stumble

equalizer442

Active Member
Joined
Oct 23, 2002
ive had this problem for quite some time and ive posted about it before but with no luck finding out the problem. my car has a "stumble" or miss some times when its cold, the scanmaster will read verry low o2 volts including 000 most of the time until the car gets warmed up and then it runs like a champ. this morning i caught out of the corner of my eye the stock boost gauge would flicker full boost for a split second every time it stumbled, my assumption is that the computers being tricked in to thinking that the car is at 15+ psi of boost and injecting fuel accordingly (as if wot) but at a low rpm and speed causing the stumble BUT that still dont account for the 000s on the scanmaster, that i think might becaused by a bad 02 sensor. im thinking that i might need a new MAP sencer (could this possably be the wastgeate selinod, what sences the psi of boost?) and a new 02 sensor. are my assumptions correct?
 
mine does that too kind of, i think it has to do with not letting the car warm up, and your talking about the boost gauge spiking real quick, well when my car first starts and i dont let it warm up enough it does that to, it stumbles, and like back fires, kind of making a coughing noise and both my stock boost gauge and my VDO boost gauge pop up for a second.
 
First, what type of chip do you have? It sounds like a bad o2 sensor to me. But, Remember the computer runs the show until the car gets up to temp and the o2 takes over. The numbers should be jumping around all over. Can you give more info...

HTH, Mike

PS Just out of curiosity, when was the last tune performed?
 
First, what type of chip do you have? It sounds like a bad o2 sensor to me. But, Remember the computer runs the show until the car gets up to temp and the o2 takes over. The numbers should be jumping around all over. Can you give more info...

i have a 19 degree jim testa street chip. ive also got a precission front mount intercooler, te44 .80 a/r exhaust houseing, rjc power plate, dual fuel pumps, k@n filter (dirty, but cleaning it this week end) adjustable wastgeate, adjustable fuel pressure regulator, scanmaster v2.1, alternator field fix harness along with some other mods that i cant remember off the top of my head.

the o2 volts jumps around after the car gets warmed up but until then the car runs like crap unless i push down on the gas and get alittle agressive (i hate to do that when its cold but its saved my butt a few times) if i get agressive with it and its cold it cycles like normal but just regular driving it feels like its on its last legs, rather embarising to owning the fastest car at both of my schools and the thing acts like its gona die while im pulling out.
 
Having same problem, just posted it ( didn't see this post until afterwards of course) It IS really embarrassing to have this happen when the car really is performing great otherwise!
 
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