Misfire under boost [Archive] - MercuryMarauder.net Forums

JimP

11-01-2015, 04:50 PM

I just made the two hour drive home with the pro-charged marauder I bought.

The car runs like a charm, but when I hit boost there is a misfire. I also noticed that the boost gauge does not go into vacuum when cruising. I'm guessing someone may have routed a vac line incorrectly or there is a bad check valve, bypass valve maybe?? Unfortunately the person I bought the car from knew very little about it.

I was going to check the obvious, plugs and coils...... it idles, and drives well, the misfire is only present under boost. Part throttle when I roll into it seems ok.

I won't get around to checking it over until Wednesday or Thursday because I work shift work but any advice would be greatly appreciated.

Thank You!

Jim

JimP

11-01-2015, 05:14 PM

I forgot to add it has a full compliment of gages but it was left outside yesterday evening so I could pick it up today and one of the gages went missing, now none of them work.

I need to figure out what gauge was in that pod, they are electric see pic. Hard to see but boost Guage is reading between zero and five while idling.

Thanks.

Toomanytoys

11-01-2015, 05:21 PM

sounds like bad tune. if its leaning out under boost you don't want to play around until you get it on a dyno with a competent tuner...

JimP

11-01-2015, 05:28 PM

sounds like bad tune. if its leaning out under boost you don't want to play around until you get it on a dyno with a competent tuner...

It had been tuned by lidio way back, as far as I know it hasn't been touched and I wasn't provided with the SCT scanner as they could not find it. Would the tune change if the battery went dead? I wouldn't think so.... but....

My last MM had a lidio tune and the converter would not lock up until in 4th gear doing about 60 mph, this one seems to be the same way.

chief455

11-01-2015, 05:40 PM

JimP

11-01-2015, 06:09 PM

the list of gauges and a picture are in this thread

http://www.mercurymarauder.net/forums/showthread.php?t=44260

you have a pic in your other thread as well.

don't hit boost anymore until you find a problem, you might have already detonated piston ring lands.

You'd better call Marty before anything.
Maybe the stolen gauge is causing a vacuum leak/electrical issue - battery dead, no tuner, it should have retained the boosted tune, but maybe not.
I'd get a new tuner with a 'safe' tune, and either get on a dyno, or tune remotely by data log with Marty.
He has done a few that way recently with success.
good luck.

Thanks will do. I didn't push it but not to say that no one else did. I just went outside and it is the 0-100 oil pressure Guage that is missing. They all seem to be electric guages. Been a long day, going to call it a night. I built my GN so I know it like the back of my hand. This car was built right and it shows. I'll get the bugs worked out and will keep it together. I'll get some under hood pics, over the next day or two.

Thanks fellas!

martyo

11-01-2015, 06:33 PM

The good news is the car has every gauge in the catalog.

8UWITH6

11-01-2015, 07:18 PM

Wut he said ^^^^^^^^^^^^^^^

chief455

11-01-2015, 07:28 PM

The good news is the car has every gauge in the catalog.

I checked....the catalog is sold out.:shake:
And no listing for a 'misfire' gauge either.

RubberCtyRauder

11-01-2015, 07:41 PM

Tune could very well be on a chip. Thus no sct unit. My trilogy car which I bought was installed and tuned by Lidio back when chips were the way to do it. Had MartyO update it to a sct xcal 4

justbob

11-01-2015, 07:50 PM

To start off you have an obvious vacuum leak which will cause a lean condition. Start there.

If it's been sitting, then bad gas or a fuel pump would be next on my list.

Builder Of Badassery

JimP

11-02-2015, 04:14 AM

Having tossed and turned last night I began to wonder if they filled it with 87 octane. It's got half a tank in it now. I'll take out as much as I can and fill it with 94. I'll post back with what I find and will call Lidio as well.

Car was supposed to have a hand held tuner come with it but it was never used. I got the car from a senior. They owned the car for 6 years only drove it for 2 and a bit.

