rx7freak13v

hey guys, i've been working on a friends 89 automatic vert. the gentleman used to drive the car as a daily until one day it seemed as if it went into limp mode. the check engine light comes on and if you press on the throttle any more than barely just right then its stalls out. it was also having an issue with the "HOLD" light coming on and not shifting into over drive. he parked the car for a really long time. then i met him and the cover came off.

its a beautiful red vert. all oem down to the factory mud flaps (i want soooo badly). since the car had set the gas tank rotted out, so i replaced the tank, pump and sender unit and fuel filter. added some new spark plugs. a small spray of ether and she started right up. idled great. then i was capable of test driving it. i made it halfway around the block, did a u turn and on my way back to his driveway the check engine light came on and feels like it dropped into limp mode. i swapped out the ecu and eomp and tried again. same result. after searching i found a melty plug at the starter cut relay (next to the trailing coil pack) cut the wiring back, spliced in a new pigtail and a new relay and problem continued. decided to check the plugs for proper spark. too my surprise, the car was running off trailing coils only, the leading coils were not firing. i swapped the coil pack and still no spark. i check the cas and it seemed to be working properly. i then checked the signal wire coming out of the ecu and had signal but not at the coil pack, i found the break in the wire and fixed it. now has spark on the leading. test drive and it has much more power as to be expected but less than 500 ft out of the driveway the check engine light came on and problem continued. i decided to run codes on it to see if it could point me in a good direction but that didn't work so well. i grounded off the connector (single green connector near the leading coil) and turned the key to the on position. the check engine light comes on like it should. waits about 4 seconds and flashes off and back on...and stays on. doesn't flash again afterward. why won't it throw codes?

i decided to try swapping out the maf off of my brothers s5 and tried test driving again and problem continued. it seems like limp mode but i cannot figure out why it's doing so. (btw, the eomp and ecu that are now on the car came off of a running car that didnt have any problems. the person did a turbo swap and he gave me the eomp and ecu) im at a loss on this car and cannot figure this out.this is the first auto fc ive worked on and even though ive been toying with fc's for 6 years (mostly s4 and s5 for about 2 years now) ive never ran into a problem like this before. if anyone has any ideas of what to try next please help. i need this car derivable again.the gentlemen had tried taking to car too a bunch of different shops and nobody would help. mazda told him if he dropped the car off and paid them $1000 they would diagnose the problem but he couldnt imagine putting out a grand and not have any work done.



ps: after the check engine light comes on and it drops into limp mode, if you quickly turn the key off and back on (while not letting the engine stall ) the cel goes off and drives fine again for another 500 ft or so, or you can just simply kill the engine and start it back up and all is fine again for about 500ft.


anyways thanks in advance. im surewith your guy's knowledge we'll get this shiny red vert ack on the road

SpikeDerailed

iTrader: (7)

Sounds like the metering oil pump failure.

j9fd3s

iTrader: (3)

does it have any codes?

jerd_hambone

He already said he swapped OMP's with no results, and that it's not throwing an error code.

But to OP, just because something came off a running car, doesn't mean it will function in yours. Try a different ECU. Being an S5 auto vert, wouldn't the Computer have to be from the same?

j9fd3s

iTrader: (3)

well if its not throwing codes its probably something other that the OMP... a plugged charcoal canister can act the same way as the OMP, but no CEL....

oh actually he does say the CEL comes on. if it DOES have a MOP code, and he changed the ecu and MOP it needs an engine harness

rx7freak13v

The ecu and mop came from another 89 vert that didn't have a cel on.

The part that confuses the hell out of me is that after the cel comes on and it drops into limp mode, if you turn the key off and back on it shuts the light off and drives fine for another 500ft or so and repeats itself.

It can idle for about 20-25minutes before it acts up and at that point the cel comes on and the exhaust tone sounds deeper but ut the cel goes back off and sounds fine and then the cel comes back on. Probably on for about 30 seconds and then off for a minute and back back on for 30 seconds and will continue to do that for about 10 minutes or so before staying on.

I forgot to mention that tge motor was rebuilt about 5-6 years ago. Unknown mileage but the motor is painted blue and silver. (The previous owner had the motor rebuilt about 6 months before my friend bought the car. He said the odometer was around 130k when he bought it and its almost at 150k now that would probably put about 25-30k on the rebuild)

He said that someone previuosly ran codes on it and came down to 1 of 3 sensors but he can't remember what they were. I can't get codes out of it though.

