acesare

hi everyone!

I just picked up my second rx7. Its a 1991 vert manual trans. the car is 100% stock besides borla mufflers. 160,xxx on the odometer.

the problem: The car starts up fine and free revs great when its initially started. however when i put the car in gear and begin to drive at around 3800-4500 rpm (depending on its mood) the check engine light comes up and the car instantly loses power. it will barely make it up a hill in first gear. it is driveable but you really have to baby it or it will begin to buck and carry on. after you shut the car off, if you restart it, it will usually give me a hard time trying to start but once it does it has a bit of an erratic idle and once in gear and driving the check engine will come back on.

i attempted to read the codes and nothing was reading. the check engine light comes, goes off, and comes back on and stays on....

things i have already tried:

-correctly set timing
-tps sensor was replaced by previous owner and according to my multimeter it is functioning properly
-cleaned and/or replaced all grounds under the hood
-sea foamed the hell out of it
-replaced plug wires
-replaced battery terminal connectors because the old ones were shot

I dont want to have to take the intake plentum off and check the injectors and 5th and 6th port if i dont have to. i read somewhere that if the ecu is burned up it may throw a "no code" code that triggers the light but isnt readable?? any input is appreciated. also if I do have to remove the intake plentum what are some things that i should look for that could also cause this problem? thanks you

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allmodded

check your OMP harness you may have a chewed up wire its below left of fan thing sticks out with 4 clear plastic lines..on s5 will have wiring harness goes up behind filler neck water pump. omp short will cause limp mode, so will any shorts in the main harness, bac ect. make sure any terminated wired are not touching, nothing is worn through. if you have to run car or it happens again turn key off while drivign and back on....clear codes by disconnecting negative terminal for 10 seconds while car is off...look up how to read flashing codes by grounding out single pin in front driverside i beilive. look it up....once you jump that turn car on not running just on and CEL check engine light will flash long and short, long flash is ten and short blinks are one , or something , lol, so its like one long flash and three shorts is 13 followed by a pause and it will do it again you may have multiple CEL codes coming on couold be a bunch or just the same one over and over...if its OMP check harness. if you need a omp i have one for turbo not sure if it'll work , have to check ...

acesare

I tried reading codes that way with the jumper and it doesnt read any codes at all. the light comes on and then goes off and then comes back on and stays on. I read somewhere that the Omp can cause the ecu to burn up and i noticed there wasnt any oil in the lines coming from the omp. So i guess my next step would be to hook up a good omp and then try a different ecu?

allmodded

i had a wire melt one time and it did that...check all electrical..did you try turning the key off while driving and back on to see if it fixes it temporarily, this would at least prove its in limp mode and electrical and not something else plugged up..sounds like limp mode for sure though

acesare

havent tried that. i have another ecu im going to try tomorrow and see what happens. and im going to go through all the electrical. thanks for the help.

acesare

Update:

If i turn the key off and turn it back on while driving, the check engine light goes away until i apply throttle then it comes back on and goes back into what i think is limp mode.

I pulled the ECU yesterday and took it apart and found no problems, no burn marks, all connectors are in good shape. I noticed a hint of a burn smell but it is barely noticeable and i pulled the ecu 10 minutes after turning the car off. So all of my grounds are good, Plugs and wires a good, it usually idles fine but you hear a miss here and there and sometimes it will shut off. Still cant pull any engine codes from it. I am at a complete loss here and dont know where to go. Should i pull the intake plentum and check the harness and injectors? or are there other things i should look for first? I daily the car so the sooner i can figure this out the better. thanks guys

lduley

iTrader: (1)

Your OMP is probably on the fritz, s5's biggest issue is the omps going bad and causing limp mode

acesare

forgot to mention that there is water on my passenger floor. maybe water damage on the ecu? would it be visible if it was water damage? i know alot of times with the omp it takes a couple minutes for the limp mode to engage. plus the omp would be throwing a code and this isnt. no codes at all. just a constant engine light. could water damage be a factor here?

satch

iTrader: (1)

Try unplugging a sensor like the TPS and see if the ECU throws a code or not. If it does not then you would think the error code aspect of the ECU is not operating properly. You could also drive the car w/o the TPS plugged in and see if the car operates better as if nothing were wrong. Also, disconnect the negative battery cable for a period of minutes and then reconnect it back up to the battery and then do as suggested above.

acesare

okay will do. ill let you guys know what happens. thank for all the help so far

lduley

iTrader: (1)

I've seen some threads on here where the OMP was the problem and wouldn't throw a code

I agree with satch, see what happens when you try and force a code and see if it saves it, if not, than your ecu is bad, and probably because of the omp

acesare

just throwing this out there, if the omp was the culprit that burned up the ecu would it show marks on the boards? like a burn mark or a burnt connector? the ecu itself looked perfect. im not very good with electrical though so im unsure.

lduley

iTrader: (1)

Sometimes it takes a well trained eye to notice something bad on a circuit board. Sometimes things are obvious, other times not as much.

If it is your OMP, the cheapest route instead of buying another one would be send out your other ECU to rtek and have them chip it, than disable the omp and run premix

New ones are really expensive, and if you buy a used working one, its a gamble on how long it will last

acesare

noted. just ordered a used ecu off ebay about an hour ago lol. so i guess ill see if it clears up the problem. If not i'll be back on here begging for suggestions. haha.

acesare

UPDATE: Turned out it was the ecu. the previous owner replaced the omp but i guess when it went bad it burned up the ecu. Put a used ebay ecu in it and it runs great. thank you everyone for your help