I'll check vac hoses etc... and get the gages working again, they worked when I looked at the car originally.

Comin' in Hot

11-02-2015, 04:26 AM

Check the spark plug gap, if it's in the factory range the plugs are gapped wrong and would cause the car to misfire under boost.

1Marauder

11-02-2015, 11:53 AM

And what everybody else was thinking, "Your car interior looks SINISTER!"

Marauderjack

11-02-2015, 03:18 PM

Having tossed and turned last night I began to wonder if they filled it with 87 octane. It's got half a tank in it now. I'll take out as much as I can and fill it with 94. I'll post back with what I find and will call Lidio as well.

Believe me.....if it has 87 octane in it you would have MORE than a misfire!!:(

Experience speaking here!!:bigcry:

JimP

11-02-2015, 03:29 PM

Believe me.....if it has 87 octane in it you would have MORE than a misfire!!:(

Experience speaking here!!:bigcry:

I figured that much which is why I barely rolled into it getting on the highway. I checked the obvious but won't have a chance to really look at it until Wednesday.

I did not hear the obvious detonation that one would expect, not to say that it's not there. I'll do more digging, my schedule is not favorable to be wrenching the next couple of days. I'm not driving it at all either until it gets sorted out. I ordered the missing gauge, hopefully the others come back to life once it's in.

chief455

11-02-2015, 07:40 PM

didn't happen to see you air/fuel reading while under boost? I'd be staring at that and my fuel pressure gauge first times in a new car...

JimP

11-02-2015, 08:25 PM

didn't happen to see you air/fuel reading while under boost? I'd be staring at that and my fuel pressure gauge first times in a new car...

No a/f or wide band, it has a Pyrometer guage. I'll install a mechanical fuel Guage I have and check once I confirm no vacuum leaks. As I mentioned it was very brief, I did not push it past 3,500 rpm and once I felt the misfire that was it. There was also a small back fire which I forgot to mention.

Wednesday I have a day off. Will check all vac lines, plugs and gap, I'll drain the tank and top off with 94 octane. I sent an email to Lidio inquiring about an sct hand held tuner as I never got the one for the car and I will also need an emission tune, I live in Ontario Canada and they hook the car up to a obd2 system and check the operation of all emission equipment.

I think it's safe to assume the tune in the car now has disabled the egr, evap systems etc.... is there a way to ckeck, I have a blue-point scanner but haven't used it yet to check.

I also want to confirm which injector is on the car, they are a blue top, I'll get a picture and post if anyone can confirm.

My GN felt the exact same way when my ignition module was failing which is why I don't think it was detonation but rather a misfire. Wednesday can't come fast enough so I can give it the once over. It's a nice car and I'll get it sorted out. Thanks for all the advice so far and smart as comments too. There's an idea for a new guage a/f, there's still some room in the dash.

Anything else anyone would need to see picture wise? I'm a turbo guy and not sure about the procharger bypass valve operation. If it helps let me know and I will get a good bunch of photos.

chief455

11-02-2015, 09:56 PM

the Gods were smiling on you when you found it, and wifey said buy it.
It will be an easy fix. ;)
Yes, Lidio tune will have emissions monitors turned off - just was no big deal back then.
scan tool needs to have emissions readiness check as a function. Plug it in, turn the key to 'on' and see what monitors are 'ready' or more likely 'na'.
You'll get better support from Marty, just sayin'.
Lidio won't have your 10 year old tune on file - bet a new born baby on that.

RubberCtyRauder

11-02-2015, 10:05 PM

Mechanical fuel pressure gauge for in the car? I don't recommend it..No reason to chance blasting fuel all over the inside. Hope you find the culprit.

justbob

11-03-2015, 06:06 AM

All them damn gauges and no AFR or fuel pressure??? Sorry, that's almost as funny as just plain wrong..

An AFR is your life line! Besides your ears.. All blue injectors normally 39's, blue tops I "believe" common for 42's.

