RPM serging

[lanechurch920]

What would make my rpms serge? Every morning ill start it will run fine as soon as I get to the end of the road and put the clutch it the rpms serge?

 

[Devilmans Hand]

Mine does that too after i had the top end all apart. I think it is caused by an intake vacuum leak.

 

[Canadianmudmen]

I assume its your 89' pickup?

Have you any engine light still? Have you disconnected the neg on the battery to clear the old engine codes? Might be running on the same closed loop the computer set it at or its not and you found out its running at lower rpms now but has a serge from normal to high rpms

Is the rpm going up then down up when stopped and clutch in?

I'm no expert on toys but on Chevy's this use to show an IAC (idle air control valve ) problem
On my Camaro it would run from 700 rpm to 1100 3 secs then back down then up again etc etc
Or TPS thorttle postion sensor Hard to give a cure not in the truck over the net

Take a look at your little emission hoses look for holes / cracks

Get yourself a Haynes manual or mitchell manual at most auto stores pepboys autozone
Best thing i ever did when i got my first car has step by steps with pictures and pages that have problem = check areas

 

[KLF]

Idle is set too high. Turn down the magic screw on the throttle body.

 

[Devilmans Hand]

Idle is set too high. Turn down the magic screw on the throttle body.

Thanks for the tip. worked like a charm.

 

[Canadianmudmen]

Idle is set too high. Turn down the magic screw on the throttle body.

Hmmm dont think it make it go up and down However there is a Factory set throttle stop screw and a idle speed adjustment screw this is the screw that adjusts the normal idle speed (after the engine has warmed up)

I would only look into this AFTER you have checked everything else Cause if the problem lays in say a air intake hose adjustment into idle speed will make things worse Dont play with the TPS ether unless you know how to use a voltmeter

 

[Kris]

I think most common surging is caused by vac leak, tps mis adjustment, or a dead spot on the AFM.

A good TPS adjustment site: http://www.4crawler.com/4x4/CheapTricks/TPS/index.shtml

 

[Devils Paw 80]

My surging was a result of the idle being set too high, and so was the OP's in this thread. Check post #5.

 

[Devilmans Hand]

My surging was a result of the idle being set too high, and so was the OP's in this thread. Check post #5.

sorry for the confusion, but that was just my solution. I'm not the OP of this thread.

 

[lanechurch920]

Well update! still not fixed have noticed that it surges when i press on the breaks and when i let off it idles normal? But it also will surge at about 1/4 throttle i was thinking break booster but it will do it at 1/4 throttle to. it idles at 1100 the smog shop said and they said it needs to be at 1000 or less but my prob it the throttle screw is all the way in.

 

[alteredraptor]

my truck had similar issues, tps adjustment fixed my issue

 

[lanechurch920]

How do i adjust/replace the tps ive been looking online and dont really understand how to do it?

 

[alteredraptor]

if you have a multimeter it's rally quite simple, it's easier with one that has little gator clips, or another person to help out, that link from a few posts back really helped me, but set the two prongs from the meter on the proper tps connectors, after loosening it, than slowly turn it, just follow the directions from that link, and basically you'll start with a few numbers on your meter on the ohm settings, than once it gets to infinite or open, tighten it down, that's what I did and it helped me out

 

[lanechurch920]

What all did you have to pull to adjust it? seams hard to get to that bottom screw?

 

[alteredraptor]

either the upper plenum or the throttle body, I would suggest getting rid of the screws that hold the tps on, and goin to the hardware store or something and getting some Allen head screws to make things easier