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Truck surges at startup when cold


Wayne6197

Member
U.S. Military - Veteran
Joined
Nov 18, 2023
Messages
11
City
Mississippi
Vehicle Year
2000
Transmission
Manual
Hi. My 2000 Ranger revs up to around 2500 on cold mornings on startup. This lasts 10-15 minutes. Then it surges up to 2500, then back to 1500 or so every 3-4 seconds and will continue this until driven. I changed out the air control sensor, no vacuum leaks and thermostat is good per my mechanic. Any suggestions? Thank you.
 
It sure sounds like a vacuum leak...

What engine is it?
 
The other alternative is a sticky iac. If you cannot find a vacuum leak, I would change the iac.
 
Just an FYI...

I moved this to the 3.0L forum.
 
It sounds like it is temperature related. You say your mechanic said your thermostat is fine.
Does your truck take a long time to warm up? A coolant temp sensor is a thermistor. One starting to fail can cause some some weird stuff.
 
It sounds like it is temperature related. You say your mechanic said your thermostat is fine.
Does your truck take a long time to warm up? A coolant temp sensor is a thermistor. One starting to fail can cause some some weird stuff.
Thank you. I told him I thought it could be that but I guess he ignored me. Lol. Anyway I will change it and see. Thanks again.
 
I am talking about the temp sensor itself, not the thermostat. I am not clear on your answer, does the truck seem to take a long time to warm up?
 
Yes, I am talking about the coolant temp sensor. I noticed one of the wires was off of the connector harness so I ordered it and the sensor today. The truck seems to warm up ok, it just does that weird surging after a while then if I try to drive it before it stops that it is almost impossible to shift. I am hoping the temp sensor and connector solve this. If not then I'll try the MAF sensor. Thank you.
 
How old is the PCV valve? I had symptoms not exactly like yours but indicative of a vacuum leak. I changed the PCV valve, and the problem was solved.
 
Probably the original one on the truck. So 24 years. Thank you. I'll check this out.
 

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