10-02-2008, 10:03 AM
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#41
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Registered User
Join Date: Apr 2008
Location: 409 TX
Age: 21
Posts: 1,079
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Re: 1991 chevy 1500 5.7 tbi erratic idle
i have no clue about the fan noise....
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Life can take the strongest man, and make him feel all alone.
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10-02-2008, 01:55 PM
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#42
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Registered User
Join Date: Sep 2008
Location: spokane valley, wa
Age: 29
Posts: 283
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Re: 1991 chevy 1500 5.7 tbi erratic idle
well my mechanic was sick today so I talked to the place where I had the fuel injection cleaning done and he said the pressure from the pump to the injectors was 12 so it checks out .. I will try to go see my mechanic tomorrow and see what he thinks...the other shop told me to try swapping out ecms and see how it runs then they will diagnose after that? I can get one from the yard here for about 70 but seems like a shot in the dark. any opinions?
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1991 chevy 1500 ext. cab 5.7 TBI
1988 chevy reg. cab 5.7 TBI lifted 8" swampers (  GONE Wife made me sell it )
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10-02-2008, 02:46 PM
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#43
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GMC RULZZ
Join Date: Mar 2005
Location: San Diego
Age: 43
Posts: 9,764
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Re: 1991 chevy 1500 5.7 tbi erratic idle
For the hard starting.
did they say how long it holds the pressure? hopefully more then a minute. could also be a faulty in tank fuel pump check valve causing the extended cranking.
did you ohm (test) the pick up coil?
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10-02-2008, 02:52 PM
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#44
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Registered User
Join Date: Sep 2008
Location: spokane valley, wa
Age: 29
Posts: 283
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Re: 1991 chevy 1500 5.7 tbi erratic idle
not yet hopefully i will have my tools back tomorrow.
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1991 chevy 1500 ext. cab 5.7 TBI
1988 chevy reg. cab 5.7 TBI lifted 8" swampers ( GONE Wife made me sell it )
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10-03-2008, 10:18 AM
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#45
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Registered User
Join Date: Sep 2008
Location: spokane valley, wa
Age: 29
Posts: 283
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Re: 1991 chevy 1500 5.7 tbi erratic idle
well its going to a shop somewhere today, but i noticed the gauge inside never gets above 160 degrees, i am going to put a heat gun on it to see if thats as hot as it is really getting if it is only getting to 160 would that cause it to idle strange looking for closed loop?
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1991 chevy 1500 ext. cab 5.7 TBI
1988 chevy reg. cab 5.7 TBI lifted 8" swampers ( GONE Wife made me sell it )
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10-03-2008, 09:52 PM
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#46
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Registered User
Join Date: Sep 2008
Location: spokane valley, wa
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Re: 1991 chevy 1500 5.7 tbi erratic idle
bump
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1991 chevy 1500 ext. cab 5.7 TBI
1988 chevy reg. cab 5.7 TBI lifted 8" swampers ( GONE Wife made me sell it )
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10-04-2008, 07:32 AM
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#47
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Registered User
Join Date: Apr 2008
Location: 409 TX
Age: 21
Posts: 1,079
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Re: 1991 chevy 1500 5.7 tbi erratic idle
If it is 160* than you need to replace your thermostat with a
185*
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Life can take the strongest man, and make him feel all alone.
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10-04-2008, 10:42 AM
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#48
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Registered User
Join Date: Sep 2008
Location: spokane valley, wa
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Re: 1991 chevy 1500 5.7 tbi erratic idle
Quote:
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Originally Posted by XLR8N
If it is 160* than you need to replace your thermostat with a
185*
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would this cause a weird idle?
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1991 chevy 1500 ext. cab 5.7 TBI
1988 chevy reg. cab 5.7 TBI lifted 8" swampers ( GONE Wife made me sell it )
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10-04-2008, 10:55 AM
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#49
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Registered User
Join Date: Apr 2008
Location: 409 TX
Age: 21
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Re: 1991 chevy 1500 5.7 tbi erratic idle
well, i would rather run 185* thermostat in a stock truck. And you are in WA also so it isnt like living in texas. I would not think that would cause your idle probs though.
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Life can take the strongest man, and make him feel all alone.
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10-04-2008, 05:44 PM
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#50
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Registered User
Join Date: Sep 2008
Location: spokane valley, wa
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Posts: 283
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Re: 1991 chevy 1500 5.7 tbi erratic idle
well finally got in to the mechanic fuel pressure is good, he says its an intake manifold gasket leak ,confirmed with some carb spray, can actually see where it got sucked in, the guy who rebuilt this must have installed them wrong... at least I know whats wrong now, hes going to replace them and put the tbi tune up kit on next week for me for $150 and said if that doesnt fix it hell be working on it for free until its fixed.... so hopefully this will do it I will post next thursday evening with results.. I know there are a few others having alike issues so hopefully this may help them too
also noticed the knock sensor wiring connector was broken and hanging down so I fixed that also
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1991 chevy 1500 ext. cab 5.7 TBI
1988 chevy reg. cab 5.7 TBI lifted 8" swampers ( GONE Wife made me sell it )
Last edited by tpulliam79; 10-04-2008 at 07:11 PM.
