Ok, I am having a very aggrevating problem with my 95 Buick Roadmaster. As with the Impala SS, it is outfitted with the LT-1 corvette motor. In the cooler months, it is amazing how fast this 4500 pound bohemouth gets moving. In the warmer months, it changes it's ways. The problem is a missing type of sound and hesitation. It is speratic. Sometimes the car runs just fine. If it has been sitting out in the hot sun all day, it is almost always bound to have the problem. Of course, running the A/C just intensifies the situation. It has been in 3 Goodwrench dealers, and 2 private garages. I have had almost everything replaced, and the problem is still there. The shops fix something and say it is fixed, then it starts doing it again on the way home. They have replaced the sparkplugs, plug wires, distributor, coil, catalytic converters, fuel pump, fuel filter, EGR valve, MAP sensor checked, and cleaned injectors and plenum. None of these have fixed the problem. The sparkplugs were replaced again, because they showed carbon striking (?). I have used octane booser a couple of times, and the car will run fine for a tank or 2, then just go back to missing. I tried just using the premium gas, but that did not make a difference. The problem is hesitation at low rpms. Whether I am just taking off or cruising down the interstate, it hesitates, spits, sputters until it gets revved up. Once it reaches the higher rpms, it pulls out of it, but it still has a surging type of feeling. During the winter months, it doesn't display any symptoms at all. If anyone has had such a problem or has any ideas on what else may be causing the problem, I would greatly appreciate any help I can get. Who else to ask about LT-1s than hotrodders, right? :confused:
I do not claim to know a lot about all the new electric gizmos and computers on the NEW stuff. I did have the same basic problem on my Silverado (5.7 Vortec) and I changed the coolant sensor located next to the water themostat housing. A buddy told me his car was doing what mine and yours is doing and he changed the sensor. I tried it. It worked.
I know the feeling
I have a 92 Caprice and I swapped engines with a 69 Chevelle 350. In doing so I neglected to reconnect any computer lines to the engine. I was running Blind basically, I had the exact problem you do, at higher temps it sputtered and jutted the engine even died a couple of times. What I did was replace the thermostat and get a flex fan. The Fan runs at the speed of the engine so it keeps it cooler even when in idle. Hope this helps.
PS: I am trying to locate a LT-1 Engine where did you get yours?
Does it have a knock sensor? If it does, maybe the excess heat is causing detonation, and the sensor is telling the computer to retard the timing.
duece, the temp gauge indicates that is running about 1/3 high. No matter hot weather or cold, it never varies after it has been warmed up. Did your gauge get hotter than normal on hot days? I will try and locate the sensor and check it.
Jeruzalem, '94 to '96 Roadmasters and Impalas came with LT-1s. You are correct. If the engine is running hot, you do experience predetonation. The problem is that the car is running a normal (fairly low) temp. The outside temperatures seem to be causing the problem.
I have heard tell of the computer gizmos being a link to the problem, but I am hesitant to sink more unneeded cash into this thing. I have spent over $2500 so far, and I can't believe nobody stands behind their work anymore. Does retarding the timing cause missing? Does that type of missing turn to surging at higher rpms? I am so used to tuning by hand, that this thing does not allow. Thanks for the tips. I will be checking them out this weekend.
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