91 GA problem

[Red2dr5spd]

i have a 91 GA base model with the tech 4 2.5 and i decided to change the plugs with winter coming soon and when i was removing the air cleaner the little black line from the map sensor to the throttle body broke. i tried removing the 90 degree rubber boot and the stem coming off the map sensor broke. so i had to drive one day without, it using lots of gas with the ses light on. so a day later i got a new map sensor and cleaned the new plugs i put in, they were covered in black ash indicating it was running very rich.i used a rubber vacuum line to go from the map sensor to the broken plastic line.it runs much better, no ses light but it stumbles when im accelerating, i dont have a tach but its when its at lower rpms, for instance when i shift up then coast for a second then hit the gas it happens but then goes away. i checked the plugs and they are very clean and gapped properly .06 inches. im gonna get a new air filter and fuel filter in a day or 2 and see if that helps any. any suggestions?

[doobiess]

if it were running as rich as you say it was.. it possible its really dirty inside the engine.. all i could say it drive it a bit now and im assuming it will clear up on its own...

[rixGAphx]

Running very rich for a while will really tax a catalytic converter, especially an old one.
The richness may have been 'the last straw', and it's now plugged except at higher engine speed when the pressure forces the exhaust thru.

Go to any muffler shop, they have a quick (and usually free) method of testing cats.

Good luck.
-Rick

[HeyDace]

Does it feel like the engine is jumping around in the engine bay? Does it coincide with accelerating and decellerating? At cruise speed its fine? Kinda sounds like an engine mount.

[Red2dr5spd]

it feels like a misfire which i think it mught be because i noticed that one of the plug boots is torn and it might be arcing on something

[4kQuad]

are you sure .06 is right for your plugs. That seems way......tight to me. .034 or .038......in that area seems a lot closer to right to me. .06 would be way close and cause bad spark, witch would expalin the build up and jumping after you let it idle a little and get back in it.

Call a parts store and recheck what the gap of the plugs should be. I bet that you got the wrong info the first time and a regap will fix a lot.

[cage47]

This is the same thing I'm dealing with. I've replaced most of the sensors on my tech 4 in my 90 ga. I'm down to the replacing the map sensor. Going to do it tomorrow.

[Red2dr5spd]

on the emmisions sheet on the front of the engine bay that says spark plug gap is .06 inches. i used just regular autolite walmart plugs would every plug have a different gap? ill retry gapping the plugs tommorow

[doobiess]

yes use .06 gap.. and I use basic autolites... they work great for me.. but also as for the gaps... i would highly recomend using a wire type gapper... and only that for setting the gap since when i used other gappers.. it wasnt even close.. and caused my car to misfire.. but now its great

[rixGAphx]

4KQ and I are from the 'old days', when ignitions had points, 'High Energy' coil produced 12,000v, plugs wer gapped at .035 to .050 MAX, and only lasted 15k miles at most.

'Modern' high energy ignitions are in the 35-40k volt range and easily spark across the SPECIFIED .060 for our ('96 3.1) engines.

Note: .0625 = EXACTLY 1/16 inch.
I don't know in Canada/metric, but this is EXACTLY equal to the rim thickness of a new US quarter.
Accurate gapping is not as important now as it was in the old days when gaps were smaller and the lightest error had major consequences.
One consequence was that oil blow-by could easily bake into a carbon chunk that would foul (totally bridge the gap) of a plug that had too-small a gap.

Even cheapo AC plugs have platinum tips, which has excellent hi-temp resistance and therefore do not burn down (like old-fashioned electrodes) for 60k+ miles.

The large gap (.060) of modern plugs creates a 'flame front' from the spark that is twice that of an old plug, and really helps the performance and emissions of modern engines.

Good luck.
-Rick

PS: And even the Wal-Mart cheapos come factory-gapped with good quality control, and a little cardboard sleeve to protect the electrode during shipping and handling.