olddirtyrake Posted February 25, 2010 Share Posted February 25, 2010 (edited) I was wondering what could cause my Ignition timing to bounce around. I hooked a timing light up and timed it it looks like its jumping up and down ranging from 10-15. So its not stable it bounces around about 5 degrees I was wondering what could be causing this. It runs great sometimes then feels boggy at other times due to timing Im assuming. Vacuum lines maybe? Edited February 25, 2010 by olddirtyrake Link to comment Share on other sites More sharing options...
Simon Posted February 25, 2010 Share Posted February 25, 2010 Was the truck warm when you checked the timing? It'll idle far more steady when warm, and should take out the bounces you're seeing. Link to comment Share on other sites More sharing options...
GrimGreg Posted February 25, 2010 Share Posted February 25, 2010 The computer can, and does, change the spark timing as needed. Link to comment Share on other sites More sharing options...
Precise1 Posted February 25, 2010 Share Posted February 25, 2010 I'll let you know when I figure it out. Mine only changes 2-3 degrees, but enough to be clearly seen and to make it hard to time. I can't bellieve it is normal function... Been waiting for a break in the rain to check a few things out. B Link to comment Share on other sites More sharing options...
PATHRIDER Posted February 25, 2010 Share Posted February 25, 2010 Im having the same problem on my hardbody...It was running fine till I changed my plugs, wires,pcv valve,filter, caps and rotors. I replaced some of the vacuum hoses also and it still idles funny. I gaped the plugs to .032 It runs fine but when im at a stop it seems to idle rough and i can see my rpm go up and down from about 700 to 800 Could I have crossed any of my plug wires? When I took the old plugs out which are also ngk I noticed the gapping on them is far wider than .032..I can almost shim a quarter on there Link to comment Share on other sites More sharing options...
Kingman Posted February 25, 2010 Share Posted February 25, 2010 I believe you need to view/adjust your timing at EXACTLY 800RPM or you'll never set the timing properly, and the engine needs to be 100% warmed up. Link to comment Share on other sites More sharing options...
PATHRIDER Posted February 25, 2010 Share Posted February 25, 2010 (edited) I believe you need to view/adjust your timing at EXACTLY 800RPM or you'll never set the timing properly, and the engine needs to be 100% warmed up. how do i set my rpm at 800? Edited February 25, 2010 by PATHRIDER Link to comment Share on other sites More sharing options...
Kingman Posted February 25, 2010 Share Posted February 25, 2010 Well, actually, don't take what I said to heart...I know it's 800RPM for MY truck which is a TBI engine, I don't know about the MPFI's RPM specifications for setting the timing. I got a little too far ahead of myself... Link to comment Share on other sites More sharing options...
Precise1 Posted February 25, 2010 Share Posted February 25, 2010 I'm fairly certain the idle specs for the MPFI are 700-800 manual tranny and 750-850 AT. I have never had to adjust it before, so I'm no help there... B Link to comment Share on other sites More sharing options...
MY1PATH Posted February 25, 2010 Share Posted February 25, 2010 (edited) I believe you need to view/adjust your timing at EXACTLY 800RPM or you'll never set the timing properly, and the engine needs to be 100% warmed up. HMM I set my timing @ 600 rpm and then turn the idle back up.... (fully warmed up, all accesories & lights turned off) Edited February 25, 2010 by MY1PATH Link to comment Share on other sites More sharing options...
PATHRIDER Posted February 25, 2010 Share Posted February 25, 2010 (edited) I'm fairly certain the idle specs for the MPFI are 700-800 manual tranny and 750-850 AT. I have never had to adjust it before, so I'm no help there... B I was about to send you a message bud...lol..Im sure somebody can chime in on how to adjust the idle..Ive never done it either and everytime I do a tune up I only adjust the timing and call it good....i was looking at the ecu and it has idle speed screw on there..maybe I should mess with it Edited February 25, 2010 by PATHRIDER Link to comment Share on other sites More sharing options...
Precise1 Posted February 25, 2010 Share Posted February 25, 2010 LOL No, I hardly know everything, thanks for the thought though... What does your Factory Service Manual say on adjusting idle?? B Link to comment Share on other sites More sharing options...
andreus009 Posted February 25, 2010 Share Posted February 25, 2010 Just to throw in my 2 cents. I've tinkered with the idle adjust screw and it did not seem to do a darn thing Link to comment Share on other sites More sharing options...
Kingman Posted February 26, 2010 Share Posted February 26, 2010 HMM I set my timing @ 600 rpm and then turn the idle back up.... (fully warmed up, all accesories & lights turned off) The sticker under the hood says to set the engine idle speed at 800RPM. Link to comment Share on other sites More sharing options...
R3DN1CK Posted February 26, 2010 Share Posted February 26, 2010 Just to throw in my 2 cents. I've tinkered with the idle adjust screw and it did not seem to do a darn thing i have a fsm, but haven't verified yet. I believe you have to unhook the throttle body postion sensor to set idle. Link to comment Share on other sites More sharing options...
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