Ok here's a snip from my sensor readings, but at 2500 rpm is what I'm concerned about. It also occurs at a little over 2000 rpm as well. This is not drivetrain related as the vibration is present revving when in neutral. Doing WOT runs shows the O2 to be rich, and pulling the plugs give a nice brown/tan look on them so I ruled out being lean. But when revving not in gear, and on highway at these constant rpm, speed, and load I get the exact same O2 and BLM counts. Lean on the O2 and high BLMs like I'm running lean, I'd run like this for a good 5 mins, then cut the engine, pull a plug and find only a brown/tan plug. Doesn't sound like a misfire.. just some strange "vibration".

Ran like this for a good 30 sec on highway, intermittent vibration, readings stay almost constant like this during that vibration.

Time 354.2
Prom 591
IAC 94
Coolant Temp 175.2
Speed 89
MAP 50.6
RPM 2350
TPS 18.1
INT 128
O2 0.035
Batt 13.7
Knock 6
BLM 142
Rich/Lean 201

Time 155.7
ID 591
IAC 40
Coolant temp 173.4
Speed 78
MAP 30.3
RPM 2075
TPS 10.8
INT 128
O2 0.049
Batt 13.7
Knock 5
BLM 140
Rich/Lean 189

 

Is the vehicle a '89-'92 TBI by any chance. The reason I ask is that it looks like it is running is a lean cruise mode (highway mode). Also, is it modified at all?

On an EFI engine tan/brown plugs are unusual. Most of the time they are bone white.

The reason I say lean cruise mode is the INT is at 128 (locked?) while the O2 is 35-49 mV. The BLM is a bit high, 140-142, which is adding fuel. If the engine is stock then I'd look into the ignition system. During lean cruise it takes an ignition system in good condition to fire off the mixture.

RBob.

 

It's an 88 TBI LO3 fairly stock.

I did a tune up about a month ago. was running great until last week when this vibration started. I put in stock AC/Delco plugs gapped at 0.045, MSD plugs and wires, taylor cap and rotor. I took it on the dyno the next day and made 261 ft/lb and 178 HP with a very smooth tq/hp curve and no hiccups whatsoever.

Yes its in its lean cruising mode when this is happeneing. It also happens in neutral. It vibrates at the same exact rpms as when in lean cruising mode.

tan/brown has been pretty much the norm color for my plugs since I can remember. Passes emissions.

My msd ignition coil is just over a year old, its a GM MSD Blaster II I think.

My mods engine wise are limited, 1.6 rocker arms (2 years old now), tbi injector spacer, custom y-pipe, magnaflow hi flow cat, flowmaster and March power and amp pulleys.

The int does vary, it doesn't stray too far from 128 though. If you can copy and paste what I type into a txt file then open in Excel, you'll have my readings from yesterday.

