And now its backfiring and idling rough. It runs better when hot then cold, but still has problems hot. Almost seems like its not firing in one cylinder, but I pulled the plugs, checked them and they were all good and they are all getting spark. Could it of cleaned it out soo much to where its getting more gas then normal? I am looking for troubleshooting information, because I dont know where to start. I did search the forum and found a few problems but not like this. Does the TBI have a adjuster? I heard that you can adjust it from 11 to 13 psi or somehting like that. THanks ahead of time for any information.

After driving to work today, it has these symptoms: When lightly accalerating the engine backfires the most. At full throttle or no throttle it does not back fire. It does run rough, almost like there is not all 6 cyl running. I did pull each plug while it was running so I know thats not the problem. After talking with a buddy and looking up different parts, I've decided to go first with a puel pressure regulator. The exhaust smells really rich and also you can smell much more gas then normal in the engine bay. A little info, the fuel pump and filter have been changed within the last 7 years. Could the seafoam of knocked something loose or what.

 

I've got an 88 with the 4.3 TBI. I think your only supposed to put a 1/3 can in the fuel tank. I only used 1/3 can in my intake and had amazing results. May have overdone it in the fuel tank. The directions show 1/3 each in fuel tank, intake and oil.

 

I have an 84 with the 2.8 and I poured 1/3 in the tank and it ran better after I did it.

 

Its been running fine since Wednesday. It just kinda went away on its own, with 1/4 tank of gas left. The can of Seafoam does say 1oz per gallon of regular gas. I filled up the 20 gallon tank and put 1 can in there. No problems since.

As a result, I did not see any improvments. Same gas milage same acceleration.

About a month ago I did do the engine with 1/2 seafoam in the oil and 1/2 down the brake booster. Saw improvments with smoothness thru the RPM band. Yet still no fuel milage improvments. I get about 17 to 19. This truck did have some bald 205/75 R15 and I got about 22 MPG then. I put some 235/75 LT 15's on (beefy tires) Primewell PA100. Then the fuel economy dropped. Attached is a video of seafoaming the engine.


http://www.youtube.com/watch?v=6f-sAsXXOJ0

 

A week after the problem went away it came back. But now its a prominent rough idle and a "upfire" into the air cleaner housing.

After talking with my mechanic, we decided to try the fuel filter first. After breaking the fuel inlet on my TBi half out and JB welding it back together it doesn't run any better with the new fuel filter. I have a new (remanufactured) TBi on its way off of Ebay for 100$ Which I thought was a good deal. This one is going to have a new idle air control valve on it, new TPS, new Fuel Pressure Regulator, and ultrasonically cleaned injectors. Maybe this will fix the problem. If not, I am dropping the tank next.

My problem consists of rough idle, upfire into air cleaner housing at lower and normal throttle (runs fine at 3/4 or full throttle without upfire). And lower MPG (like 12 to 14). Also I have tried 87 and 89 octane gas with no difference. Also checked the timing which was perfect.

 

i'm experiencing something similar, i ran like 1/3 or more through the intake, and the rest in the tank, filled up the tank, then a tank or two later ran 1 full can in the tank, now i've been foolin with timing, it sputters and black smoke comin from the exhaust. Does it really help to run seafoam in the brake booster and engine oil?

 

I really didn't notice too much of a difference. My problem ended up being the spark plugs had a bad gap. They were gapped to about .033 or so each and needed to be at .045 Giving it premature spark. I spent lots of money trying to figure out the problem.

Also, please note, the seafoam didn't mess up the plugs, it was my fault. And yes, you ask, why didn't it run bad before with the wrong gap, don't ask me, but as soon as I took them out gapped them and put them back in its ran fine ever since.

As far as your black smoke it could be premature ignition leaving unburnt fuel coming out of the tail pipe.


Also, I don't think seafoam is a good idea, after research, I have seen lots of people knocking lots of carbon out of their engine only leading to further problems like oil seeping past cylinders.