[sagamol]

that is how it feels, like a semis air brakes. it happens after the car has been driven for about 5 miles and the engine is warm. it only happens at speeds of 50 mph or higher. i have to push the accellorator to keep constant speed. the "hesitation" is sporatic and goes away if i apply thrust, like going up an incline. if driving on level surface or downhill, the engine bogs down, or hesitates a second then its smooth again. a few seconds later it bogs again.
i have replaced the resonator so far ( it had a leak in the pipe) i also replaced a vaccuum line that was almost collapsed and my mechanic is wondering if there is a diagram we could get , so he could check the rest of the vaccuum system for collapsed lines. he thinks this is part of the problem. it has gotten better since he replaced said line, also, after taking the car out on a "cleaning the pipes" mission, it was better ... went for about 5 miles @ +90 ..it really made her purr....wow... another tought was to have the injectors cleaned. not sure how to do this. the idle is very smooth at about 700 rpm and the oil pressure in idle stays just below the "1" mark. the engine starts perfectly, even after sitting a week or so. there is no smoke coming from the tail pipe while driving. it all seem very normal, until about 5 minutes into a trip, when the motor seems to lose power. anyways, the hesitation or boging down is back and i need some help figuring this out...any suggestions are appreciated..(sorry this post is so long, tried to get as much detail as possible)
Thanks, Tom

 

[neanderthal]

do a tuneup. plugs, wires, cap, rotor, fuel filter, air filter. you can use fuel injector cleaner, i use chevrons, i get it at costco. use premium grade gasoline.

that should be your first step.

 

[augapfel]

You car's problem sounds suspiciously like a clogged catalytic converter. How many miles on it? Your mechanic should know how to test for that problem but here are two ways:
1) with the car parked and running, hook up a manifold vacuum gauge and watch readings as you increase engine speed. A severely clogged converter will block exhaust flow to the point that the pistons have difficulty stuffing more air into the exhaust system. Hence, the manifold vacuum readings will start to decrease (that is, the vacuum numerical value will start to decrease).
2) temporarily remove teh oxygen sensor and install a fitting there that allows you to hook up a pressure gauge. You can drive the car watching exhaust system pressure. It should never go over 2 psi.

Were this my car I would swap over the complete exhasut system from one of my other cars. It's remarkable easy to do since thre are few fasteners and the whole thing drops in one large piece. It would sure tell you if the exhaust system was the problem!

 

[sagamol]

Thank you for the replies. the car has 89.000 miles and i just replaced the resonator, but the symptoms happend even before that. the AC doesnt work anymore either and neither does the cruise control. not sure if there is a relationship between them. also the SRS light comes on every once in a while. there are a few minor other bugs, but nothing major. i also ordered that famous OVP relay and when i got it, the pins of the new one didn't fit the plug on the wire to be plugged into. there are more pins on a new relay then the old one had, so i send it back..
anyways, i will have them do a check on the manifold pressure , next time i take it in for service. i also will do the injector cleaner, since the car has been sitting most of the winter. i only drove it 3000 miles since jan of '07. but like a good German, i washed it every saturday, if it needed it or not..LOL

you all have a great week...
Tom