2.3 intermittent chug/bog when cold

[RobertISaar]

i'm copying this from a PM i sent pocket-rocket on another forum, so if things don't seem 100% there, that's why.

92 2.3/5 speed 2WD, i think 3.54 gears

when cold, sometimes with any kind of throttle will cause a massive amount of bogging/chugging for what seems to be random amounts of time, then clears up instantly all the way to redline, upshift, then it sometimes comes back, sometimes goes away entirely. when this happens, if you're idling, you can BARELY tell the difference in exhaust note, RPM seems stable, but as soon as any throttle gets applied, it gets progressively worse. usually if it happens my father in law or i just put foot to floor and hope no one is behind us. sometimes it goes away in a second, sometimes 30 seconds.

anyways, the truck was down for a while due to a brake line exploding at the rear, i took the time to check out the normal stuff, plug wires were ancient, plugs were ancient, so replaced those. one of the plug wires for the driver's side had corroded quite badly inside the coil, so i did my best cleaning it out, looks relatively new underneath all of the green power that was generated. didn't ohm check it yet, but the other 3 coils tested out well.

but the problem still exists. the ICM(or what was referred to as the ICM) was replaced ~4 or 5 years ago(with a junkyard unit) due to the issue happening at all times(motor cold/warm/low or high RPM). coils are probably original, but the 3 i tested did ohm check out the way they should have.





ideas?

 

[Mark_88]

Vacuum leak...TPS perhaps...maybe just needs some TLC...fuel filters? air filter? what have you checked? Could also be fuel pressure regulator or a pump going south...

Too many variables really to say but maybe someone with similar symptoms will offer more constructive advice...

 

[RobertISaar]

a couple of the plugs from the driver's side were kind of white, but since it's intermittent i don't want to go down that route yet.

air filter is brand new, fuel filter, no idea, but it doesn't act like it's starving for fuel, more like a lack of spark.

haven't checked pump/pressure either.

 

[Mark_88]

not sure if you have a MAP sensor (on the firewall above the heater box usually) but that was the cause of a similar situation with my 89 Tempo...it would die, bog, or just idle really erratically for no apparent reason...had the codes pulled and the first was MAP...second was O2 sensor...and the price went down in parts from there...I drove to a junkyard and bought a MAP for $5 and it cleared it up...

The tempo also had a low pressure pump in the tank that would go out frequently...giving similar symptoms...

The MAP, if you have one could be wonky...but if you can pull the codes it will probably tell you what is causing the issue...you could try unplugging the battery for a bit to see if it clears the codes and the situation but it could come back right away...

 

[RobertISaar]

this has never actually throw any codes. or at least the SES has never been triggered on by them.

and according to the factory wiring diagrams i pulled through alldata, no MAP sensor is used in this application.

the pump, off hand i wouldn't really suspect it, since the condition always clears up, but the bed is getting pulled off in a few days to deal with more brake likes, so i'll likely pull the pump then and bench test it, or just leave it in the tank and apply power, see if it starts acting funny.

 

[RobertISaar]

update: had to pull the bed to mess with brake lines, once off, we discovered the non-existance of the rear leaf spring shackles, fuel lines that are ready to disintegrate, fuel filler neck needs replaced, junk leaf springs, among many other issues...

anyways, the truck may or may not be repaired, though if it goes the repair route, we're either going to swap ICMs/move coils around, etc, since it looks like the fueling system does it's job.

 

[Mark_88]

Ouch...

Well, the good news is I've been there and done that...had to replace all my brake lines and the shackle on the passenger side...'

The really good news is you can do the brakes yourself complete for under $200...including brake cylinders, connectors, and lines...right up to the master...and front flex lines...

Not hard to do the shackles either if you have an impact gun and a bit of patience...

 

[RobertISaar]

yeah, i looked into parts from rockauto, both shocks, both shackle brackets and the shackles themselves came out to a little under $100 with shipping.

after that, the big ticket items are the leaf springs themselves, which will likely be a junkyard item.

i forgot to mention that at least one of the cab mounts are completely destroyed as well, not sure what is going to happen with that yet.

brake lines are nothing to me, i've needed to do them on every single vehicle i've owned/driven regularly.



anyways, assuming he doesn't want to get rid of it entirely, these items will set back the ignition issue a bit.

 

[RobertISaar]

well, an update...

it took long enough, but the suspension stuff is now more or less finished, just have to throw shocks on it and it will probably ride like it was new.

cab mounts..... are probably going to be fixed with significantly less finesse.

new brake lines from the master cylinder to the wheel cylinders are also going to be run very soon.



so, now it's down to it's original issue of what seems to be intermittent ignition issues. truck was started and run for a few minutes yesterday, didn't seem to be having any problems. when it does happen, you can slightly hear it at idle before you put your foot into it, just idles.... with a different tone. didn't hear or experience that.

when it does happen.... i have the idea of disconnecting one of the coilpacks connector from the ECM(or ICM, i haven't studied the diagrams too much) to see which one is cutting out. see which one causes no change when it's idling and that's the one that isn't functioning during the problematic phase.

