engine surge
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engine surge
I have a 90 model F-150 4X2 equipped with a 4.9L in-line six engine and manual transmission. I have an engine surge problem. At cold start, the surge is very slight, but before the engine becomes fully warm(while driving), the engine surges badly under load at mid throttle position. After the engine fully warms up, it surges only slightly, much smoother but still noticeably there. Thus far, I have changed; spark plugs, wires, cap, rotor, Air By-pass valve, MAP, TPS, EVR, air and fuel filters. I removed the EGR valve, but it appeared to function properly. I also inspected the fuel pressure regulator and it was OK. NO FAULT CODES RECORDED.
When the truck was new during cold start, the engine RPMs were high for several seconds, then would drop to a lower RPM. The idle RPM was also higher then. Now when cold starting, the RPMs are high but for a shorter time, and the idle RPM is lower.
Any suggestions would be appreciated
When the truck was new during cold start, the engine RPMs were high for several seconds, then would drop to a lower RPM. The idle RPM was also higher then. Now when cold starting, the RPMs are high but for a shorter time, and the idle RPM is lower.
Any suggestions would be appreciated
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Joined: Feb 2000
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engine surge
There have been several posts with simliar problems to yours(mine as well). One solution that did get some air time was building a restrictor plate for the EGR. The theory being , that the older engine with a speed density EFI cannot compensate for the 4.9's decreasing ability to utilize EGR gases in the firing cycle. The restrictor plate suggested was a stainless steel plate cut using the EGR gasket as template. A 1/4 inch hole would be drilled to allow some EGR passthrough.
To help you with the diagnosis, you can plug the egr vacum line that goes to the EGR valve from the EGR solenoid and see if the problem(surging) persists. Unfortunately EFI needs EGR feedback for mixture calibration so this is not a permanent solution.
WHaynes
93 F150 4.9L 4x4
4" ProComp StII Lift
BFG 33in 4.10's
Detroit TrueTrac's
To help you with the diagnosis, you can plug the egr vacum line that goes to the EGR valve from the EGR solenoid and see if the problem(surging) persists. Unfortunately EFI needs EGR feedback for mixture calibration so this is not a permanent solution.
WHaynes
93 F150 4.9L 4x4
4" ProComp StII Lift
BFG 33in 4.10's
Detroit TrueTrac's
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Joined: Feb 2000
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From: Wichita USA
engine surge
Remove the vacuum line from the EGR valve and drive it for several days. If the problem is gone the build the restrictor plate. It fixed mine.
2000 XLT Flare Supercab Sport 5.4-Auto-355LS-Tow pkg-Bedrug-Xtang Tonneau
2000 XLT Flare Supercab Sport 5.4-Auto-355LS-Tow pkg-Bedrug-Xtang Tonneau
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Joined: May 2001
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engine surge
Nope, don't think so. My 91 is speed density, and I know that Ford sells maf conversion kits for lightenings so they were still doing SD in 1992. I don't know when they moved everyting to maf.
John.
91 F-150 5.8L 4X4
John.
91 F-150 5.8L 4X4
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