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1990 RX-7 GXL Idle and Stalling Issues

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Old 12-07-17, 04:53 AM
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1990 RX-7 GXL Idle and Stalling Issues

Hi, Iíve had my RX-7 GXL for a little over a year now. It was bought out of a field in non running condition. It hasnít hit the road yet, but lots of progress has been made. Currently, my roadblock consists of two issues. My first issue is that it appears as though itís misfiring while idling, and my second issue is that it stalls while being driven after being warmed up. The fuel pump, fuel filter, spark plugs, and pedal assembly have all been replaced. Currently injectors and vacuum lines are on their way. Iíll leave a link at the bottom of this thread of the car idling to give you guys a better idea of whatís happening. Does anyone have any insight as to what my problem may be? Thanks in advance.
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Old 12-13-17, 06:25 PM
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Old 12-13-17, 08:29 PM
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I'm not sure if its the video, but it sounds like your only running on 1 rotor. Compression test, make sure you have spark at all 4 plugs, and if that all checks out, put the injectors and new vacuum lines on and it should help greatly
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Old 12-13-17, 11:06 PM
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Yeah, does sound like it could be on one rotor. Do what lduley says. First, check that you have all of the spark wires in the right place and that you are getting spark at all of them. If that checks out, do a compression check. Pull one plug and make sure the pulses are even, then replace and the same on the other side, then take out one on each rotor and make sure they are roughly the same. If that checks out, move to the injectors. Not sure of an easy way to check it, but it sounds like you have new ones coming it.

Also, the video is too short to tell for sure, but it sounds like you have a hell of a vac leak somewhere.
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Old 12-13-17, 11:17 PM
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its not running on one rotor, its doing the S5 idle dance, by retarding and cutting fuel in an attempt to get the idle to settle down at 1100 and below, usually unsuccessfully. this is caused by an idle thats set too high or a thermowax that isn't opening as it should.
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Old 12-14-17, 01:31 AM
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Thanks a lot for the responses! Iíll definitely start by making sure Iím getting a spark at all 4 plugs and that theyíre in the correct locations. While I donít have access to a compression tester at the moment, I will check for even pulses from both rotors, and if need be, pick up a compression tester. For some extra information, the car does have a nasty exhaust leak, which is whatís causing a lot of the noise. Also, when going through itís cold start procedure, the car seems to run perfectly. However, once the procedure ends and the idle drops, the issues surface. Iím thinking about checking the BAC valve and, after your comment, the thermowax to make sure those are in order. The TPS has already been adjusted, so I donít think thatís the issue. Vacuum lines and injectors should be coming soon. Any extra opinions would be appreciated.
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Old 12-14-17, 07:48 AM
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Originally Posted by insightful View Post
its not running on one rotor, its doing the S5 idle dance, by retarding and cutting fuel in an attempt to get the idle to settle down at 1100 and below, usually unsuccessfully. this is caused by an idle thats set too high or a thermowax that isn't opening as it should.
that would explain the dead rotor sound then, the retard is trying to retard itself more retarded
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Old 12-30-17, 03:54 PM
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Alright, so after reading your replies a decided to step outside and get ready to do a compression check. As I did this, however, I found that my two leading spark plugs were switched. Now Iím in the process of putting some stuff back together so I can start the car with the plugs in the right spots. Once Iíve done so I post a video of how it sounds.
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Old 12-30-17, 05:59 PM
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Okay, so I got everything back together. After double checking that all of the spark plugs were in the correct places, I starting cranking the car. After some hesitation, the car started. It ran for roughly 15 seconds, made its way up to ~3000 RPM for the cold start cycle, then it died instantly. It was as though I had pulled the key out of the ignition. In my excitement to start the car, I completely forgot to get it on video. I do, however, have some clips of me cranking it after the fact, but the car wouldnít start. Does anyone have any theories as to why my car may have done this? As for a compression check, I wonít be doing one tonight as itís dark out, but I will tomorrow if you guys think itís necessary. Thanks.Link:
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Old 12-31-17, 08:00 AM
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technically the leading spark plug wires can be switched, since it's a waste spark system and both leading plugs on both rotors fire at the same time.

but if the problem is worse for whatever reason, you can always switch the wires back and see if it goes back to the way it was.

your battery also sounds extremely weak, which isn't doing you any favors with starting issues.

