98 s10 won't idle, makes knocking sound

l have a 98 s10 with the "x" code 4.3l. While driving the cel started flashing and it lost all power. after got home i scanned the codes and revealed a MAF sensor error. replaced the maf sensor, which did not help. then replaced the cap, rotor, and wires as they were burned through. This made the truck run fine when given gas, but makes a knocking sound at idle and stalls. any ideas?

Have you checked fuel pressure and leakdown?
Are you sure the cap is wired correctly?
Easy mistake to transpose the wires for
#1 & #3 on the cap ;)

http://i561.photobucket.com/albums/ss58/cwhook/96newer43Lplugwires.jpg

checked all of the wires, and they are in the right place. it also appears to be getting too much fuel.

Next step is check fuel pressure and leakdown. Most auto parts stores rent/sell/loan fuel pressure testers. Do you have access to one?

can see if can get one. the only diagnostic tool have is a obd ii scanner for my pc

When you have the tester, let us know and we'll help you with the diagnosis, (it's not difficult at all).

I did go back out today and check the MIL codes, this time they are showing P0123 and P0124 which I believe are TPS errors.

Do you have the fuel pressure tester? If not, let us know when you have it and we can explain how to check fuel pressure and leakdown.

If you follow this flow chart, (there are 2 pages), it will pinpoint the throttle position sensor DTC's.

http://i11.photobucket.com/albums/a187/swartlkk/2000%20Bravada/P0123_diag1of2.gif

http://i11.photobucket.com/albums/a187/swartlkk/2000%20Bravada/P0123_diag2of2.gif

So I ended up replacing the TPS, which cleared up those codes and made the truck idle. At the same time it also got a brand new fuel filter. The only problem it has now is a bit of a rough idle, code P0101, and a flashing SES light occasionally while driving. It has a brand new MAF sensor, so im not sure what would be pulling the P0101 code.

The flashing SES light indicates the engine is misfiring and the misfire can damage the catalytic converter. Retrieve the DTC's again, the flashing SES light should have set a DTC in the P0300 series, (it may be in the pending file). P0300 series DTC's are almost always caused by faults in the secondary ignition system, (spark plugs, plug wires, distributor cap, rotor & ignition coil). It can also be caused by low fuel pressure and incorrect camshaft retard. The P0101, (mass air flow sensor or circuit problem) can be set falsely if fuel pressure is low. Do you have access to a fuel pressure tester?

I haven't been able to obtain a pressure tester as of yet. Have driven it a bit and it still occasionally flashes the SES light, and the fuel economy is horrid. I did take this video of the startup and idle sound, as well as me hitting the gas a bit.

http://www.youtube.com/watch?v=kO05-RcKwFg

When you have the fuel pressure tester, let us know and we'll help you with the test. Most auto parts stores rent/loan the tester. You get your money back when you return it.

55PSI is what the tester shows, and it holds there with the key off. When I drain the pressure and turn the key on it comes right back up to 55 PSI.

Your fuel pressure is too low. Key ON engine OFF, fuel pump running, it needs to be 60psi to 66psi. Your reading of 55psi tells us there's a problem, but it doesn't tell us what it is. The next step is disconnect the quick connect fitting from the fuel filter, and connect the pressure tester to the fuel filter. This will require some "creative plumbing" on your part. All fuel pressure and flow must end at the fuel pressure tester. With the tester connected like this, key ON, engine OFF, fuel pump running pressure must be 73psi to 108psi and it must remain above 55psi for at least 10 minutes after the pump shuts off. Post your resutlts.

Well the fuel pressure at the filter is 95PSI and it holds pretty well. It falls slowly but I attribute that to my creative plumbing.

As long as it remains above 55psi for at least 10 minutes, it's fine. Your results show the pump is able to build sufficient pressure, which means the problem is in the plenum. Reconnect the fuel line at the filter.

Double check regulated pressure. Connect the tester to the service port by the distributor. Key ON, engine off: pressure must be 60psi to 66psi while the pump is running. If it's low, the fuel pressure regulator needs replacement.

Well took a look at the pressure regulator, and the vacuum line for it is missing. Guess that could be a problem.

The inside of the plenum has manifold vacuum so no vacuum line is necessary. What were the pressure readings with the pump running, and 10 minutes after the pump shut off?

It didn't hold pressure for 10 mins, but I believe that was due to my plumbing at the filter. At the schrader valve it held that 55PSI for a full 10 mins just fine.

I found that one of the poppets on the injection system was damaged on the end. I think i'm just going to pick up a MFI unit for it.

The problem is the regulator is set too low. The upgraded injector assembly comes with the regulator, and if you get a Delphi unit, it comes with the new mounting bracket for the injector housing, (necessary). Check pressure and leakdown after replacing the unit, and post back with your results.


http://ww2.justanswer.com/uploads/Bluegorilla/2010-10-25_003337_injector_conversion.pdf