Builder Of Badassery

hotford

11-03-2015, 06:21 AM

Wrong plugs///wrong gap...start from there.......vac lines.leaks etc......
is the by-pass venting to the atomsphere or recycled back into the inlet.....

Lidio saves all his tunes from customers you will need the name its placed under in order to get.......

lifespeed

11-03-2015, 11:27 AM

Yes, Lidio tune will have emissions monitors turned off - just was no big deal back then.

While things may have changed over the years, my tune from Lidio does not have the emissions monitors turned off. It doesn't lock the converter until 60 mph, however. I revert the tune to stock for towing as it seems to be too hard on the converter clutch to try and lock at 60 mph with a load and the higher engine torque that comes with higher RPM.

JimP

11-03-2015, 03:41 PM

Wrong plugs///wrong gap...start from there.......vac lines.leaks etc......
is the by-pass venting to the atmosphere or recycled back into the inlet.....

Lidio saves all his tunes from customers you will need the name its placed under in order to get.......

Thanks for all the help guys. Plugs were gapped at .060!!! That's huge., my GN is gapped at .028 and 22psi is no issue.

I also found a vac line that goes no where. What plugs (heat range) would you suggest?

It looks like bypass valve does not vent to atmosphere from what I can see.

Hotford, we live in the same province, any issues with emissions test on yours?

I ran out of day light so that's it, I had an hour when I got home.

Off tomorrow so I will sort out what ever I can.

I'll contact either Marty or Lidio for an sct xcal as well.

Do these cars not have adjustable fuel pressure regulators? I also notice it's a non return fuel system.

Some pics, fuel rail where sending unit is mounted, blower, a plug, and where boost guage is mounted. You can see the blue injector in one of the pics. Will get part number off of it tomorrow.

MOTOWN

11-03-2015, 03:44 PM

Use an NGK TR6 (4177) gapped @28 , the cars didn't come with adjustable fuel pressure regulators.

JimP

11-03-2015, 03:51 PM

Use an NGK TR6 (4177) gapped @28 , the cars didn't come with adjustable fuel pressure regulators.

How is fuel pressure increased with boost? Does the ecm see it via the MAP sensor? I don't see any fuel pressure regulator anywhere on the car. Sorry my last MM was naturally aspirated.

Thank You for the plug recommendation. I'll get them after dinner.

So who wants another Marauder LOL!!! I wish the wife would say no now and then :) As if I didn't have enough stuff to work on, so much for free time.

Jim

MOTOWN

11-03-2015, 04:05 PM

Fuel pressure is controlled by the FPDM , its a returnless system from the factory, there isn't a MAP sensor on Marauders.

justbob

11-03-2015, 06:17 PM

Those appear to be Ford Racing 39# injectors.

Builder Of Badassery

Marauderjack

11-04-2015, 03:39 AM

How is fuel pressure increased with boost?

Pulse Width Modulation with constant fuel pressure!!:beer:

hotford

11-04-2015, 05:51 AM

Thanks for all the help guys. Plugs were gapped at .060!!! That's huge., my GN is gapped at .028 and 22psi is no issue.

It looks like bypass valve does not vent to atmosphere from what I can see.

Hotford, we live in the same province, any issues with emissions test on yours?

II'll contact either Marty or Lidio for an sct xcal as well.

Do these cars not have adjustable fuel pressure regulators? I also notice it's a non return fuel system.

Some pics, fuel rail where sending unit is mounted, blower, a plug, and where boost guage is mounted. You can see the blue injector in one of the pics. Will get part number off of it tomorrow.

Mod motors like the gap alot tighter than the older push rod motors
I run a tight 22 and never had any issues with misfire, TR6 is the choice of plugs

No problems with Emissions even with the monitors turned off, you should be good to go.

Those are factory Cobra (03-04) inhectors rated at 39 lbs.

Looks like all the added sensors use GM type connectors, I have no idea why he has a Map sensor on your car.?

