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4.0 missing and stalling
Hello, I have a 95 4.0 ranger that seems to be missing mainly noticeable at idle. Smell of unburt gas out the exhaust. The day it started driving home if let off the gas to slow down the engine would die but start right back up. MAF and IAC are new. Getting spark on all cylinders. Also tried to pinpoint to individual cylinder running with each plug wire off and runs consistently with any individually pulled. No codes, can’t find any vacuum leaks, no exhaust leaks, any ideas what to check next? video of engine running and exhaust... I couldn’t get the idle to drop to really show how rough when trying to take a video but can hear more from exhaust. https://photos.app.goo.gl/Cnq6PIn8oDKBKmoD2 https://photos.app.goo.gl/Fi0jEO57pppLD0Zl1 Been searching and reading through endless forum posts just don’t know which direction to try first to avoid just throwing parts at it. thanks for any help! |
It sounds like it has a vacuum leak. (from the video)
When truck is fully warmed up, pull the plug off the IAC valve, engine should drop to 500 rpm or stall. Either is good, if it continues to run, then you have a vacuum leak. It also sounds like it's running rich. Replace your coolant temp sensor, don't get it confused with the sender for the gauge, that will have one wire on it. The coolant temp sensor will have two wires on it. They're inexpensive. If the coolant temp sensor is faulty, it tells the PCM that it's either running rich or lean and in your case, too rich. EDIT: It's only 13 bucks. https://www.rockauto.com/en/moreinfo...138047&jsn=483 https://www.rockauto.com/en/catalog/...+/+sensor,4748 |
Also check the Fuel Pressure Regulators(FPR) Vacuum hose
behind alternator on top of lower intake manifold FPR has a Fuel line and a Vacuum line connected, check vacuum line for gasoline FPR can leak internally over time and raw fuel gets sucked into the engine via the vacuum line, causing rich running and poor running as well |
Thanks for the ideas. I will pick up a collect sensor tomorrow and swap one out. And check the fuel pressure regulator too once it’s light out tomorrow. The IAC valve I already replaced and when I unplug it the engine dies as it should. The hissing that sounds like a vacuum leak I do not believe is.. We have searched all around to try to pinpoint the sound with no luck. Last owner said that sound was always there and could never find it either and everything was working fine... I do not know what it is though. |
I changed the temperature sensor. Still runs the same. Fuel pressure vacuum line is dry. I got a better video of it running now. Motor is surging at idle and dropping to lower rough idle than it was when I took the last video. Is the surging a clue to possibly another cure? Here’s new video if it helps anymore https://photos.app.goo.gl/5AQOFLOACe9pemSR2 Thanks again for any ideas! |
I just put mine back to stock after pulling the supercharger and it acted like that. It was a vacuum leak. Check the vacuum lines. There aren't many. Mine was the line to the egr. It pulled out of the main fitting at the manifold.
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Also check with a vacuum gauge. Mine read 15 or so and it's normally at least 20. Could be higher but my boost gauge only read up to 20 in on vacuum.
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After engine is fully warmed up and idling, unplug the IAC Valve
IAC Valve will close and RPMs should drop to 500, engine may even stall, either is GOOD, it means no vacuum leak If idle stays high then there is a leak |
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