Hi, I have an '89 Formula w/ a 5.0 TBI/ Auto. The problem arose after I took the car out of storage for the winter (my parents driveway). When the problem first started, I treated it like water in the tank and added water remover. After about a month and about 8 bottles of water remover the problem still came back occasionally. There have been No check engine codes since I replaced my EGR valve, so I suspected a cloged fuel filter, not the case tho. What the car does about 50% of the time I drive it is It Idles fine and when I go to take off and go through every gear (accelerating), the car backfires (through the TB), maybe detonates? But when I let off the gas, its fine...unless I pull all the way to a stop, then it idels horrible. I suspect that the problem maybe spark related now... maybe what ever advances my spark when I accelerate???? ;Like I said the problem is intermitant, so my base timing is fine. Please Help, thanks, Ben

 

Are you sure your base is fine? What is it set at with the EST unplugged?

 

Sounds like the problem I had a couple of years back. I tried the things you did and finally took it to the shop. They found "gunk" in the distributor cap. I have no idea what it was or where it came from but he said it was greasy. It is worth a look.

 

have you tested the fuel pressure?

 

Yeah check your fuel pressure, could be a bad pump, which in case you should buy a Walbro 255l/hr pump

 

Sounds like the timing or something to do with the distribor. I had a simalor problem with my S10(4.3L TBI) and after many hrs of searching I found the pick up coil wires inside the distrober had some of the coating wore off in a couple of spots. You have to remove the distribor then take the ingition modguel out to really inspect them & then remove the drive gear to get the pick up coil off. I broke the distribor housing doing this and just bought a new distribor($90) but the truck ran fine then. Mine only spit & poped when you floored it but was fine untill 75% or more throttle.
Thanks, Bobby

 

I had the exact same problem on my stock 1992 5.0 automatic and after spending way to much time and money I found it to be the rubber hose between the fuel pump and the pick-up tube in the gas tank. All other numbers checked good until I put a load on the engine in gear (brake torque) with a fuel pressure gage hooked up. Nobody could explain why the gage was inconsistently bouncing around- thought it was the gage itself. I decided to change the pump and found the torn line after I pulled the pump out.

Just another thought.

 

Sounds like its going lean on accel. Check the fuel pressure first before proceeding with anything else.

 

i have a very similiar problem please read my post in the tech forum.i really need help guys.like he said mines will idle good but when i give it gas 10% 25 % full w/e i do it rans bad.they told it can be a bad manfold but i have it for 14 months and never had a problem.its a edelbrock dual plane performer for 87 up heads with a tbi adapter on it

 

Hey Carl I had the same problem with my lo3 with the gunk in the dissy, it happened about 8 months after I put on a new intake cap and rotor. I still have no clue as to how it happened. It was a kinda yellowish greese stuff with some water. almost filled to the top of the cap.

 

Sounds like coolant. My L03 had blown head gaskets and coolant and oil would find its way into the dist. around the bushing and seal. Basically it was all wet and nasty inside all the time

 

91RedFirebird,

I had put on new cap and rotor a few months earlier too!! What is that all about. That was a few years back and I haven't had any problems like that since. That is a good thing too since I have a Caprice with the distributor up under the cowl - what a pain in the butt to work with.

 

I could see oil and water working their way up the shaft but I never had any cooling problems and never had it happen again.

 

The same thing happens to my car, I put a team-G single palin intake and adapter on and then it ran like a bag of ****.

Never did it before the intake swap. I Know it is running lean because during cold start when it is pounding fuel in it will peel the tire all the way through first and lay a 5-10 foot patch into second. Is there any way to fix this problem without chip burning, Uping the fuel pressure or some thing. If not I am going to put that carb on that I have in my shed.

 

well i swap manifolds to but i had it for like 14 months running fine and now i have this problem

 

i replace the p/u coil and still have the same problem change coil to and still the problem so its either spark plug wire or manifold leaking or fuel system

 

Check fuel pressure first. Also check the vacuum passages under the throttle body. Sometimes these get gummed up and cause a slight delay to the map sensor when the throttle is opened. Hope this helps.

 

i'll check all that later

 

Im kind of having the same problem as these guys, but i have a new fuel pump, so im sure that isnt the problem. Anyone have any more suggestions?

 

try replacing the pickup coil most of these problem lead to the p/coil

 

Check your Catalytic convetor. I had the same problem and turned out over the winter the cat fell aprt internally and casued the problem.

 

Well, im also positive its not the cat cause i dont have one

As far as the pickup coil, i will try that, but heres a thought thats been running around my head............
could i swap my distributor with a "coil in cap" one wire distributor and still retain injector function? I have swapped the motor with a pre-86 model 350 and i have one lying around, i was just wondering if the computer would still operate all the other crap without being able to control the dist. for advance and such. I would also unhook the wire on the passengers side that bypasses the EST. Anyone done this? Yes, i know my ses light will stay on all the time, but it is doing that anyway now.

 

check your dist for side to side play founnd this to be the problem after replacing everything else in the ignition system 100dollar fix. mine when you get on it would ping and bog down about 3000 rpm.now crisp all the way to 5500. the play in the end of the distributor cause your air gap to be of and you have a misfire...

 

my problem is driving me crazy.i have replace alot of stuff including a new distributor.so im about to dump the car in a shop and tell them untill it doesnt run perfect i dont want it back