2003 mazda tribute 3.0 v6 with automatic transmission

Half of the time on cold days, the engine will start normally (revs to 2kish), but will quickly drop to below 1k rpm and surges +/- 500 rpm to the point where the vehicle is nearly stalling. Sometimes I'll have to put the car in neutral and keep my foot on the gas at a red light, but otherwise the car drives normally. The surging typically goes away when the engine reaches normal operating temperature, but a few times will persist even on a warm motor.

If I turn off the vehicle after the engine is warm, it will briefly stall upon restarting, but will resume normal idle on its own immediately after almost stalling out

Based upon the threads I've searched and read on here, I have replaced all 6 spark plugs, all 6 coils, upper and lower intake manifold gaskets, all fuel injector seals, pcv valve, IAC, and throttle body gasket. I've cleaned the MAF with MAF cleaner and inspected the air filter. Vehicle has new battery and new fuel pump. Even after these changes the problem persists. Any suggestion on what to try next?

Thank you.

 

Wow. You've put a fair bit into this. May I ask what that list of parts is worth in the US? To replace all that over here would cost more than the car is worth. I hope the question not rude.

I have an '04 V6 that I bought from a Wrecker who has a lower reputation than most wreckers. After I found the Issue that had stumped them, I realised it was a bloody good little rig. Am trying to sort through a short list of deteriorated bushes etc.

Sorry I can't help with your question.

 

Parts are relatively cheap in the US from rockauto or parts geek. Might have paid $150 or so for all of the stuff minus the pump and battery (replaced previously).

 

Sometimes i source parts from RA and even with postage they still be much cheaper than out here , what a rip off here , but onto the topic , the temp sensor can do strange things if playing up when pretty cool (ambient) .
I suppose you have not got any codes btw?

Another thing "maybe" is the crank or cam sensors , also clean all connector plugs with proper cleaner and re-lube , the main ECU big one also , that's what i'd go for next imo as you have just about covered most , good luck

 

No check engine light. Would a faulty coolant temp sensor give faulty readings on the gauge within the instrument panel (I don't seem to have any faulty readings)

I need to replace my coolant anyways, so it's cheap enough to replace the sensor while I'm doing so.

 

There does not have to be a check light on for a code to be thrown , only the real important ones ignite the engine check light , one needs a code reader and they be cheap enough .
Also i have seen the temp sensor playing up even though the gauge is still showing ok , the temp sensor interacts with the ECU 1st , good luck .

 

Ok, that's interesting. Maybe I'll get it checked with a reader.

This morning the car was surging heavily and I turned the car off to see how it would do on a restart. It took 4-5 tries to get it back running again. I'll report back after I check for codes!

 

Using a Foxwell NT301, no codes showing and coolant temperature and air intake temperature sensors appear to be functioning normally, however the car did not surge during startup today. If the sensors are working normally during open/closed loop while the car is surging, any other advice on where to look or what data from the reader to watch?

Thank you

 

You sure got a tricky one there , tbh it really sounds like the IAC OR MAF or there still is a vacuum leak somewhere , did you try the exhaust thingy (can't recall what its called) , the round vacuum servo just behind the IAC , it has a rubber diaphragm in it and its attached to the intake vacuum , ha just thought of it the EGR but generally that will throw a code , or just thought of something else , the throttle position sensor just below the IAC , good luck as i'm outta ideas .

I told a fib- just added , Fuel Pressure? , and last a compression test .

 

I'll look for vacuum leaks again and will try to capture PID data while the vehicle is actually surging.

Thank you