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GM TBI Engine Idles High


2018-02-04

If you've been to this site before, you might be familiar with my 1991 Chevrolet C1500 project truck. Long story short, I needed to swap the V6 in the truck for another engine (it had a rod knock). I got another 4.3L TBI V6 from a salvage yard. I recently got to the point of starting the new engine up, and it would idle at 2,000 RPM for 30 seconds or so and then drop to 1200 RPM. Both of these speeds are too high for idle.

I reviewed my copy of the Haynes manual for this truck (you should buy one here if you haven't, they're extremely helpful: 1988 - 1998 Chevrolet and GMC Pick-up Repair Manual). Here's a list of troubleshooting items for a high idle:

  • Sticking throttle linkage
  • Idle speed incorrectly adjusted
  • Valve clearances incorrectly adjusted

I'm surprised they didn't include "vacuum leak" as a possible cause. That's essentially what mine ended up being, except it wasn't located at a vacuum tube or port. I found my solution here: [SOLVED] extream high idle problem on 1990 chevy 1500, 4.3 v6 TBI, with this post:

Hi NID FTL

Two things come to mind very quickly.

1. Leaky throttle body base gasket.Very comon on this engine.I don't know if you serviced this when you pulled the intake.

2.Misadjusted or bent throttle linkage.You don't know what was done before you got to it.

If these ck ok there are other more complicated issues you would need a scan tool to ck.

IAC count, EGR percent,TPS etc.They all have an effect on idle speed and may not set codes in an OBD 1 system.Don't forget a leaking pcv valve (Too obvious).Also a bad coolant temp sensor or connecter.Try wiggle test on 2 wire connecter near thermostat housing with it running.You may get lucky.Harness has been known to go bad at sensor connecter.

Good luck,Cardoc.

I popped my throttle body off and the gasket was in terrible condition with multiple sections missing, as you can see in the picture above. I still had the gasket from the previous engine and throttle body, so I threw it on there to see what would happen. Boom, perfect idle! So if your GM TBI engine has a very high idle, check your throttle body gasket. It might be letting in too much air and be causing your issue.

Chevrolet C/K 1500 Centurion Conversion


2018-01-14

Chevy CK 1500 Crew Cab Centurion Conversion Advertisement, Field & Stream Magazine July 1997

Mentions of production numbers

About Centurion

  • Southern Comfort buys Centurion in 2006
  • Here's a little info on Chevy Centurions... Centurion is the leader in automotive conversions and is well known for their crew cab conversion trucks featuring the most popular Chevy 1500 using 100% GM parts that are warrantied through your GM dealer. They are known for building extremely rare models that few have heard about... or ever seen! The 1997-1998 half ton models are hard to come by and if you do they are still worth a pretty penny! The 97-98 1500 crewcab/short bed is extremely rare so if you own one then you have a needle in the haystack! Centurion Conversions had a very limited production number of these trucks. Aprox every 4 months one was picked off the assembly line and sent to Centurion. After the conversion most seemed to have been purchased by GM employees. The 4wd models were fewer and started just under $40k at $39,975. All GM dealership brochures in the 90's only offered a standard & extended cab in the 1500 series trucks... however a limited amount of 2500 & 3500 crew cab longbed W/T (work trucks) were available by special order only. Centurion Conversions were bought out by Southern Comfort Conversions 1/24/06... link

Chevrolet C1500 Cost


2018-01-10

1991 Chevrolet C1500

An ongoing list of maintenance and non-fuel costs for the 1991 Chevrolet C1500.

| Date        | Miles  | Item/Work                      | Cost     |
|-------------|--------|--------------------------------|----------|
| 2017-08-05  | 140000 | Bought truck                   | $1200.00 |
|-------------|--------|--------------------------------|----------|
| Total       |        |                                | $1200.00 |
|-------------|--------|--------------------------------|----------|

