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Random Difficulty Starting + Valve Clatter With Throttle Input?

alwcurlz

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alwcurlz Enthusiast

alwcurlz

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I searched on the forum here and didn't find a topic so I'm creating one.

 

1999 Chevrolet Silverado, GMT800, 5.3V8, 135,800 miles.

 

I'm starting to have the same problem again as I did before I did the below items, except the plugs.

Already put new plugs in, gaped according to spec. I've had the intake fogged, fuel system/injectors purged, new fuel filter.

 

What's happening is this: When starting the truck, it acts like it's not getting fuel and tries to start and stutters/sputters, spinning up the starter till it starts, and won't start until I run the starter long enough. It runs rough, shaking some and then smooths off some. The other thing that's really bugging me is the valve clatter. The valve clatter happens when the truck is good and warm. It occurs while driving whenever I give it throttle, going straight down the road or uphill. It happens at lower speeds like 40mph if I tap the accelerator. I'm using Chevron gas with the Techron added and have used the Premium and Regular octane with no change. Shouldn't the computer be correcting this or detecting it? It isn't a knock so the knock sensor won't pick it up. Maybe it's pre-detonation? Bad injectors, spark plug gap wrong? Bad MAF or TPS?

 

 

 

Anyone with experienced ideas?

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superjim Senior Enthusiast

superjim

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Noticed in your SIG LINE...you have HP Tuners.

 

What is your initial timing and what is the max timing advance.

On older cars...valve clatter (we used to call it labor knock) was usually caused by too much TOTAL timing..ie..plugs are firing too far before TDC.

 

Might try pulling the advance back just a little.

 

Just a thought....

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alwcurlz Enthusiast

alwcurlz

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Noticed in your SIG LINE...you have HP Tuners.

 

What is your initial timing and what is the max timing advance.

On older cars...valve clatter (we used to call it labor knock) was usually caused by too much TOTAL timing..ie..plugs are firing too far before TDC.

 

Might try pulling the advance back just a little.

 

Just a thought....

 

I havn't uploaded a configuration yet, been real busy but am really eager to do some things. It's all stock yet in the computer.

 

Thanks for the tip!

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alwcurlz Enthusiast

alwcurlz

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sounds like pre-detonation and may be a bad fuel pump relay...I know the older chevys had a deal where if the FPR went out you could crank on it untill it built up oil preassure then it would start .....similar to what you described

 

Hmm...fuel pump relay. Well, this is a GMT800, you mean older Chevy's like, GMT400's?

Thanks for that info! I'll provide more detail here as well if it helps. When I first start it cold, it starts great, runs great. Once warmed up and sitting for 30 minutes, it's sputtering on startup and I have to hold the key over till it starts. If it sits for several hours, it'll start, but runs a bit rough.

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alwcurlz Enthusiast

alwcurlz

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Fuel pressure regulator leaking fuel to vacuum lines, causing rough running when started up

 

So, there is a fuel pressure regulator that is controlled by vacuum? I'll have to take a look and try finding that.

Thanks!

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alwcurlz Enthusiast

alwcurlz

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Fuel pressure regulator leaking fuel to vacuum lines, causing rough running when started up

 

Thanks!! I checked online to see where that was located and found a topic on automotiveforums.com where several people encountered the same issue and resolved it with that part replacement. I'll let you guys know how it turns out! Been wondering what went wrong lately with the fuel mileage drop I was getting!

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alwcurlz Enthusiast

alwcurlz

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Well, I bought a replacement fuel pressure regulator and that fixed the difficult starting! Starts noticeably quicker.

 

Here are some pictures of the regulator and location, as well as pictures of the fuel present on the vacuum side which should not be there at all.

 

20090221_01490.jpg

 

20090221_01491.jpg

 

20090221_01492.jpg

 

20090221_01493.jpg

 

Here are pics of the regulator and replacement. The new replaceent was a little different and likely an

improved design. Notice the collar which is plastic on the old one is built into the unit and metal on the

new one.

 

20090221_01494.jpg

 

20090221_01495.jpg

 

20090221_01497.jpg

 

Another note: This unit was quite difficult to re-install with the new seal so I used some oil to make it a

little easier to seat into the hole.

20090221_01498.jpg

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alwcurlz Enthusiast

alwcurlz

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Nice job on the install and grabbing some pics. Let us know how it runs out on the road now. Did that clatter disappear?

 

Thanks. Unfortunately, the clatter is apparently there yet. I think it's poor gas in this area. Texas is the only state that does not guarantee the quality of fuel we get. :lol::mad:

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bylekurch New Member

bylekurch

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My 5.3 has the same problem when starting. . . I'm going to try that part change you did.

And as for the pinging while going up hills. . . I'm not sure what causes that but when I'm in town under 50 mph I run my trany in third gear so it don't lug out up hills.

My truck likes it more since Chevys don't have low end they seem to bog out when there in over drive under 50 mph.

As for the ping run a higher grade gas or octane booster. . .

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  • 1 month later...
spdam068 New Member

spdam068

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I have a 2002 Chevy Avalanche with a similar problem. It starts very hard and when it is cold out (below 30) it also idles rough (kind of a rolling idle) until it warms up. It also had the raw gas smell. I took it in and they replaced the fuel pressure regulator and it seems to fix it. It happened to be warm at the time time. The fuel smell is gone but the it still starts really hard and the idle will roll if it is cold out until it warms up. And other suggestions to fix this? Thanks

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