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240 revs to 2200 RPM few seconds after head gasket replacement


New member
May 26, 2023
Bellingham, Washington. United States
This is a tid bit chaotic to say the least and I am lost!, few things happened so let me start from the beginning. I came to the conclusion I had a head gasket leak for a few reasons, -loss of power -misfire on cold mornings -harsh idle etc. so I see little bits of oil in my coolant but none the other way around. Weird.
I rip off the head that day and to surprise my gasket was bad, head gets machined (said he took 12 off and it was warped but good now) and I put it back on with new seats and seals but old valves and springs, everything seems put back together as my green book says to do and I’ve NEVER heard it run this good in the 3 years I’ve owned this car. No more lifter tick. Way smoother running with IPD cam since installation. Seems it fixed a series of other (problems) I had while using it daily.

This is where caca hits the fan. (I believe)

I decided to use my IPD throttle body cleaning kit while my intake was off, I didn’t think my TPS “sensor” needed adjustment but my father broke those two Alan bolts loose and I tightened them back up where the oxidation was on that bracket PERFECTLY back to where it was, and it clicks as it should when opening the throttle.

While I’m here and my head is super shiny I think i might aswell clean my intake with the leftover carb cleaner while it’s off.

My dad takes off the IAC bracket to clean it up (400,000 mile car w tons of servicing so she dirty) I decide to clean the IAC that was previously stuck shut. I assume it was stuck due to having to hold my RPM’s every morning and having a wacky idle.
Clean the flametrap to get carb juice in my eye. 💀

now, when she starts up it’s AMAZING for the first 30 seconds or so. when I put the accelerator pedal down a bit, it responses WAY better than before. then idle raises itself up to 2200-2400 RPM or so touching the pedal or not.

I am no mechanic and I am lost. I need my car for work in a few days as well :/ I believe it has something to do with the intake side of things.
any thoughts, tips, or answers are greatly appreciated!
Unplug the IAC and see if it doesn't jump up. It may be sticking open now. If it jumps up Right on start disconnect the IAC hoses and plug them, and start again. If low idle now then IAC is having issues, if still high Idle than something is messed up with the throttle body
I tried starting it unplugged, tried crimped IAC hose in a separate attempt, it wanted to stall the second time I started it and with it crimped, giving it a bit of gas to idle for a second it gradually made it to 1300rpm by its own and then shot to around 2200 every time I tried starting, I’m ordering a new IAC today and praying it’s my only issue. Anything else I could try?
You should wait for responses to your test results. IAC valves are very dependable. The most unreliable thing in 240's is the wiring. The IAC controller gets its engine speed information from the pulse rate at the low side of the ignition coil.
I don't believe I swapped connections but it wouldn't hurt to try it the other way around next time I am at my shop! ill get back to ya on that, i figured while I'm there i can post pictures of vacuum lines as well just to make sure i didnt get any plugged into the wrong spot as i did not work on the car alone!
i did remove the copper looking bolt on the head by the firewall and put a new crushwasher on to make it fit with the intake gasket hole it has there, could that throw in any problems?
It would take a pretty big vacuum leak to rev that high, like the hose to the firebox under the intake is off or the cold start injector port is completely open, but then a leak that big would also make it run terribly. It seams like there is a internal leak, not an external
today I tried numerous things. First thing I notice when I get to the shop was the blue sensor on the head under the manifold wasn’t plugged in so k started with that and tried to fire her up. it’s just made the idle go down from 2300 down to 2000 rpm flat. I see my throttle body bolts were finger tight so I gave em a good torque down then began with a good ol starter fluid vacuum test. No vacuum leak from air intake to the block. Head gasket isn’t leaking.
I noticed my IAC was backwards so I flipped it to flow normal and it wanted to choke out first start up, second start up it lasted a decent amount of time at 1k rpm before shooting up to 2k again.
I unplug my MAF and give it a start. It went a whole minute before going up to 2k rpm.. although it was never touched (til now) throughout this whole process and again I drove my car to the shop. MAF was clean as hell (cleaned it last year) and so was my air filter. Now I am REALLY lost.
not to bug you on it, but did you check the tps and iac plugs? tps is a 3 pin plug with only pin 1 and 2 occupied(at least on a 2.4 car) and iac is a # pin with all 3 pins occupied
i can vouch a fully open LH2.2 iac can do 2500rpm+ at idle. Have you tried grounding the idle speed test point? if everything is working correctly, grounding it will cause the ECU to command the IAC fully shut. You should be able to physically see it close if you look in the pipe. The LH2.0/2.2 IAC valve will not self close when unplugged fyi.
I can vouch y’all are correct! My IAC is the culprit! I f**ked up somewhere along the way even tho I did headbolts in order and to spec and degree. Resurfaced head idk mannn. Any tips? My grandpa wants me to tighten the headbolts where the tinyyyy leak is. Also it wanted to hold rpm for a bit Before coming off the accelerator. Any ideas what that could be? Maybe I put the IAC backwards, Does the arrow point towards the motor or driver fender?