I have an 86 coupe stock engine. If I put the pedal to the floor from a standstill the car will take off great then it seems like it cuts off for a second. The engine does not stall it just seems like you took your foot off the pedal and then floored it again. This does not happen at all if I just take off at a normal speed. The transmission shifts smoothly and does not pause at all. I can take things apart and put them back together but I don't know where to start with this. Plugs and wires are all new, fuel filter is new, new k&n air filter. I have owned the car for a year and it has always had this problem, I just spent all my time replacing the whole interior and it drives great, just that slight pause when I hammer it. The car has 80k miles on it. Any suggestions would be greatly appreciated. Thanks

 

 

Any trouble codes? Any significant engine modifications? Smoke on startup? How does the exhaust smell? rich? lean? oily?

Suspects:

Fuel delivery:

A partially clogged fuel filter will cause these symptoms. A fuel pressure regulator should adjust the fuel pressure upwards when the RPMs increase and vacuum decreases. You can test this with a fuel pressure gauge. Disconnect and plug the vacuum line to the FPR to see if pressure goes up with the vacuum line disconnected. Tape the gauge to the windshiled and see if fuel pressure drops when you experience power loss. Low octane gas could cause knock which causes loss of power when the comp retards the timing. Clogged injector/poor spray pattern etc could cause the engine to bog under heavy load. Ohm the injectors using the method in the sticky post. Listen to the injectors with a mech's stethoscope to see if they all sound the same at idle.

Air/metering/exhaust:

Anything that greatly reduced air intake/exhaust could cause this. If the air filter looks dirty change it. A clogged catalytic converter or any other obstruction in the exhaust could cause this too. A dirty/worn out MAF could under report the amount of air and result in a lean condition. (Google "MAF K&N Filter") A failing TPS could result in the computer not tracking the degree to which you've opened the throttle. Back-probing the TPS should show it reporting almost zero to almost 5 volts smoothly as the throttle opens. A vacuum leak could screw up the AF ratio and cause various sensors and devices to mis-report the engine load to the comp. Check all vacuum lines.

Spark:

Pull the plugs and compare them to one of the various spark plug diagnostic charts. (since yours are new did you save the old ones? Did they all look the same? Did they indicate any problems? What gap were the new ones set to?) Ohm out the plug wires even new ones can be faulty. Check for spark "leak" in a dark garage by watching for arcing. Does the inside of the dist cap look ok? What about the rotor button? I think the L98 advance is handled by the computer maybe an L98 guy will post a test to make sure advance is happening.

 

Have you checked your fuel pressure ??

 

wow, you guys gave me a ton of things to frazzle my rookie wrench mind. Thank you for taking the time. I had this problem both pre and post new plugs, wires, air filter, fuel filter. I do use 87 octane. The car runs great except for the quick pause, it happens right around 2nd gear. Car rips off the line, pause for maybe a second almost like no gas then it goes like hell again. I have not changed distributor/cap/rotor since getting car. I had never changed a flat let alone get into an engine. I put in new cat converter and 02 sensor because it initially failed emissions, passed after I did that.Radiator leaked so I replaced that and cleaned out all the crap between the condenser and radiator. I guess I will attempt to do all of your suggestions it scares me a bit because I am having a ball driving it everyday and I don't want to be the cause of bigger problems due to incompetence. A least right now it goes great, I just can't stomp on it at every light and stop sign, which is probably a good thing. lastly, it does let out a puff of blueish smoke on start up, but not every time. I guess there's only one way to learn. thanks again and hopefully you guys will help me again when I have engine parts all over my garage

 

I would lean toward the fuel injectors. When you are at WOT and your injectors are dumping the max amount of fuel, any small hiccup in delivery might be felt. If you are unexperience and just want the problem checked, find someone you trust and have them diagnose the problem. They will pressure check your system for leaks; but if you have changed everything and are still using 25 year old injectors..............

 

I would check the throttle position sensor first. I've seen bad ones cause this problem. Find someone with a scan tool to check the readings.

 

If the smoke is on hot restart it's the valve seals very common with old chevys. Not anything to worry about just keep a eay on the oil level.

 

If you fill out your profile, someone in your area might be able to come and take a look for you.

