Okay guys need your expertise. For those who don't know me or my RX, I have a 87 TII, new engine, clutch, springs, brakes etc. Just bought it, a very nice southern car. My problem is this, I could not push the car during the test drive due to the very new engine. After breaking it in, I noticed a problem at around 4000 RPMs. At first I assumed it was the 3800RPM hesitation that most TII have, but after thinking more about it, and driving it, its more then a hesitation the car falls flat on its face after 3800 and even before then at full boost. The car leaps and bucks and refuses to rev.

I check everything I could think of that was obvious, with no luck.

In desperation I took it to the oldest Mazda dealer in NY state. The tech that worked on my car was around every since it opened so I assume he was competent. Anyway after a couple hour of work he informed me that this car had a "very very strong engine" It "passed all the diagnostic tests and compression test with flying colors" He went on the tell me that the problem I was having was not the typical 3800 RPM hesitation. He said his "theory" was (get this ) when the new engine was installed, the "fuel boost aculators on the secondary injector were installed improperly". I asked him to explain and he basicly said that they were put in backward or upside down or something (he didn't know) and were not opening up enough to give the car the proper amount of fuel. He said the only way to be sure is to rip the car open and take a peak,...he wanted a least 500 bucks to do it. Guy, what the heck is going on with my rex, any info will be helpful. I may be unable to reply right away but i will eventually. Thanks

There's no such thing as a full boost actuator for the injectors. Your problem is either fuel or ignition related. Make sure that your plugs and wires are all connected properly. I had the problem you're having, and it turned out to be the ECU. If you're close to me I could let you try out a new ECU before you start digging into things.

By the way, I'm in Long Island.

it could be many things. possible bad/clogged fuel injectors. how much boost are you running do you have an FCD. you might be detonating.... i would take it to an rx7 only shop. if you ask real nice 13BAce might check it out for you he is in LI. your in NY ?

dammit 13BAce by the time i clicked post you posted already. your too sneaky :dontgetit:

I'm alot of things. https://www.nopistons.com/forums/pub...IR#>/devil.gif

Yeah, fuel cut could also be the cause. I forgot all about that. :notify:

Thanks guys, I'm going to school in NC, but i will be home in mid march, Ace, if you could take a peak i would be extreamly grateful, I just know its that second injector, for example (if you are gently crusing,.....even with out boost , just slow reving down the road as soon as it hits 3800, it cuts out. If you try to force it, it will just get very grumpy, i no longer push it pass 4K because i don't want to damage anything,...the engine seems so strong low end however,...it really wants to go, like a caged animal,.....it sucks, i have to bogg the engine and shift at 3500 for it to do anything,...hondas are beating me. :-( (by the way the engine is bone stock, so what is that, anywhere form 7-9 lbs of boost right?)

A stock 87 TII runs 5.5 PSI, 6.2 PSI max. Fuel cut is at 8.6 PSI. Have you tried the usual 3800 RPM hesitation fixes? If I'm around in March I could take a look.

vosko has a good point, i was talking to him in a chat, and he suggested that the injectors were simply clogged, with 160K miles on them that would prolly be the problem don't you think?

They may be clogged, but I've never seen any clogged THAT much. Either way it would be a good idea to have them cleaned. Marren Motorsports, http://www.injector.com , has done a great job for me twice so far.

i'm thinking its most likely his injectors cause 4k rpm is when the secondaries come online right ??

Yeah, they come on at 3800 RPM, but when you get the hesitation the motor should pass through that point, right? He should check the ECU for codes:

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

DUDE... I had this same exact problem!



After replacing a crap load of parts I finally found the problem.



Your 2nd injectors are needing replaced. I replaced mine and the problem went away. Although it feels like the 3800 RPM bug it's MUCH worse!

Yeah, they come on at 3800 RPM, but when you get the hesitation the motor should pass through that point, right? He should check the ECU for codes:

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

Yup I would check the codes first and make sure that coolant sensor plug is all the way in and making contact. Checkign the codes will help find if a sensor is malfuntioning. iF not we can move on to the injectors.



C

I had the same problem....mine started out as what felt like a misfire when entering boost...and at first it would go past that...then the problem got worse, and it started misfiring all of the time...I checked and replaced everything you can think of...no luck.... I then got fed up with it and bought the haltech...problem solved.... I think that my problem was caused by my mass air flow sensor though...that or the ecu itself... but the problem i had doesn't sound like the same thing you're having...i would lean towards the secondary injectors as well...

Standalone ECU's make the world a better place. https://www.nopistons.com/forums/pub...#>/biggrin.png

I figured that the 2nd injectors were clogged, the problem is to bad for that,....How much for the replacement? Also like i said it bucks and misfires, but when i push it to bout 6K RPM it stops the nonsence and throw you back smoothly,..like they start to fire correctly,...any new ideas?

You can get all 4 injectors cleaned for about $100 shipped at Marren Motorsports, http://www.injector.com . Have you checked for codes yet? This may be a long shot, but you could try driving with the TPS disconnected.

I personaly have not, but the tech that did check it out said he did,....he said everything was correct and in order. He checked the sensors and also did a compression test. I should prolly check it myself to be certain, i'm going on what he said as of right now.

If everything checked out ok then the car would be running properly. https://www.nopistons.com/forums/pub...DIR#>/wink.png

yeah you would think so. What is a good price to pay for simply replacing the injectors rather than cleaning them?

by the way i have a really rough and sugging idle,..could that have anything to do with the problem? it very strange, let me see if i can explain it.

The car will start and rev at about 1500RPMs from there it will go up and down radomly,....but won't go far beyond that,...now,....if you bog the car down below 1000,...it will stay below there and almost stall out,....if you give it some gas, it will shoot back up to 1500. if not it will stuggle to stay running,......ideas?

New injectors from Mazda are about $250 each. :0 You can find used injectors for about $50, but cleaning yours is the best bet.



Any vacuum leaks?

How do you test to see if the fuel injectors are clogged or are shot? A compression test wouldn't do it, right? or would it? I'm unsure. Also, do you need to replace all 4 injectors or just the ones that are clogged/shot?

You really need special equipment to test them. Having al 4 done would be the best idea.

Get a Fuel Pressure Tester and measure the amount of drop each injector has with KOEO. You will have to manually activate your injectors. Notice your fuel gauge when you activate them, slight or no fuel pressure drop will indicate clogged or misbehaving injector.