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454 Tbi running like a lawnmower

BigYuke

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BigYuke New Member

BigYuke

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After much searching couldn't find a post that mirrored my symptoms. 
454 tbi 220 Dually with 3 speed auto. In a 1988 Sierra. Got it one year ago, ran great. 3 months ago noticed a hesitation at first few accelerations of the day. If you dropped off the throttle and tried again it would go away. Only on the first few accelerations of the day. 
Then it gradually got worse. Eventually getting to the point of happening every day and if you tried to give it more throttle when it bogs down then it sounds like the engine cuts completely out for half a second - all goes silent but then comes back and runs normal. Sometimes the silence is preceded by what sounds like a bang. Sometimes not. 
it gradually got worse and worse. Never better. Always worse. Now every acceleration is like this. I can barely make it up a slight hill. You have to be ever so light and gentle with the throttle so it doesn't big down and/or cut out as I described. 
A couple days ago it also began losing rpm at a steady speed on a flat level highway. It would stumble and quickly recover. 
Now at highway speed it sounds like it is missing every so often at a steady cruise. Throttle is very gently pressed so as not to bog it down or cut it out. I can pull out into traffic but it's a very slow acceleration. If I hit it too much it starts cutting out for a half second And then I go super gentle on the throttle. 
Checked all sensors, and tested good. One injector has a little wetness on the top near the electrical connector. One doesn't. The air filter smells strongly of gas and has a couple stains of liquid gas on it. Inside the air cleaner cover has a film of gas on the underside and smells strongly of gasoline. 
Wanted to drop the exhaust to check for restriction but o2 sensor has been on there forever and exhaust is fully welded so I'll have to cut the cat off to try it without. Cat is after the muffler. Muffler sounds loud but not from the tailpipe from the muffler or maybe the cat itself. I'm wondering if maybe the cat is plugged. Otherwise Maybe a fuel pressure or volume issue with the pump or FPR.
i ran a vacuum check from the vac line for the air system and it seemed to be around 17 inches and came back up pretty fast after playing with throttle and holding throttle kept vac steady. I wish I could get the o2 sensor out to check back pressure. I used an IR temp gun. Exhaust temp steadily decreased from engine compartment (553 degrees f) to pipe before muffler (303 degrees) to pipe before cat (240 degrees) to pipe after cat (180 degrees). This was after a short trip in town of 20 mins.
Ever since I kept the engine at a higher idle for 10-15 seconds while checking vac reading it now runs like complete crap, wants to die as soon as I put it in reverse or in drive when not on the gas. 
I have a fuel pressure tester. But no adapter for tbi. I was thinking of splicing into the rubber hose near the tank with a tee I have and using a brass hose mender with a couple fuel line clamps to seal it up when done. It is likely my only way to check fuel pressure and I hate to buy a pump without first checking pressure. I'm not sure if splicing in back there will work. I know it's not a good idea, but the truck is no longer driveable so I have to do something. 
Anyone have any advice besides tps, ect, etc? Seems like a fuel pressure issue. However it has always started on the first crank, even if it sometimes cranks a second longer than I'd like. Never ever had trouble starting it. And until this week never had trouble running it on the highway. I've never had a plugged cat so I don't know what that would be like. I spent many years as a welder and can easily cut the cat off but don't want to if not likely to produce results. 
Please someone tell me they had the exact same thing and it was -----! That would be great. Even if we could somehow eliminate something I haven't thought of. 
I have a timing light and will check injector spray pattern tomorrow as well as timing. But I don't think timing in the issue. It still runs better at idle than any other time. 
Ses light hasn't worked for years. And I dont have access to a pre odb2 scan tool so I have to get this without the help of codes.
i will fix this truck in the next 48 hours. I drive it 80km each way every day. Can't afford to use it as a lawn ornament. 
Thoughts? I'm sure I've said something that  someone will pick up on that I have missed. Questions and answers welcome.      

BigYuke New Member

BigYuke

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  • Author
Posted

Read it, was cts. Checked already. Sensors are all good. I wish it was that. If be up and running in no time. 

BigYuke New Member

BigYuke

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Incorrectly routed plug wires cooked from exhaust and shorted to ground in multiple places. Injector spray pattern is ok for injector one and like a garden hose on injector two. It was when I was watching the spray pattern with my timing light that I noticed I had no spark on certain wires because the light would not flash. Anyway, new set of plug wires has put an end to the miss it had and injector replacement tomorrow morning will hopefully do the trick to get back the performance and fuel economy. Will report back after injector replacement for anyone interested. 

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