Thanks in advance for reading what's happening with my ride.

It started on a trip from Montreal, Qc to Edmunston NB last winter.

I arrived barely and when I checked the engine, \I had a sparkplug whith the gapper completely melted.

I replaced the plugs, wires and headed back to Home.

Now since then, the engine stumble when i just release the brakes on the corner, you definitely feel that one cylinder if out of commission.

I replaced Distributor, wires (again), Injectors, [ulled the intake in order to replace plennum gasket and found out that the last bolt on passenger side was broken so I replaced it, ran compression on cold engine ( all are R ABOUT 90 PSI COLD ) checked with a vacum gauge and has a steady 22'' of Hg drop. the engine pulls hard when leaving the corners, gets 22mpg (us) or 13.5L per 100km ALL the time. Does not feel this '' hesitation anywhere else on the power band. Pulled PCV valve and does not get the '' pumping effect'' from the hole but a steady stream of light pressure ( I believe normal for a 366,000km engine.

I do not know where to look for as I replaced again this week sye sparkplugs with no better success.

The compression is still good BUT still stumble ( pumping) as I let go lightly on the breaks,

I have a friend of mine that works in a Dodge dealer in canada and dhe says that I<ve checked and replaced almost everuthing that should have been.

PS: I do not have codes on the engine ( no check engine light )

H E L P.......

 

"Stumbles when I let go of the brakes".

Bad booster causing a massive vacuum leak at one spot on the rod travel on release?

Don't do this in traffic! But - how about removing the vacuum line to the brake booster (plugging it with something) and seeing if it makes a difference.

Don't forget to check for the cruise control dump valve some vehicles have on the brake pedal arm (it serves to dump the vacuum on the cruise control servo in case the electronics don't release cruise on a brake tap or hard braking).

RwP

 

Hi and Thanks for the reply,


I will try this new ''test'' this very morning


goddamit...


Thanks

 

I agree on the brake booster likely being a possibility.

There is NO mechanical dump valve for the cruise control on the brake pedal arm however. The dump valve is electrically operated and part of the cruise control servo.

 

OK. Didn't know for his car, there is one on my 1991 Cougar. (May be one on the 88 Dak, I haven't crawled up there to check yet, but will while swapping out the booster/master cylinder.)

RwP

 

there's also a vacuum check valve I believe that can fail and cause a vacuum leak to the booster, if the booster itself is good.

I think you said you showed 22 inHg of manifold vacuum? That would be a MAP reading of around 11 PSIa I THINK, where 14.2X PSIa is zero vacuum (28.4X inHg). I will have to check my truck, but that doesn't sound totally out of whack if my memory serves correctly. I know the 14.2X is correct because my truck showed 14.28 with engine off and key on this morning.

 

18-22 in hg. would be "normal" for a healthy engine at idle.