Time SENSOR:PROMID SENSOR:IAC SENSOR:Coolant Temp SENSOR:SPEED SENSOR:MAP SENSOR:RPM SENSOR:TPS SENSOR:INT SENSOR:O2 SENSOR:Battery Voltage SENSOR:Knock counter SENSOR:BLM SENSOR:rich / lean counter
1.1 591 89 194.4 71 41.7 2700 17.1 135 0.787 13.5 5 138 181
2.3 591 88 194.4 72 40.6 2725 17.1 132 0.782 13.4 5 139 181
3.5 591 88 194.4 74 41.4 2800 18.1 132 0.659 13.5 5 140 181
4.7 591 106 192.8 74 50.9 2875 21.9 132 0.071 13.5 5 128 182
5.9 591 128 192.8 76 74.9 2975 35.5 128 0.924 13.2 5 128 182
7.1 591 128 192.8 80 73.8 3125 35.5 128 0.928 13.3 5 128 183
8.3 591 128 192.8 84 69.8 3225 33 127 0.071 13.4 5 128 183
9.5 591 128 192.8 86 63.1 3300 29.2 134 0.8 13.5 5 130 184
10.7 591 128 192.8 87 53.9 3325 23.4 138 0.906 13.5 5 142 184
11.8 591 128 192.8 89 49.5 3400 22.4 134 0.765 13.5 5 143 185
13 591 128 191.4 90 49.1 3400 22.4 130 0.857 13.4 5 144 185
14.2 591 128 191.4 91 48 3475 22.4 128 0.491 13.4 5 144 185
15.4 591 128 191.4 94 48 3525 22.4 127 0.442 13.5 5 144 185
16.6 591 128 191.4 94 47.6 3550 22.4 127 0.804 13.5 5 144 186
17.8 591 127 191.4 96 46.9 3600 22.4 127 0.778 13.4 5 144 186
19 591 126 191.4 97 46.9 3650 22.4 127 0.186 13.4 5 144 186
20.2 591 126 191.4 98 46.1 3675 22.4 127 0.849 13.4 5 144 187
21.3 591 126 190 98 46.1 3700 22.4 127 0.857 13.5 5 144 187
22.5 591 126 190 99 46.1 3725 22.4 127 0.097 13.4 5 144 187
23.7 591 127 190 101 45.4 3725 21.9 127 0.499 13.4 5 144 187
24.9 591 125 190 101 45 3800 21.9 127 0.566 13.5 5 144 188
26.1 591 123 190 102 43.2 3800 21.5 127 0.097 13.4 5 144 188
27.3 591 120 190 103 42.5 3825 21 127 0.08 13.4 5 144 188
28.5 591 117 188.6 103 42.5 3800 20.5 127 0.844 13.5 5 144 188
29.7 591 115 188.6 102 41.7 3875 20.5 127 0.186 13.5 5 144 188
30.9 591 114 188.6 104 42.1 3875 20.5 127 0.557 13.4 5 144 188
32 591 112 188.6 103 39.5 3875 19.5 127 0.787 13.2 5 144 189
33.2 591 109 188.6 103 39.5 3850 19.5 127 0.102 13.3 5 144 189
34.4 591 108 188.6 104 38.8 3850 19.5 127 0.685 13.5 5 144 189
35.6 591 107 187.3 103 39.1 3850 19.5 127 0.707 13.5 5 144 189
36.8 591 106 187.3 103 39.1 3800 19.5 127 0.809 13.5 5 144 189
38 591 106 187.3 105 39.1 3850 19.5 127 0.813 13.5 5 144 189
39.2 591 106 187.3 103 39.1 3825 19.5 127 0.831 13.4 5 144 189
40.4 591 106 187.3 103 39.1 3850 19.5 127 0.84 13.5 5 144 189
41.6 591 106 186 103 39.1 3800 19.5 127 0.849 13.5 5 144 190
42.8 591 106 186 103 39.5 3850 19.5 127 0.835 13.5 5 144 190
43.9 591 106 186 103 36.6 3800 17.6 126 0.734 13.5 5 144 190
45.1 591 94 186 102 28.4 3725 14.2 124 0.69 13.5 5 143 190
46.3 591 81 186 102 32.9 2725 14.2 124 0.164 13.5 5 142 190
47.5 591 74 186 102 38 2625 15.2 128 0.044 13.5 5 142 190
48.7 591 74 184.7 102 38 2650 15.7 128 0.049 13.5 5 142 190
49.9 591 74 184.7 100 38 2675 15.7 128 0.053 13.6 5 142 190
