High RPM on start

Joined
Sep 13, 2009
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Vermont
Hey all!

As the title says, my engine hits higher than usual rpm’s on start. Doesn’t matter if it’s cold or not. On average it peaks around 2k-2200 for about one to two seconds then falls back down to the 600/800 range. My air intake hose (from MAF housing to throttle body) has a huge crack… almost completely severs, which I have sealed up I think about as well as anyone could.

I guess my question is: would that be enough to be the causative agent here?… OR should I start checking for other vacuum leaks/a dirty MAF sensor/injector gumming?

Possibly related, but I’ve also been pretty regularly throwing a PO171 code (running too lean). I’d say every 30-40 miles after reset it pops back on, almost always while under decent load.

Then there’s the PO420… which I’m almost certain is due to a couple of exhaust leaks I’ve noticed in the past few weeks.

Thanks a ton y’all!
 
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I'd try spraying contact cleaner on the linkage just to eliminate any oil/grease contaminated dirt in the linkage gaps. I wouldn't use brakeleen or carburetor cleaner - it's not good for the TPS housing.
 

FMC80

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Your RPM rise is expected; it should be higher upon initial start. Mine roars to 1800-2000 or so before settling down to 625-650. Yours may be higher due to your Band-Aid fix on your intake tube. Just buy a new one already.
 
Joined
Sep 13, 2009
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Vermont
I just noticed this. Are you referring to air temperature, or the hot/cold status of the engine?

You *definitely* shouldn't be seeing 2k+ RPM if you're restarting a warm engine.
Engine temp. I could be driving it for an hour and let it sit ten min… startup would still bring it back up to roughly the 2k mark (sometimes 1800, sometimes an even 2k). I checked vacuum lines and all seem to be in good shape, probably a a couple that could use a replacement which I’ll be doing over the weekend.

Things that I unequivocally know are going on: major crack (and jerry rigged for now) in the air intake hose between the MAF housing and throttle body, at least one exhaust leak before the cats… possibly a second further back (muffler area), both upstream and downstream o2 sensors were replaced about two-three weeks back (how I found the corrosion and confirmed leak), idle control has been corrected tightened and lubed also about 2-3 weeks back, dizzy checked for correct timing with timing light, plugs and wires inspected, MAF sensor inspected & cleaned. Fuel filter is getting changed this weekend along with the vacuums lines.

I feel like without remedying the exhaust and intake I can’t really troubleshoot much further? I will add that I never have a tough time getting it fired up, it just hits that high mark that has always seemed to in the past (in other non-fj’s) a precursor to a bigger issue. Maybe it’s just been coincidence.
 
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idle control has been corrected tightened and lubed also about 2-3 weeks back

No such thing. This may be contributing to your problem. You do *not* control the idle by adjusting the throttle cable. Idle is controlled by the idle air controller. If you try to mess with the idle by adjusting the throttle cable, you're just plastering over one problem and creating others.
 
Joined
Jun 24, 2008
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Seems that it starts at a high rpm to heat the converters to operating temperature quickly, thus meeting California’s ULEV rating…
Just noticed that this was on the 80 page…My bad..
 
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