JimP

11-04-2015, 03:28 PM

Mod motors like the gap alot tighter than the older push rod motors
I run a tight 22 and never had any issues with misfire, TR6 is the choice of plugs

No problems with Emissions even with the monitors turned off, you should be good to go.

Those are factory Cobra (03-04) inhectors rated at 39 lbs.

Looks like all the added sensors use GM type connectors, I have no idea why he has a Map sensor on your car.?

Not sure either, the boost gauge is hooked up to that as well as a vacuum source. still doesn't work and I fixed one vacuum leak. I accomplished what I set out to do today, luckily for me a Ford buddy came over. He was a big help. Hotford you're would love his car, I'll grab a pic off his Facebook page.

I put in the tr6's at .028. Changed the belt, topped off with 94 and zero misfire. I even took off the blower and fixed a belt alignment issue.

Car runs very strong and puts down rubber with ease even when rolling. It has a funky exhaust set up but I like the sound, not repulsive and very throaty, it's super quiet in the cabin.

I won't push it until I'm satisfied I haven't missed anything. I'll have a hoist to work with this weekend.

If it passes emissions with the monitors turned off I'll be extatic.

I even had time to clay bar the trunk rear bumper and quarters today. Paint came up very very nicely.

Thanks everyone for the assistance.

Jim

MOTOWN

11-04-2015, 03:32 PM

Glad to hear it all worked out for you, does the car have a methonal injection kit on it?

JimP

11-04-2015, 03:38 PM

Glad to hear it all worked out for you, does the car have a methonal injection kit on it?

Yes it has a snow performance kit. I need to check the pump and turn on time, I think it comes on at 3psi. It's progressive and maxes out at 7 psi.

MOTOWN

11-04-2015, 04:23 PM

Yes it has a snow performance kit. I need to check the pump and turn on time, I think it comes on at 3psi. It's progressive and maxes out at 7 psi.

The map sensor is probably what triggers the meth kit.

chief455

11-04-2015, 04:35 PM

The map sensor is probably what triggers the meth kit.
^this.
I'd be certain your motor is working and you have meth in the tank, if the car was tuned for it.
Julio at Alkyinjection says the motors lose pumping ability with age, and if let set for time, should be rebuild to get full pressure as fast as designed.

lifespeed

11-04-2015, 05:10 PM

Fuel pressure is controlled by the FPDM , its a returnless system from the factory, there isn't a MAP sensor on Marauders.

You learn something new every day. I thought all cars had a MAP sensor even if they use MAF also. How does the PCM map spark timing to load without a MAP input? Just MAF vs RPM? How do you get a known fuel flow vs injector duty cycle when the pressure across the injector is varied with boost and you don't have a boost-referenced pressure regulator? If the PCM knew MAP it could "boost-reference" the FPDM signal. Or is the fuel pressure sensor boost-referenced in a blower install to provide this function?

MOTOWN

11-04-2015, 05:14 PM

There's a FRPS fuel regulator pressure sensor on the passenger side fuel rail that tells the pcm the fuel pressure.

chief455

11-04-2015, 07:35 PM

Marty just tunes it, so it knows. :D BOOST!:banana:

justbob

11-04-2015, 08:22 PM

There's a FRPS fuel regulator pressure sensor on the passenger side fuel rail that tells the pcm the fuel pressure.

^This. Plus the vacuum to it is boost referenced assuming you are still return less. If not, then your boost referenced regulator.

Builder Of Badassery

JimP

11-04-2015, 08:38 PM

chief455

11-04-2015, 09:11 PM

Well, finally figured out why boost Guage wasnt working. It needed to be connected to a 12v source that would stay live when cranking the engine to start. You need to turn key to acc, give the Guage a second to zero itself then you start the car. The gages all self calibrate this way each time you start the car. They all work now.
WINNING!
The car was for you, wifey was right :)

now, get and air fuel and fuel pressure gauge somewhere in that cockpit ;)
I said it = cockpit.