51.1 591 80 184.7 101 40.2 2625 16.6 128 0.04 13.5 5 142 190
52.3 591 84 184.7 100 41 2625 16.1 128 0.049 13.6 5 142 190
53.5 591 70 184.7 100 22.5 2550 6.5 128 0.04 13.6 5 128 190
54.6 591 42 184.7 99 15.2 2425 3.1 128 0.027 13.6 5 128 190
55.8 591 44 184.7 97 15.2 2350 3.1 128 0.022 13.5 5 128 189
57 591 44 183.5 95 16.3 2300 3.1 128 0.009 13.7 5 128 189
58.2 591 44 183.5 94 16.3 2250 3.1 128 0.004 13.7 5 128 189
59.4 591 44 183.5 92 16.6 2200 3.1 128 0.004 13.7 5 128 189
60.6 591 44 183.5 90 16.6 2150 3.1 128 0.004 13.6 5 128 189
61.8 591 44 183.5 89 17.4 2125 3.6 128 0.004 13.7 5 128 188
63 591 40 183.5 86 17 2100 4.1 128 0.027 13.6 5 128 188
64.2 591 35 182.4 87 17.7 2100 5 128 0.027 13.6 5 128 188
65.3 591 32 182.4 85 18.8 2075 6 128 0.031 13.6 5 128 188
66.5 591 30 182.4 84 18.8 2100 6 128 0.027 13.6 5 128 188
67.7 591 32 181.3 84 29.2 2200 11.3 129 0.031 13.5 5 128 188
68.9 591 53 181.3 82 34.7 2225 12.8 133 0.248 13.5 5 130 188
70.1 591 53 181.3 84 32.1 2200 11.3 135 0.088 13.6 5 131 187
71.3 591 46 181.3 84 28.4 2150 10.4 137 0.835 13.6 5 133 188
72.5 591 41 180.2 83 28.1 2200 10.4 137 0.72 13.6 5 134 187
73.7 591 44 180.2 82 31.4 2225 11.8 135 0.893 13.5 5 135 187
74.8 591 44 180.2 85 31.8 2225 11.8 134 0.888 13.6 5 136 187
76 591 44 180.2 83 32.1 2175 11.8 133 0.853 13.6 5 137 187
77.2 591 44 179.1 84 32.9 2200 11.8 132 0.791 13.6 5 138 187
78.4 591 44 179.1 81 32.1 2175 11.8 130 0.088 13.6 5 138 187
79.6 591 44 179.1 83 32.5 2175 11.8 130 0.765 13.6 5 138 187
80.8 591 44 179.1 82 32.5 2175 11.8 130 0.066 13.6 5 138 187
82 591 44 179.1 82 31.4 2150 11.3 130 0.822 13.6 5 138 187
83.2 591 43 178.1 82 29.9 2150 10.4 131 0.062 13.6 5 138 187
84.4 591 39 178.1 81 27 2150 9.9 128 0.062 13.6 5 138 187
85.5 591 35 178.1 81 27 2125 9.9 128 0.057 13.6 5 138 187
86.7 591 34 178.1 80 27 2100 9.9 128 0.053 13.6 5 138 187
87.9 591 33 178.1 80 27.3 2050 9.9 128 0.053 13.6 5 138 187
89.1 591 35 178.1 79 29.2 2100 10.4 130 0.897 13.6 5 138 187
90.3 591 36 178.1 78 29.9 2075 10.4 132 0.084 13.6 5 139 187
91.5 591 36 177.1 78 29.9 2075 10.4 132 0.871 13.6 5 140 187
92.7 591 36 177.1 78 29.9 2025 10.4 131 0.349 13.5 5 140 187
93.9 591 44 177.1 76 32.5 2025 11.3 129 0.292 13.6 5 140 187
95.1 591 44 177.1 76 33.2 2025 11.3 129 0.884 13.6 5 140 187
96.2 591 44 177.1 76 33.6 2025 11.3 128 0.672 13.6 5 140 187
97.4 591 44 177.1 76 33.6 2000 11.3 128 0.8 13.6 5 140 187
98.6 591 44 177.1 76 33.2 2000 11.3 127 0.729 13.6 5 140 187
99.8 591 44 177.1 76 34 2000 11.3 127 0.075 13.6 5 140 187
101 591 44 176.1 76 34 1975 11.3 127 0.765 13.5 5 140 187
102.2 591 44 176.1 75 34.3 2000 11.3 127 0.716 13.6 5 140 187
103.4 591 44 176.1 75 33.6 2000 11.3 127 0.08 13.6 5 140 187
104.6 591 44 176.1 74 34.3 1950 11.3 127 0.849 13.6 5 140 187