Maintenance:

| Date        | Miles  | Item/Work                      | Cost     |
|-------------|--------|--------------------------------|----------|
| 2017-08-07  | 140000 | Oil filter                     | $4.11    |
| 2017-08-07  | 140000 | Oil                            | $13.05   |
| 2017-08-09  | 140000 | Hose for coolant overflow tank | $10.40   |
| 2017-08-09  | 140000 | coolant overflow tank          | $16.34   |
| 2017-08-09  | 140000 | valve cover breather plug      | $7.62    |
| 2017-08-10  | 140000 | hose clamps for overflow hose  | $5.14    |
| 2017-08-13  | 140000 | Throttle position sensor       | $38.14   |
| 2017-08-13  | 140000 | Heavy duty oil stabilizer      | $14.16   |
| 2017-11-18  | 140000 | Engine (Salvage Yard)          | $492.75  |
| 2017-12-15  | 140000 | Spark plugs                    | $16.28   |
| 2017-12-15  | 140000 | Spark plug wires               | $25.06   |
| 2017-12-15  | 140000 | Exhaust manifold gaskets       | $14.16   |
| 2017-12-15  | 140000 | Air filter                     | $6.53    |
| 2017-12-15  | 140000 | Thermostat                     | $8.71    |
| 2017-12-15  | 140000 | Thermostat housing gasket      | $3.26    |
| 2017-12-15  | 140000 | Distributor cap and rotor kit  | $23.97   |
| 2018-01-27  | 140000 | TPS pigtail                    | $16.34   |
| 2018-01-31  | 140000 | Vacuum hose                    | $6.53    |
| 2018-01-31  | 140000 | Belt tensioner                 | $54.49   |
| 2018-02-02  | 140000 | Manual transmission fluid      | $18.07   |
| 2018-02-03  | 140000 | Serpentine Belt                | $33.23   |
| 2018-02-07  | 140000 | Coolant temp sensor            | $19.61   |
| 2018-02-08  | 140000 | Seat to floor bolts            | $9.35    |
| 2018-02-08  | 140000 | Wiper blades                   | $21.78   |
| 2018-02-08  | 140000 | Muffler                        | $40.32   |
| 2018-02-08  | 146000 | Temp sending unit and pigtail  | $39.85   |
| 2018-02-11  | 146000 | Exhaust (muffler back)         | $50.00   |
| 2018-02-12  | 146000 | Tires, Cooper Cobra 235/70/15  | $450.64  |
| 2018-02-20  | 146000 | Mount and balance tires        | $54.50   |
| 2018-02-20  | 146000 | Lug nuts                       | $35.96   |
| 2018-02-20  | 146000 | Grille                         | $96.98   |
| 2018-03-09  | 146000 | Passenger side drip seal       | $28.70   |
| 2018-03-14  | ------ | Knock and oxygen sensors       | $46.31   |
| 2018-03-28  | 147000 | Front corner lenses            | $19.75   |
| 2018-05-19  | 147000 | Transmission rebuilt, clutch,  | $1400.00 |
|             |        | pressure plate, clutch master  |          |
|             |        | cylinder, clutch fluid line    |          |
|-------------|--------|--------------------------------|----------|
| Total       |        |                                | $3142.09 |
|-------------|--------|--------------------------------|----------|

"Unnecessary" items:

| Date        | Miles  | Item/Work                      | Cost     |
|-------------|--------|--------------------------------|----------|
| 2017-09-10  | 140000 | New front seats (Craigslist)   | $200.00  |
|-------------|--------|--------------------------------|----------|
| Total       |        |                                | $200.00  |
|-------------|--------|--------------------------------|----------|
|-------------|--------|--------------------------------|----------|
| Grand Total |        |                                | $4542.09 |
|-------------|--------|--------------------------------|----------|

Removing Paint from Vehicle Windows


2018-01-01

1990 Chevrolet K2500 with Camper Shell

I bought a camper shell for the 1990 Chevrolet K2500 and it's great except for one thing: the previous owner painted the windows black on the inside. This looks cool (as much as a shell can) from the outside and is perfect for sleeping in. It looks like the darkest tint you can get and is nearly pitch black when you spend the night in it. However, you can't see at all when trying to back up. So I needed to remove the paint.

1990 Chevrolet K2500 with painted windows in the camper shell

The best tool I found for the job is a razor blade scraper, like this one:

1990 Chevrolet K2500 with painted windows in the camper shell

Soon I will have it back to clear windows so I can see when I back up and not run into anything. If you're looking for a scraper, you can get one on Amazon: Stanley 28-500 Razor Blade Scraper with 5 Blades.