silverbullet

I've had this problem for a while now. The car stutters or misfires between 3500 and 5000 rpm in third or forth gear. It only does this at complete WOT. The boost rises correctly but the car jerks and shudders at around 4000 rpm. Driving around town or at almost WOT doesn't induce this, it's only during extreme acceleration. Sometimes it does't do it at all, other times it's real bad. Can someone list all possible causes for this? I am going to replace chips, wires, cap and rotor to see if it will fix it. I just want to know any causes so I can narrow it down.
Thanks, Josh

J Chen

Pressure test the system for leaks. Check your spark plugs.
Remove your plug wires & measure the resistance of each
wire by using a DVM also check rotor & cap.
BTW is this a recent problem ? If you're still running an AFM
there could be a problem there. How to check, I don't know.
Perhaps someone can chime in on this. Oh, also check the
boot after AFM/MAF.

Dash01

Sounds like overboosting to me...my dad's car did that same thing too exactly how you described it. That being said, in your sig it says autothroity chips. My understanding of aftermarket chips is they have no over boost protection.

silverbullet

Yes, I have the Autothority chips in it. Does that rule out overboost protection? I looked at the distributer cap today. Should the contacts be bright and shiny; or is a little charring normal? I hope by getting new wires, cap, etc; I'll solve the high rpm stumble. What else could it possibly be, a fuel system problem?
Thanks,
Josh

hosrom_951

looks like this problem is rising with some of use here (including myself).

Take a loook at the coil, plugs, wires etc (the ignition system). Make sure the cap doesn't have any cracks or parts missing.

UK952

Its also worth checking the copper earth leads and cleaning up the cconnections, between battery and chassis and chassis and engine.
Tony

ehall

second the batt leads. They can deteriorate and can(it happened to me) cause this kind of symptom. Replaced the + lead from the battery as well as the ground. all gone. You appear to have a borla exhaust so it shouldn't be cat blockage.

silverbullet

My Borla is cat-back. Could a clogged cat cause these symtoms? Thanks, I didn't think to check the battery and grounds.

silverbullet

By the way, I noticed that a rotor from Performance Products is around $25 vs around $45 for Bosch rotors. Is the Bosch really better?

ehall

Rotor? don't know. Cat? It could, but I would think that it's not very old, and those are pretty good systems. It should take some pretty good time to clog a new cat. My stock cat took about 17 years to really clog. Too long. Yep. Probably could have been changed 4yrs? earlier? However, what would happen too me was that I would stomp on the trhottle, all was normal then an almost split second shut off/ stutter(call it what you want) It will scare the crap outta you in the wrong situation. After replacing fuel filter, pump relief valve, cat(deleted all together) timing belt. the positive cable burned in half. It was touching somewhere on the back of the engine area, and just burned up.
i think that the thrust of being at full throttle would get the damaged area to ark with some part of the housing. the jolt moved the cable marginally, thus stopping or creating proximity for an arc. We still aren't sure. we do know that it is all gone. After replacing both battery cables completely, I found that the voltage reg wasn't working and replaced it.; (entirely too much work to change a 15.00 volt reg) As if by magic...err ...electricity, the entire electrical sywstem functions beautifully. Who'd a thunk it huh? I think all of these posts are worth really checking out. Old wires+ brittle, unreliable electric signals. Use Clarks garage, and forum to help w trouble shooting if you can't isolate it. You'll find it. Good luck.

Tom M'Guinn

I bet a penny it goes away after changing your cap, rotor, plugs, and (importantly) wires. Weak ignition parts show up first under heavy boost.