1997 4.2 litre idles perfect but misses under load
01-04-2018, 11:13 AM
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1997 4.2 litre idles perfect but misses under load
Sorry for the long post. But I know you guys need details if you are willing to help.
I bought a 1997 ford reman 4.2 litre with under 13,000 klms on it. I then installed it in my 1997 f150. Small hack for the newcomers. I left all wires on the engine and unplugged the one end of the engine harness from the main fusebox. No broken clips!
Symptoms are:
A. It idles perfectly, honestly, it could not idle any better.
B. it misses a bit upon acceleration with no load, ie in neutral
c. It misses fiercely under load ie. it wouldn't climb the one inch abutment from the street into my garage. I had to back up and take a run at it.
D. Once the engine revs up to 3000 plus it sounds really good.
Extenuating circumstances:
1. The scanner tells me the imrc valves aren't closing, ie always open. Throws codes P1537 and P1538. I suspect I have the vacuum lines plugged in wrong. I will play with them when I get back to the truck. About 4,000 miles away now.
2. I will also change the fuel filter as it's simply a good idea.
3. I have spare everything from the other engine as it is still in my garage.
My thoughts:
First, manually close the IMRC's and see if that allows it to run better. I suspect with the added volume oif air as the runners are open it makes the engine run leaner than it should. That would be exacerbated when you put a load on it.
A. Change the fuel filter and spark coil
B. Fuss with the vacuum lines and make sure I get those right.
C. Listen to what the pros have to say and try that stuff.
d. I wonder if it's fuel related as it started quite well at -30 not plugged in. It did fall of idle and stall twice though.
e. I think this motor is really solid because it idles and starts so well, also it really revs clean once it hurts a certain point.
f. I initially leaned to spark but now am more thinking fuel. because it idles so well misfires stutters so much at the bottom but cleans up once the computer gives it more gas at 3500 where the manifold should be opening up.
Attempted stuff.
A. I changed the spark coil pack but I did it wrong I must have run the wires wrong as it wouldn't start and the timing seemed way off. The spark plug wires and the spark plugs look new. (Both Motorcraft)
Thanks for all thoughts help and ideas. All input is welcome.
I bought a 1997 ford reman 4.2 litre with under 13,000 klms on it. I then installed it in my 1997 f150. Small hack for the newcomers. I left all wires on the engine and unplugged the one end of the engine harness from the main fusebox. No broken clips!
Symptoms are:
A. It idles perfectly, honestly, it could not idle any better.
B. it misses a bit upon acceleration with no load, ie in neutral
c. It misses fiercely under load ie. it wouldn't climb the one inch abutment from the street into my garage. I had to back up and take a run at it.
D. Once the engine revs up to 3000 plus it sounds really good.
Extenuating circumstances:
1. The scanner tells me the imrc valves aren't closing, ie always open. Throws codes P1537 and P1538. I suspect I have the vacuum lines plugged in wrong. I will play with them when I get back to the truck. About 4,000 miles away now.
2. I will also change the fuel filter as it's simply a good idea.
3. I have spare everything from the other engine as it is still in my garage.
My thoughts:
First, manually close the IMRC's and see if that allows it to run better. I suspect with the added volume oif air as the runners are open it makes the engine run leaner than it should. That would be exacerbated when you put a load on it.
A. Change the fuel filter and spark coil
B. Fuss with the vacuum lines and make sure I get those right.
C. Listen to what the pros have to say and try that stuff.
d. I wonder if it's fuel related as it started quite well at -30 not plugged in. It did fall of idle and stall twice though.
e. I think this motor is really solid because it idles and starts so well, also it really revs clean once it hurts a certain point.
f. I initially leaned to spark but now am more thinking fuel. because it idles so well misfires stutters so much at the bottom but cleans up once the computer gives it more gas at 3500 where the manifold should be opening up.
Attempted stuff.
A. I changed the spark coil pack but I did it wrong I must have run the wires wrong as it wouldn't start and the timing seemed way off. The spark plug wires and the spark plugs look new. (Both Motorcraft)
Thanks for all thoughts help and ideas. All input is welcome.
Last edited by 72javeloon; 01-04-2018 at 04:58 PM.
