I have a 92 300 engine that was rebuilt .030 over with RV cam( as told to me) I installed in my 89 F250 (AOD with 3.55 gears and stock tires) after the 302 ate a cam sproket.

Now the issue I have is the stupid thing will not give any good MPG and almost no power after 65MPH! I get only 13 to 14 MPG(same as the wore out 302) But my 84 F250 300 I6 with 3.55 gears and EFI(converted it about 15 years ago) gave me 16 to 18 MPG without a OD tranny and bury the speedo with more ***** left! This engine can''t pass 75mph floored in 3rd gear!

I have no codes set after fixing the EGR issue, engine is set at 10deg base timing. Under load I still get engine ping at interstate highway speeds(70mph with 3" to 5" engine vacuum, the 302 gave 8 to 10" vac at that speed) and EGR is functional as is the knock sensor(finally found a good one!!)

The only thing done was the wore out 302 V8 swapped out with the rebuilt 300 I6, same transmission(AOD) and exhaust system(no cats), all new plugs/wires, cap,rotor, t-stat(192deg), water pump, and new harmonic balancer. I am using the 84's EFI ECU (its a 90 4.9L manual ECU Z0S1 programming). So I know its not a ECU problem. I even tried 3 other ECU's I had and still get the same results.


Now I wondering if the engine rebuilder munged up the engine some how or miss timed the cam or put a wrong cam in. ....

Any thoughts on this or anything I missed? I know the 300 I6 should give better that this.

About ready to stuff a nother timing set into that wore out 302
and be done with it....... at least I can keep 70mph and bury the speedo it I wanted.....and got the same MPG

 

Hi Eddie,
Sorry to hear about the trouble you're having. Hopefully it's just something that's not set right on the engine.

Have you done a compression test? What's your intake manifold vacuum at idle?

Those two things can tell you a lot about the state of your engine.

 

What make and model cam? "RV cam" is so generic a term that it is nearly meaningless.

Since it is a fresh rebuild it might be a bit doggy until fully broke-in.

 

Here's the history:
Its got about 3K miles now on it. I got the engine with only 500 miles on it from a friend who gave up on the 92 F150 truck. Before that engine was rebuilt it was leaking oil from all gaskets but ran very good and gave good MPGs with is lead foot.

Once we got it back, then other issues happened like the tranny was not rebuilt(diffrent rebuilder there) properly then they dropped it busting the case and refused to do anything else to replace the E4OD(still have a court date on that..). We finaly got another E4OD, I got the truck running but that E4OD had problems! He took it to a well known tranny shop who rebuilt that one, but still could not find out why it was slam shifting(they gave up on it). It was the PSOM dead I found after getting the truck back. I sure busted some chops on that at the that tranny shop and He got back $500!!!

He drove it for about 500 miles and did not like how it drove and gave up on it. Dang lucky I got it before he scrapped it! Rebuilt 300 and E4OD worth it(so I though)


At idle I get around 18 to 20" vacuum and no wiggle on the needle at all. I did not to a compression test, may do that to get ##'s. I am about ready to pull the front timing cover off to verify it's not one tooth off.
My friend hopefully still has the rebuild sheet from the machine shop, I asked a few times and he still has to find it.

Not sure if the head or block was milled but I am thinking that may has occured with the issues of pinging. 93 oct gas did better with the pinging but not with MPGs and as a daily drive that $$$$ gas adds up!

It just makes me mad this engine is a dog!! All other 300 I6 engines I drove out preforms this one by far!

 

Sounds to me like it is stuck in "limp home" mode.. Bad mpg and no power..

My first suspect would be the HEGO sensor (controls fuel/air mixture). Check into that and let us know what you find..

 

Not in limp mode with no codes, even swapped the ECU out with 3 others(diffrent programs) I have in my parts collection with same results .New O2 sensor went in with engine. I am going to hook up a O2 monitor to it to see how it is switching.

Also going to check fuel pressure, might be the HP pump is not up to the 55PSI of the I6 requirements(just got to find my fuel pressure gauge now...)

