86 trans am tpi cutting out
 

My car is running great at part throttle but for some reason if I floor it from a stop the car revs to about 1.5k and then cuts out and then revs to about 2.5k again and cuts out. It keeps doing it until it gets to about 3 or 4k and then it clears up. Just did a tune up, checked tps, and replaced injectors. Not sure what else it could be. The car starts up fine and runs great other than this issue. Any ideas?

Re: 86 trans am tpi cutting out
 

Symptoms may be fuel pressure. What is your fuel pressure? Is it steady when accelerated?

Re: 86 trans am tpi cutting out
 

I checked it at idle when I installed the injectors but never ran the car on the street with pressure tester hooked up. I took the car for a ride tonight and realized that If I floor it from 15mph or up it will not cut out. Just from a dead stop. Fuel pump is also brand new. Are you thinking pressure is too high or too low?

Re: 86 trans am tpi cutting out
 

What I think Eaglemark was suggesting is that you may be loosing fuel pressure due to a restricted fuel filter or sucking air at the tank under hard acceleration. If your filter isn't new replace it just as insurance. Connect a fuel pressure guage so you can monitor pressure while you drive and watch for any pressure drop when this problem occurs.

Re: 86 trans am tpi cutting out
 

Sorry i didnt post it earlier but I also changed out the fuel filter. I also checked the fuel pressure regulator to see if it was leaking by disconnecting the vac line and priming the pump a few times to see if it spit out any fuel and it seemed fine. I will see if i can pick up a fuel press gauge to mount in the car to monitor pressure

Re: 86 trans am tpi cutting out
 

This could also be caused by low injector resistance causing the drivers to over load. Use back probes and test leads to connect a noid light in parallel with an injector and attach the noid where you can see it while you drive. look for injector pulse to drop out. The ignition module sends a crank referrence pulse to the ECM which is used for injector timing. This crank pulse may be dropping out as the ign module is stressed under hard acceleration. The crank signal travels on the ppl/wht wire from the dist to the ECM. Use a DVOM, back probe and test leads to tap into this circuit and watch for the DC voltage to drop off when this cutout occurs.

Re: 86 trans am tpi cutting out
 

thanks for the info. I will give it a shot tomorrow.

Re: 86 trans am tpi cutting out
 

Ok I tested it with a noid light and it is cutting in and out while this happens. I also realized that the injectors are actually out of an lt1 (ran the numbers on the injector). You think the issue is the module in the distributor or the injectors? Also, I installed headers on the car today and when I took it for a ride I floored it from about 35 and it seemed to run good but when I got to about 80 mph my check engine light started flickering, my tach started twitching and my speedo started jumping. Think this could be related or is it multiple issues?

Re: 86 trans am tpi cutting out
 

I had my tach start twitching after I installed headers once. Turned out to be an plug wire touching a header tube and burning it. I'm pretty sure it's related if it just started after the header install. Look for any electrical connections that may have been disturbed during the install. At 80mph, you might be getting enough wind up into the engine bay to upset a poor connection.

Re: 86 trans am tpi cutting out
 

I figured out the twitchy gauge issue. It turned out to be my positive batt cable. It was touching my header. Got that fixed but still having the cutout issue when flooring it from a dead stop.

Re: 86 trans am tpi cutting out
 

It sounds like a fuel starvation problem. Time to start testing. MAF voltage, fuel pressure, TPS voltage. Check injectors for resistance.

Re: 86 trans am tpi cutting out
 

Checked my fuel press today and it's good. Checked tps and it's dead on. Checked the injectors and they are all within spec (although they are too much injector for this engine).

How do i check the maf voltage?

Re: 86 trans am tpi cutting out
 

You need to find a can tool. Connect the scan tool to the ALDL and read ECM data.

Re: 86 trans am tpi cutting out
 

I just reviewed this thread and found your post saying that your injector pulse is dropping off when this happens? That is not MAF. More likely a problem in the distributor or wiring between the distributor and ECM. Try wiggle testing the ECM harness and look for the engine to studder or otherwise change idle.

Re: 86 trans am tpi cutting out
 

Update* I replaced the injectors again because the set that was installed ended up being 24lb. The cutting out has seemed to stop but my intermittent misfire has gotten worse. It doesn't seem as noticeable when in open loop but is very noted when in closed loop. At times it even seems like the computer is jumping back and forth between open and closed loop.

I also did the wiggle test just for piece of mind and it did not seem to make any kind of difference.

*ASE doc*- thanks for all of your help so far. It seems like everytime I get one problem fixed another pops up. I just can't give up on the girl just yet.

