still cant figure out the miss. may need new motor

[stinkydogfilms]

Hello,
I'm kinda getting frustrated. I cannot get the miss figured out.
I'm thinking about the FPR or O2 sensors even though I feel like it is electrical. I say electrical, because when i turn the lights on or use the electric seats, the car misses more.
So far I have thrown at it all new
distributor cap, rotor, egr valve, egr sensor, pcv valve, screen and grommet, IAC valve, TPS sensor,
new plugs, all the past week
PIP sensor, ECT sensor, Coil, TFI module in June and July.

Cold or hot it had a miss just before the shift points.
I had been able to drive it about 20 miles each day last week and yesterdayalso by using a light throttle, then just before the shift point let up on the gas so the car shifts and the RPMs are lower. light throttle the car would goup to 50 mph without a miss. I stayed on local streets, no freeways. With a Mid to heavy throttle it would miss. Heavy throttle would result in a bad miss and misfire.


Its frustrating because the car ran great until I took it to an electrical shop in July to fix/replace the alternator wiring harness. Upon return of the car to me on july 5th, it ran like crap. The shop did a smoke test and said/showed a lot of smoke coming from under the intake at the rear of the intake. It must have a vacum leak. They replaced the ECT sensor and said that took the engine light off, but did not clear up the miss. I found the vacum leak from the front of the intake and put the hose on. Still had the miss.

This past Labor Day I took it to another shop that had put the motor in 3 years ago. This time they said the same thing as they did before they replaced the motor.
They said the motor needed to be replaced. The valves were bad.
I do not trust their opinion and feel that they only want to rob me.

This weekend, I am going to check the fuel pressure,
try to clean the MAP sensor that is 1 year old,
remove the G Force chip I have been running the past year with no problems.
take off the intake and replace the gasket, maybe the FPR.
Now that the PCV valve has been replaced, I want to put a NOS throttle body on that I have.

Should I think about replacing the fuel injectors, they are 3 years old on being cleaned and rebuilt, if so which ones should I buy? LOPO or HO.
I have an HO long block in, that is running the HO firing order, with the LOPO intake and throttle body.

I have an NOS LOPO throttle body I want to put in.
1. Would it work ok with HO fuel injectors?
2. Do i need a stronger FPR and fuel pump to run the HO fuel injectors?
3. Will the LOPO fuel rails and fuel injector harness work?

I found a remanufactured HO engine on EBAY to put in.
It has a 3 year, 100,000 mile warranty. The seller has 100 percent feedback on lots of motors sold.



4. How hard is it to swap the remanufactured long block in?
I swapped engines and transmissions between 69-70 Mustangs with carbs and C-4 trans.
I am at the point i don't trust anyone to do my work for me.
If anyone puts another motor in, it will be me.

I'm sorry to ramble so much.

Thank you again,
Mike

[85crownHPP]

I just looked at some of your old threads to try to get caught up... have you done new spark plug wires too? I didn't see it mentioned anywhere.

Do you know exactly what the shop did as far as wiring? What all looks new under the hood? There are fuse links on the fat hot post of the fender starter solenoid - these could have gotten disturbed if they replaced the charge cable. Give them all a decent tug to make sure the connections are good and no links are half-burnt. There is also a very important ECM ground going to the negative battery post clamp, it's a thin black wire with a connector on it that is in that area too, they can get corroded or come loose.
Also there are a couple engine grounds for the ECM wiring, at least one is on the back of the block. Also clean up where the negative battery cable attaches to the engine and/or frame and look for corrosion in the cable at both ends.

You say it get worse when you use the headlights or power seats (both pretty big loads) - this makes me think something has a bad ground, like the coil or some sensor. I think the newer boxes have a ground right from the battery to the radiator support too, if this is gone (and it is the main source for body ground) it could cause trouble.

Should I think about replacing the fuel injectors, they are 3 years old on being cleaned and rebuilt, if so which ones should I buy? LOPO or HO.
I have an HO long block in, that is running the HO firing order, with the LOPO intake and throttle body.

I have an NOS LOPO throttle body I want to put in.
1. Would it work ok with HO fuel injectors?
2. Do i need a stronger FPR and fuel pump to run the HO fuel injectors?
3. Will the LOPO fuel rails and fuel injector harness work?

What injectors do you have in it now? To make a HO motor with a HO cam happy, you need all the rest of the HO stuff. What ECM are you using in it?

[gadget73]

I wonder if you don't just have a crappy alternator. If all of this started when the alternator changed, that has to be the common link. Dirty power or low voltage could explain this. If the rectifier assembly is wonky, it will put AC into the electrical system, and the computer doesn't like that. Bad grounds, too high or too low voltage, or intermittant connections will also play hell with things. Get a voltmeter and connect it to the cig lighter. If its under 13.5 volts or over 14.5 volts while driving, something isn't right. If the needle dances with a steady rhythm that gets faster with engine speed, thats a dead rectifier.

If you want to confirm a tired valves diagnosis, a leak down test will do it. If the leakage is excessive, just listen for where the air comes out. If its out of the throttle body, the intake valves leak. Tailpipe is exhaust valve, valve cover is piston rings. I highly doubt this is why it misfires. It may be that you have a worn out engine, but that just acts like a worn out gutless engine. They don't misfire or do more dumb things when you turn on the headlights. I kind of suspect that unless you figure out why the current engine does what it does, you'll put a new motor in and it will not be any better.