 

Ok a update. Fuel pumps prime up to 60psi and held fine, at idle it was 53psi and without vac line to fuel pressure reg was 58psi. Looks normal, but I could not road test as the fuel pressure gauge was too short of a hose.



I think I found my problem, bad ole boozed up gas(E10) has "cleaned" my tank and lines and plugged up the new fuel filter. I did replaced the fuel filter back in January and never though more of it till my friend told me of the boater's having exact problems I am having!


Turns out in SW Florida area we finaly recived the E10 gas in March or April. That crap is plugging up filters and eating up carbs in lawn mowers. My friend replaced a fuel filter in a Mercruser EFI engine back in Febuary, the owner came back with issues I had at full power(lack of power and engine ping!) Well 1st thing boaters do is clean the fuel tanks, lines and replace filters(figured water got it) That fixed the problem there. Out of curiosity he drained the fuel filter, it had black crud coming out of the inlet side and it was plugged to the point he could not blow through it!!

SO I pulled down my fuel filter and what I found..... its full of black crud!! Well a new filter is going in and hopefully THAT fixes my problem.

 

That'd be great if that was it!
I've known people who've had to be towed home due to fuel filters. They can do a lot of harm to performance when clogged!

 

Ok, a few months later, pinging along still and only getting 12 to 13 MPG. I had to back timing to 0deg insted of the usual 10deg just for I won't bust a piston with pinging(93 gas helped marginally ) !


After reading on the Ford Six Performance site a thread of engine pinging with a 268H comp cam with EFI head and intakes would give excessive dynamic compression leading to pinging.

I found it may very well be a wrong cam is install. I never got what kinda of cam is install(friend lost the paper work).


I now have a 2nd 300 engine which is stock(hopefully) and its going in after I check bearings on it.


PS, that **** gas E10 really messed up all my family's vehicle's, had to change all the fuel filters, but now its all clean......

 

Maybe ur injectors have clogged as well due to bad fuel. Get a laser temp guage and check temp of all exhaust ports may tell u something there

 

Allready did that when I removed the EFI system off the 84 F250, those injectors ran the 84's 300 fine. Had them sitting there so I tried it after the fuel filter replacement.

As a side note, I got the 84's engine back running and it sounds so much better at idle than the 89's engine. The 89's engine sounds like its being strangled at idle and rev up compaired to the other engine.....

 

I forgot about this thread! Much needed update on what I found. This all occurred in January/February 2016


After pulling my hair out, I just ran it, till one night going home, the engine quit running. It failed just like the 302 did when the cam sprocket failed with backfiring and after burning in exhaust. I thought the engine jumped timing, but when cranking it, the engine sounded normal but would not start. I checked for spark and got a good blue arc from the coil.

When my Dad arrived with the car hauler, we took one more look. he pulled off #1 plug wire and it had no spark!!! Well looks like a cam gear went I thought, but before come-alonging it onto the hauler, He pulled off the distributor cap and we found the rotor off the distributor shaft!


Turns out the upper bearing of the distributor was so wore out the rotor finally hit one of the posts and was knocked off. Put it back on and the engine started back up to its usual self.

That weekend with a "new" distributor installed at 10deg, that engine really came to life with NO MORE PINGING. The MPG came up to solid 14.5 than the 12 to 13 I was getting before.

That wore out distributor sure caused some pain there and I though it was a new distributor installed on the engine at the rebuild shop. They did a good job of cleaning it up when they installed it.


As for the solid 14.5MPG, I just found out the rear axle is a 4.10 NOT what the axle tag on it says of 3.55! Some bo-bo put the wrong axle tag on it!

I found out after getting a nice clean diesel cluster with tach and installed it(after recal the tach to gas engine use) verifying the speedo and tach with a online RPM to MPH calculator. The 3.55 ratio just was not computing to what I was getting on the truck till a put the ratio to 4.10. Then every thing matched!!!

Now its time to swap in the rebuilt E4OD as the AOD did not like towing home a 14K load!

 

Thank goodness for the little things.

 

I agree, that has to be a relief!

And thanks for coming back and letting us know. You never know who you might save in the future.

 

Please elaborate how this was done? Thanks.