Re: 86 trans am tpi cutting out
 

Wow! 24lb injectors in a 305 must have been drowning it. I wonder what sort of shape your O2 sensor is in. It's been loaded with fuel for as long as those injectors have been in there.

Check your spark plug wires carefully. Maybe use a spray bottle to spray water on them with the engine running and see if you find any leaks. What do your plugs look like? If the ignition checks out okay and a new O2 sensor doesn't help, test for injector pulse at each injector. You may have to wiggle the injector harness since the problem is intermittent.

Re: 86 trans am tpi cutting out
 

Im off work today so I will check my plugs, wires and replace the u2 sensor just to be safe. I will let you know what I find. Thanks again

Re: 86 trans am tpi cutting out
 

If injector pulse is still cutting out, suspect the distributor.

Re: 86 trans am tpi cutting out
 

replaced the plugs,wires and 02 sensor again just to be sure that those are not a cause of my issues. I also reset min idle and TPS. my missfire is pretty stead now. I have to double check to see if the signal is cutting out but that will have to wait for another day since its getting dark outside.

Re: 86 trans am tpi cutting out
 

is there any way to test the dist with a multimeter to see if something is out of whack?

Re: 86 trans am tpi cutting out
 

You can test the pick up coil with an ohmmeter, should be 800-1000 ohms. You can sort of test the crank referrence pulse(ppl/wht wire) using the voltmeter set on the lowest scale, it will start as a low voltage DC signal and increase with engine speed. The best way to test this signal though is with a scope where it will be a digital(on/off) signal 0v to 5v, with frequency increasing with engine speed. I have removed the dist and turned it in my hand with the key on to produce and measure the signal. you have to run a test lead to ground the dist body. A steady misfire whether it's ignition or injectors is fairly straight forward. Test spark at every plug. If you have an engine analyser I would tell you to do a power balance test. You can perform a simple balance test by pulling or shorting one plug wire at a time. I generally use a test light to ground out one wire at a time by piercing the boot at the cap. Look for cylinders that don't drop rpm when you kill them. Once you know which cylinders are missing, figure oput why by testing injector pulse, compression, etc.

Re: 86 trans am tpi cutting out
 

i just got my '92 trans am runing for the first time in almost 6 years, the transmission blew and i never had time to get to the rebuild, anyway it a pain in the *** to start, its fuel injection, but i have to turn key on and off, pump throttle, etc... and it still take at least 5 mins to start, once its started it idles fine on open circut for about 30 seconds then trys to die unless i feather throttle just right to bring it back to idle, and i can only bring the rpms up it i work the throttle like crazy. when i go to put it in gear it dies almost every time, and it wont idle very long in park. my dad let the car sit with E85 in it for about 4 years, i had to replace fuel pump and tank, and fuel fitler, (tank was rusted to hell) could my fuel lines be clogged? the only thing thats throwing me off the idea of my injectors being out is the fact that it idles so nice when it finally starts, any ideas? i'm gonna try to blow out the lines with an air chuck tomorrow. any help will be greatly apperiatied, ive been working on this car off and on for 2 years, i wan to drive it already :(

Re: 86 trans am tpi cutting out
 

You really should have started a new thread for this.

I doubt blowing lines clear will help, but at this point it is worth a try?

Need to check fuel pressure?

Probably need to pull injectors and have them serviced. Mr Injector is excellent if no one in town and you have to mail them.

Pumping the gas pedal does nothing to help a fuel injected engine to start like it would a carb, feathering it will help get it running when there is an issue. HTH!

Re: 86 trans am tpi cutting out
 

i know pumping the gas pedal dosent do anything for fuel injection, for some reason my grandpa thinks it dose though -.-... and do you really think my injectors are goin out? the car ran great when the transmission went out, im starting to think the pumps getting weak, im gonna test fuel pressure when a get my hands on a pressure tester. would the car still idle perfect then die after about a minute or so if the injectors are goin out? there is not check engine light on either. and im new to the forum and could figure out how to start a new thread, sorry :/

Re: 86 trans am tpi cutting out
 

Injectors sat for years is why I said may need service. Ethonal gas is horrible on things in storage... You said a new pump so I didn't think that was an issue. Checking fuel pressure at this point would porbably be a good test!

Re: 86 trans am tpi cutting out
 

the pump wasnt "new" it worked though and my dad made me put in instead of letting me get a new one 2 years ago. -.-

Re: 86 trans am tpi cutting out
 

:doh:

You gotta check fuel pressure!