The engine in my F-100 was new in 1988. 300 E.F.I.The timing retards very badly ( around 25 degrees )upon acceleration.It hasn't always been doing this nasty little trick. Result is; very poor milage,very low on power. The engine is now in my " new " 1971. 18 months off the road undergoing ground up rebuild. It has been suggested to me that the E.G.R. position sensor may be to blame.I've carried out various checks, all results within range. Where do I buy a computer?

 

Gp , Have you checked it for any trouble codes ? Has the base timing been set correctly ? The Ecu controls the timing from various sensor inputs . Have you checked the Egr postion sensor ? It will retard the timing if senses the egr flow is low . Check all the vacuum lines to & from the egr , & the egr control solenoid as well .

 

Late 87-96 they had the highest compression 8.7 the earlier ones are 8.0 motors from the factory. You can put a carb on a late model and if you are going to do a rebuild then it don't matter you can get the compression you want iam putting togather a 300 for my truck and it will be about 9.5 compression motor 4 barrel carb cast iron factory dual exhaust. 1.94/1.60 valved head 270h cam

 

G'Day Paul, Thanks for your reply. I cannot buy an E.G.R. transfer tube in Oz so don't have any flow at all.(No tube ). The E.G.R. sensor operates, and is very close to range. When I first performed the transplant I was getting unbelievable milage.In fact the maiden voyage returned well over 20mpg.My O2 sensor suffered a nueclear melt down and the milage tumbled to around 12mpg.I've since installed a new 02 sensor. The vehicle has been off the road for about 18 months or so and I've only travelled about 15 miles in it over the last couple of days, however the same old power lag exists and I'd like to solve problem. The TAD and TAB valves are not connected. Do they need to be, and if so do you have any info on the plumbing? As you can probably imagine this is some what of a nightmare having a 300 EFI inserted into a '71 vehicle. I don't require a smog pump or converter.
While I have your attention, I can't seem to find an engine number on this block. I have another block with the number at the rear on the cam side where the transmission meets. Are you aware of any other locations? Thanks for your intrest.
G.P.

 

Gp , If the egr is operating / opening & closing , And if the tube from the exhaust manifold to the egr valve is missing then when the valve is open you now have a huge vacuum leak . Its no wonder the O2 sensor died . The Ecu is trying to compensate for the added air by making the fuel air mixture rich . With the emission control stuff my idea is either its all on the engine & working properly or get rid of it all . One part not working or missing creates problems . Im not sure of the laws in Oz governing emissions equiptment removal . If you cant get the egr tube then the egr is worthless . I think whats going on is that the Ecu is getting the proper signal from the EVP but its getting conflicting info from the 02 sensor & thus you have the problems you describe . Thats the best I can do w/o ever having seen the engine .

 

Paul, thanks again for your intrest. Although I don't have the egr tube connected, I have blanked of the oriface and therefore don't have an enormous vacuum leak. Last night I removed the bridging pin and set the timing CORRECTLY. What a huge improvement. The advance is still not operating properly because it still retards, but not as dramatically. Did you give some thought as to where my engine number might be? Also, where should I go to obtain a wiring diagram for my '71? gp

 

Sorry Gp , I dont have any info on engine numbers . A good quality repair manual is about the only place I know to get a complete wiring diagram for your truck .

 

Hi Paul. I read in a another e-mail about blocking off the EGR with a plate (it has a small hole to let some vacuum through). I did that this weekend to my 88 F150, 300 motor, 5 speed, and while it doesn't seem to be a night and day difference, I think it does run smoother (I mean it purrs now). What do you think of doing this (good or bad for miles per gallon)?

 

It shouldnt hurt anything or affect your mileage one way or another . Ive not had any egr related problems with my 300 . The truck was about a yr old when I replaced the egr valve because it would rattle when it was open , very annoying noise on a long drive , thats been the extent of the egr problems Ive had on my engine . The egr systems main role is keeping cylinder head temperatures cool(er) A lot of times brief spark knock , predetonation noise can be a result of poor egr flow . On the 300 like ours the passage thru the upper intake can become carboned up over time reducing the egr flow .

 

THANKS