 

[RobertISaar]

MOAR update:

now that it's consistently cold outside in Michigan, i'm experiencing this pretty much every time i try to take off while still cold...

odd observation: when it starts chugging, the more throttle you give it, the worse it gets.... right until you hit WOT and then it suddenly clears itself up and runs normally until the RPMs start coming down.... then back to chugging. makes for tough snow/ice covered hill climbing.

so.... what changes between 90% throttle and 100% throttle at lowish(~2000 or less) RPM?

tried various sources and blends of fuel, anything from 87 to 93 octane and it still happens. did notice that if i pull the oil filler cap off while running, the idle changes significantly, so it seems like the PCV is stuck open.... i should probably stick my vacuum pump/guage on it to get some idea of where it's running at idle...

sometimes i can take off normally and half a mile down the road, in 3rd or 4th gear by that point, it will start acting badly, foot->floor, fixes it every time... sometimes comes back after releasing throttle, if so, i jump into the highest gear i can that won't cause the engine to shudder at full throttle and just hold it there for at least a good 10 seconds, at that point it's usually warmed up enough to not have it happen.



so now, fuel or spark, i don't really know which. still no SES light. i need to see if i can dig around and find a fuel pressure guage...

i'm used to GM electronics, it's too bad there's no way that i know of to hook a scanner up and read sensor data... i get the feeling it's something simple.

 

[modelageek]

MOAR update:

now that it's consistently cold outside in Michigan, i'm experiencing this pretty much every time i try to take off while still cold...

odd observation: when it starts chugging, the more throttle you give it, the worse it gets.... right until you hit WOT and then it suddenly clears itself up and runs normally until the RPMs start coming down.... then back to chugging. makes for tough snow/ice covered hill climbing.

so.... what changes between 90% throttle and 100% throttle at lowish(~2000 or less) RPM?

tried various sources and blends of fuel, anything from 87 to 93 octane and it still happens. did notice that if i pull the oil filler cap off while running, the idle changes significantly, so it seems like the PCV is stuck open.... i should probably stick my vacuum pump/guage on it to get some idea of where it's running at idle...

sometimes i can take off normally and half a mile down the road, in 3rd or 4th gear by that point, it will start acting badly, foot->floor, fixes it every time... sometimes comes back after releasing throttle, if so, i jump into the highest gear i can that won't cause the engine to shudder at full throttle and just hold it there for at least a good 10 seconds, at that point it's usually warmed up enough to not have it happen.



so now, fuel or spark, i don't really know which. still no SES light. i need to see if i can dig around and find a fuel pressure guage...

i'm used to GM electronics, it's too bad there's no way that i know of to hook a scanner up and read sensor data... i get the feeling it's something simple.

At WOT you go to open loop and are only using a few sensors. The maf, ect, etc. You are not using o2's

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sent from DROID Bionic using tapatalk-2. (Ranger, 1999, reg cab, 2.5, 5 speed, 2WD) (2006, Vibe, 1ZZ, Auto, AWD)

 

[RobertISaar]

right, but at the coolant temps where this is happening, closed loop should already be disabled.

i might try disconnecting the O2 and seeing how it reacts...

 

[modelageek]

right, but at the coolant temps where this is happening, closed loop should already be disabled.

i might try disconnecting the O2 and seeing how it reacts...

He did not say specifically when it happens or if he did I missed it . Just cold out. My truck goes into closed loop pretty fast. When the coolant temp hits around 55f it is closed. Maybe his heater in the o2 is toast so it takes until the temp hits 600 to run better. I will read the thread again.

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sent from DROID Bionic using tapatalk-2. (Ranger, 1999, reg cab, 2.5, 5 speed, 2WD) (2006, Vibe, 1ZZ, Auto, AWD)

 

[RobertISaar]

hmm.... this is true. Ford started using heated O2s a lot earlier than GM did...

a lot of the GM OBD1 stuff wants a minimum coolant temp of ~100*F or so before it will allow closed loop, along with a time delay.

the only temp reference i have is the guage, and it acts quite oddly at times.



actually, a thought: if it is going into closed loop really early, shouldn't i be able to let the engine get cold again and attempt to start moving pretty much immediately after it fires up? shouldn't be in closed loop at that point, and if it does act up while driving, i could assume that it when it drops into closed loop....

assuming all of that does happen, if i unplug the O2 and it doesn't happen anymore, by process of elimination, that should point to the O2 being the issue, right?

 

[modelageek]

I would change the fuel filter if it is not done. I think you have a maf sensor in the air intake. Clean it with crc. The precat o2 is the only one you need to worry about. If the trouble goes away when it is warned up and goes away at wot when cold my guess is the precat o2 sensor is bad

______________________________
sent from DROID Bionic using tapatalk-2. (Ranger, 1999, reg cab, 2.5, 5 speed, 2WD) (2006, Vibe, 1ZZ, Auto, AWD)