 

in the past 3 months the "check engine" light has come on a couple of times and then when I shut car off it was gone at restart. It has not been on for awhile. If I pay to have car scanned will it read a problem if the light is not currently on? My inexperience has cost me a few bucks so far so I don't want to pay and hear that there is not currently a code. Thanks for the replies

 

Short out the terminals and get a code. To answer your question, yes and no. Usually, if the CEL is on, there is a code stored. HOWEVER, after a certain number of start cycles without the code appearing, it will be wiped off.

http://www.corvettebuyers.com/c4vettes/codes.htm

 

This is probably a stupid question but I am new to this so here goes. When I looked for the ECM I can't find it. There is a metal mounting bracket on the bottom of the carpeted panel which is under steering column but nothing is there. I crawled underneath and can't find it. I have the FSM so I know what it looks like and where it should be. I had the whole interior out of this car and do not ever remember seeing this and at the time I wondered what attached to that bracket. Any way, the stupid question is could this car run without it or been rigged in some way. I am taking everything apart again to try and locate it thinking it has to be buried in there some where. Any thoughts? Other than "this guy is an idiot"

 

does it do that with more than 1/2 tank of fuel?? if it is low on fuel then the initial take off will slosh all of the fuel to the back of the tank starving the fuel pump for a second.

i have an 86 and i bet $50 that your fuel pump is going out

 

This is probably a stupid question but I am new to this so here goes. When I looked for the ECM I can't find it. There is a metal mounting bracket on the bottom of the carpeted panel which is under steering column but nothing is there. I crawled underneath and can't find it. I have the FSM so I know what it looks like and where it should be. I had the whole interior out of this car and do not ever remember seeing this and at the time I wondered what attached to that bracket. Any way, the stupid question is could this car run without it or been rigged in some way. I am taking everything apart again to try and locate it thinking it has to be buried in there some where. Any thoughts? Other than "this guy is an idiot"[/QUOTE]

there is a terminal that if you are sitting in the driver's seat should be right about where your right knee would be

 

How about this thought. "This guy bought a car from an idiot.". Sorry but I think the Previous Owner screwed up. My car was FUBAR from the PO. He cut out all the FX3 actuators and replaced it with cheap shocks and pulled out the light. Same with the Airbag. Many other things were hacked up. The ignition wouldn't crank so instead of replacing the melted relay and the relay holder, he put in a "Security Mod". There is a button you push to crank it. You turn the key to run and push that button to crank. wtmf!!!!!

I don't think you need to find the ECM at this time. In fact, I can't even advise you since I have no clue where it is in your car. In my car, it is behind the left wheel above the battery but your car might be different. You only need to find the port attached to that metal piece. That or you have to trace wires to the ECM to find where it is at this time. It might be in that bowl of spaghetti under the steering column.

 

there is a terminal that if you are sitting in the driver's seat should be right about where your right knee would be[/QUOTE]


That terminal under your right knee is not the ECM its the ALDL its used to recover ECM codes from the 1984 through 1993 Corvette. If your 86 is like my 87 the ECM location is behind the bread box passenger side of car. If you have the Electrical Diagnosis Supplement to the FSM look up component location

 

That terminal under your right knee is not the ECM its the ALDL its used to recover ECM codes from the 1984 through 1993 Corvette. If your 86 is like my 87 the ECM location is behind the bread box passenger side of car. If you have the Electrical Diagnosis Supplement to the FSM look up component location[/QUOTE]

The FSM does say and show the ALDL being where my right knee is. All that is there is the metal bracket that would hold it. I think the guy who said I bought this car from an idiot was right. So far there have been lot's of hack jobs that I had to redo. It has to be on there somewhere so I guess all the dash trim is coming out again because I just can't find the terminal. Thanks again to everyone who took the time to read and post.

 

Actually, it happened a few days ago and yes the tank was close to empty. will fill today and burn up some rubber to see if thats it. If it is $50 sounds fair to me. Thanks

 

You said you were looking for the ECM," When I looked for the ECM I can't find it" The ALDL is just a open connector its not located at the bottom of the column check back behinde the radio and heater controls maybe he stuffed it somewhere check up under the knee bolster Good Luck

 

The ECM is on the passengerside behind the dash. Your car can't run without it.