f1501999

I have a problem with my 1999 F-150 4.6 106,000 miles on it. The code says it is miss firing in cyclinder 5. The plugs and wires where changed and the coil block for that side was also changed today. It runs really rough and it you can feel and hear it back fire, could someone tell me what the problem might be. The engine light went off after it was changed. Now after driving it around the engine light came back on and it still reading miss firing in cyclinder 5

bipolardave

Fuel injector?

Long shot, but my truck had a leaky exhaust manifold gasket that caused some EGR codes and a misfire code.

It was really loud when cold but gradually grew more quite as the engine warmed up.

cvz_finezt

u can check to see if the injector is getting power. and if it is and still nothing, then u have a bad injector. if it was something else in ur fuel system or ignition, u would be having multipule/ random misfires.

f1501999

He did a compression test and found out that the cylinder is losing compression. It could be a possibility. would this cause a miss fire and this did not happen until after the plugs and wires were changed.

cvz_finezt

u need 3 things in order for the engine to start. 1.Spark, 2. Fuel, 3. Compression. without these u got a paperweight. and the EGR will cause a misfire, cuz to simplify it u have too much air and not enough fuel to burn it.

f1501999

EGR will cause a misfire would that also show low compression test, he told me i would need a another engine... Should i take it to the dealer to see what they say?

cvz_finezt

low compression cane be caused by a few things, the mostly likely in ur case would be worn piston rings. a used engine would cost far less then a rebuild. but with the rebuild u can add higher compression pistons and forged rods. if memory serves, the 99 4.6's had 9.4:1 CR, so 10.5:1 would be a good jump but still staying streetable. granted u would have to use premium fuel, but u will have more power, cleaner burn, and some added MPG's. u would probably seean increase of power in the 10% to 13% range. and u have the excuse to put better heads and more aggresive cams too. just some food for thought

f1501999

I notice now that when i first start my truck up all the gages are doing funny things ie they all going back and forth for a few seconds this never happened before. is this something elerctrical could be causing my problem ?

cvz_finezt

thy should all do it once, from min to max, it's self checks. but if they are doining it more then once then ur dash is messing up

BolletuH

I would agree with the worn piston rings, but something that needs to be noted is whether the compression changes dry or wet.