4th Gear Misfire Help

[Ronnie's.930]

This is my newest/latest running issue.

I attempted a pass on the freeway today - was cruising in 4th at about 70-75 mph at around 3K rpm and when I rolled into the throttle (not a pedal to the floor but gradual pressure) the thing appeared to only make about .4 bar boost and stumbled/hesitated/misfired terribly. I repeated this many times on the way home and it seemed to misfire/chug/bog down/not build boost at around 3500 rpm in 4th gear and then suddenly pull hard. In all other gears I can stomp the throttle, or roll it on, and it rapidly builds boost to .8 bar and hauls major ass without problem.

It has a Brian Leask WUR, K27 HyFlow, RarlyL8 muffler, Garretson intercooler, but pretty much stock otherwise.

I don't have my LM2 wideband hard mounted yet so don't know the AFRs when the miss happens (will have it in in the next couple of days).

I know I need to check for boost leaks but was wondering why there is no miss in the other gears if I have a boost leak.

Any ideas given this limited info?

[Ronnie's.930]

I guess you guys, except for TK Chris, must think I am a Richard-head!

Chris suggested that this is likely ignition related and I am going through the things he recommended.

Question about voltage ouput - A few months ago, I changed the voltage regulator, but did nothing with the alternator, and have been experimenting with an Odyssey PC680 battery, and due to this I check the voltage regularly out of paranoia (need to install a VDO volt gauge). So today I unhooked an amp that a PO installed and tried running the car that way. I thought the problem was gone but about a 1/2 hour into the drive, the same misfire described above returned. I have now swapped a battery from my E350 into the car and while measuring voltage, am only seeing 13.1 at about 1100rpm at the battery but 13.8 at the engine bay fuse pannel. I'm wondering why this is? Maybe the battery ground? Do the lugs on the starter have anything to do with the alternator?

Anyway, I am going to see if the thing still misses with the full-size battery, and if so, have a lot more trouble shooting to do . . .

[pete3799]

Alt. out put ( red wire) goes to the starter then to the battery.

[Ronnie's.930]

Thanks Pete - I will remove and clean the terminals.

[mark houghton]

3.1 volts, not good. I too would agree with ignition, and you would see it most likely under high load conditions (4th gear). Makes sense.
I don't want to hear about this, since I too just replaced my voltage regulator and don't have any more than maybe 40 miles on it (lucky for me it's working fine so far). Don't you dare jinx it, dude :-)

[Ronnie's.930]

Ha', sorry Mark, I meant "13.1" volts (drops to 12.6-7, at battery with lights on and 13.5 at fuse block/lights on), which isn't terrible, but strange as to the difference between the battery and the rear fuse block. I'm going to clean the starter terminals tomorrow and start working through the misfire problem as the big battery did not improve that situation at all . . .

[mark houghton]

Stupid question: I can't remember if you're running with MSD or stock CDI. I ask because I'm thinking about the dizzy rotor and built-in resistor....which of course you don't want with MSD. Maybe something is fried in there. Bad coil maybe too. Could be a zillion things but I know you'll sort it out. Still a pisser....

[Ronnie's.930]

I'm running the stock CDI. I plan to test the coil, among other things, tomorrow.

[Ronnie's.930]

It's hard to believe that I started this thread back in April and I am just now getting around to addressing the problem!

However, success - no more 4th gear misfire and the thing pulls like a fu**in' freight train in all gears!

I followed the advice of others and went about "checks" as systematically as I cound - checked coil for resistence and was good, checked sparkplug wires/ends and found all good except the coil wire seemed too loose at both ends so I spread out the tabs slightly. I pulled the CDI off and opened it up - couldn't see any problems in there, but I went ahead and cleaned the terminals on it and the wire harness plug as well. The distributer was recently rebuilt so I decided to leave it alone for now and the plugs are new so I waited on taking those out as well.

I finally hard mounted my repaired LM2 and set the idle AFR at 13.4 +/- (unit is still working perfectly). The cable I currently have for it only allows me to put it between the seats so I can only really read it at idle and steady cruise (both readings are perfect) and will have to have someone along with me to check boost onset and steady boost (or figure out how to use the software and RPM reading function - need to work on that).

Anyway, all is good now, but I can't really say what the "fix" was as I did several things at once.

[krasuskyp]

dayum... uncanny the timing of your update here

my car's been running ohso most fantabularly since I got it back again in May, prob a 1/2 dozen tanks of gas thru it easy

then I park it last 1.5-2wks as it's been thunderstorm season here every day

drive it to werk Fri, I get the exact same thing you describe... cruise in 4th go to throttle / boost it and it stumbles, downshift and it goes like raped ape (and when I slightly lift after doing that, I get a real off/on jerk)

idle when I pull in hot is somewhat high @ 1100-1200 instead of my normal 1025 or so

sprayed brake clean around various vacuum bits while @ idle thinking I've got a leak somewhere, no change

plugs new, wires / cap / rotor were newer when I'd sold it so not many miles on all that

this was Fri tho and I simply parked it - have yet to start the diag process, but your post timing is just eerie 8-)

I don't get why it onset out of nowhere - nothing changed other than sitting for 2wks (but it'd only done 200mi in last 18mos w/ guy I'd sold it to) - wtf?