Thanks for the replies guys, lets keep the ideas coming

vrracing

iTrader: (1)

You might search on MOP and OMP (two acronyms for the same thing) but IIRC if the MOP goes bad on an S5 it can take out the ECU. And plugging in a new ECU to test burns that one out too. See this thread for example...

Good luck!

rx7freak13v

I had replaced both the eomp (yea that's another one sincing its s5) and the ecu at the same time. Both in known good condition.

Its tough to diagnose because after the cel comes on, if u shut the kwy off ans turn it back on it clears the cel until you drive it again and the cel comes back on. About 2-3 minutes while drive or 20+ minutes while idleing. It boggles my mind

satch

iTrader: (1)

The CEL should provide you w/the error codes. If need be just ground the single wire check connector near the leading coil and w/key to on the CEL should throw the error codes.

At first the car will go in to limp mode and then start up fine the next time and behave properly for a short time and do the same thing over and over until the system damages the ECU and it will then constantly stay in limp mode.

rx7freak13v

So your saying to ground out the connector and drive it until the cel comes on and read the codes without shutting the key off? As soon as you turn the key off the cel clears. If so then I'll try to test it late tonight when I finish working on my car.

Thanks for the advice. Ill let you guys know if I can pull codes off of it.

satch

iTrader: (1)

W/the connector wire grounded and key to on the CEL should spit out the codes.

rx7freak13v

hey guys, it' been a while on this project. i had gotten very well side tracted and just finally was able get some real progress on it last night.

i tested it for codes while the engine was running, this worked great! it gave codes 8 & 1o (both referring to maf) and code 27 which is oil metering pump.

i had been skeptical of a used alternator that i had picked up for the car because all the idiot cluster lights stay on. so i ventured into swapping the brand new alternator off my brothers s5 and what does it do? the damn idiot lights still stay on.wth is going on here?

ok they're just idiots no big deal, i'll figure that out later. but heres a cool trick, if you unplug the alternator plug and start it up, the idiot lights are off. any ideas on this one?

so i swapped the maf off my brothers dd s5 (it's nice to have dd parts to test with instead of testing used parts, this way you DO know they are good 'cause if not the car wouldnt be a dd)

this worked incredibly. she roared to life with a nice steady idle. revved very nicely. then it got even more weird. im expecting it to throw a code still for the eomp (27) but yet she doesn't? huh strange. ok lets take her for a spin. i get halfway around the block and u turn back. i get halfway back and she falls into limp mode. so without shutting her off we re test for codes and she spits out 8,10 & 27 again. i know this maf is good because if not my brother wouldnt be dd his car with it on there.

im not to sure what to think at this point, im leaning towards a new wiring harness for the engine sincing it still threw the maf codes with a new maf installed. but then the alternator plug on s5 comes from the drivers side harness, not the engine harness like the s4 does. so even if i do replace the engine harness, the idiot lights will still be on as long as the alternator is plugged in.

if anyone has any ideas at all, it would be muchly appreciated. thanks guys

jackhild59

iTrader: (7)

Keep driving it and you will burn up the ecu.

rx7freak13v

im not 100% sure about that. im not sure what's causing the actual problem. when i first swapped on my brothers maf, the car didn't throw ANY codes and after driving it for about 3 minutes it fell back into limp mode and started throwing all 3 codes again, 2 for the maf and one for the eomp. it shouldn't have thrown a code for the maf that time around.

on another note, how come the idiot cluster lights come on ONLY when the alternator is plugged in? if i unplug the alternator the lights all go off and when i plug it back in they come back on again.the idiot lights were all on since this gentleman bought the car, i assumed they were on because the alternator was bad. we picked up another used one from a good friend of mine and installed it. when the lights came back on we thought maybe this one had gone bad after sitting and tried the brand NEW alternator off my brothers car. the lights came back on again.

im thinking maybe i should replace the engine harness? but the alternator plug is on the chassis harness (with the coil packs) so that wouldn't make since of the idiot lights coming, but could make since of the eomp and maf codes, even after replaceing the maf.

anyone have any better suggestions on where to start? what to check on?

i read somewhere that the little cpu for the flashers and turn signal and such could cause the warning lights to come on, can anyone confirm this? and is the s4 one the same as s5? ((i have spares for s4 but none for s5 atm). if anyone can confirm this, i'll try replacing that before i a invest in a harness.

im running out of ideas, i've never been so stumped on an rx7 before.

jackhild59

iTrader: (7)

I am. 100%.