105.8 591 44 176.1 74 34 2000 11.3 127 0.897 13.5 5 140 187
106.9 591 44 176.1 74 34.3 1950 11.3 127 0.217 13.6 5 140 187
108.1 591 44 176.1 74 34 1975 11.3 127 0.517 13.6 5 140 187
109.3 591 44 176.1 73 34.3 1950 11.3 127 0.831 13.6 5 140 187
110.5 591 44 176.1 73 34.3 1925 11.3 127 0.08 13.4 5 140 187
111.7 591 44 176.1 73 34.3 1950 11.3 127 0.588 13.6 5 140 187
112.9 591 44 176.1 73 35.1 1950 11.3 127 0.601 13.6 5 140 187
114.1 591 44 176.1 73 34.7 1925 11.3 127 0.075 13.6 5 140 187
115.3 591 44 176.1 72 34.7 1950 11.3 127 0.888 13.5 5 140 187
116.5 591 44 176.1 71 35.1 1925 11.3 127 0.813 13.5 5 140 187
117.6 591 44 176.1 71 35.1 1925 11.3 127 0.075 13.6 5 140 187
118.8 591 44 176.1 71 35.1 1900 11.3 127 0.88 13.6 5 140 187
120 591 44 176.1 71 36.9 1900 11.8 127 0.071 13.6 5 140 187
121.2 591 49 176.1 70 38 1900 12.3 127 0.172 13.6 5 140 187
122.4 591 49 176.1 72 38 1900 12.3 127 0.853 13.6 5 140 187
123.6 591 49 176.1 71 38 1925 12.3 127 0.345 13.6 5 140 187
124.8 591 49 176.1 71 38.8 1900 12.3 126 0.261 13.6 5 140 187
126 591 49 176.1 71 38 1900 12.3 126 0.84 13.6 5 140 187
127.2 591 49 175.2 70 38.8 1900 12.3 128 0.04 13.6 5 140 187
128.4 591 49 176.1 71 38 1875 12.3 128 0.04 13.6 5 140 188
129.5 591 49 176.1 72 38.4 1900 12.3 128 0.04 13.6 5 140 188
130.7 591 49 176.1 72 38 1925 12.3 128 0.04 13.6 5 140 188
131.9 591 49 176.1 73 37.7 1925 12.3 128 0.04 13.6 5 140 188
133.1 591 49 176.1 73 37.3 1950 12.3 128 0.04 13.6 5 140 188
134.3 591 49 176.1 73 37.3 1975 12.3 128 0.04 13.6 5 140 188
135.5 591 49 176.1 74 36.6 1950 12.3 128 0.04 13.6 5 140 188
136.7 591 49 176.1 74 36.9 2000 12.3 128 0.04 13.7 5 140 188
137.9 591 49 176.1 75 36.6 2000 12.3 128 0.04 13.7 5 140 188
139.1 591 49 176.1 76 35.4 2000 12.3 128 0.044 13.6 5 140 188
140.4 591 49 176.1 76 35.8 2025 12.3 128 0.04 13.7 5 140 188
141.4 591 49 175.2 77 35.8 2000 12.3 128 0.04 13.6 5 140 188
142.6 591 49 175.2 77 35.1 2000 12.3 128 0.044 13.7 5 140 188
143.8 591 49 175.2 77 35.4 2050 12.3 128 0.04 13.6 5 140 188
145 591 49 175.2 78 35.1 2050 12.3 128 0.044 13.6 5 140 188
146.2 591 48 175.2 78 31.8 2050 10.8 128 0.044 13.6 5 140 188
147.4 591 44 175.2 78 30.6 2050 10.8 128 0.044 13.7 5 140 189
148.6 591 42 175.2 78 30.6 2050 10.8 128 0.044 13.7 5 140 189
149.7 591 41 175.2 78 30.6 2075 10.8 128 0.044 13.6 5 140 189
150.9 591 40 174.3 78 30.3 2050 10.8 128 0.044 13.6 5 140 189
152.1 591 40 174.3 78 30.6 2050 10.8 128 0.049 13.7 5 140 189
153.3 591 40 174.3 79 29.9 2050 10.8 128 0.049 13.7 5 140 189
154.5 591 40 174.3 78 29.9 2075 10.8 128 0.044 13.6 5 140 189
155.7 591 40 173.4 78 30.3 2075 10.8 128 0.049 13.7 5 140 189
156.9 591 40 173.4 79 29.2 2075 9.9 128 0.049 13.7 5 140 189
158.1 591 36 173.4 79 27.3 2075 9.4 128 0.049 13.6 5 140 189
159.3 591 31 173.4 79 24 2000 7.9 128 0.035 13.7 5 128 189
