I am almost completely finished on the 4.3 to 5.7 swap in my 94 c1500. Now it's a matter of tuning. It idles smoothly. It accelerates smoothly and sounds great in neutral. But when driving it, it doesn't want to accelerate at all. If I push the gas pedal slowly it does just fine.
How are the vacuum hoses supposed to be routed? If I don't have the smog pump hooked up to a vacuum hose, could that do it?
Otherwise, it's got plenty of power and starts right up every time.
Check the fuel line. If its having trouble underload something is bleeding power away. Could be exhaust as well.
Did you change the computer... ( need the one that came with the 5.7
Yeah I put a new chip in the computer for a 5.7. It's not missing on any cylinders. It doesn't want to accelerate under full throttle. Not like it should at least. I had an exhaust leak and I fixed it and it ran a little better.
The EGR on the 5.7 doesn't have any place to plug in the wire that went to the EGR on the 4.3. And the smog pump has no plug either. The vacuum line that goes to the EGR, throttle body, and that sensor thing also goes to the smog pump. Should I just disconnect the line from the pump and bypass it? Will the smog pump cause the O2 sensor to misread since the O2 sensor is just before the cat converter (3 wire) and the old one (one wire) is on the exhaust manifold?
And I think I got the chip for a automatic tranny and my truck is a 5 speed manual. Will that affect how it runs? Is that why the "Shift" light stays on now?
And for some reason the temp guage is not showing it getting warm. I've ran it on the road for around 20 minutes at a time so far and the guage doesn't move. Do the temp sensors work differently or something on the 4.3 versus the 5.7 or should I just buy a new one?
I think it doesn't have a thermostat. I seem to remember it overheating once about 5 years ago and being told it was removed. Could that have anything to do with it?
Just trying to cover all my bases. When I slowly depress the accelerator it hauls ass. I mean, it's just freaking fast compared to my Ranger I was driving. If I can get it to accelerate properly it should be plain scary.
I unhooked the smog pump. Made it run a little better. It doesn't act like it's flooding out now. Still doesn't accelerate properly.
Are the temperature sensors the same between the 4.3 and the 5.7? If so I can change the one in the 5.7 and see if it's a bad sensor telling me the engine hasn't warmed up yet.
try looking the part up online at autozone, and see if they are the same. wouldn't buy much from them, oil, spark plugs is about it. But their online catalog is good for cross referencing part numbers between vehicles.
Whitelightning
Are you sure the timing is advancing properly? Retarded timing will slow acceleration. Regards, JR
I'm not sure anything is doing anything properly. I don't know squat about timing an engine or checking sensors or whatnot. It's one of the reasons I am so amazed that it runs at all. I've changed the engines in my lawnmower about 5 times, but there's really nothing much similar about changing the engine on a walkbehind and extracting the engines out of a 94 Chevy truck and 93 Caprice and then making the Caprice engine work in the truck.
It's kind of odd, but since I have been driving it a bit, it's been running much better. It still stutters on occasion, but mostly it accelerates smoothly and runs fine. I've been trying to find a hill steep enough to make me have to shift out of 5th and ain't found one yet. I can take 5th all the way from below 30 mph to 85+ and it doesn't slow in accelerating or miss or stutter. In fact, it just keeps on getting quicker and quicker. I wish the speedometer went to more than 85. It pegs and the engine just wants to keep going like it's doing nothing. Will it break the speedo if I peg it too far? I've done that before with the old cable type speedos. Don't know if it'll happen with the computer and all.
When I disconnected the smog pump and sealed up the couple exhaust leaks from my home made Y pipe it started running much, much better.
But my "SES" light is still on and I know it's still throwing all those codes. I need to know how to fix them. Still don't know what a QDM sensor is or what it's used for.
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