Okay, this is the third time I have posted regarding my truck idling like crap.

I just changed the plugs for a third time, so it wasn't the bosch plugs causing it. I removed and cleaned the IAC, it wasn't very dirty anyway, but that didn't help anything. There are no vacuum leaks anywhere. I have 2 different MAF's a granatelli, and the factory MAF, it idles the same with either. I pulled the wiring harness off of the AC condenser and that helped for about 3miles, and then it all started again.


So, WTF is this, it all happened at about 700miles ago for no apparent reason. It started after I changed my plugs out, and has continued ever since. Does anyone think one of my COP's is going out? It's not a consistent misfire, it's a random 1200rpm-500rpm and everywhere in between fubar idle... and sometimes it idles like it's got huge cams in it, other times it just drops, and drops, then dies.

It's not only my idle either, when the truck isn't in gear I can hold the throttle at say 2500 rpm's, then it dips to 2000, then 1000, then flies back to 2500, then 3000, it's way messed up.

Anyone have any idea what this is, it's driving me to the point of destroying my goddamn pos truck. I swear I'm gonna drive it off a cliff, and never look back!!!

Thanks for any help.

 

Could be the Vortech V1/ Aftercooled @ 10psi, Race bypass valve, BBK 75mm TB, Gisbon headers, Granatelli MAS,Flowmaster 40 series exhaust.

My supercharged 5.8 Bronco did stuff like this.

I gapped the plugs a little hotter and it fixed alot of it.

You said it happed for no reason but started after you changed your plugs. I would think it did happen for a reason. The plugs.

It probably runs ok at WOT? How are your wires and coils?

 

I actually have had this exact setup for the last 3yrs with no problems whatsoever.

When I initially changed the plugs I ran Bosch double-tip plats (cannot gap), and then the problem started. So I swapped those for Bosch single-tip plats (gapped at .058) and the problem ended for about a week. As it got worse I decided to swap the plugs one more time. I installed auto-lites (gapped at .044) just to determine any change.

No change, problem is still there. I suspect perhaps it may be a COP, but like I said it is not a consistent misfire. I had my #4 COP go out due to a leaking heater hose, but the misfire was very different than it is now. If it is a COP how do I determine which one it is?

It misses while going down hills in gear with no load, and occasionally at WOT.

 

Man... sounds exactly what Mine did. Are you running the stock fuel pump?

Its got to be something with those plugs. I had autolites in when I had the problem then switched to motorcraft.

Good luck though. These kind of things are frusturating.

 

Could be a fuel delivery issue.

Then again, it could be a computer problem. Once my '97 hit the 100k mark, for some reason it took the computer forever (like 4 to 5 days of a 60 mile round trip commute) to get the idle adjustment back under control whenever I would unhook the battery.

 

Did you ever change the plug boots? They can cause your symptoms. Because your problem started after a plug change I would suspect the boots.


JMC

 

I have a Walbro 190lph at home awaiting installation, so I can remove the stupid inline T-rex pump.

My truck only has 63k miles on it, so I don' think it's the computer, but maybe. It has only thrown a CEL one time so far, even when it's running like crap. Perhaps a fuel filter or something?

Does anyone else think that I should install the Ford Motorsport platinums again? That is what was originally in the truck. I hate to have to pull everything out again to change the plugs, it's a massive PITA.

Any other suggestions? Thanks for the help so far guys, I appreciate it.

 

Its spark or fuel.

The fact that the problem happened after you changed plugs then was still there after you changed the plugs again, the problem is probably something that happend during the install/re-install. Like a torn boot.

As much of a PITA plugs are to do on these motors, I would pull everything out and inspect.

 

Is there any way I can inspect the plug boots? What exactly would I be looking for in the case of a malfunctioning boot? You guys are referring to the wire coil inside the boot having a break or poor contact.

 

I also had a phenomenon on my '97 that occurred whenever I would crank it, back it out of the garage and then crank it a short time later and pull it back in... like whenever I washed it or just needed the room in the garage.

Whenever I would crank the truck several hours later or the next day... it would idle and run like chit for about 30 seconds or so like it was flooded, then it would clear itself out. The last time it happened, I had done the wash thing and when I went to leave for work the next morning, it was idling and bucking like crazy. Normally it would clear itself out before the end of the driveway, but that time it continued on out into the street and finally threw a CEL. I'm assuming because of the rich condition. I unhooked the battery to clear the CEL and that's when my wacked out engine idle (low-high-low-stall) really got bad. Took the computer nearly a week to straighten it out.

Could possibly be a fuel filter but I would think it would be more constant if it were that. Easy enough to change out though.

 

I know you said you checked them all, but I was having something just like this today, and the vacuum line on the pressure regulator had popped off while I was removing the FMU. Also, with all that boost, run some copper plugs or irridiums at .035 and you'll get better fire

 

I was looking at the denso's I think the IT20 or whatever it is, one step colder, but I don't think that is the cause of my problem right now. I just finished putting everything back together this morning and all the vacuum hoses are attached...

 

have you checked it for any codes?? Also when it acts up try unpluging the idle air control motor and see if that calms it down. sounds as though it may be sticking and trying to overadjust. I have used the denso plugs for 2 years now and they are good but that is not you're problem. also you may need to clean the throttle body, also when it's acting up pull the vacume line from the egr valve see if that helps, you have to isolate the problem area. Check for any small air leak between the mass air and the engine you could have a small hole that is opening up at times.

 

How small of a hole do you think would cause an issue? One of my temp sensors may leak a little around it's seal I think... would that contribute much to the issue?

 

Spray some BPC or WD40 around the suspected leak. If the motor increases its idle, or studders, its a bad enough leak that needs to be fizixed