160.4 591 28 173.4 79 24.4 2000 7.9 128 0.031 13.7 5 128 189
161.6 591 28 173.4 78 24 1975 7.9 128 0.035 13.7 5 128 189
162.8 591 28 172.5 77 24.4 1950 7.9 128 0.035 13.7 5 128 189
164 591 28 172.5 77 24.7 1950 7.9 128 0.031 13.7 5 128 188
165.2 591 28 172.5 76 24.4 1925 7.9 128 0.035 13.7 5 128 188
166.4 591 28 172.5 76 24 1900 7.9 128 0.027 13.7 5 128 188
167.6 591 28 172.5 75 24.4 1875 7.9 128 0.027 13.7 5 128 188
168.8 591 28 172.5 75 24.4 1900 7.5 128 0.027 13.7 5 128 188
170 591 28 172.5 73 23.3 1800 6.5 128 0.027 13.7 5 128 188
171.2 591 28 171.6 74 17.4 1775 3.1 128 0.031 13.7 5 128 188
172.3 591 44 171.6 72 19.6 1725 3.1 128 0.022 13.6 5 128 188
173.5 591 44 171.6 70 21.1 1575 3.1 128 0.022 13.7 5 129 188
174.7 591 44 171.6 68 22.2 1500 3.1 128 0.013 13.6 5 129 188
175.9 591 44 171.6 66 23.3 1425 3.1 128 0.009 13.6 5 129 188
177.1 591 44 171.6 62 24.7 1325 3.1 128 0.013 13.7 5 129 188
178.3 591 44 171.6 59 25.9 1225 3.1 128 0.013 13.6 5 129 188
179.5 591 44 171.6 56 27.7 1150 4.1 128 0.018 13.6 5 134 188
180.7 591 44 171.6 55 43.2 1575 11.8 131 0.084 13.7 5 129 188
181.9 591 35 171.6 55 24 1225 2.6 127 0.075 13.6 5 129 188
183 591 32 170.8 52 23.3 1250 3.1 128 0.057 13.6 5 129 187
184.2 591 30 170.8 48 24 1125 2.6 128 0.049 13.6 5 129 187
185.4 591 29 170.8 45 24.4 1100 3.1 128 0.053 13.7 5 129 187
186.6 591 29 170.8 42 25.1 1050 3.1 128 0.049 13.6 5 129 187
187.8 591 28 170.8 40 25.9 1000 3.1 128 0.04 13.6 5 129 187
189 591 28 170.8 36 28.1 925 3.1 131 0.561 13.4 5 135 187
190.2 591 28 170.8 29 27.3 975 3.1 134 0.906 13.4 5 135 187
191.3 591 28 170.8 24 28.8 925 3.1 130 0.884 13.6 5 135 187
192.5 591 37 170.8 22 46.9 1150 9.9 128 0.822 13.5 5 135 187
193.7 591 66 170.8 23 62.4 1475 16.6 128 0.911 13.6 5 132 187
194.9 591 124 170.8 26 73.1 1700 21.9 131 0.747 13.3 5 142 187
196.1 591 124 170.8 31 72 1775 21.9 128 0.831 13.6 5 142 188
197.3 591 124 170.8 35 70.9 1825 21.9 126 0.827 13.6 5 141 188
198.5 591 124 170.8 39 70.1 1875 21.9 124 0.508 13.6 5 140 188
199.7 591 124 170.8 42 69.4 1900 21.9 124 0.539 13.6 5 139 189
200.9 591 119 170.8 45 65.3 1800 19.5 126 0.128 13.7 5 139 189
202.1 591 103 170.8 46 53.2 1525 12.3 126 0.049 13.6 5 135 189
203.2 591 78 170.8 48 45.4 1450 7.9 128 0.734 13.7 5 135 189
204.4 591 47 170.8 47 26.6 1225 3.1 128 0.04 13.7 5 129 189
205.6 591 28 170.8 46 23.6 1175 3.1 128 0.049 13.7 5 129 189
206.8 591 28 170.8 43 24.7 1100 3.1 128 0.049 13.7 5 129 189
208 591 28 170.8 40 26.6 1025 3.1 128 0.044 13.4 5 129 189
209.2 591 28 170.8 37 27 975 3.1 131 0.875 13.5 5 129 189
210.4 591 28 170.8 35 29.2 900 3.1 128 0.057 13.5 5 135 189
211.6 591 28 170.8 34 25.9 1075 3.1 127 0.884 13.7 5 135 189
212.8 591 28 171.6 34 25.9 1050 3.1 128 0.066 13.6 5 135 189
