Last weekend I was on the highway and I was near redline in third gear at WOT. All of a sudden the engine lost power and started running like garbage. The PFC recorded a peak knock of 99 when this happened. I limped it home to find that the map sensor hose got blown off.

I reconnected it and the car seemed to be running fine. I took it out last night and got into boost only to have it break up at high rpm. If I put it in forth and go to WOT at 70mph you can see the car holding boost at 14psi and then it eventually starts breaking up around 5,500K RPM.

I recently installed a twin power and I tried changing the spark plugs which didn't help. I also went through every vacuum line to make sure that they were all connected.

Could my coils be going bad all of a sudden? Is anything bad known to happen when the vacuum hose gets disconnected from the MAP sensor at WOT? Any help would be great.

 

did the car run fine with the twin power before? I recently installed a twin power and the ground was not sufficient which caused massive break up around 4-5k rpm. Properly grounded and its working great.

 

Yes the car ran great. But I'll double check the ground just to make sure.

 

Just compression checked the motor and it's pulling good compression. It's got to be something else then. Anyone have any tips for checking the coils besides measuring the resistance?

 

what plugs did you install? Are you positive you didn't accidentally swap a pair of spark plug wires?

 

I bought four brand new bur9eq's . What's interesting is that when I pulled the plugs today the top trailing plugs still looked brand new and the bottom leading plugs looked darker and like they had a uneven buildup of carbon on them (I barely drove the car yesterday after I installed the fresh plugs). I'm starting to really suspect my leading coil. It's just odd that the leading coil would decide to stop working properly at the same time that I blew the vacuum hose off the MAP sensor. I'll check it out tomorrow and report back with what I find. I have a extra used leading coil that I'm going to swap in.

 

check the filter to be sure it isn't blocked up with some crap and/or the line isn't kinked.

 

I replaced the fuel filter exactly one month ago. I'm starting to doubt my Walbro though. I installed it 25k miles ago and I heard they can die out.

 

anything can die out - there isn't anything lacking in quality by walbro . turn the switch on and listen for the pump to engage. if you can hear it then it's probably fine. I seriously doubt this is the problem. people give walbro a bad name because the insist on buying walbro knock-offs of ebay.


goodfella asked about the PLUG WIRES. Make sure you have the plug WIRES routed correctly. I'd be highly surprised that it's a coil problem, also. FDs aren't known to have coils go bad.. obviously it's possible, just unlikely.

 

Well, I was having ignition breakup problems before. I ran B10EGV plugs which seemed to cure the problem temporarily but the problem eventually came back. I installed a twin power hoping that it would solve my problem, and it didn't (I switched back to bur9eq's for this). I was running magnecore's that were only about 20K miles old but I decided to test them anyway. Sure enough one of the wires going to one of the leading plugs was bad! I couldn't measure any resistance across the wire. I switched out the magnecores with a old set of NGK wires that I took off the car when I installed the magnecores. This solved the problem and the car ran perfectly. This is until my incident when the vacuum hose popped off the MAP sensor. Ever since then I'm experiencing ignition breakup worse then when I was running the bad plug wire.

Also, I didn't think it mattered which way the leading plug wires were hooked up. I know that the trailing wires are properly hooked up.

 

there is a filter on the vac line from the UIM to the MAP sensor, its a black plastic thing that looks kind of like the viton valves. He was talking about that, not the fuel filter.

 

yep, sounds like either the MAP sensor isn't reading the boost correctly and not compensating or there is another issue, probably in the fuel system that is coincidental.

 

Problem Solved! I don't know which one of these things solved the problem but this what I did.

-I tested the leading coil and it was within spec but I replaced it anyway with a backup coil that I had laying around

-I noticed that the connection from the harness going to the leading plug looked a little off. I looked inside the plug and the orange rubber gasket didn't look like it was properly seated. I reseated the gasket and it fit a little bit better.

-I looked at the filter in between the map sensor and the UIM. Air was moving through it pretty well when I'd blow through it but I noticed that something was loose inside of the filter. If I shook it I could hear something moving around, it was almost like the filter element inside of it was loose. So I cut a new piece of vacuum hose and bypassed the filter. BTW is this filter really necessary?

I just took the car out and did a WOT 3rd gear pull to redline and the thing is running perfectly now. Thanks to everyone for your suggestions and help!