Rough Idle and no WOT
#1
Rough Idle and no WOT
We have an 89 F-150 that we had problems with it not starting so we replaced the TFI but when that didn't help we replaced the PIP sensor but still no luck. we had some oil leaks so we decided to check the timing chain. It was stretched a little so while we were there we put a cam in it and new timming set. Everything was done by the book. We knew speed density doesn't take cams well so we converted to mass air. Now the truck starts when I advance the timing but won't when it is set a 10-12 degrees with the SPOUT removed. It also runs good to half throttle but from there up it falls on it's face. It Idles extremely rough if it does at all. I had pulled the fuel filter off and It had some fine dust on the Inlet side. My question is if some of that dirt could have gotten into an injector and be causing our problems or if it is something else. PLEASE HELP, becomeing extremely frustrated and don't want to keep just throwing money at it because it isn't throwing any codes.
#4
sounds more like a fuel pressure problem we had this same problem .. it was the fuel pressure regulator or the fuel pump .. i cant remember now.. it was 10 years ago.. when we bought the truck
so chek the pressure at the rail it should be 36 at idle ant 40 at WOT ( correct me on this im not 100 % )
so chek the pressure at the rail it should be 36 at idle ant 40 at WOT ( correct me on this im not 100 % )
#5
#6
yes.. buy an pressure guage to chek fuel pressre or you can buy one that mount in the truck its up to you. the easiest is offcourse the one to chek the fuel pressure.. the way to chek it is on te fuel rail itself.. there is an schrader valve ( just like an tire valve ) ...
its something like this.. you can buy it at your local parts store
http://store.summitracing.com/partde...5&autoview=sku
then chek the pressure and see if its ok .. if its more than 40psi at wot your fuel pressure regulator is bad... if its less then your fuel pump is bad.. but dubbel chek the PSI for the 302. i know the psi for the 351w but not the 302 so dubbel chek it
its something like this.. you can buy it at your local parts store
http://store.summitracing.com/partde...5&autoview=sku
then chek the pressure and see if its ok .. if its more than 40psi at wot your fuel pressure regulator is bad... if its less then your fuel pump is bad.. but dubbel chek the PSI for the 302. i know the psi for the 351w but not the 302 so dubbel chek it
Last edited by DJdemon6696; 02-12-2008 at 12:57 PM.
#7
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#9
#10
The cam has the windsor/HO firing order. I'm not sure which cam it is with out going to the shop and looking at the cam card. It was a cam the Comp cams guy recomended for a mostly stock engine with long tubes, dual 2.5 in exhaust, and converted to mass air. I already double checked my wiring and changed my plug wire order. I know the exhaust isn't pluged because we had hollowed out the cats when we got the exhaust work done 1 1/2 years ago. The truck sounds good at 2000 rpms. hopefully I can get a pressure gauge and check the fuel pressure this week.
#11
I checked the fuel pressure yesterday and I could only get 20 psi at the most so I thought I would replace the regulator first being that it costs less and that brought my fuel pressure up to where it should be. The truck still wouldn't run quite right so I thought I would replace the coil even though I had spark. The truck fired right up. I belive the old coil had enough power to show spark untill I reinstalled the plugs into the engine when it would then under compression fall short of what was needed. Thanks for all the help, It sure kept me from scratching a ballad spot on my head.
#12
#13
Since I put the new regulator on the fuel pressure is right where it should be, about 35-36 at Idle and right on 40 at WOT for both tanks. I believe the old regulator might have been stuck open causing it to bleed off pressure too fast. The fuel filter was replaced right before I checked the fuel pressure because I had been told it could have an effect on the pressure. It has been running realatively good since I replaced the coil and the idle is getting better the more we drive it.
#15