7.4 rough idle

[1998454]

My truck has had a rough idle as long as i have owned it and it's finally getting on my nerves a little. It has had the injectors and fpr replaced. Also had the entire ignition system replaced and the rough idle has never changed. I have done the usual ether check of the lower intake gaskets and they seem fine. I thought it was just normal for these engines until i drove my friends truck and it idles real smooth. Has anyone here ever had this issue and resolved the idle problem?

[454cid]

Mine doesn't run all that smoothly, either. It's done that for years.

[Steve 68]

I am also having missfire problems at an idle. I have done fpr, injectors and ignition and 0411 swap. The only thing I have not done is the aluminum distributor. Not sure if this will work but this is what I was told.

stroker97k1500
Posted: Mon Mar 26, 2012 2:16 pm

One great upgrade I would recommend is to replace the distributor with the $50 aluminum one on eBay
The aluminum distributor has a new gear( this is why the random misfires usually occur on the 5.7 & 7.4L engines.) They eat off the distributor gear. Also the plastic base cracks where the cap tightens down.... The aluminim fixes this.... Has new cam sensor, rotor, and cap for the price of a cap and rotor.

stroker97k1500
Posted: Mon Mar 26, 2012 1:00 pm


The distributor gear WILL wear out and need replacing. It causes random misfires and surging. The aluminum one has a everything new and does away with the plastic crap also for the price of a replacement own gear.

[454cid]

I've got a new Delphi to put in my truck.

[1998454]

Mine has a newer distributor but still plastic. It idles like it has a big cam in it. Sometimes when restarted hot if i put it in gear too soon it will stall the engine.

[99urbansuburban]

how is the coil? also regap plugs to .045 .050 that helped mine

[1998454]

Coil is new, it idles the same with the plugs gapped at .045 or .060. Strange thing is my truck likes .060 as far as fuel mileage goes. I'm starting to think the lower intake is leaking even though I can't find it with ether.
how is the coil? also regap plugs to .045 .050 that helped mine

[1988 GMC 355]

That would cause a surgy idle, probably hard to find with ether if it is the lower, is it losing coolant at all?

[1998454]

No coolant loss at all. As soon as it comes off idle even 100rpm over it is real smooth.
That would cause a surgy idle, probably hard to find with ether if it is the lower, is it losing coolant at all?

[1988 GMC 355]

Wierd, maybe just carboned up? Have you tried seafoam through the vac hose?

[1998454]

No i haven't. I will try that tomorrow. Carbon buildup may also explain the noise i started hearing last week. when the engine is hot and i pull a hill at maybe 30 mph in second gear there is a chattering noise that sounds like pre ignition. It sounds exactly like an older engine that has had the timing advanced way too far.
Wierd, maybe just carboned up? Have you tried seafoam through the vac hose?

[1988 GMC 355]

Is base timing correct? and if you have never done it then it will definitely help, it is cheap and worth a shot.

[1998454]

I would have to get ahold of a scan tool to check it. It was set with a tech2 hooked up when the distributor was replaced. the idle has never gotten worse but this new noise may be a timing issue. I'm going to hook the programmer up and return it to stock and see if the noise goes away.

[454cid]

My truck uses coolant. It always has. I had the lower intake gasket replaced several years ago, and the mechanic that did it said that it looked like GM didn't get the sealant on it, in one spot. He then used the wrong stuff on the bolt threads so it's leaking somewhat again....... started not to long after he worked on it. I pulled a bolt out and it looked like he had used some sort of thick black sticky gunk on it. GM specifies what is essentially blue loctite. It doesn't leak a lot, and I've been keeping the overflow filled. The place where it leaks is the front passenger side where the block, intake and head all come together.

[99urbansuburban]

My truck uses coolant. It always has. I had the lower intake gasket replaced several years ago, and the mechanic that did it said that it looked like GM didn't get the sealant on it, in one spot. He then used the wrong stuff on the bolt threads so it's leaking somewhat again....... started not to long after he worked on it. I pulled a bolt out and it looked like he had used some sort of thick black sticky gunk on it. GM specifies what is essentially blue loctite. It doesn't leak a lot, and I've been keeping the overflow filled. The place where it leaks is the front passenger side where the block, intake and head all come together.

That is where mine leaked also, I replaced the lower gasket used gasketcinch on the gasket and mateing surfaces, used silicone for the front and back of the intake and the bolts

[98454]

Check the modulator inside the distributor... it gets too hot back there for them sometimes

[buick_93]

Check the modulator inside the distributor... it gets too hot back there for them sometimes

What would be the remedy for this adding heat sink grease? Mine runs smooth until it gets warmed up and then I get a random misfire that is very noticeable with the exhaust. I checked my distributor gear when I did the lower intake gaskets and it was not knife rolled at all. Would having non-adjustable rockers arms cause this or would it misfire all the time with loose valves? I though I read somewhere that going to adjustable rocker arms made it run smoother/quieter?

[98454]

What would be the remedy for this adding heat sink grease? Mine runs smooth until it gets warmed up and then I get a random misfire that is very noticeable with the exhaust. I checked my distributor gear when I did the lower intake gaskets and it was not knife rolled at all. Would having non-adjustable rockers arms cause this or would it misfire all the time with loose valves? I though I read somewhere that going to adjustable rocker arms made it run smoother/quieter?

I honestly don't have a remedy I just have always replaced them on a regular basis (8-10 thousand miles )

[EmersonHart13]

http://www.ebay.com/itm/BILLET-vortec-V8-5-7-350-5-0-305-7-4-454-distributor-/320605212568?pt=Motors_Car_Truck_Parts_Accessories&hash=item4aa58f4f98&vxp=mtr#ht_13371wt_1170

http://www.ebay.com/itm/BILLET-vortec-V8-5-7-350-5-0-305-7-4-454-distributor-red-/220959301604?pt=Motors_Car_Truck_Parts_Accessories&hash=item3372335fe4&vxp=mtr#ht_13224wt_1170

Lifetime Warranty:
http://www.ebay.com/itm/BILLET-vortec-V8-5-7-350-5-0-305-7-4-454-distributor-/330690534208?hash=item4cfeb11b40&item=330690534208&pt=Motors_Car_Truck_Parts_Accessories&vxp=mtr

Anyone know the difference between the first two? The third has a better warranty...

Thanks,

John

[454cid]

One has 2 pictures, the other has 3...... I see one has a higher price. I suspect they're trying to find a sweet spot on price. I've seen sellers do that kind of thing before. I'd rather go OEM than buy a chinese distributor. There is another company that sells US made billet distributors....... they're a lot more expensive, Though. They're on Ebay, too.

[EmersonHart13]

I know I need to do a cap and rotor and figured if I could do the Distributor for not too much more I would do the whole thing. I have seen mention of it before on the site and I am yet to see a bad review. Decisions, decisions...

[454cid]

I'm not sure what the price is now, but I got a new Delphi distributor on Amazon for about $100. Delphi is the OEM. Cheap caps are generally considered sub-par on these distributors since the connections pass very close to each other. Buying the Delphi from Amazon is like getting a dealer part at a discount parts store price.

[EmersonHart13]

I have a Delco Cap and Rotor sitting on my parts bench... This wouldn't even be a question if I wasn't having such a hard time doing it. I was considering paying someone and if I am going to do that I was going to pay them to do the whole thing so I knew it was good for a long, long time...