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Generations 8-9 1987-1996 F150 + 1987-1997 F250, F350

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Old 02-13-2018, 01:26 AM
Kaajot Kaajot is offline
Join Date: Jul 2014
Posts: 107
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Question 300-6 Power Fluctuation and Galloping rpms


So, I have not cleaned the engine bay out to show how fantastic Red IX is now, but my heavily-modified F-150 received another $1200+ worth of parts and labor in the garage about 10 days ago.

However, since last Thursday (a week after it got out of the garage), it has had a new check-engine light.

Previously the check-engine light was egr/aic related. At the end we found out the Smog Pump had actually broken and we replaced it with a new one and rebuilt all of the evap lines with new 5/32 rubber lines (plastic was 25+ years old and brittle).

We tore apart the manifolds intake and exhaust, resealed it all with new gaskets, swapped the 17-19 PPH injectors with 14-15 PPH injectors (correct size for 300-6 inline), and also changed a gasket on the cover rod on the left side near the distributor to clean up an oil leak.

Fast-forward to last Thursday and the truck started shifting really hard (E40D). I had to pull over and then limped along at 20-30 mph to a friend's house in town near the mechanic's shop. At the end of that the truck continued to gallop and the battery's voltage fluctuated. Finally it died in place and we had to charge the truck later to get it to restart and move.

The battery had plenty of voltage and the alternator shows its supplying power! The only thing I can think of is my mechanic forgot an electrical component or crimped/broke a wire in the harness during the uninstall/reinstall on the evap side? He also originally couldn't get the truck to start up and played with the distributor cap (thinking the teeth had been misaligned) for quite some time before he realized a plug on that side had not been reconnected for the vehicle wiring harness to the distributor.

Finally, we shot codes for 2 hours on Friday night with a regular ODB-1 mechanic's code reader and a really nice tough-book SNAP-ON code reader. None of the machines could pull codes from the engine light or even begin the "Engine On/Engine Off" tests that start with a rev, then ask for cycling the wheel, pumping the brakes, turning the OD on and back off. The tests would not initiate.

The only fault we did see is "Can not detect Engine Cylinders." This is similar to the problem it had in the Fall where it said "Can not detect Engine Cylinder #4"

So, I've got Engine Light on and can't even start the EOR/EOE tests. and have really hard shifting with lots of transmission fluid in. I threw in two extra quarts tonight just to be sure as it looked a little low but was serviceable.

I'm really lost and so is the mechanic. Help?
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