'85 Corvette with Ed Wright Chip, Car was running good, but now...

For some reason, there is a stumble in acceleration. I don't just mean a hesitation, but when your in 1st gear... and you start slowing pressing the throttle...you get a bout 1/4 inch down and it feels like the car just shuts off. Then, as you keep mashing slowly... it comes alive again and throws you back in the seat. It does this in every gear... and I have noticed that sitting at idle... if I "nail" it really hard and fast... it about goes dead... or there is a hestiation before the RPM's go up. Sometimes the hesitation gets the best of it, and with the gas on the floor, the RPM's don't pick up at all... the car is just fluttering with the Throttle wide open at like 700 RPM's.

I HAVEN't been up and around every sensor on this car for the past 15 years... but I have made lots of checks. BTW, I get absolutely no computer codes. I check the Voltage in the MAF, and it reads normal all the way from .58 volts up to just over 5 volts. FP is good, and BTW, it even does the same thing if I bypass the supercharger, and I have tried 2 air flow meters, so thats not it either. There are no Error codes stored or intermitent... reads 12's everytime I check it.

What did work (temporarily)

I disconnected the battery cable for about 10 seconds... set my idle... and the TPS voltage... and I could rev up normally. I thought, HOT DANG, all it needed was reset. This actually fixed it, all was normal again - BUT, I went for a drive, and it did great up to where I turned around (bout 5 miles) and then started the same crap on the way back.

Any Ideas on what to check or what the problem might be? I really need to get this car going. I have done so much work on it lately my wife is about ready to divorce me.


[Modified by 85Procharged383, 3:58 PM 8/30/2002]

 

You could have a dead spot in the TPS.... just a guess

 

I agree ........the tps sounds like it has a bad spot ..........the thing that confuses that is the change in the way it ran after unhooking the computer... it would be nice to be able to look at the tps with a lab scope... :seeya

 

I put a DMM on the thing, and very slowly opened it up.... a little at a time and it worked perfectly. I even loosed it up and moved it around alot, and then reset it. No change.

The only thing that made it right was reseting the computer... and then that didn't last long.

What is the purpose of the CAL PAK, I read somewhere that if your computer sees a problem witha sensor, it runs the car off of data in the Calpak instead... is this true?

And... if it was the TPS, why would resetting the computer fix it temporarily?

 

That's the thing that bothered me ......... if it WERE the tps then it wouldn't have changed by rebooting the puter.......... I hope someone smarter than ME chimes in to help you :seeya

 

Hey ....Hello to all....I have an Ed Wright chip that does the same....355 superram 30 lb injectors....car falls on its face...I have tried everything...It wasn't a tps...I did a throttle sweep. I emailed ed about it and he wants dyno numbers with all the sensor readings...Like who does that???The chip that I got does have a tech bullitin on it for stalling....I was going to try defeating my knock sensor , thinking it was that....and a new esc ... But seeing that i am not the only one makes me think there may be nothing wrong with the car......Please e-mail me if someone finds an answer

oh by the way when I reset the computer by removing the battery terminal my car also runs good "around the block" then returns to the same falling on your face crap.


[Modified by LIV4VETTES, 5:01 AM 8/31/2002]

 

85procharged383 :flag If you EVER and I do mean EVER need someone to polish the underside of your frame for hours for free then IM your man. That is an awesome 85. Sorry I cant help your problem, but if you can give me any go fast parts tips for my car that would be great.

 

It sounds like your MAF Sensor is on it's way out. They don't always give a code eg MAF high MAF low. If you are lucky enought to have a friend that has a MAF car borrow his. There is a check but it's very crude. Thump it with a screw driver while the car is running. If it stumbles or stalls change the MAF sensor.

What is probably happening is the car runs fine till it warms up and goes into closed loop. At that point you loose your fuel enrichment and run off the 02 sensor. When you crack the throttle you go to lean and stumble.

Another test you can do is totally unplug the MAF sensor. You car will run in "limp home mode" fixed timming and pulse widths for fuel and spark.

Most likely your problem is MAF sensor or 02 sensor, but really to be of any other help I would need to see some Diacom readings.

On another note you are running a SLOW computer if you still have the factory 85 set up. It would help you a lot to upgrade to the 86-87 variety.

Sorry I rambled on so, but , I think you get my point. Good luck.