2nd Generation Specific (1986-1992) 1986-1992 Discussion including performance modifications and technical support sections.

car is running really bad under 4k

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Old Dec 5, 2009 | 02:22 PM
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car is running really bad under 4k

I have tried a search and can't find anything that helps. I have a stock 87 that was running good. I put a Lucas Fuel Treatment in with my gas and it all went down hill. I have used the Fuel Treatment before and on different vehicles and haven't had a problem. Now when the car is cold it will run fine but it will now get high on the temp gauge and as soon as it starts to come down it will start running bad. Any speed under 4k rpm and the car surges real bad and I can't hold a steady speed. I have cleaned the plugs and put a new fuel filter I thought that it might be the catalytic converter so I unbolted the exhaust and drove it but it still is running the same. What next?.... Fuel tank? Fuel pump? Injectors? ......HELP PLEASE
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Old Dec 5, 2009 | 02:32 PM
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sounds like a primary injector might be clogged, but im not sure why it would run fine until it heats up then.

Maybe it has to do with the BAC
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Old Dec 5, 2009 | 02:40 PM
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I was leaning that way too.....but it just doesn' t add up???
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Old Dec 5, 2009 | 04:56 PM
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anyone else have any ideas?
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Old Dec 5, 2009 | 06:57 PM
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if i put something in my tank that fucked my car up the first thing i'd do is drain the tank and fill it back up with fuel.
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Old Dec 5, 2009 | 07:37 PM
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I just went through the same thing. Mine would not rev past 4500RPM and progressively got worse over the course of 3 weeks. By week 3 the car was very difficult to start, especially when it was hot. I could not rev past 3500RPM and top speed was about 45MPH. It also sounded like a car wash pressure washer, when you squeeze the handle, while I tried to accelerate.

On Monday I had the car parked on top of a puddle and when I came out of the store I could see the exhaust blowing into the puddle from underneath the passenger seat area.

When I got home I raised the car as high as I could safely get it. Once underneath I could clearly see that I had blown the gasket between the 2nd pre converter and the main catalytic converter. To my surprise I found that just 4 bolts held the main catalytic converter in place. I unbolted the converter and chunks of stuff started falling out.

Assuming that the converter would be between $200 - $300 I decided to chip away at the rest of the stuff inside. Once it was all removed I bolted the Main Converter back in place. The car fired rite up, so I took it on a test drive. Let me tell you, it was like a whole new car. I had hard acceleration from 4000 RPM to 6000RPM; it felt like a turbo kicked in!

Latter on that night I went to start it and, Click, Click, Click. I must have burned out the starter while it was hard to start. While pricing starters on line I also checked the main Catalytic Converter Price. It was only $85.00. At the auto parts store I ordered a new starter with a lifetime warranty for $95.77 including tax. I bolted it in 2 days later and it fired rite up again.

It has been 3 days now with no problems, knock on wood. Next week I plan to purchase the new catalytic converter and gaskets.

Sorry for the long post. Good luck with your RX7
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Old Dec 6, 2009 | 10:16 AM
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It sounds like the fuel cleaner may have dislodged crud that otherwise would not be an issue, and sent it right through the injectors. Make some checks for things like vacuum leaks and a misadjusted TPS, dirty BAC, etc., but it sounds like you should have your injectors professionally cleaned.
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Old Dec 11, 2009 | 12:34 PM
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how hard is it to pull the injectors? Anyone know where I can get them cleaned around the Houston area?
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Old Dec 11, 2009 | 04:40 PM
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I don't know about around the Houston area but Witchhunter Performance is about 100 bucks for all 4 injectors. Hell of a deal if you ask me.
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Old Dec 11, 2009 | 05:40 PM
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Umm.... I only see 2 fuel injectors????
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Old Dec 11, 2009 | 05:56 PM
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The 2 you see are the secondary injectors. They come on line at 3800 rpm. The other two are your primary injectors which are on the engine under the intake manifold.
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Old Dec 11, 2009 | 08:01 PM
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Thats right...Thanks..... Is there anyway to clean them yourself?
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Old Dec 12, 2009 | 11:01 AM
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No, you need to have them professionally serviced.
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Old Dec 14, 2009 | 09:44 AM
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Originally Posted by onefastrx712a
how hard is it to pull the injectors? Anyone know where I can get them cleaned around the Houston area?

