head gasket - service engine light

[kimsam317]

I just bought a 1994 s-10. I found out it needed the head gasket replaced, so I had that done. I picked it up last night, and found that when I'm going at speeds over 55 mph, the service engine soon light comes on. When I let off the gas and slow down, the light goes off. The engine soudns fine, and the service engine light has never been on before in the month that I've had the truck. The oil and coolant levels are good. There is no hesitation when going at higher speeds. The only problem is that the light comes on. Any input would be appreciated!

Thanks
Sam

[gmtech1]

Will need to have the codes read, this can be done at most parts stores for free, but in the meantime check for any loose or broken connectors/plugs at sensors, anything that was disconnected for the headgasket repairs.

[kimsam317]

Hey, thanks for replying... I would normally do just that, but the light only comes on while I am driving 55 mph or over. As soon as I decelerate, or just let off the gas for afew seconds, the light goes off. I thought the light had to be on for the code to be read? If thats not the case, I will definitely go that route. I was posting to ask if anyone knew a reason for this or had had a similar problem. Thanks!

[kimsam317]

oh and thanks for the other suggestions, I will definitely look around for anything loose.

[j cAT]

Originally Posted by kimsam317

I just bought a 1994 s-10. I found out it needed the head gasket replaced, so I had that done. I picked it up last night, and found that when I'm going at speeds over 55 mph, the service engine soon light comes on. When I let off the gas and slow down, the light goes off. The engine soudns fine, and the service engine light has never been on before in the month that I've had the truck. The oil and coolant levels are good. There is no hesitation when going at higher speeds. The only problem is that the light comes on. Any input would be appreciated!

Thanks
Sam

we had a 1994 s10 PU v6 vin Z 4X4.

the engine /TBI was a good runner. did use a little more fuel than we expected.

what do you have in this S10 you have ?

I will guess its the O2 sensor

[kimsam317]

j_cAT:

my s10 is a 4 cylinder 2.2. Manual trans 2wd. I have noticed something new with the problem (check engine light coming on). The other night we had a snow storm, and I was driving in 3rd going pretty slow for a few miles when the light came on again. I starting thinking, and I believe that the engine rpms were the same at that point as they would be driving on the highway in 5th. I'm wondering if that is a coincidence, or if the light is coming on when the engine has been going at a certain rpm (2500-3000) for a certain amount of time. As before, as soon as I let off the gas, the light went off again. Like I said, I would love to just be able to have the code read, but the light won't stay on long enough to do that...

I'm going to try reading the obd1 tomorrow..someone told me i can check it with a paperclip in the slots.

[j cAT]

I thought that this was a 2.2 . the 4.3 I did not see much about head issues.

with the chk eng Lt I would also guess its a mis fire . remove plugs compare. could be a cracked spark plug damaged plug wire plug wire routed wrong not properly secured and got melted/short.

using a ohm meter measure the wire resistance they should all be the same or close to the same resistance.

if a plug looks different from the others then check compression compare all should be close.

with the headgasket the O2 does get damaged if your gasket issue allowed coolant to be injested by the engine. also the O2 could be the original. these usually last 10 yrs/100,ooomi. some get more than 100,ooomi with mostly hwy driving.

[kimsam317]

I have new plugs & wires - put in at the same time as the head gasket. The engine doesn't seem to misfire at all. it runs really well. Do you think the o2 sensor would cause the engine light to come on only at certain times & then go off though? i know thats s very common issue and not too serious - but in the past when I've had o2 sensor problems, the check engine light had come on and stayed on.

[chronomafia]

It very well could be as little as an EGR solenoid or something of that nature. When the engine throws a code it stored in the memory for several ignition sycles. Have it read and see if it will give any issues