bucking 94 Rx7, I'm going crazy
 

I bought a '94 automatic 7 and I can't figure out what's wrong with it. The car seems to idle ok but when you try to accelerate it loses power and backfires like crazy. The tach goes crazy too. I bought it as a fix up. Had new turbos installed and dealer gave up. I went in replaced all vacuum lines,fuel filter , checked fuel pressure andhooked up wires dealer left undone. However it still does the same thing. No error codes,tach is erratic and no power when I accelerate,plus backfires. I took out precat and put in a downpipe. Still does it. Compression seems fine. HELP I'm goin crazy!!!!! Rob Allen.

Could be a major boost leak in the pipings? Damn man, dont go to a dealer...

your injectors might be SOL

How many miles are on it? Maybe the apex seals are blown. Good compression comes from side seals, so even if you have bad apex seals but have good side seals the compression will still be good. However it may be just a bad sensor or something, but don't take it to a dealer. If you are in VA take it to PFS or KD rotary, i'm sure they cna help you out

did you check it for codes? or is the light not on? there are codes that do not turn the light on that will cause a limp home. check it for codes if you havent.

mike

No error codes. I don't think it is the side seals. May be the ecu, but at a 1000 dollars i don't just want to get one and that not be it. I'm calling Dave now. Any more help appreciated!!! Car has 70k.

There is a diagnosis section in the shop manual on hesitation\surging. Leaking injectors is one of the fixes. Some of the bucking can also be from bad grounding.

Plug wires switched?
~Tom

ATF!!!

Wires are not backwards. What is atf? Any more ideas guys. I appreciate all the above. How can I tell if my ecu is fried?????????? Rob.

$1,000 omg luckiest son of a bitch ever

ok, don't kid yourself. Take it to a REAL professional. I would recommend KD Rotary in PA. The 3rd gen is extremely complex machine, more so than most cars. If you are in the condition where there are hoses not connected.... Boy your in trouble. Take it to KDR
Good Luck
Matt

check this out
 

This sounds dumb. Check your electrical connections to the battery and the alternator. I have had 2 FDs do this and it ended up being a bad connection. It drove fine in low RPMs but if you punch it hard it would buc real hard.

its not the ecu, it could be a bad disconnected ground

mike

It idles ok but you can hardly accelerate at all. It has no power and then backfires. Not just buking, it's powerless. Barely drivable. Starts up and idles nice. It has an aftermarket alarm. Could that have screwd the ecu????/ Rob.

Check your Throttle Position Sensor (TPS). I had a similar problem when I bought mine, something Mazda's geniuses couldn't find for the guy I bought the car from. The car would idle fine, but if you stepped on the gas, the tach would go to 1500, drop, up to 2500, drop, and then repeat. If any of the wires are loose going into the plug for the TPS, or if the plug has become loose itself, this will cause your problem. When you wiggle the wires, assuming you have kinda the same problem, go try the accelorator. If this didn't work, wiggle the wires around again. Try this a few times. You may also want to consider a new TPS. Also, as many have stated before, you might want to upgrade the grounds as well. Battery-Chasis, Chasis-Engine, Battery-Engine.
Ricky

Thank you Ricky, did the tach go a little crazy with just the key turned on? Could you accelerate at all? What you say makes sense, because of the tach problem. Thanks a lot Ricky,I really appreciate it! ROB.:) How much did the part cost?

sometime my rpm tech goes crazy.. when its hot...
jumpin up n down .......

rx7r3, where are you located in Va? I had a problem like that and it was a fried ground, the one on the passenger side, beside the abs unit. Plastic had melted from around the wire! Sounds like it could be bigger problem than that, but start small, then work up. Also check to see if an exhaust manifold bolt is broken off and caused a leak... also happened to me. Good luck.

at what rpms does the bucking takes place??

Any rpm above idle!

^^^^^^

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What is your boost pattern? Check it the proper way. See the instructions on my site, URL below. Go to How-to --> Turbos. This will tell us quite a bit.

The tach in the 3rd gens are very prone to failure. Mine died at 8K miles. Stuck at about 3K, only moves to zero when I shut the car off. That has nothing to do with your acceleration problems, but I just want to make sure the tach is jumping due to other problems, and is not just messed up itself.

Let us know the boost pattern and we can go form there.

Cheers,

Steve
http://www.ScuderiaiCiriani.com