1998 Chevrolet Suburban Repair Question
My K2500 Chevy Suburban 7.4L runs fine cold but within 5-10 miles starts to falter.
what is the fuel pressure. also try tightening your intake bolts down if they are 10mm heads. they loosen up with that motor and cause a vacuum leak. it shold be 60-66on a CSI system or 56-62on SFI check for a vacuum leak by apraying choke cleaner around manifold. clean throttle plate with choke cleaner on both sides as well. if you have a J in vin that is engine code for SFI
Thanks for the reply. I'll have to borrow or buy a tester that I can read while driving.
everything can be done with just turning thekey on not driving
While I'm at it, is the ECM module's reported psi good enough to use, or do I need to get a tester? Also, what Is acceptable Vacuum on this engine?
20" at idle if at 15' or belwo suspect a clogged converter/exaust system. you really should check fuel pressure with a gauge. yours should be 56-62 psi
Fuel pressure is 60-62psi under load. At idle maybe 10-15psi lower. Exhaust back pressure was measured by mechanic. He had been so convinced it was clogged converters he had already ordered replacements. He said the pressure was fine, but didn't tell me the actual pressure reading.
I'd still like to know where the ignition ground point is. It still seems like an intermittent ground... like not enough current flows to something when I get up to speed on the highway and things heat up. If I take my foot off the pedal, it runs fine. Just a little bit of acceleration causes it to start missing.
fuel pressure should be 56-62 at idle not under load, so try changing your fule filter first. Also thos eused toloosen the intake manifold bolts as they are only 8 mm. so makesure that they are tight. they sould be 30 ft.lbs. the ignition ground is at teh right top of cylinder head it is a black w/white stripe wire and they are porbably a few there . One other thing to check is the shield around the konck sensor, some were loose and hit the knock sensor an dit retards the spark it's on eithe rside of engine by motor mount..
Great ideas, I'll try. I've already replaced the fuel filter twice... once before replacing the pump, once after.