Irradic idle, Hard Start, Random issues.

[katugly]

I thought i would post this in case any one else is experiencing the problems I have been having.

1987 GMC Jimmy 350 TBI 4wheel

Iratic Idle: Caused by a faulty TPS sensor, Hooking up ALDL reads -.15 volts and jumps around at idle to -.41v Threw Codes 22 and 33. Verified after change of TPS idle sits around .22v tanslation into 1% throttle where as before was sitting at -18% to -4% throttle. At some points while driving comming to a stop cuased the check engine light to come on then while sitting at idle, idle speed jumped up and down.

Hard Start: Took about 5-15 seconds of cranking to get the truck to start. Tracked this down to a faulty Fuel Relay up on the fire wall. When turning the key to start pos. the fuel pump did not come on took relay out tapped it on the bench with a screw driver replaced into position. truck fired up on the first crank. The new relay costs 8.99 from autozone.

Overheat: Truck would come to OT as normal but surpass 195 and keep going to the gauges max. If you were driving you can shift the AT into Neutral turn the truck off and restart the gauge will drop back to 195. This issue I am still wondering about I did turn the CTS connector and make sure it was seated. This seems to have fixed the issue as far as a i can tell at this point. The thermostat was replaced not to long ago. I will shoot the Bung with a laser temp gauge when i can get around to it.

Smoke on start: Suspect the Valve stem seals to be bad or rotted I have the replacement parts to fix this issue.

If any one has any more questions please Post or PM me I will be happy to help with what i can.

 

[katugly]

Overheating: This issue is not solved the truck over heated again on the way to the parts store. Only thing i can think of is that the thermostat is slightly sticking and the decreased pressure when turning the truck off pops the thermostat open. Will do more testing on this when i can. Radiator cap may need looked at as well. Might be worth it to replace the radiator assembly if the shop cannot rod it out due to age. Will look at this next week.

 

[chevyuser74]

your tps sensor should read .55v at idle and koeo of course thats at the sensor with a dvom

 

[katugly]

Ok I changed the thermostat but this did not solve the problem will check other options to figure this issue out.

 

[dyeager535]

If you KNOW its overheating, then I'd expect the radiator to be bad if it's old. If they can rod it cheap, and charge nothing to tear it apart, go for it. If there is a base cost just to look at it, buy new. They are less than $200.

 

[Thunder]

Re overheating: Is your fan clutch operating? Does it overheat on the highway or in town?

 

[kd7kmp]

If you are still overheating, get the system pressure tested. It's a great diagnostic procedure to see if you have a small leak you cannot identify. Check out the radiator...if it's original, it's probably shot and needs to be reconditioned (cheapest option, usually) or replaced. Check the cylinder compression. This can help you solve the rough idle problem as well as oil burning and overheating. If you have a blown headgasket or cracked heads, it will show up during the compression test.

Kevin