Hi Guys,
I have a miss and don't know where to start. The car has lots-o-mods and new parts. I'll be installing a QH soon, so worse case, the datalogging should at least point me some direction.
Anyway, I could just be crusing along at constant speed or under accleration or even just idling and the car will just humm along and miss.... hmmmmmmmmmmmmmmmm...mmmmmmmmmmmmmmm
. I'm guessing one cylinder doesn't fire. i can't see a pattern, it seems to happen sporaticaly. cap rotor wires and plugs are fine. i could cruse for 15 minutes and not hear or notice it and other times, it's more frequent. I was thinking i could have a dead spot on my TPS, but not sure. It doesn't seem to be affected by pedal placement.
I'm still shaking out other stuff too like a 2000 rpm idle that pops up out of nowhere. base idle is around 1000 rpm and for no apparent reason it goes up to 2000. sometimes i can knock it down by burping the throttle, othertimes it goes back down on it's own.
Any Ideas?
First ideas for me woulod be check the timing
the TFI and PIP
mine did the same thing and it was the ignition switch just pop the plastic cover off the steering collum and make sure it aint coming apart or burnt.
im no expert this is just from my expirince
The occasional high idle could be a failing TPS. CHeck TPS closed throttle volts to be sure under 1 V, and returns to same value each time throttle is closed. Key on engine off, slowly open throttle while monitoring TPS volts. is should smoothly increase to around 4.5V @ WOT.
Thanks, I'll take a look. I got my QH and now I'm looking to see what software i want to use.
Years ago when I first installed QH...found out a couple of my sensors where acting up...oddly the car did go 12.9 that way????
Nice looking ride.
Travis
I love your Maverick! Had 2 of them back in the late 70s. Dropped a 302 / 4 speed into one along with seats from a 71 Tbird. Fun cars, and soooo easy to work on.
Well, I installed the Quarterhorse and was playing with it. The TPS is about 0.94v and slowly increases without any hickup to about 4.53v @ WOT. So the TPS seems to be working fine.
The car idles around 950 RPM's. I haven't messed with the idle yet. The miss does seem to be sensitive to the position of the throttle. i could be cruzing and if my foot is just at the right spot, it'll miss alot. if I back off the throttle a little or give it a little more gas, the miss goes away.
One odd thing, while in neutral or Park, slowly increasing the RPM's, at about 0.99v on the TPS, the RPM's are just slightly over 1500 RPM. But at 1v on the TPS, and the RPM's go upto 2000 RPM's. i was playing with it for a half an hour and i couldn't get it to hold steady RPM's in neural between 1500 and 2000 RPM's.
Everyonce in a while, the tach jumped at the same time as the "miss". the datalogger showed the rpms jump to 16000 for like 0.20 sec.
So far, the only changes I've made to the tune is to have the fans kick on a little sooner. All of those charts and functions are a little over my head. the BE software isn't for dummies like me.
I would use a analog meter or a scope to monitor the tps signal, sometimes a dvom will not show a spike, my 2 cents.
I finally finished installing the Inovate O2 sensor and gauge.
I got to admit, tuning this thing is over my head.
I haven't done any dataloging while driving yet, but the O2 gauge is wild. the ECU tries to keep it around 14.4 ish, but under full throttle, its dropping down in the 9's and under deceleration, it goes to 20. I guess I didn't realize how much it swayed.
Anyway, the Miss is still there, usually under light cruzing, when it's running between 1500-2000 rpm. now, i did notice that when the throttle possition changes from closed to part throttle, the spark advance changes from 25 to 47. This is causing it from being able to hold RPM in neutral between 1500 and 2000.
Could the spark advance be causing my miss as the spark drops from 47 to 25?
I'm still thinking that it's some part not working right. It happens when its cold and wonce it warms up.
Do you still run an EGR Valve?
If you are using stock tables, then I wouldnt worry about the tip-in spark advance... those aren't unreasonable values for low rpm, low map conditions.
Nice car, great project.