[Ronnie's.930]

Hello Paul, maybe my car shook off its running issue and passed it to yours by way of the force?!

The first thing I would check is the primary coil wire - see if it is clean and tight on both ends, and then check and clean the CDI prongs and socket - I used fine sand paper and electric contact cleaner for this. Your can easily remove the CDI without having to take the intercooler off, and that way, you can better clean the male portion of the socket . . . also measure the voltage output of the alternator at 2K+ rpm.

Mine started misfiring in 4th gear with no warning whatsoever, as well.

[krasuskyp]

dood, I'm tellin ya - that's weird!

thanks much for the motiviation / instigation / inspiration / awesomeification!

will have a looksee this week - parked mostly still tho, heat wave here again

enjoy yours!

[T77911S]

use the record function on the LM, it is much better than trying to read it while driving.
also get the tach adpater for when you really need to see what is going on. without it, you cant really tell what you were doing when looking at the recording.

also go to their site and do an update on the LM. you may have to download other software to do it.

[Speedy Squirrel]

Are you sure it's not fuel pressure? It can cause a similar symptom, and can also be intermittent.

[Tippy]

I had the same issue on my Carrera 3.2. In 4th gear, I'd be seeing 1.2 bar. Occasionally, the car would stutter and you'd have to let off and hit it again. The PO tried to figure it out before. 3rd and lower gears aren't a problem since they see 1 bar, .8 bar, and .3 respectively - my point I'll get to.

One day it snapped on me. The higher the boost, the more intense of ignition you need to jump the spark plug gap.

The stuttering is essentially "flaming out" of the plugs due to high cylinder pressures.

Single coils really struggle with this due to the frequency required to discharge and fire all 6 plugs.

Now, I stated my theory to the PO and proved it once I went to Ford EDIS. The wasted spark design uses 3 coils instead of one. So now, I have triple the fire power.

And like before, I still hit 1.2 bar in 4th and the car never stutters a bit, ever.

I learned this trick in the '90's when running 1.7 bar in a Chevy 350. I'd run .020" plug gap and it worked to keep flame out at bay.

[Ronnie's.930]

Originally Posted by Speedy Squirrel

Are you sure it's not fuel pressure? It can cause a similar symptom, and can also be intermittent.

No I'm not sure about that. If the problem comes up again, this is one of the things I will look into.

Tippy - interesting writeup!

[krasuskyp]

I know what you mean, it does feel like flame out

doesn't explain my somewhat / seemingly highish idle when hot out of nowhere but I'll start looking @ spark 1st and go from thar

thanks

[Ronnie's.930]

Originally Posted by krasuskyp

I know what you mean, it does feel like flame out

doesn't explain my somewhat / seemingly highish idle when hot out of nowhere but I'll start looking @ spark 1st and go from thar

thanks

Paul, do you still have the vacuum limiter (aka decal valve) in place? I ask, because when mine began leaking badly, I had a very high idle, especially when warm, but it was more like 1500-2000 rpm, so probably not your problem. When I say "leaking", I mean, air leaking into the manifold (not into the atmosphere).

[krasuskyp]

funny you ask

yes/no

it was disconnected and plugged w/ golf tee aka awesome McGyver rig

least I thought it was

I note just the UFO disc there w/o any hose (or golf tee) - first place I was going to start looking, haven't probed it much yet

thanks tho!

prob is I've got so much removed / capped / re-routed it's hard for me to remember what I did years ago after it was gone for 1.5yrs 8-/ and I'm not dat smahhht

[krasuskyp]

Originally Posted by krasuskyp

plugs new, wires / cap / rotor were newer when I'd sold it so not many miles on all that

Ronnie-

Did you ever sort your issue here?

It's your thread, but I thought I'd share my resolution.

I FINALLY had a moment to eff around w/ mine - I started by pulling the cap and looking @ the contacts. Tough to get a good angle on it w/ the wires attached and see the contacts, but they didn't look great.

I scuffed them up, and - voila - misfire begone!

And here I thought they weren't that old, but after I started thinking about it I realized they probably had 15k on them - flies by!

Ordered new cap/rotor from our host and installed last night, love me these cheap easy fixes! Car running fantabularly once again - when it's good... it's GOOD!

Whilst probing, I did note my fuel pump fuse in front and the whole block in rear were greening up again. Will have to go thru them all and clean them up again.

Hope you're well otherwise...