inconsistent surge. hard to pinpoint the problem.

#1
hey guys ive been having a real hard time pinpointing the source of a bad and inconsistent surge/missfire on my 87 ttype project. ive replaced plugs and wires, replaced the Ignition module, and coil pack just incase it had to do with ignition ( which i dont think it is ). replaced the fuel filter and i also swapped out my older fuel pressure regulator for a newer one not too long ago aswell.

fuel pressure is at 38-40psi at idle, and my voltage is reading 13.5 - 14, so all seems good there. checked and tweaked my TPS and my IAC to the right readings too because they were way off. ive basically done a good, and probably well needed spring cleaning on the car just trying to figure it out..

the car idles AMAZINGLY, but when I put it in gear and drive it around it'll sputter at any given time. it doesnt do it at any specific rpm. its completely random ( although it tends not to do it at low rpms when cruising around the block. but usually it happens when you give it gas, mabye 1/4 throttle or so. but like i said, not every time. its confusing... it'll even handle boost when it wants to, but rarely lets me climb to 5 psi before surging ). whenever this surge happens the car never dies completely, I take my foot off the gas and it cuts in and out for mabye 2 -3 secs, check engine light flashes on and off like mad. and sometimes even resets the computer whenever it happens. my scanmaster readings will flip out and give me a bunch of different error codes and then go back to 00 once its done having an aneurysm lol what is happening?!?!?!

could it be my fuel pump going out? i have an aftermarket high volume fuel pump ( hotwired ) that was put on years ago, not sure if that could be part of the problem. i really hope its not :(

i dont think its a vaccum problem either. ive replaced most of my vaccum lines, and the only bad ones i can tell are on the EGR, which i intend on deleting very soon.

my transmission is garbage but is still functioning, and is getting replaced soon as well, i dont think its got anything to do with that either but who knows.

any ideas? im at loss, ive been at it for some time now. i have a strong feeling its the fuel pump, but if theres anything else you can think of that can cause something like this to happen, let a brother know. :) the engine only has 60k miles, and has been rebuilt once before, so i doubt its anything internal.
 
#3
stock MAF. i have the LT1 MAF and the translator, but i havent installed it yet. it has a chip but not exactly sure what kind. My father bought the car back in 2000 and let the car sit in a yard for years, so he has no idea. its got red stripe injectors, thats all i really know :/
 

earlbrown

runs with scissors
#5
My vote is injectors. (and that ancient chip doesn't help).


First things first, you already have a good MAF and a Translator... Spend the 5 minutes it takes to install that and see if if fixes the problem.

...I'd still get a set of 60s and a TT chip from Eric though. and a new fuel filter.
 
#6
installed the MAF + translator. still surging, but running magnificently otherwise lol. im not that tech savy when it comes to chips so i cant really figure out what kind of chip this is just looking at it.
 

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87gn-newbee

Active Member
#7
Make sure the settings are correct on the translator.

Pull the big chip out and see if there is any writing on the other side

Replace the stock fuel filter
 

NY Twin Turbo

All the good stuff.....Times 2.
#11
whenever this surge happens the car never dies completely, I take my foot off the gas and it cuts in and out for mabye 2 -3 secs, check engine light flashes on and off like mad. and sometimes even resets the computer whenever it happens. my scanmaster readings will flip out and give me a bunch of different error codes and then go back to 00 once its done having an aneurysm lol what is happening?!?!?!
Sounds like the ECM is intermittently loosing power.
 

mikestertwo

Well-Known Member
#13
Sounds electrical to me. The fact that the computer resets says it's loosing power momentarily. Could be a bad computer, bad connector on the computer (corroded), or the orange power feed wire coming from the battery is intermittent. Also try reseating the chip in the computer.
 

NY Twin Turbo

All the good stuff.....Times 2.
#16
Try what's easy first.

Shake some wires around while the car is running. Pull the ECM out of the kick-cover and shake it a bit.

Then move on. Injectors, crank sensor, flick the TPS with your finger, Have someone slightly power-brake the car while you do it all. Try to get it to stumble or cut out. Try what Nick recomended. All easy stuff.

Then move on to the real diagnostics.
 

Mr.Spool

Well-Known Member
#17
could it be my fuel pump going out?
verify fuel pressure rises 1to1.a can of xylene or 2 will help clean the injectors if that is an issue.pull codes off scanmaster and troubleshoot properly.make sure you tightened the screws for tps down and check throttle blade angle.pull the plugs, check gaps and condition.check headers for cracks and also intercooler hoses and the intercooler itself for cracks.
 
#19
Remove that cable from the ECM if that’s attached and see if it runs better. Are you using direct scan? If not there is no good reason to keep that flat cable attached.


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berserker6

Assistant to the regional manager
#20
Check and make sure the cable coming off the back of the alternator running over to the battery isnt shorting out on your drivers side exhaust manifold where it snakes down. Mine was a long time ago