New issue with hesitation, stumbling.

[3Bar_Mopar]

Ok, so I got my rewelded intake back on...car makes plenty of boost now. I got into it some on the way home and managed to get about 25psi. The car starting missing pretty bad at part throttle and idle immediately after the pull. I pulled the plugs, they all looked fine, no oil, brownish color. No connectors loose, no codes....coolant level hasn't moved and the car don't get any hotter.

The messed up part is that more than 1/4 throttle and the car pulls smooth as ever with plenty of power....I can blow off the tires at 40. Under that it runs like it's intermittently on 3 cylinders.....surging and a terrible miss. Timing hasn't jumped....fuel pressure is rock solid and hasn't dipped....I'm lost. Probably going to hook a scanner up this weekend and drive it. Any ideas?

[spooling]

My first thought is, is MAP responding quickly enough? I just had an issue with crap in a vacuum fitting causing poor idle/low speed driving

[3Bar_Mopar]

My first thought is, is MAP responding quickly enough? I just had an issue with crap in a vacuum fitting causing poor idle/low speed driving

That's some great advice! I'll check it out. I have a vacuum block and just sealed it up with Teflon tape!

[3Bar_Mopar]

Blew out the vacuum block before work.....no obstructions in the lines. I guess this enhances the sleeper status because people think I'm a lame duck in the lane with my car farting and missing out...then it just pulls away smooth as ever with all the power....yanks the steering wheel hard at 60.

Gonna connect a scanner tomorrow and see what's up.

[spooling]

The scanner should be helpful. Another quick thought- do your spark plugs have tips that are threaded on? Had champions with those, and again my car ran like crap at idle, and low speed-, the tips worked themselves loose

[3Bar_Mopar]

The scanner should be helpful. Another quick thought- do your spark plugs have tips that are threaded on? Had champions with those, and again my car ran like crap at idle, and low speed-, the tips worked themselves loose

Yeah they do...I noticed a couple of them were a little loose. I'll tighten them up and see if that works....that'd be awesome if that's what it was.

edit: No dice. No change

[Gaboon]

I had a broken valve spring that acted the same as you're describing. Ran on 3 until about 3000 rpm where id picked up and ran fine.

[3Bar_Mopar]

I had a broken valve spring that acted the same as you're describing. Ran on 3 until about 3000 rpm where id picked up and ran fine.

This seems throttle specific instead of RPM....like anything under a quarter pedal runs like butt....but lean into it a bit more and it smooths out and runs great. Hooked a scanner up this past weekend and didn't really get any results....sensors seem to be reading correctly...

[moparman76_69]

Hooked up an OTC and looked at the live data, MAP and O2 seem to both respond normally. Seems like the cal has either antilag or a staging limiter than kicks in and causes the car to hit a RPM limit and sometimes stumble and go full lean.

[3Bar_Mopar]

Been driving it the last few days and the level of crap running seems to change....but these are some symptoms I've been dealing with.

1. Went to leave work at 8PM...it was dark! Headlights decided not to work. Got it home with the flashers.

2. Drove to work the next day and looked at it on my lunch break....the wires for the headlight relay had laid against the alt belt and eaten through the plastic sheathing, shorted and blew a fuse....then the force of the alt belt pulled off the spade connector from the relay. I wrapped the wires with electrical tape and zip tied the wires out of the way and reconnected the spade...I used the only 30 amp fuse I had (the seat belt light?) and replaced the blown one. Left work and immediately noticed that my radio and gauge cluster (digital dash) is out. Go get gas and the car will not go above 3K rpm....it's like it's on the limiter. I manage to get the car home after driving 50 MPH because it will not go any faster. I figured out that the speed sensor is tied to the gauge cluster and since the fuse for the seat belt was missing and causing the gauge cluster (digital dash) to not work, the speed sensor has no way to tell how fast I'm going (apparently the digital dash doesn't use a physical drive gear like the other cars of that year)...so the staging limiter built into the cal doesn't know I'm going faster than 5mph or whatever speed it's programmed to shut off. So it was either drive all the way across town with no headlights, or not being able to go faster than 50. Replaced the fuse when I made it home and all is well.

3. Now...the car runs excellent while in boost...however if I get into it then let out....the car stumbles and runs rougher for a little while.....then if I lean into it just a little without actually building boost yet, the wideband will show almost dead lean and you can feel the power plateau and get a dead spot....if you give it some more, the wideband richens up and car will build boost and take off. I have noticed that lately sometimes while just cruising on the interstate, the car will show almost dead lean on the wideband for a while and you can hear the difference. You feel like you're having to give it a little more gas because it's wanting to slow down. Fuel pressure stays rock solid around 40 psi.

4. The idle surges...up and down, up and down, all the while popping and missing...I've had it die a couple times at the light...you take off and it's shuddering and popping until you get to over a quarter pedal and it's like a switch...smooths out and runs fine.

The car has a cheap autozone coil from what it looks like....is it normal for them to be hot after driving a while? A decent napa coil is about $20...I may get one this weekend and see what happens.

[3Bar_Mopar]

Ok, so I got a new coil from Napa and a set of BR9ES plugs. All the old plugs looked fine...pulled number 4 and it looked fine...then I tilted the plug for some reason and the ceramic insulator slid down to the tip of the plug. Apparently the insulator broke way down in the plug and fell down to cover the electrode completely. When you pull the plug and hold it up to look at it, everything seems normal because the insulator falls back down where it's supposed to be. Gapped the new plugs to .25 and the car runs perfectly...slight roughness at idle due to the tight gap but laid into it and destroyed the tires from a 40 roll...tire smoke in the cabin!

[DaveSkrab]

Glad you got it sorted! My next suggestion was going to be the primary O2 sensor.