previous owner did not clean them, and instead adjusted the throttle stop to compensate for the build-up. When I cleaned them, I should have re-adjusted them to make sure they were in the right place. Word of advice to everyone - when you clean out your throttle plates, measure to make sure there is no clearance between them and the bore when closed. Hold the cold start cam lever down to disengage it so you can see where the throttle plate is actually stopping.

Eric - I can't tell if the fuel pump resistor is being used or not, but the mixture is VERY different. The downpipe does not glow at all at idle now. The acceleration is very smooth as well, and deceleration is now very forgiving. Also, since the primary throttle plate is set right now, I am not getting the 'boost when I even think about touching the gas' effect. I can drive the car with normal acceleration, or get on it and boost smoothly up to 10psi. I am not sure my problem is completely over yet, but this was a major step.

cruser

I've got a question about the learning function of the PFC. When I had my engine rebuilt the mechanic put in my PFC at the same time. I don't know if he started it a let it idle for a certain amount of time or not. The car now has about 1k miles on it and still hunts for idle and will sometimes just idle around 1100. I had the engine ported and switched over to single and am still running off the base maps since I am just breaking in the engine and not boosting at all. He also removed the butterflies in the throttle body. I am going to send the ecu off to XS to get reprogrammed and maybe that will help. Do you think the PFC would have learned by now and is just confused by the extra amount of air that is flowing through the engine due to the port and the butterfly removal. I would think the base maps at idle would be fine and the engine should idle smoothly but when it will very occasionally go down to around 800rpm the engine just kinda lopes. I am obviously very confused by the matter.

Eric Michel

Jon,

Glad to here you getting it sorted out, if you want to know if the PFC is using the dual stage fuel pump voltage just pull the fuel pump relay and start the car. Of course do not run the car under boost with the relay out. If the car runs the same with the relay out then the PFC is using it .... Based on what you have already reported the PFC is probably running with the resistor bypassed all the time. The person who owned the car before you probably played with the throttle stops trying to correct for this fuel pump problem. This would make sense with everything that has happened, if this is the case you may just need a little more fine tunning of the throttle plates and you should be all set.

Good luck,

Eric

supercell

Cruser - I don't know much about the PFC yet, so I'd say ask the pros in the PFC forum here. There are a few people doing some major tuning there. Sorry I can't help more, but I'm still learning how the stock system works with the PFC!

Eric - I PM'd you my address. It looks like I may have this problem down. I think you are right. I suspect one of the two previous owners modded this car, and changed the throttle stops to account for the rough idle/lack of fuel at idle, then de-modified it to sell it with legal emissions but did not reset the throttle plates. There is evidence everywhere to suggest this. My precat studs came out of the turbos fairly easily and the cat studs were gone - there were SS bolts and nuts there instead. There was residue on the stock column cover like there used to be a turbo timer glued to it. There was also a pre-drilled hole and grommet for me to put my boost gauge line through the firewall. Even the ECU looks like it had been removed a couple of times from the wear marks where the nuts make contact with the mounting brackets.

I'll update this post when I have some more info to share.....maybe this will help some other people out there when they have idle problems as well. Thanks for your help Eric!


Jon

djs2571

I had an engine bucking prob, and part of the prob is a vacuum leak or something I haven't found yet, BUT. worn / loose engine mounts make this bucking worse. I stiffened mine up and it helped a great deal. May not be the case with a 3rd gen, but may be another possiblity to check into for a little help.

damian

iTrader: (2)

great thread guys, i have fixed all my idle issues from the great info poted here

here is my thread:
https://www.rx7club.com/forum/showth...hreadid=170731