I have a 91 Chevy k1500 4X4 p/u with a idle.

Tiny
BRANDON .SPURLOCK@YMAIL.COM
  • 1991 CHEVROLET SILVERADO
  • 225,000 MILES

I have a 91 Chevy k1500 4x4 p/u with a idle issue. Truck starts and runs fine at first. Starts up, high idle comes on and than goes down. After driving for a while (approx 30 miles) when I shut off the truck and re-start it the idle is really fast. I have to fight the engine with the brakes to get it stopped. The idle never drops back down untill the engine has sat for a while and cooled off. When this happens the truck will go approx. 15 - 20 Mph and not slow down unless I use the brakes to stop
It. Also this weekend a new issue started where the brakes have no real pressure and I can push the pedal to the floor. Don't know if these are related or not? I've read so many diffrent things and don't want to just throw parts at it and get no where. Thanks, -Brandon

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Monday, December 3rd, 2012 AT 9:16 PM

13 Replies

Tiny
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Check your base of tbi unit for a blown gasket you can spray choke cleaner at the base and normally the rpm will change if it leaks. It probably is as this is one of the problems that crop up due to age. You'll just need to replace the gasket. Also check for soft hoses going to pcv and map sensor on firewall. Have your brakes checked and mkae sure master cyclinder is full of fluid it may be a master cylinder going bad or brake wear or both.

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Monday, December 3rd, 2012 AT 11:15 PM
Tiny
BRANDON .SPURLOCK@YMAIL.COM
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If it was the gasket or the hoses wouldn't this be happening all the time? It only seems to happen after the truck is warm. Once cooled back down everything goes back to normal.

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Monday, December 3rd, 2012 AT 11:21 PM
Tiny
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Not necessarily, heat expands things, also when engine is cold it's not in closed loop so it's running a little rich, whenit warms the computer can't make teh difference up to richen the fuel pmix enough to overcome the vacuum leak.

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Monday, December 3rd, 2012 AT 11:23 PM
Tiny
BRANDON .SPURLOCK@YMAIL.COM
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Ok.I'll check those tonight. Thanks.

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Monday, December 3rd, 2012 AT 11:41 PM
Tiny
BRANDON .SPURLOCK@YMAIL.COM
  • MEMBER

I tested the gasket with carb cleaner. It did not show sings of being blown, but I had already purchased the gasket so I went and changed the gasket anyways. It did make a significant difference. How ever I am still having a high rpm after I shut the truck off. Yesterday I drove home from work (aprox. 30 miles) and never had an issue. Parked the truck, went back out about 30 minutes later and the idle/rpm came back to being high/fast. Went into a store for about 15 minutes, started the truck and the idle/ rpms was back to normal. I checked the hoses and they appear to be ok. When I was working on the truck I removed the IACV to check what it looked like. The pintle had one shinny spot that was about a 1/4 of the pintle, shiny spot started from the top and tapered down. The rest of the pintle was black, almost looked like it wasn't seating flush inside the TBI when it was out? Any ideas on what I should check/do next? Thanks for all the help.

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Thursday, December 6th, 2012 AT 2:01 AM
Tiny
BRANDON .SPURLOCK@YMAIL.COM
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FYI I checked the breaks and found the pass side rear wheel cylinder leaking. Going to change the d/s and p/s cylinders this weekend.

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Thursday, December 6th, 2012 AT 2:02 AM
Tiny
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Try cleaning iac then I fyou haven't already. But for it to reset you have to drive 40 mph for it to reset it self correctly. Only other thing I can think of is that iac is bad.

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Thursday, December 6th, 2012 AT 2:17 PM
Tiny
BRANDON .SPURLOCK@YMAIL.COM
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I cleaned the iac when it was out of the truck. I have driven already 120 miles so it should be set already? Have you ever heard of this before where it is only after the truck is shut off than turned back on that the problem is there?

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Thursday, December 6th, 2012 AT 2:24 PM
Tiny
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No but stranger things h ave happened, I dorn' tknow what to suggest. Unless throttle is sticking due to age/mileage.

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Thursday, December 6th, 2012 AT 2:26 PM
Tiny
BRANDON .SPURLOCK@YMAIL.COM
  • MEMBER

I'm back. So today driving home the check engine light came on. Checked the codes. Got 22 (Tps- low signal voltage), 24 (vss- this I know about, the spedo has been out for some time, I have changed the vss and inst. Cluster, still not working, maybe a broken wire somewhere?) & 34 (Map sensor voltage low). Are all these parts somehow related? I really don't want to change the map and tps and find out the sensors really weren't bad. What do you think I should check?

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Friday, December 7th, 2012 AT 2:36 AM
Tiny
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Remember I said to check the hose leaing to the pmap sensor to make sure it has no holes or soft? That's on the firewall that is what I suspected but wasn't sure but it hink you saidhoses were ok, well pull it off map and see if you ae getting vacuum through it. If you are replace it. Check wiring at tps and see ifyou are getting voltage through any of the wires. And the vss may be why your speedo isn't working or the wiring is bad. It all relates to each other when vehicle is running and warm.

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Friday, December 7th, 2012 AT 1:55 PM
Tiny
BRANDON .SPURLOCK@YMAIL.COM
  • MEMBER

Ok. So to make sure I am doing this correct. I am going to pull the vacumm line off the map sensor and check for vaccum. If I have vaccum replace the map sensor? Also check the tps wires for voltage with a multi meter. If I do have voltage what would be next? R/R the tps? I have replaced the vss and the inst. Cluster. Broken wire possibly? With the miles on the truck and the electrical problems I am having do you think it is possible the ECM is going out? Thanks for the help on this stuff I will definitely be donating some more money to the website.

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Friday, December 7th, 2012 AT 8:45 PM
Tiny
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Follow the charts i'm sending. And look at th pics so you can probel the right places.

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Friday, December 7th, 2012 AT 8:55 PM

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