You can ask this question in the regional forums.
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Old Dec 16, 2009 | 04:33 PM
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I just really don't want to pull the injectors and that not be the problem. It is my only means of transportation right now.... and im really not sure that is what it is going to be. Like I said it runs normal before it warms up, no surging at all...then the temp will go up..(way up..Higher than normal) Then the temp drops and it runs like crap? That wouldn't be injectors would it? Any leads would be appreciated.
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Old Dec 16, 2009 | 05:12 PM
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Did you check the BAC
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Old Dec 31, 2009 | 04:51 PM
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Well im about to pull the injectors... any advice? Will the top come off in all one piece?. Any advice would be great. Thanks
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Old Dec 31, 2009 | 04:54 PM
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Also it started smoking at start up, and when i get on it... Should I be worried? I have read that it can be from the side seals leaking...
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Old Jan 1, 2010 | 12:13 PM
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This makes more sense than anything else to me.
Originally Posted by Aaron Cake
No, you need to have them professionally serviced.
Good call Aaron

I'm new to this rotary thing but I am not new to emmissions.

This is a problem that has always plague us with carbs ecspecially the holly double pumpers and anything else that has to rely on air to fuel mixture.

1) You put lucas fuel treatment into the tank and it did its job. The questions is or should be "Do you need another bottle"

The Lucas cleaned or loosened some crude within your emmissions and your emmissions are set perfectly for a dirty system. I myself would get another can of the lucas and run it through to make sure all the debri is cleaned out.

2)After throroughly cleaning out your system, recheck and reset your fuel to air mixture. (How?)

If the cleaner worked, You are dumping more fuel and maybe a more accurate spray pattern.

I would first try adjusting the throttle position sensor, and 9 times out of 10 your idle will also be increased once thats done because with a clean system you are dumping more fuel. No Blockages.

So just go through the normal emmissions checklist. You may find out that your MPG's will go up.

BTW- Get you a can of carb cleaner and clean out your throttle body while you're at it.
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Old Jan 1, 2010 | 01:00 PM
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Originally Posted by onefastrx712a
I just really don't want to pull the injectors and that not be the problem.
Even if it's not the problem, having your injectors cleaned and flow tested can only be an improvement. It is 100% beneficial any way you look at it. If they're stock injectors, odds are they aren't spraying as well as they should be anyway.
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Old Jan 1, 2010 | 01:08 PM
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Originally Posted by Hazard15301
Even if it's not the problem, having your injectors cleaned and flow tested can only be an improvement. It is 100% beneficial any way you look at it. If they're stock injectors, odds are they aren't spraying as well as they should be anyway.
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Old Jan 1, 2010 | 01:37 PM
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Well I did try putting a second bottle of the Lucas And now the car will barley go. I towed it to my dads garage and am getting ready to pull the injectors....any tips..tricks to make the process smooth???
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Old Jan 1, 2010 | 02:34 PM
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O.k. What is the green (check valve?) under the intake ..where it bolts to the throttle body? Could this be the culprit that is making my car run (and almost not run?)
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Old Jan 2, 2010 | 10:57 AM
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Originally Posted by onefastrx712a
Well im about to pull the injectors... any advice? Will the top come off in all one piece?. Any advice would be great. Thanks
Just follow the instructions in the Haynes/FSM. Label all lines and connectors. Yes, the upper plenum are will come off in one piece after you remove the bolts/nuts that connect it to the lower intake.

Originally Posted by onefastrx712a
Also it started smoking at start up, and when i get on it... Should I be worried? I have read that it can be from the side seals leaking...
Could be oil o-rings on the way out, but smoking can also be caused by excessively rich mixtures.

Originally Posted by onefastrx712a
Well I did try putting a second bottle of the Lucas And now the car will barley go. I towed it to my dads garage and am getting ready to pull the injectors....any tips..tricks to make the process smooth???
Maybe you should stop dumping snake-oil into the car? Additives in general are nothing but a waste of money.

Originally Posted by onefastrx712a
O.k. What is the green (check valve?) under the intake ..where it bolts to the throttle body? Could this be the culprit that is making my car run (and almost not run?)
There are about 6 million green check valves on the FC. You are going to need to be more specific, but to answer your question, no. A failed check valve won't cause the car to run this badly. Many of the check valves are simply part of the emissions system.
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