I just put my new motor in after a rebuild on Thursday went driving around and mashed on it a bit and it had a little studder over 4000 RPM , so far in trying to solve the problem I have done these things and it seems to be getting worse. I have cleaned the back of the head for the grounds, changed plugs, wires , coil pack and module. The car runs great until it sees over 4,000 RPM and now its getting worse now its popping and backfiring but not lean O2's are in the low 800's and I only have 10psi on it. BTW it also has new fuel pump , injectors and fuel filter (less than 1,000)miles. I was thinking mass air or cam sensor. Any ideas would be great. Thanks
New motor now car breaking up?
- Thread starter Nojug
- Start date
pwr.slave6
member
- Joined
- Jan 8, 2005
Check valve springs. Mine had same symtoms,fell flat at 4k.
sounds like valves are floating (possibily)
good luck.
sounds like valves are floating (possibily)
good luck.
trading t/a
I'm Angry!!!!!
- Joined
- Aug 6, 2001
Someone had mentioned to me that the crank sensor could do that as well. Being that has you increase the rpms the stock crank and balancer/pulley will move away from the cover mounted sensor causing it to miss. I'm looking into that possibility as well....
83ttypecooled
Active Member
- Joined
- Sep 14, 2003
Hi,
Wow, you have done it all! What a pain it must be. Bad parts? You don't have access to one of those coil /module testers, do you? It hits good on all 6 cylinders until breaking up, right? I could see spark knock at your boost level, but even a crappy ignition should fire it. I don't believe a cam sensor can do this. How was it running before the rebuild? I'm sorry I don't have better ideas. Please keep us posted about developments. Good luck!
Wow, you have done it all! What a pain it must be. Bad parts? You don't have access to one of those coil /module testers, do you? It hits good on all 6 cylinders until breaking up, right? I could see spark knock at your boost level, but even a crappy ignition should fire it. I don't believe a cam sensor can do this. How was it running before the rebuild? I'm sorry I don't have better ideas. Please keep us posted about developments. Good luck!
To test the cam sensor, unplug it after you start it up and see if the problem goes away. The tach signal starts with the crank sensor so if that is flaky you should see the tach dropping and bouncing around. Did you degree the cam? Any chance you missed a tooth on the gears? Otherwise, I think we're back to valvesprings. Oh, once you get misfiring you absolutely cannot trust anything the O2 sensor says - the unburnt fuel in the exhaust totally confuses it.
I see you neglected the TPS sensor. I've had a bad TPS create the same symptoms you have discribed.
To test if if you aren't familiar with a OTC 4000E or one of the other laptop diagnostic systems. The old multimeter works fine for a quick test. This is the way I check to see if it's functioning ok. I take a thick needle or common pin and push it into the middle wire going into the connecter of the TPS. Try to work it in between the silicone weather insulator and the wire. Keep pressure on the pin until it bottoms out. Now turn the ignation on just so the dash idiot lights and cooling fan come on. Take the positve lead of the mutimeter (set to the 0-20 volts DC )and clamp it to the pin and then gound the black lead to a bare metal engine surface. You shoud get a voltage something under 1.0 volts and when moving the throttle back slowly the voltage should increase steadly up to 4.90 volts or higher. If it skips or jumps at 2/3's or 3/4 throttle like when you reached your 4000 rpm then there's your culprit.
To test if if you aren't familiar with a OTC 4000E or one of the other laptop diagnostic systems. The old multimeter works fine for a quick test. This is the way I check to see if it's functioning ok. I take a thick needle or common pin and push it into the middle wire going into the connecter of the TPS. Try to work it in between the silicone weather insulator and the wire. Keep pressure on the pin until it bottoms out. Now turn the ignation on just so the dash idiot lights and cooling fan come on. Take the positve lead of the mutimeter (set to the 0-20 volts DC )and clamp it to the pin and then gound the black lead to a bare metal engine surface. You shoud get a voltage something under 1.0 volts and when moving the throttle back slowly the voltage should increase steadly up to 4.90 volts or higher. If it skips or jumps at 2/3's or 3/4 throttle like when you reached your 4000 rpm then there's your culprit.
Under Pressure
New Member
- Joined
- Feb 8, 2004
check fuel pressure under boost and run a cr43ts spark plug gapped at .035 i had issues with plugs before
Nojug
You probably have a rich backfire. I had this same problem when I ran a mass air on my setup. My car would do it after 15 lbs of boost. It would backfire and hestitate very badly. Drove me crazy
I replaced my module, coil, injector harness, crank sensor, cam sensor, new plugs, new plug wires, TPS and tried 3 different mass air meters no help. I ended up installing a FAST system and the car pulled hard to 27 lbs of boost without one hestitation nor pop. I was using 72 lb inj and a ATR double pumper setup. Good Luck!!
You probably have a rich backfire. I had this same problem when I ran a mass air on my setup. My car would do it after 15 lbs of boost. It would backfire and hestitate very badly. Drove me crazy
I replaced my module, coil, injector harness, crank sensor, cam sensor, new plugs, new plug wires, TPS and tried 3 different mass air meters no help. I ended up installing a FAST system and the car pulled hard to 27 lbs of boost without one hestitation nor pop. I was using 72 lb inj and a ATR double pumper setup. Good Luck!!