213.9 591 28 171.6 34 25.9 1050 3.1 128 0.053 13.7 5 135 189
215.1 591 28 171.6 34 25.5 1075 3.1 128 0.075 13.7 5 135 189
216.3 591 28 171.6 35 36.6 1400 8.9 126 0.88 13.7 5 135 189
217.5 591 28 171.6 36 31.4 1400 4.1 126 0.362 13.7 5 129 189
218.7 591 28 172.5 36 27 1050 4.6 128 0.044 13.7 5 135 189
219.9 591 40 172.5 36 44.7 1500 12.3 127 0.075 13.6 5 135 189
221.1 591 50 172.5 38 51.3 1350 12.3 131 0.893 13.6 5 135 189
222.3 591 50 172.5 40 50.9 1400 12.3 133 0.155 13.6 5 137 189
223.5 591 50 172.5 41 50.9 1400 12.3 133 0.84 13.7 5 139 189
224.6 591 50 172.5 42 50.6 1400 12.3 131 0.548 13.6 5 139 189
225.8 591 106 173.4 42 96 2975 95.8 128 0.95 13.6 6 128 190
227 591 128 173.4 51 96 3350 95.8 128 0.884 13.6 6 128 191
228.2 591 128 173.4 59 95.2 3750 95.8 128 0.919 13.6 6 128 193
229.4 591 128 173.4 66 94.9 4150 95.8 128 0.941 13.5 6 128 194
230.6 591 128 173.4 73 94.1 4550 96.3 128 0.933 13.6 6 128 195
231.8 591 128 173.4 78 96 3150 96.3 128 0.866 13.6 6 128 196
233 591 128 173.4 83 95.2 3250 96.3 128 0.915 13.6 6 128 197
234.2 591 128 173.4 87 95.6 3400 96.3 128 0.866 13.6 6 128 197
235.3 591 128 173.4 93 94.9 3575 96.3 128 0.893 13.4 6 128 198
236.5 591 128 173.4 95 94.5 3700 96.3 128 0.654 13.6 6 128 199
237.7 591 128 173.4 99 94.5 3800 96.3 128 0.813 13.6 6 128 199
238.9 591 128 174.3 101 94.5 3875 96.3 128 0.919 13.6 6 128 200
240.1 591 128 174.3 107 95.6 4050 96.3 128 0.822 13.6 6 128 201
241.3 591 128 175.2 108 94.9 4175 96.3 128 0.844 13.6 6 128 201
242.5 591 128 175.2 111 94.9 4250 93.4 128 0.911 13.6 6 131 201
243.7 591 123 176.1 112 29.9 3275 9.4 124 0.884 13.7 6 128 201

 

.045 plug gap?.
Me thinks your into a lean miss, with BLs at 140.
Might try backing some timing out, and adding a little fuel.

 

I did a tune up 3 weeks ago with no ill effects.

New cap, rotor, wires and plugs.

taylor cap/rotor, msd 8.5 wires, and ac delco plugs at 0.045

Then last thursday, it just started vibrating out of nowhere at those highway cruising speeds.

The coil is a MSD GM Blaster 2 coil which has been in the car for 2 years now.

I have the timing already backed off to stock 0 degrees. The vibration doesn't care what timing I have.

I also added some FP as well with no change. I'm pulling all plugs weather permitting to see what I'm dealing with regarding all cylinders.

 

I am having the same problem with my car running lean while cruising after I added my avenger 670 carb the air fuel meter reads perfect except when cruising barely on the throttle.Since we both have a .045 gap I wonder if gapping it at .040 would help??
If your engine is vibrating while it is out of gear it could either be the flywheel or the harmonic balancer could be warped or your even worse your engine bearings are worn and the crank and rods are knocking around.