I've got a '94 S10 Blazer. On friday, when starting the truck, the "Service Engine Soon" light turned on, and the engine had a rough idle. The truck was left in the driveway since, but when we tried to drive it today, the light was still on, the rough idle was still there, and when after pulling out of the driveway, it died after a couple feet. The truck started back up without issue, but had the same rough idle to it.

The idle sounds is a high rev for a second, then reducing to a low rev.

Anyone have any idea what is wrong? Would the cold weather be the issue (we've hit freezing temperatures recently)? Any help would be appreciated.

 

1st thing you need to do is check the codes. You can do it yourself with a paperclip. Find the diagnostic port above your right leg underneath the steering wheel. you will see some silver pins in it. the top 2 pins on the right is what you want to jump together.

With the blazer completely off insert each end of the paper clip into the pins. Do not crank the blazer! but turn the key to the on position. What your service engine light flash. It will flash in series...Like at 1st it will flash 12.

flash........flash flash....

that means 1...2 = 12.

it'll do that 3 times telling you that the computer knows your about to pull any codes stored. after it flashes 3 times it will flash the 1st code 3 times again..if its say 11.....flash.....flash. if thats the only code it will flash 12 again saying its finished. Do not crank the blazer until you pull the clip out.

take the numbers you wrote down and look at this :
GM common codes for OBD1 (for vehicles made before 1995)
12 System normal
13 oxygen sensor circuit open
14 coolant sensor high resistance or shorted
15 coolant sensor circuit low or open
16 direct ignition system (DIS) fault in circuit
17 cam position sensor fault
18 crank or cam sensor error
19 crank sensor circuit fault
21 tps sensor out of range
22 tps sensor signal voltage low
23 intake air temp sensor out of range, low
24 vehicle speed (vss) sensor circuit fault
25 air temp sensor sensor out of range, high
26 quad-driver module (computer) circuit #1 fault
27 quad-driver module (computer) 2nd gear circuit
28 quad-driver module (computer) circuit #2 fault
29 quad driver module (computer) 4th gear circuit
31 cam position sensor fault
32 egr circuit fault
33 map sensor signal out of range, high
34 map sensor signal out of range, low
35 idle air control sensor circuit fault
36 ignition system circuit error
38 brake input circuit fault
39 clutch input circuit fault
41 cam sensor circuit fault, igntion control circuit fault
42 electronic spark timing (EST) circuit grounded
43 knock sensor
or electronic spark control circuit fault
44 oxygen sensor lean exhaust
45 oxygen sensor rich exhaust
46 pass-key II circuit or ps.pressure switch circuit fault
47 pcm-bcm data circuit
48 misfire diagnosis
51 calibration error, mem-cal, ecm or eeprom failure
52 engine oil temperature circuit, low temperature indicated
53 battery voltage error or egr or pass-key II circuit
54 egr system failure or fuel pump circuit low voltage
55 a/d converter error or pcm not grounded or lean fuel or frounded reference voltage
56 quad-driver module #2 circuit
57 boost control problem
58 vehicle anti-theft system fuel enable circuit
61 a/c system performance or degraded oxygen sensor signal
62 engine oil temperature high temperature indicated
63 oxygen sensor right side circuit open or map sensor out of range
64 oxygen sensor right side lean exhaust indicated
65 oxygen sensor right side rich exhaust indicated
66 a/c pressure sensor circuit low pressure
67 a/c pressure sensor circuit or a/c clutch circuit failure
68 a/c compressor relay circuit failure
69 a/c clutch circuit head pressure high
70 a/c refrigerant pressure circuit high
71 a/c evaporator temperature sensor circuit low
72 gear selector switch circuit
73 a/c evaporator temperature circuit high
75 digital egr #1 solenoid error
76 digital egr #2 solenoid error
77 digital egr #3 solenoid error
79 vehicle speed sensor (vss) circuit signal high
80 vehicle speed sensor (vss) circuit signal low
81 brake input circuit fault
82 ignition control (IC) 3X signal error
85 prom error
86 analog/digital ecm error
87 eeprom error
99 power management



Tell us what flashed.

 

Thank you for the handy reply. I did as you said and I got 34: Map Sensor Signal Out of Range, Low. Now I have to ask: what does that mean? I'm guessing some sensor somewhere is reporting low fluid or something similar. Is this correct, or am I way off?

 

MAP == Manifold Absolute Pressure. The MAP sensor is one of the main sensors the ECU uses to determine engine load and, there by, how much fuel to inject into the cylinders.

The MAP sensor is located to the right of the throttle body, kind of on top of it and should be easily accessed without removing anything other than potentially a hold down clamp.

I have posted the outputs from the MAP sensor specifically for newer vehicles, but the actual MAP sensor hasn't changed over the years so they will work for you as well. You can find that information in this thread --> 95 Blazer runs crappy.

Good luck with your problem! Please let us know the outcome when you get it fixed!

 

WHat he said!
It's reporting your manifold vacuum APPARENTLY doesnt correspond with the other sensors and rpm. Thus suspects a faulty MAP sensor.. ie; signal low.

Definitely will not run good with a bad MAP sensor!