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DuaneS
09-07-2005, 11:08 AM
I've had a tough summer with my 98 VRS Maristar 5.7 TBI. After idling between skiiers on the next acceleration it boggs down. The remedy seems to be trottle up to about 3000 rpm and within about 15-30 secs it clears itself and is now ready to ski. On the other hand if I shut the motor off between skiiers the next acceleration is just fine. I've replaced both inline filters several times. Sorry for the length but next stop for the boat is the shop.

erkoehler
09-07-2005, 11:42 AM
JIMN or enginenut should be around to help out :dance:


Could it be that one of your injectors is stuck??

Leroy
09-07-2005, 11:51 AM
If not what Erk suggests, I would guess something in the fuel, or spark plugs going bad. I would drop in can of HEET and change your plugs. Cheap things to do.

rektek
09-07-2005, 03:56 PM
sounds like your engine is loading up at idle, ecm injecting too much fuel. 2 major sensor inputs are TPS and map sensor. my guess would be faulty tps giving incorrect idle info to the ecm, increasing injector opening at idle. either one is a easy diagnose and repair for someone qualified. is the engine surging at idle as well ? exhaust, smoke ?

post more details please

gregg
09-07-2005, 04:59 PM
sounds like your engine is loading up at idle, ecm injecting too much fuel. 2 major sensor inputs are TPS and map sensor. my guess would be faulty tps giving incorrect idle info to the ecm, increasing injector opening at idle. either one is a easy diagnose and repair for someone qualified. is the engine surging at idle as well ? exhaust, smoke ?

post more details please

Sounds like a pretty good call. Mike a MYMC told me they see a lot of trouble with the MAP sensors getting a thin film of oil on the sensing diaphram. Enough for performance problems, but not for a check engine light or code. If you want to try one, call any GM car dealer parts dept. and give them the number on your sensor, they will probably have one in stock.

DuaneS
09-07-2005, 05:37 PM
Great info. I'll try the MAP sensor first. What does MAP stand for? Where is it located and can it be removed with common tools or something more specialized?

gregg
09-07-2005, 07:15 PM
Great info. I'll try the MAP sensor first. What does MAP stand for? Where is it located and can it be removed with common tools or something more specialized?

Manifold Absolute Pressure......Should be on the end of a short vacuum hose on the back side of the throttle body with a 3 wire connector plugged into it, or at least thats where it is on my 2002 Maristar with the 310 hp tbi engine.