JimP

11-05-2015, 05:37 AM

WINNING!
The car was for you, wifey was right :)

now, get and air fuel and fuel pressure gauge somewhere in that cockpit ;)
I said it = cockpit.

I have an aem digital failsafe a/f Guage which I had bought for my GN but never got around to installing this summer.

I'll likely take the gauge that's in the GN now and put it in the Marauder, GN is stored for winter so it will have to wait. Marauder has the procomp fuel pressure gauge, I'm missing the oil pressure gauge as someone stole it, they must have been spooked because they had another gauge halfway out.

The dash (cockpit) does attract a lot of attention, I've had the car less than a week and it's back to its former glory. I've already debated putting in digital gauges as the hard part has already been done.

I'm glad I was able to save it, who knows where it would have ended up. Like I said before, I didn't really need it but was looking as I was curious to see what was out there and stumbled across it. If my situation ever changes and I decide to get rid of everything, the MM will go up here and my GN will go up at the turbo Buick site. I've had a rediculous offer on my GN in the past and said no because it wasnt the right guy.

I'll be yanking the whole meth/water kit, servicing any serviceable parts, it comes out in 5 minutes and is located where the battery used to be.

Emission test is next when I have a moment and then it goes into storage for the winter as well. I could also use the break away from cars, I have two other dd's that will need some love.

chief455

11-05-2015, 06:28 AM

^^that is all good.
Now you can update your sig :)

hotford

11-05-2015, 07:44 AM

You learn something new every day. I thought all cars had a MAP sensor even if they use MAF also. How does the PCM map spark timing to load without a MAP input? Just MAF vs RPM? How do you get a known fuel flow vs injector duty cycle when the pressure across the injector is varied with boost and you don't have a boost-referenced pressure regulator? If the PCM knew MAP it could "boost-reference" the FPDM signal. Or is the fuel pressure sensor boost-referenced in a blower install to provide this function?
The computor has lean/mean load tables it refrences which can be modified.
Only Ford cars that have both from the factory equipped supercharged cars
03-04 cobra
07-14 Shelby
All Eco Boost eqipppied vehicles

hotford

11-05-2015, 07:50 AM

^this.
I'd be certain your motor is working and you have meth in the tank, if the car was tuned for it.
Julio at Alkyinjection says the motors lose pumping ability with age, and if let set for time, should be rebuild to get full pressure as fast as designed.

Good eye...I personal would use a Hobbs switch....but to each there own I guess.......

My bro had Julio kit and is a great peice of engineering...only down side is the pump fail continuously.....make sure you have a A/F gauge this what saved our AZZ on his car......

chief455

11-05-2015, 11:18 AM

Good eye...I personal would use a Hobbs switch....but to each there own I guess.......

My bro had Julio kit and is a great peice of engineering...only down side is the pump fail continuously.....make sure you have a A/F gauge this what saved our AZZ on his car......

I used a Hobbs switch from manifold vacuum/boost set at 1psi to activate my 2nd fuel pump, on a car with a return line system. But the Julio kit comes with a MAP sensor to trigger his meth pump progressively, rather than on/off. Which is nice to meter the spray with boost opposed to full spray at a little boost etc.
JimP will be all set with his failsafe AEM a/f guage :)

JimP

11-05-2015, 04:39 PM

I use a hobs switch in my GN, it has an smc kit in it and dual in tank walbro pumps, pump 2 and the alcohol come on at 15psi. The GN smc kit is equipped with a prime button to test it, I know it sprays when the car stumbles at idle and I also see the Intake temperatures drop.

I filled the Marauder kit with 50/50 water / meth. I'll try and duck out of work tomorrow and give the alky kit a once over, I already saw a connection I didn't like. The way the kit was done it sits where the battery used to be, comes out in 5 minutes, battery is now trunk mounted. Hopefully the pump is good, the pockets are a bit lighter as I bought the car outright.