cessman

I am new to the forum and hopefully someone can help me.

I have a 1990 RX-7 convertable, non turbo, 5 speed. The car was running fine and one day I drove into my driveway after running some errands and the car died. If I try to start it when cold it will rev to about 3000 RPM for about 5 seconds and then die, if I keep trying to start the car the same thing happens but the RPM is lower and lower each time. If you touch the gas at any time when the car is actually running it will die right away. I towed it to a shop because I didn't know how to check the ECU codes. They showed that the Mass Air Flow sensor, the Throttle position sensor and the intake air sensor were all bad. I replaced the fuel pump, the mass air flow sensor, the throttle position sensor and filled the fuel tank with gas. Same Thing. Here is the wierd thing, if I unhook the mass air flow sensor, the car will run, idle and rev up when i hit the gas, it just runs rough like it is too ritch.

Any Ideas? I went through the trouble shooting guide of the wonderful Hanes manual and the only thing I can think of to replace is the computer itself, it is an N353 if anyone has one. I havn't replaced the intake air temp sensor, I was under the impression it was part of the mass air flow sensor. Is there a way to test it? could it cause this problem? I love this car and want to get it back on the road again, any help or suggestions would be appreciated,

Thanks,

Stephen

yearrgh

That's very, very, strange. If the maf is disconnected it should immediatly rev to 3k then die. The ecu might be bad, but I'm really not sure. At least I gave you a bump.

New2ndgen

dont worry I will bump it for you. could that be a vacume leak some where?

cessman

Checked for vacuum leaks, found one, didn't make a diference.

Is there any way to test an ECU besides just getting the computer codes?

ilike2eatricers

Did you check to see if the AFM had shaken loose or maybe the plug shook loose somehow? My car wouldnt idle when it had shaken loose. Might be worth checking if you havent already.

twistedriver

I had computer and fuel injection control class before. Forgot the name but is close enough. Any ways but if the shop you went to is right about the codes and did replace all those things than you might have wasted some money. But i could be wrong. My computer teacher told me once. There is almost impossible for everything to go out at once. So it could be something that is connected to all the sensors that are messing up. Things like the battery. I know it sounds weird or impossible. But since the battery is what the computer is running off of and the waltage stablizer if the battey is mess up the computer could go crazy. The second thing is that check the computer ground. Since there might be only one or two grounds from the computer if the ground mess up the ecu would also go crazy. The last thing i can think about is the ecu it self. Well the battery could be load tested and the ecu ground can be check with a Voltmeter. Not too familar with ecu grounds yet but working on learning more about them. I hope you fix your problem.!!

cessman

Thanks, I will check the grounds and charge and test the battery. The afm connection is on and tight. Do RX-7's have problems with the ECU going bad? it seems I am reading a lot of posts where people end up with bad computers. Or is this a rareity?

ilike2eatricers

I think when ecus go bad it is because of a short in the system or owner's fault such as maybe putting the battery connectors on backwards which could possibly fry alot of stuff.

cessman

Ok, I tried chargeing the battery, and load testing it, everything good. Cleaned the battery connections, cleaned the computer grounds and engine to chassis grounds. Same problem. I recovered the codes from the computer. After clearing the codes, and not starting the engine I get a code 32, after running the engine I get the same code. If I am right this is (Solenoid valve - switching)

Does this mean anything to anyone? I am still looking for a good computer I need an N353 or equivilent.

HAILERS

Reconnect all the plugs. Install the jumper in the fuel check connector near the r/h strut tower. What happens when you start the car?

cessman

Everyting hooked up, fuel pump jumper installed, I can hear the pump constantly running. No change, car still starts and runs at 2000 RPM for about 2 seconds and then dies, if I touch the gas pedal at any time it is running it will die right away. Thanks for the help, any more ideas?

HAILERS

Pull the jumper out. That isn't it for sure. Sounds a touch like a huge air leak. Those small vacuum hose won't do it. I mean some hose as big as, say the brake booster hose where it comes off the intake manifold. Or, on a series four, the black intake duct b/t the afm and the throttle body has a half inch hose that feeds off it. Maybe it fell off?

I don't know about a series five, but on a series four I can get a wrench on the banjo bolt on the secondary fuel rail, and slightly loosen it with the fuel jumper in, and get a spray of fuel out near the banjo bolt. Does that happen with your car???? I'm curious if the fuel is making its way to the fuel rails.

Oh. Once I left one of my three plugs off the ECU and the car would start like yours is doing until I remembered that the plug was off. Shot in the dark.

cessman

OK, tried some new stuff, plugs are all on the computer, brake booster hose secure ( it was already) checked all other large hoses coming from the intake manifold. Same thing.

Unhooked the Mass Air sensor and car runs good up to about 1/4 throttle. Ran the car for about 15 minutes to get to operating temp and hooked up the Mass air sensor. No change, it will only start for about 2 seconds and die.

I did notice this time on the Mass air sensor plug that there is a shield over a aqua blue wire that turns in to a wire that goes no where. Should this shelding pigtail be grounded? and to what? If someone could look at their car and see where this wire goes that may help, it is a bare wire. I checked it with a meter and it is grounded. I grounded it to a chassis ground and nothing is different. I also noticed that one of the mass air sensor wires was rubbed through and could have grounded out. would this hurt the computer? Any way, I dont think the fuel system is the problem.

See what you think,

pd_day

iTrader: (6)

free bump...
I want to know what happened =)

cessman

The last owner changed the fuel pump right before I got the car when he was trying to figure out this problem. He installed the pump wrong and the seal was leaking fuel into the tank instead of the fuel line. I put the pump back in correctly and everything is fine. It was only getting enough fuel pressure to run the car when the mass air flow was unhooked and the computer was in full rich mode. Thanks for all the help everyone. The car runs great and I love driving it.

One more problem though, The 6th port valves right above the exhaust manifold are both stuck closed, how much does this effect performance? Should these be serviced to be working properly?

Thanks,

chiefnobum

the valves increase your performance lots over 4k RPM's...one of mine was stuck and I was too chicken to do it so my dad fixed it but putting some grease on the shaft and whacking it about 3 or 4 times...hard...works fine now...

3RotorRocket

I resently had the same problem and it ended up I needed a new MAFS.Now she works fine except fluctuating sometimes at idel.Look into it.