I’ve seen this posted quite a few times now, but with no solutions.

Mine just started doing this. It starts up ok, but a couple seconds later the idle drops and it almost stalls, but then it jumps back up higher to level off and it’s ok.

I recently replaced the spark plugs, and cleaned the throttle body and MAF. 2008, I5, mileage is around 260kms.

Im wondering where I should start to look for the problem. So far, no check engine light.

 

Say what? Search it, or better yet, LOOK in the H3 FAQ section. Acts like it wants to stall/rough idle -No CEL -What To Do:

When you cleaned the MAF did you use MAF cleaner? Throttle Body cleaner on the TB?

 

Check for an intake air leak somewhere since you disconnected all of that I assume to dot he plugs.
Check the wiring for the MAF & the TB wiring. Make sure all connectors do not have gunk and krud in them too.
Did you use MAF cleaner to clean the MAF?
Also, check the plastic intake fasteners they sometimes shake loose.

 

Beat him to it by a minute.

 

Thanks for the quick replies. It didn’t do it today, but I had a look under the hood anyway. Simple fix, the air inlet tube connected to the air box was loose (doh!!). I also had a bolt missing from a coil pack (already knew that), which I replaced today. All is good.

I’ll try to remember to search next time before I post. I’m so used to just searching with Google, I forget there’s a ton of info on here that doesn’t necessarily show up in Google.

 

Well s***!! It started doing it again tonight, only worse now. Now I don’t know what to think.

Yes I used MAF cleaner for the MAF, and I couldn’t find the TB cleaner so I used the MAF cleaner instead, and then polished it with nevrdull and cleaned throughly after.

All plastics are tight, all coils secured, spark plugs are OEM...

I guess I’ll start tomorrow with cleaning the coil contacts. And maybe move onto inspecting the camshaft actuator solenoid.

im thinking it might be the injectors..?

 

when did you last do your spark plugs?

 

I just did them.

 

FWIW, mine was doing the same thing last year - starts ok, idle quickly starts to deteriorate, would recover but sometimes stalled, driving was normal. Thought I had fixed it with a new gas cap (seal looked suspect) but it came back 600 miles later. Eventually got a CEL. What fixed mine permanently was replacing the evap canister vent valve. My Tech II was saying fuel trims were a little off, and there is a well-documented procedure to quickly diagnose the operation of the valve using a scan tool (search youtube). Apparently mine was stuck open. If you can get the truck up enough to work on it, it's not a bad job to replace it. Part is readily available and inexpensive. If you do decide to investigate, be careful with all the hose connections associated with the repair (tip: the clips become brittle and break easily but they are readily available).

 

You never cleaned the TB with TB cleaner, there is your problem. I got no idea what made neverdull enter the equation, bit then you said it was cleaned thoroughly after??? With what? Use the correct cleaner for the correct function and things will go a bunch better.. Part of what you are cleaning is the Throttle Plate shaft as it enters the stepper motor section (seal, spring, plastic gears) and TB cleaner is designed to break up deposits in the TB so it can move the Throttle Plate smoothly. Carb cleaner destroys the plastic TB gears, electrical cleaner (MAF Cleaner) is not going to cut it.... literally. That is why you should use only TB Cleaner for cleaning a TB.

CRC TB Cleaner is not hard to find.