i bought this truck for $200 the guy said it needed a motor and the valves where bad in the 7th cylinder when i got it home it started but barely ran i checked the fuel pressure first and it had none after i changed the fuel filter it jumped to about 38psi then i changed the plugs from autolite to motorcraft got it started but still ran rough and idled at around 600 rpms ive cleaned all injectors its getting fuel and fire to all cylinders but still only running on 1-3-4-and#8 cylinders ive got the light to come on and pulled code p0340 camshaft sensor malfunction makes some sense cause it sounds like its off timing to me so what do u think? please help!!!

 

Have you done a compression test yet? If it's got bad compression in one or more cylinders there's not much point in chasing down electrical issues.

 

Which V8 are you referring to? The two 8's have different ignition systems, - so it would be a good idea to let us know. How did the previous owner determine bad valves ? - What happened to it ? Were the heads off at some point ? How many miles on that 98 ? Hopefully, you know a little more about the engine than what's posted so far. If the previous owner reports bad valves, - then he knows something alright lol, - just about has to.

Isn't the PCM throwing misfire DTC's at yuh ? You only have a 340, that's it?

Somethings goofy here, I don't think it's me.

Well, so far, IMO and if you hadn't mention the "bad valves" , AND you were running a CoilOverPlug system, I would think it was a PCM problem.

Bad valves on opposite sides of the engine and all at once? Like I said, sound like it could be coil drivers (PCM). I can't believe it's not giving you more direction, -other than the 340. - You should have a list of dtc's as long as your arm, if your only running on 4 cylinders.

BTW, - Compression Test is a good idea, - that should have came before the new fuel pump tho, - since you were informed about the valves. Doesn't matter now, I'm just sayin.


So..... - What's the scoop mks ?

 

the engine is a 4.6l the kid i got the truck from knows nothing and sent it to the garage and they said that the valves in the #7 cylinder got sucked into the head im not shure how they came up with this theory they never pulled the heads off all they did was took the plugs out! keep in mind this garage was a one bay backyard mechanic!! with **** for tools! ive checked all the valves and they are good this truck has 185k so ill do the compression test like u suggest and let u know if i get more codes ill be shure to post them oh and i changed the cam sensor but still no change still only running on #1 #3#4and #8 cylinders?

 

I'm too lazy to search for the coil pack/cylinder assignment, but I don't *think* 1, 3, 4, and 8 are all on the same pack. The 98 4.6 uses 2 coil packs and plug wires, not COP.

I wonder if some of the plug wires are crossed? You need to find the cylinder assignments and verify that the wires are all run correctly. Stop throwing parts at it and troubleshoot with what you have.

If the valves on #7 are sucked in, why isn't #7 missing? Strange. A compression test and verification of correct coil to plug wiring will help clear things up.

Are you sure you are calling the cylinder numbering correctly? #1 is front passenger side, 2, 3, and 4 go back from there. #5 is front driver side, with 6, 7, and 8 going back from there.

Have you pulled the plugs out yet and looked at them? I guess you will be when you do the compression test.

 

i've double even triple checked some things the wires are all in the right location and all are firing iv'e checked all the plugs and i just put new ones in two days ago even if the #7 valves where bad it wouldn't account for the multiple cylinders not working ill do a compression test tomorrow n let you know and i'm very familiar with the cylinder order what iv'e said is correct #1 #3 #4 #8 all not working iv'e determined this by pulling the plugs one at a time while running and no difference iv'e unhooked the injectors pertaining to those cylinders and they are working iv'e checked each plug on those cylinders all are firing perfect! with all that said does anyone think it could be anything else other than compression? cause i'm going to do the test tomorrow and i think the only thing left is the pcm?

 

Have you checked to see if those plugs are actually firing with an inductive tester that you hold up to each plug wire? You can also do this with an old-school timing light with an inductive clip.

All 8 plugs look good - not burned or fouled?

 

Sounds like the PCM is toast. A strange way for it to go out.

How did you check the valves, - finger over the blow hole lol ?

Say the PCM is good and your misfiring on 3 out of the 8 cylinders. Misfire is low grade, so monitor count is within parameters. (Often, low grade misfires do not log a DTC until they become worse yet.) Crap I have to get out of here, - just try this. -Bypass the EGR valve. These engines misfire like hell when that valve hangs open. Hit it with a hammer a couple times or just by-pass / plug it up/cap it of/ start the engine.

 

okay so i just went out and started my truck i put some injector cleaner in and wanted to let it run for a bit it started and idled at 600rpm's after about ten minutes it idles up to 700rpm's and when i rev it up it vibrates bad until it gets over 2000rpm's then smooths out and almost runs fine!! lol almost shortly after it stalls and spits out two codes for me p1131 p1151 okay so the sensor goes to the pipe which connects the EGR to the exhaust upon inspection the pipe wasn't connected to the exhaust manifold the nut was completely rusted off i'm sure its y the light came on but not y my truck is running the way it is but i told u i would post any new codes i pull so here y'a go

 

Have u checked your coil packs them selves? Wires? U said you changed your plugs but nothing else? I have a 4.6 as well 97 and if one little dumb thing is wrong it has a grenade effect. U fix that one thing and everything is fine.

Hope that helps

 

Compression test, please. That is going to REALLY help develop this story........

 

Posting everything that's going on is to your benefit, not ares lol. So, - still, don't think your to smart for us. I don't care if the EGR pipe is broken or not. If that valve is stuck open, IT can make her miss like freakin crazy. You do want help right. Confirm valve is closed, - since that's the easiest thing to do and quick.


Then compression test. I'm thinking that engine is spent honestly.... You might get lucky.

 

BTW -CompressionTestProcedure = My Sig -