Burn it up. Rewire the car, put in a 'new' used unproven wiring harness. Drive around with no alternator.

Come back to the FS section and buy another ECU to burn out. Knock yourself out.

OR you could use diagnostic testing rather than just replace old non-functioning parts with other old untested parts.

https://www.rx7club.com/2nd-generation-specific-1986-1992-17/s5-mop-ecu-failure-diagnosis-710938/

https://www.rx7club.com/showpost.php...8&postcount=38

Seriously, not to hurt your feelings or anything, but do you think that you're special? That you are the first to have this problem? If you have MOP code, you have a MOP problem. Or an MOP wiring harness problem. It *will* burn out your ECU if you keep driving it. There are threads that claim the MOP will take out your TPS as well. Focus on *one* thing at a time. MOP first.

Good Luck.

-Jack

rx7freak13v

thats just it it jackchild, i did run diagnostics. it threw codes for the MAF and the OMP. i pulled the MAF off of my brothers daily driven fc and tested it on the convertible. it ran great and then fell back into limp mode. when i ran diagnostics again it was still throwing a code for the maf and it shouldn't have been. that's the reason why i used the maf off of my brothers dd, that way i know it's a good maf.

anybody know why the idiot lights stay on when the alternator is plugged in (again this is the brand new alternator off my brothers dd, it's about 3 months old)?

it's hard to tell someone to spend money on parts when your not really sure whats needed. had it not of thrown the MAF code again, then we were going to pick up MAF, OMP and ECU and been done, but since it did throw the MAF code again after replacing it with a good MAF it's hard to say whats 'causing the issue.

i think im going to invest in an engine harness and go from there.

satch

iTrader: (1)

If the alternator is bad that would be one cause, and many a new alternator have come out of the box in a non-working order so don't let that fool you. On the back of the alternator is a two wire plug. B/W on top and W/B on the bottom. If the White/Black wire has a ground signal on it then the idiot lights will come on w/key to on, either engine running or not. If the wire has battery voltage then the lights would not turn on. You should remove this plug and turn the key to on and doing this should cause the lights to not light up. If they do then either the W/B wire is accidentally grounded or the alternator warning light relay is stuck closed. If the lights stay off with the plug disconnected but light up w/the plug connected then the problem lies within the alternator.

And perhaps disconnect the battery ground for a few minutes then reconnect and see if this clears the stored codes and then retry pulling codes.

rx7freak13v

the new alternator i tried is the one off my brothers daily driver, and he doesn't have any issues with it. but on this car, the warning lights stay on and when i unplug the plug on the back of the alternator they go off. maybe someone in the past spliced the wires back together wrong, i;ll look into that. the motor has been rebuilt before (blue and silver paint very clean looking) so the motors been out in the past. i'll try looking into that tonight.

jackhild59

iTrader: (7)

Test your MOP('s)-use the guide i posted up. It is more comprehensive than the FSM. You can also test the MOP harness If they do not pass the test, you are wasting your time.

Two things cause limp mode: AFM and MOP.

OK, three things can cause limp mode: AFM, MOP and an ECU burned out by the MOP. Get it?

Lots of threads on here where people get limp mode. They try EVERYTHING else, including the ECU They finally replace the MOP. Still limp mode. They try the old ECU. Still limp mode. They try the old MOP. Still limp mode. Sound familiar?

Problem is that they have now burned up the MOP output section of both ECU's.

Here is a little known fact: Did you know that in Section 4a page of the FSM you can actually find the details to *TEST* the AFM? You don't even have to take it off the car.

Diagnostic testing is *free*. Wait, you do have a VOM meter, don't you? Now that is a good investment.

When you finally run some diagnostic testing on the parts that can cause limp mode, you will find your problem. And while you are at it, get that Alternator tested. It's Free at any parts store.

Good Luck.

epic

iTrader: (3)

Did you install a new Ecu? usually what happens when the MOP goes out is that it burns out the ECU and that will also need to be replaced. If it's not replaced the car might still "act" like it is in "Limp Mode" and the MOP will not send the right amount of oil even though the MOP has been replaced. (p.s in class so didn't get a chance to read all the posting if this has been posted already)