When I put a decent load on my rx7, the rpms max at 3-4 rpms. It never did this before. There's no check engine light. Also, at 3-4 rpms the car like shakes, and when i put even more load it shakes more violently. Any suggestions to the cause of this??

My friend said it might be in limp mode because of a missfire, but there's no check engine light, and i reset the ECU, and it still doesn't want to run normally.

 

put a timing light on the plug wire to see if the coils are firing.

 

I know you mentioned no check engine light, but you still might want to go through the code checking procedure: http://www.johnr.com/cpucodes.html.

 

not all codes turn on the check engine light, so it is worth checking.

 

Limp mode is not likely the answer--it normally is in open loop (same as limp) under acceleration anyway.

A variety of things change in that rpm range: secondary injectors come on, primaries cut back; egr valve closes; port air opens.

It might be useful to hook up a voltmeter to your O2 sensor circuit, or a lamp to the 'green lamp' connection on the test connector. If the voltage goes down below 0.5v (lamp goes out) during acceleration the O2 sensor is indicating a lean condition, which would direct you to air or fuel delivery problems.

Some possibilities to check, if it shows lean:
1. Clogged or inop secondary injector. If one secondary is not working, or not working well, at an beyond the transition point you would have one rotor in lean misfire. If both aren't working, you would have two rotors in lean misfire.
2. Unmetered air coming in through some malfunction of one of the systems
3. Misadjusted or faulty TPS
4. Short or open circuit to one or both of the secondary injectors

first check for codes, closed loop ops (steady rpm), and rich O2 report (acceleration); timing and proper advance; TPS.

 

Other possibilities:

1. clogged fuel filter
2. clogged/restricted fuel line
3. clogged/restricted return line
4. Faulty fuel pressure regulator
5. weak fuel pump

any one of these ought to show up in either the green lamp or O2 voltage test as the engine going lean at the rpm where the trouble is. If it is showing rich (lamp on, O2 voltage above 0.5v) then none of these would likely be causing the difficulty.

 

Check your plugs. This is common when they are worn.
Thanks Robert

 

Gee. What year car is this???? No limp mode on a series four car, so if series four...forget limp mode.

Non turbo or Turbo???? Say non turbo. Then go look at the secondary injector elect plugs and see if one fell off or got pulled off and not put back on.

Hard for me and others to figure things out if the year/series isn't given in the thread.

A secondary plug off the injector would simulate what your seeing.

I like the Calpatriot idea when he mentions the Green light etc. On all three of my clunkers I"ve a LED laying on the instrument cluster. It's tied to pin 1C and a switched source of batt pwer. IF the car goes in closed loop (happens a lot more than some think), the little red LED flashes on/off at about three or four hz. indicating closed loop. Stomp the pedal the light goes solid red showing rich. Let off the pedal all the way and the light goes out (lean). Run E-85 and get the mix too lean and the LED stays off.

I'm easily ammused. LED on/off, on/off, on/off. See Jane run, run Jane run. Whatever.

 

Is there a way to check codes at home? or do i have to bring it somewhere? i read soemthing about making your own code checker with like 12v batts, 3 fork plugs and wires or something.

for the O2 sensor, i just put it anywhere on the circuit?

 

http://www.teamfc3s.org/info/article...odes/main.html

 

so that LED is run into your dash? can't you hook up those air/fuel mixture gaugues instead?

 

LED cost??? a buck fifty????? AFR gauges cost????? And I already have a wideband (Zeitronix) plus a couple of RTEK2.0 mitt der Palm.

Never owned a narrow band 02 gauge. Used a common Fluke 88 to monitor the 02 input.

So. What year car? What series car?

 

I have a 89' s5, will the LED tester still work the same? and i just read it differently?

 

On a series five you jumper the initial set coupler and turn the key on and watch the ENGINE light............I think.

Someone with a series five will post on this thread telling you how. I don't have a series five and don't care to search for how. Codes for the series five are in the free online series five FSM. The Fuel and Emissons section of that FSM.

Maybe try this: http://www.banzai-racing.com/FD&S5_error_codes.htm

Or this, but isn't as good as the one above: http://www.rx7city.com/ecucodes.htm

 

FSM pg. 4A-21 indicates the various fail-safe modes for the S4 NA. For code 5 (O2 sensor) the failsafe mode specified is "stops feedback correction". This is what I meant by limp home mode. If the ECU decides the O2 sensor is bad, or not present, the emissions system runs in open loop mode, and the mixture is arbitrarily set at a safe (rich) setting. Same thing can happen if the thermosensor does not work correctly; if it fails to tell the ECU that the car has reached the set minimum temp, the ECU stays in open loop.

In fact, in this mode the car does not really limp much; it is the same as what it normally goes to under acceleration. But you do not want to be in it all the time, as it ruins your emission performance, causes the cat to overheat and destroy itself internally, and may eventually result in fouled plugs and such.

But in limp mode or open loop or whatever you want to call it, the mixture is normally well-adapted for full-throttle acceleration.

If the car is in open loop mode and runs poorly, something else is wrong.

If the car is in closed loop and running poorly, it may be that the O2 sensor is deteriorating, but the ECU is tying to use it anyway and arriving at incorrect answers as to what the fuel delivery should be, hence poor running, usually lean misfire.

 

Mine is an S4, so I am unfamiliar with the S5 process. However, at this link

http://www.johnr.com/cpucodes.html

they discuss how to jumper one connector and then read the trouble codes by watching flashes of your check-engine light. Apparently, you do not have to build a test lamp assy like us S4 owners do.

If you check out the S5 FSM (available on links in the FAQ), there should be some way to check the emissions system for cross-counts, or closed loop operation. It may or may not be the same as the 'green lamp' test we do on the S4.

 

Here's the link to the FSM emissions section for a S5 NA.

http://www.teamfc3s.org/main/factory..._non_turbo.pdf

There is a very complete description there of what the various codes are, and what they mean. There is also a good troubleshooting guide.

 

turbo or na ?

 

I added the links on how to download faults for a series five in post #14.

Since it's a series five, then your friend might be right about the limp mode. As in the OMP going out. From what I read on this forum, the series five will more or less run crummy if the OMP circuit is bad. But they always seem to mention how if they turn the car off, and then back on, they can drive for a short time and the car acts normal. But it always will go back into limp mode after a few minutes. Odd that you don't get a engine check light though.

Again, this from Banzi Racing; http://www.banzai-racing.com/FD&S5_error_codes.htm

Yeah, turbo or non turbo.

Might help to know how well this car runs below the 3-4000 rpms you mentioned. Idles normal? Acts normal until 3000 rpm?

 

This thread reads like most limp mode threads: https://www.rx7club.com/showthread.p...=LIMP+MODE+OMP

 

Just throwing out another possibility -

A friend of mine and my brother both had the exact symptoms you described, their cars could not rev beyond a certain point and if they tried to push the cars they would shake quite violently. Both ended up having clogged cats.

Granted one was a '98 VW GTI and the other was a '98 Ford Explorer.