Last edited by insightful; 12-31-17 at 08:03 AM.
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Old 12-31-17, 04:34 PM
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I started the car twice this morning, both starts wielding very similar results to yesterday, however, I got both starts on camera this time. For the first start I left the throttle completely alone, letting it do whatever it wanted. For the second run I attempted to keep the car alive, which you can hear at the end of the second clip, but to no success. Also, I started the car on its own for the first clip, which meant it took a few seconds to start. On the second clip the car was jumped, which made it start near instantly. If anyone has any input itíd be greatly appreciated, Iím going to do a poor manís compression test tomorrow to make sure thatís in check. Clip One:
Clip Two:
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Old 12-31-17, 06:08 PM
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your battery is toast, and likely your afm as well, or the car has some rather big vacuum leaks. try jumpering the fuel pump test connector and see if it stays on, but your battery needs a serious charge or to be dumped for a new one.
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Old 12-31-17, 07:46 PM
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Originally Posted by insightful View Post
your battery is toast, and likely your afm as well, or the car has some rather big vacuum leaks. try jumpering the fuel pump test connector and see if it stays on, but your battery needs a serious charge or to be dumped for a new one.
Sorry, not sure what you mean by jumping my fuel pump test connector. Do you mean to do this and check if the car stays on? Also, Iíll get my battery charged soon and see if it needs a replacement.
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Old 12-31-17, 07:52 PM
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theres a yellow 2 pin connector by the right front strut tower off the engine harness. use a wire to bridge the 2 terminals. this will keep the fuel pump on whenever the key is turned on and omit the fuel pump relay and afm switch.
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Old 12-31-17, 08:33 PM
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Originally Posted by insightful View Post
theres a yellow 2 pin connector by the right front strut tower off the engine harness. use a wire to bridge the 2 terminals. this will keep the fuel pump on whenever the key is turned on and omit the fuel pump relay and afm switch.
Okay, Iíll definitely try that soon. Thanks.
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Old 01-05-18, 04:36 PM
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I just got around to jumping the fuel pump test connector. When jumped, I was able to hear the fuel coming through the fuel rail (should the car be started this way?). This leads me to believe this is either a vacuum leak or a MAF problem. I decided to tighten up the bolts/nuts on the throttle body and upper/lower intake manifold, as they were taken apart recently and are spots where vacuum leaks could occur. I wasnít able to start the car because the battery is dead, but I should be able to get it charged tomorrow and see what happens.

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Old 01-05-18, 08:25 PM
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yes the pump should be running with the key on while jumpered, that's normal. you can start it like that and see if it stays running, if it dies when you remove the jumper then the afm pump switch is bad.
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Old 01-05-18, 11:14 PM
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Originally Posted by insightful View Post
yes the pump should be running with the key on while jumpered, that's normal. you can start it like that and see if it stays running, if it dies when you remove the jumper then the afm pump switch is bad.
Okay, after I get my battery charged Iíll try that. Thanks a lot for the help, appreciate it.
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Old 01-07-18, 03:52 PM
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Just got the battery charged and started the car. It started quickly and ran smoothly for a few seconds, holding perfectly at 3,000 RPM before it shut itself off. After this, I jumped the fuel pump test connector and started it again with the same exact results. There may have been a vacuum leak at the upper/lower intake manifold or the throttle body, because after tightening those up the car started running much better. Hereís the clip of it starting:
Thoughts?
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Old 01-08-18, 01:54 AM
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After some further reading, it seems as though the AFM could be the problem. Currently the car runs well during the cold start cycle, but dies after it ends. Since the car only starts to rely on the AFM after the cold start cycle ends, it would make sense that if the AFM was giving no reading, the car would cut air and fuel, shutting it off. Just my theory. Iíll probably do some testing on it tomorrow.
Edit: It just occurred to me that I havenít tried kicking it out of its cold start cycle. Iíll try starting it tomorrow and kick it out of its cycle and see if it returns to idle or dies. Iím thinking this could give some helpful information.

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Old 01-08-18, 06:32 AM
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I'm having a similar issue as well, 89 s5 na. It' starts no problem, does the normal cold start but as it gets close to operating temperature idle will bog for about 15secs or so then idle like normal when it' fully warm. I changed fuel pump, got the injectors flow tested n cleaned, checked timing, changed uim and lim gaskets, replaced the t- wax valve, replaced old or cracking vacuum hoses, cleaned all engine grounds and adjusted the tps with the banzai racing tps adjuster. The only thing I can think of is the throttle diaphragm on the tb that has a vac line to the t-wax. I don' see that diaphragm move when engine is on, and moving it by hand doesn't effect the engine. Or my bad sensor is bad, afm (changed 3 times) or tps(changed 3 times as well)
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Old 01-08-18, 12:22 PM
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I started the car 3 times today. On the first start I tried kicking the car out of its cold start procedure, resulting in it dying. On the second start I unplugged the AFM, which resulted in a lobing, bridgeport like idle. On the third start I still had the AFM unplugged, but I attempeted to rev it, which didnít do much, presumably because the AFM wasnít there to give more air. The car didnít die, however, when it was running without the AFM. Any thoughts? First no AFM run:
Second no AFM run + revving:
As for your idle problem, I really donít know what to tell you. I wouldíve jumped to the TPS, but you already did that.
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Old 01-09-18, 03:07 PM
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Anyone? In the process of removing th AFM to see if it needs replacing.
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Old 01-09-18, 08:32 PM
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Originally Posted by FcGoesBrap View Post
Anyone? In the process of removing th AFM to see if it needs replacing.
have you done a ohm test on the afm?
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Old 01-09-18, 09:17 PM
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Originally Posted by GuiltySoul View Post
have you done a ohm test on the afm?
Just finished an ohm test on the AFM. All readings seemed to be within spec, however, when slowly pushing the mechanism back, there were a few dead spots throughout the range that showed up sometimes. What do you think?

Last edited by FcGoesBrap; 01-09-18 at 09:45 PM.
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