Ad Radar
Item Posts    Sort Order

Fuel problems 97, 5.7

 
raymak
I love my Chevy Chevette!
Posts: 5
Joined: 11/12
Posted: 11/10/12 12:37 PM

I have a 97 chevy van with a 5.7 fuel inj. engine. At highway speeds above 75 mph there is a miss or pulse under easy throttle, usually after cresting a hill.Found a split vacume hose, fixed it and that helped. put in a new fuel pressure regulator and it helped a little also but still have a bit of a pulse. I've changed the fuel pump two or three years ago and replaced the fuel filter regularly.Checked fuel pressure and it was 64 psi. Any help would be greatly appreciated!  

Post Reply
waynep71222
My first time was in a Chevy
Posts: 218
Joined: 04/12
Posted: 11/10/12 02:02 PM

i am taking that it is a VORTEC motor.. with spark plugs wires coming horizontal out of the cap..

carefully so you don't loose them.. pull the cap... turn it over and check the insides for carbon tracking..   examine the rotor.. or just flat out replace both..  if you have not already done that..

while you have the cap off.. grab the rotor or the top of the distributer shaft.. see if it wiggles side to side.. it should NOT..  the distributers do wear out...  

again grab the rotor and rotate the shaft...   does it move any .. the drive gears have been found worn away...  just paper thin layers of gear teeth left..  

look at the ignition coil for signs of high voltage leaks...  i have had to replace almost every vortec distributer cap and rotor.. and i have had to replace the Ignition COIL on every one i have worked on the first time..

do you have the air inlet properly secured down?? the big hose into the throttle body.. from the air cleaner with the maf sensor.   usually they clip down at the front of the throttle body and have a Plastic Tall T nut to hold the back of it down...     air leaks between the MAF sensor and the throttle body will cause issues...

before you get any idea about changing the timing.. or removing the distributer... be aware that it has to be PERFECT.. and set with a scan tool...  the ignition timing is controlled by the crank sensor in the bottom of the timing cover.. the distributer contains the camshaft position sensor.. and the rotor to distribute spark to the closest cap terminal...  

lastly.. next time you are under the front.. you might want to take a 5/8 six point socket and a short extension..  on a breaker bar... try to adjust the breaker bar.. and use plastic bags over the square drive ends to tighten the fit of the extensions and sockets...   see how much slack you have in your timing chain set..  if you can rock the crank back and forth.. about the MAX the system will contend with is about 9/16" of movement on the outside of the damper..   you will be able to feel this as you rock the crank with the breaker bar..  

Post Reply
pepsi1
Big Block power for the win
Posts: 940
Joined: 03/11
Posted: 11/10/12 03:12 PM

raymak
I have seen new fuel pumps that were changed in a couple months prior to a fuel problem. Turn out to be the fuel pump again.

I wish there was an easy way to check the fuel pump, but there really isn't. You need to find up what the pump is doing under a load. After doing what Wayne has suggested. Look at the spark plugs really well. If they are sooted and the distributor checks out, get on the fuel rail and check that fuel pressure.

Bob  

Post Reply
raymak
I love my Chevy Chevette!
Posts: 5
Joined: 11/12
Posted: 11/10/12 03:15 PM

Thanks, yes its a vortec engine, new gm replacement that I put in ten months ago so the cap & rotor are brand new with 10,000 miles on new engine. Haven't replaced the ignition coil though.
I was looking more at the fuel system for the problem since the fuel system is vacuum regulated.
I will check out the ignition coil, thanks.  

Post Reply
waynep71222
My first time was in a Chevy
Posts: 218
Joined: 04/12
Posted: 11/10/12 06:07 PM

hmm....   new motors don't always come with distributers and caps...

do to the cross over conductors embedded in the cap.. they tend to create issues when they go bad... at least with a van.. you can pull the inner cover to get at it without needing to climb on top of the motor..

look at whats hidden inside the cap..

Vortecv8distributercap

do me another favor...  with the engine idling.. find the fuel pump relay and PULL it out ...

the engine should NOT die.. i have had terrible issues with the oil pressure switch failing to supply enough power to operate the fuel pump properly...
you can see the contact bar.. that raises up when the oil pressure comes up and bridges the contacts in the cap below..
Gmoilpressureswitchfuelpumpswitch1

what happens.. the contacts get dirty.. don't conduct power properly..  forcing the relay to handle all the current all the time.. melting the relay terminals and socket terminals..
the relay contacts also get worn ..
Gmoilpressurefuelpumpswitch3


this is from a 98 C2500 pickup... the contacts in these get dirty also..

Chevyignitionswitchtornapart


it takes either an E4 or E5 torx external socket to get the column shroud off and to remove the turn bolts holding this and the turn signal switch to the column.
probably won't cause the surging issues you kinda describe..


lastly...   if you can find a professional scan tool... get into the factory tests...  find the EGR...

sit there and with the key on.. engine off..    ramp the EGR valve open to 100% and down to 0% a few times....

then start the engine...   bring it up to 2500 rpms.. or so... ramp the EGR valve open to about 40 percent.. perhaps 50 percent..    if you have a friend to drive the van.. take it out with the scan tool... get up to 40 or so.. on a long stretch.. ramp the egr to 70 percent for no more than about 10 seconds.. this blows any crud through,   go to the live data.. the EGR should start at 0% and open to about 45% at 45MPH or so..    amounts vary.. but you should see 45%..  

Post Reply
raymak
I love my Chevy Chevette!
Posts: 5
Joined: 11/12
Posted: 11/10/12 07:19 PM

Thanks! I'll give it a try.  

Post Reply
TO TOP