Suddenly ran like poop!

[fireguy12117]

so i was going across town today with the 93 4.0, when out of nowhere it felt like i downshifted and then had no acceleration. i pulled off of the freeway into some parking lot where the truck acted like it had a bad IAC. i limped the rest of the way to my destination, but it acted like it wanted to stall, when i'd try to accelerate it would feel like it was holding in a gear, not speed up hardly at all, then bark a shift and take off. i did pull the IAC to see if the rpm's changed, and i know i had all kinds of problems in the past with the IAC, but all this was new to me. wondering if anyone has a direction they can point me in. ill be doing my best tomorrow to test the usual suspects, but this all started while doing 70 down the freeway, so it was like something suddenly gave up the ghost- just gotta find it...

 

[Wicked_Sludge]

check your spark plug wires, one may have popped off.

could be about a million things. if a visual inspection doesnt reveal anything, you'll have to break out some diagnostic equipment and go to work on it.

 

[fireguy12117]

yeah...i knew it was a long shot...but hey, i might have -er- would have overlooked something obvious like spark plug wires. even checking my CEL light since the light didnt come on for such an obvious change in the engine.

 

[Wicked_Sludge]

a '93 is running fords version of on-board-diagnostics known as EEC-IV. it isnt nearly as picky about driveability as newer cars are.

heck, a few years ago, i had a lifter seize in its bore on my 3.0, causing the #3 exhaust valve to come in contact with the piston, bending the valve. the valve wouldnt close anymore so i suddenly had zero compression on one cylinder. the engine ran much like your discribing (i might add that my "gutless" 3.0 easily maintains 60MPH on 5 cylinders). the CEL never came on once during the 5 mile drive back home...even with raw, unburnt fuel from the dead cylinder flowing past the O2.

 

[MAKG]

My Prizm has a very late OBD-I (final year) computer. I had a spark plug wire come off once on a mountain highway. I felt the engine shake at low RPM, so I pulled over and popped the hood. The cat was glowing (on this vehicle, you can clearly see it from above). So, it was missing BAD; one cylinder was probably completely dead.

It did NOT set the CEL. I would have expected a lean code. This one is sophisticated enough to have a downstream oxygen sensor.

It was an easy repair, at least.

 

[fireguy12117]

nothings ever easy, is it...

well today the 98 decided to take a crap on me. i used lucas fuel treatment last week it and bit me today. that truck wouldnt get up past idle after i got to work. i had to leave for an errand and got stuck on the side of the road. long story short, got the biotch to rev, blow out what came loose, get the truck home, and swap in a new fuel filter.

i bring that up because the 93 acts an aweful lot like the other truck did today. the only thing casting doubt was doing a wiggle test before nightfall where the main harness from near the batter crosses to the block. when the engine was cold, i wiggled that and got some response from the engine, but as it warmed it, i couldnt get it to happen anymore. checked the vacuum, fuel pressure, PCV, and kind of called it quits there...

 

[Wicked_Sludge]

i'd back up and start with the basics. every engine needs 4 things to run: air, fuel, compression, and spark.

i'd do a compression test and check the spark at each cylinder.

did you rev the engine with the fuel pressure tester attached? you might be getting plenty of pressure at idle, but if your pump isnt able to supply sufficient volume, pressure will drop when the engines load increases.

 

[fireguy12117]

ive never done a compression test, but i do have the tester...

fuel pressure did go up a couple pounds when i gently reved the engine. havent pulled plugs and wires yet...bigger problems with the 98 not running worth a damn.

 

[fireguy12117]

i got under the hood again, played with some vacuum lines, that doesnt seem to be it. i can only get a couple shots in on this truck as im trying to get the 98 running. anyhow, i started looking at some of the plugs and wires. the plug wire near the wire bundle i was messing with, i checked resistance and got 7.7kohms for about a 2 long plug wire. tried getting that plug out, no luck. the plugs all look pretty old. got a different one pulled out, and its obviously worn down, so right now im thinking of trying to get all 6 replaced.

i did notice that the engine didnt want to respond around 2-3000 rpms. it would rev, get into the 2.5k rpm range and start to 'lug' for a lack of a better description. as i pressed the accelerator, the rpms didnt want to match. what i used to get. dont know how helpful that is, but im dealing with problems ive never had before....perhaps i need to go back to the fuel delivery and spark basics? seemed like the fuel pressure was ok though...

 

[Wicked_Sludge]

im starting to run out of idea.

if you have a vacuum gauge handy, i'd hook that up and see what readings you get throught the power band. it almost sounds like a plugged exhaust system....but then again it sounds like it could be a lot of things.

just because you have good fuel pressure doesnt mean the injectors are firing the proper amount at the proper time...

 

[fireguy12117]

plugged cat....

somethings been smelling weird lately, like some funky burn smell, but drivablity never changed. if ive been running rich with bad plugs, dumping rich exhaust...who knows. i feel like im beating my head into a wall without proper tools and knowledge, and now both my trucks are down...thank gawd i got the old ladies car running. i sense a lease on a hybrid soon....

thinking im sticking with some new plugs and wires ASAP and going from there...

 

[Wicked_Sludge]

a vacuum gauge is the proper way to diagnose a plugged exhaust system. might be worth your time to buy/beg/borrow a gauge to check it.

 

[MAKG]

Vacuum gauges (well, really hand vacuum pumps) can be very cheap. They often get labelled as "one-person brake bleeding kits" but they aren't really useful for that. These are VERY useful for vacuum diagnosis of all sorts.

An ignition miss (like a bad plug) can cause rich running, but it won't make the truck stumble at 2500 RPM. Even on a 4banger. It would make the idle rough. It may eventually plug the exhaust, but that won't be sudden.

 

[fireguy12117]

so what am i looking for with the vacuum? im tee'ed off at the manifold distrobution fitting, with a cold engine getting 20lbs, that drops to zero if i floor it. i put it in drive, it drops to 10, and idles 500 rpm. i was able to rev it past 3000 rpm with a cold engine...

i noticed that perhaps the reason it bogged so bad lastnight was leaving the stupid spark wire off of the coil pack when messing with that one plug, whoops...

 

[fireguy12117]

screw the vacuum...how do you get busted spark plugs out of the block...

driver side, closest to bump plug just snapped on me. wasnt reefing on it all that horribly hard and it popped. the ceramic is spinning by hand and the hex head is just loose sitting spinning too...this sucks.