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10-06-2008, 07:32 AM
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#51
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Registered User
Join Date: Apr 2008
Location: 409 TX
Age: 21
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Re: 1991 chevy 1500 5.7 tbi erratic idle
cool, good price.
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Quote:
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Life can take the strongest man, and make him feel all alone.
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10-06-2008, 01:53 PM
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#52
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Registered User
Join Date: Sep 2008
Location: spokane valley, wa
Age: 29
Posts: 283
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Re: 1991 chevy 1500 5.7 tbi erratic idle
going to replace thermostat ans temp switch and put tune up kit on throttle body and injector pump. Is there anything else I should do while its apart?
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1991 chevy 1500 ext. cab 5.7 TBI
1988 chevy reg. cab 5.7 TBI lifted 8" swampers ( GONE Wife made me sell it )
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10-06-2008, 02:26 PM
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#53
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Registered User
Join Date: Apr 2008
Location: 409 TX
Age: 21
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Re: 1991 chevy 1500 5.7 tbi erratic idle
I would replace the water pump too if it was me. 30 bucks for a brand new one and im sure the mechanic wouldnt charge you much more if not anything. maybe the pcv valve too. clean it up real good and you'll be set.
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Quote:
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Life can take the strongest man, and make him feel all alone.
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Last edited by XLR8N; 10-06-2008 at 02:26 PM.
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10-09-2008, 08:05 PM
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#54
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Registered User
Join Date: Sep 2008
Location: spokane valley, wa
Age: 29
Posts: 283
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Re: 1991 chevy 1500 5.7 tbi erratic idle
well the intake gasket was replaced and it needed it and the tbi all tuned up ran great until we reved the engine then back to a surging idle not as bad but still there. he only charged me 1/2 of the labor and is going to do some more diagnosis this weekend. Boy I do love my truck but ive put almost 1000 into it in the first two weeks, any ideas?
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1991 chevy 1500 ext. cab 5.7 TBI
1988 chevy reg. cab 5.7 TBI lifted 8" swampers ( GONE Wife made me sell it )
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10-09-2008, 08:13 PM
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#55
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chevy driver
Join Date: Sep 2007
Location: usa
Posts: 15
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Re: 1991 chevy 1500 5.7 tbi erratic idle
just a thougt try unpluging the lockup tork converter it may be draging or not unlocking completly
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something burning? nope! its just me.
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10-09-2008, 09:08 PM
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#56
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Registered User
Join Date: Oct 2008
Location: Scandia, PA
Age: 35
Posts: 24
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Re: 1991 chevy 1500 5.7 tbi erratic idle
Where did you get the CTS? I went through 2 of them from Autozone in 2 months, I fixed the problem with one from the dealer. The CTS can be checked with an ohmmeter. Did you clean the EGR valve yet?
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Dan
'91 5.7 4x4 Chevy
'05 4.2 4x4 Trailblazer
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10-09-2008, 11:14 PM
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#57
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Registered User
Join Date: Sep 2008
Location: spokane valley, wa
Age: 29
Posts: 283
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Re: 1991 chevy 1500 5.7 tbi erratic idle
the egr passages in the intake were completely clogged but clean now. coolant temp sensor is new from autozone . how does the ohm test work?
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1991 chevy 1500 ext. cab 5.7 TBI
1988 chevy reg. cab 5.7 TBI lifted 8" swampers ( GONE Wife made me sell it )
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10-09-2008, 11:42 PM
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#58
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Finally got the Dmax!!!
Join Date: Jul 2008
Location: Lincoln, NE
Age: 23
Posts: 899
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Re: 1991 chevy 1500 5.7 tbi erratic idle
just looked at my haynes manual for the coolant temp sensor ohm test. with the engine cold, test resistance across the terminals (wire harness disconnected, one test probe on each of the connections) readings should be anywhere from 2200ish at ~85* to 5600 at ~55*F. Warm the truck up, and repeat the test. Readings shoud be in the hundreds of ohms. Like below 500 or 600. The sensor is made to vary resistance with temperature, so the warmer the engine gets, the less resistance there is in the sensor.
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10-09-2008, 11:57 PM
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#59
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Registered User
Join Date: Sep 2008
Location: spokane valley, wa
Age: 29
Posts: 283
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Re: 1991 chevy 1500 5.7 tbi erratic idle
thanks. also I was comparing some parts to see what all vehicles I can get a ecm out of, does it have to be same year and all or just the same part number off the ecm?
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1991 chevy 1500 ext. cab 5.7 TBI
1988 chevy reg. cab 5.7 TBI lifted 8" swampers ( GONE Wife made me sell it )
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10-18-2008, 01:01 AM
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#60
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Registered User
Join Date: Oct 2008
Location: oklahoma
Posts: 1
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Re: 1991 chevy 1500 5.7 tbi erratic idle
Try replacing the broken spring inside the fuel pressure regulator.
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