5.0 WOT, no power

[gear_grinder]

hey,

i've gotta 97 gt40p, its got: HO mustang cam, roller rockers, brandnew rebuilt fuel injectors, SRI, "catback" exhaust, and a TF 1" spacer.


after i installed the new(rebuilt) fuel injectors and reset the PCM, the truck feels like it has no power under WOT, like massive amounts of hessitaition. It doesnt feel like a stumble or a dead stop of power, but it accelirates faster when i run about 3/4 throttle vs WOT. I'm almost guessing MAF/TPS/CKP because along with this after you shut the truck off from a med length trip or it happens to be warmed up for a while i'll get small chugs out of the exhaust just after the engine has stopped rotating. My CPS has less then 15k miles (the whole thing, not just cap).

prior to the change in fuel injectors it didnt run perfect @ wot but there was no real noticable loss of power/hesitaion. However i have noticed that my fuel economy has improved (subsatialy) sence the rebuilt injectors.

Thanks!

 

[blakshukvw]

That sounds like a timing issue when you say after you turn it off it chugs.

 

[2000StreetRod]

correct flow rate?

Are you sure that your rebuilt injectors are the same flow rate as the originals? If your fuel economy has improved but your WOT performance has decreased then maybe your engine is running lean. Do you have any diagnostic trouble codes set?

 

[gear_grinder]

i dont understand how it could be a timing issue with a distributorless ignition

no trouble codes, i tested my fuel pres. on wednesday and got a whoping 26psi with the regulator disconnected @ idle. After further inspection (aswell as last fall when i changed my fuel filter) i found a single red wire looped around the loom going back to the tank; and through the deduction of the fact that pulling the pump relay and hitting the inerta switch did nothing to stop the pump from operation, i'm beliving that it has been jerry rigged and is reciving a very poor amount of power.

 

[blakshukvw]

i dont understand how it could be a timing issue with a distributorless ignition

no trouble codes, i tested my fuel pres. on wednesday and got a whoping 26psi with the regulator disconnected @ idle. After further inspection (aswell as last fall when i changed my fuel filter) i found a single red wire looped around the loom going back to the tank; and through the deduction of the fact that pulling the pump relay and hitting the inerta switch did nothing to stop the pump from operation, i'm beliving that it has been jerry rigged and is reciving a very poor amount of power.

Well this explains your loss of power but not really the chugging after you turn it off.

 

[gear_grinder]

exactly, on that i'm leaning twords maf/TPS/ckps faults

 

[Explorer Junky]

I have a 5.0 also. I have noticed a severe "dog" when going straight to WOT. Your new cam could very well be the problem. Sometimes, when you go too radical on the cam for the Ex's, you need to get it re-tuned. Either custom tune or a SCT tuner along those lines. Could be that the new cam was not compatible with the timing set in the Ex's ECU. I have seen some cams in catalogs that will say next to the description of the cam "Not computer compatible" Thats why I only went with the 1.7 roller rockers instead of the stock 1.6 stock ones. I got the extra lift from the rockers only. Didn't mess with my timing. Call SCT or a similar company and see if they can help.

 

[blakshukvw]

exactly, on that i'm leaning twords maf/TPS/ckps faults

The last poster may be on to something. I also continue to come back to the chugging after you turn the truck off. I assume it's some sort of run on. That combined with the poor performance makes me think cam timing. Although if it's not engine run on you're experience, could it possibly be that your cats are clogged and the chugging you hear is the unburnt fuel detonating in the cats after you shut it off?

 

[gear_grinder]

clogged cats sounds closser, due to the fact that "chugged" after shutoff befor i rebuilt the engine when it was completely stock (internaly).

the OEM HO 5.0 cam is not really that crazy (not like a e303), so i wouldnt think that the OBDII PCM would have this much trouble adjusting to it

 

[blakshukvw]

clogged cats sounds closser, due to the fact that "chugged" after shutoff befor i rebuilt the engine when it was completely stock (internaly).

the OEM HO 5.0 cam is not really that crazy (not like a e303), so i wouldnt think that the OBDII PCM would have this much trouble adjusting to it

Yeah but what junky is saying is that you did a cam and rockers where as he did rockers alone. The rockers are giving you even more lift than the advertised cam specs.
Start by sorting your fuel pump wiring debocle and then check the cats and lastly cam timing.

 

[gear_grinder]

Yeah but what junky is saying is that you did a cam and rockers where as he did rockers alone. The rockers are giving you even more lift than the advertised cam specs.
Start by sorting your fuel pump wiring debocle and then check the cats and lastly cam timing.

Um stock ratio rollers (1.6)? dont asume that they are 1.7s

I have faith in my cloyes timing set after compairing it with the stock double roller chain "dot to dot" marks

fuel pump is rewired (12ga wire) i picked up aprox 10psi across the board, but the press is still low. Through testing and prosess of elimination, the regulator/fuel filter is good but the pump is weak/bad.

 

[gear_grinder]

The last poster may be on to something. I also continue to come back to the chugging after you turn the truck off. I assume it's some sort of run on. That combined with the poor performance makes me think cam timing. Although if it's not engine run on you're experience, could it possibly be that your cats are clogged and the chugging you hear is the unburnt fuel detonating in the cats after you shut it off?

the chugging is not part of a run-on (diesel), the engine has completly stopped and then chuggs.

 

[2000StreetRod]

Correct firing order?

hey,

i've gotta 97 gt40p, its got: HO mustang cam, roller rockers, brandnew rebuilt fuel injectors, SRI, "catback" exhaust, and a TF 1" spacer.


after i installed the new(rebuilt) fuel injectors and reset the PCM, the truck feels like it has no power under WOT, . . .

Thanks!

Are you running the correct firing order? I seem to recall that the firing order for all 5.0L roller cam engines is 1-3-7-2-6-5-4-8 and the firing order for the early 302 is 1-5-4-2-6-3-7-8.

 

[gear_grinder]

Are you running the correct firing order? I seem to recall that the firing order for all 5.0L roller cam engines is 1-3-7-2-6-5-4-8 and the firing order for the early 302 is 1-5-4-2-6-3-7-8.

the HO was introduced in 86, its always been a roller cam/bock. so im running the OEM firing order (13726548)

and a side note, got the pump in and it made perfect pressure. After that the truck came to LIFE!